Process Safety Taxonomy/Definitions

^* indicates work in progress.

Contents

1 Management
2 Technical Tools
3 Science

1 Management

Management

Any individual(s) or legal entity (public or private) having decision-making responsibility for the enterprise, including owners and managers.

Reference: S2S (safety to safety website: OECD Environment, Health and Safety Publications Series on Chemical Accidents No. 10, Annex 1, 2nd Ed., 2003.)

1.1 Management Principles

Management>Management Principles

(Keywords: Management>Principles)

Leadership

Leadership is the critical part of any management system. It drives a management system. For chemical process safety management, it is essential to provide visibility, momentum, a sense of organizational commitment and direction and ultimately reinforcement, through the distribution of rewards and punishments for variable levels of performance. Leadership is needed at every level-from chemical engineer to the first-line supervisor. In the absence of strong, effective, continuing leadership, the desired level of safety performance will not be achieved.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Commitment: Management establishes policy, provides perspective, seta expectations and provides the resources for successful operation. Assurance of operations integrity requires commitment visible to the organization and accountability at all levels. Operations Integrity Management Systems, managers and supervisors credibly demonstrate commitment for operations integrity, promote an open and trusting environment, and understand how their behavior impact others. Commitment is demonstrated through active and viable participation.

Reference: Exxonmobil: Operations Integrity Management System

Continuous Improvement: A continuous improvement process is an ongoing effort to improve the system. These efforts can seek “incremental” improvement over time or “breakthrough” improvement all at once. Delivery processes are constantly evaluated and improved in the light of their efficiency, effectiveness and flexibility. Continuous improvement uses findings from assessments, and from verification and measurement activities, to enhance system suitability, capability and effectiveness.

Reference: Wikipedia

Benchmarking and Metrics: Safety benchmarking is a planned process by which an organization compares its safety processes and performance with a reference point-standard or others to learn how to reduce accidents; improve compliance with safety law; and/or cut compliance costs. And metrics, which are composed of a series of indicators, are used to measure and evaluate the efficiency and effectiveness of this system.

Reference: CCPS Guidelines for Process Safety Metrics

Safety Culture ^*: Safety cultures consist of shared beliefs, practices, and attitudes that exist at an establishment. Culture is the atmosphere created by those beliefs, attitudes, etc., which shape our behavior. An organizations safety culture is the result of a number of factors such as:

Management and employee norms, assumptions and beliefs
Management and employee attitudes
Values, myths, stories
Policies and procedures
Supervisor priorities, responsibilities and accountability
Production and bottom line pressures vs. quality issues
Actions or lack of action to correct unsafe behaviors
Employee training and motivation; an
Employee involvement or “buy-in.”

Reference: Occupational safety and health administration (OSHA)

Safety cultures reflect the attitudes, beliefs, perceptions, and values that employees share in relation to safety.

Reference: S. Cox, T. Cox, “The structure of employee attitudes to safety: an European example”, Work and Stress, 5 (2) (1991), pp. 93–106

The concept that the organisation’s beliefs and attitudes, manifested in actions, policies, and procedures, affect its safety performance.

Reference: L. Ostrom, C. Wilhelmsen, B. Kaplan, “Assessing safety culture”, Nuclear Safety, 34 (2) (1993), pp. 163–172

The collective mental programming towards safety of a group of organisation members.

Reference: Berends, J.J., “On the Measurement of Safety Culture” (Unpublished graduation report), 1996 Eindhoven University of Technology, Eindhoven.

The safety culture of an organization is the product of individual and group values, attitudes, perceptions, competencies, and patterns of behavior that determine the commitment to, and the style and proficiency of, and organization’s health and safety management.

Reference: Lee, T.R., “Perceptions, attitudes and behavior: the vital elements of a safety culture.” Health and Safety October, 1–15, 1996

Safety culture and culture of safety are frequently encountered terms referring to a commitment to safety that permeates all levels of an organization, from frontline personnel to executive management. More specifically, “safety culture” calls up a number of features identified in studies of high reliability organizations outside of safety management with exemplary performance with respect to safety.(1,2) These features include:

acknowledgment of the high-risk, error-prone nature of an organization’s activities
a blame-free environment where individuals are able to report errors or close calls without fear of reprimand or punishment
an expectation of collaboration across ranks to seek solutions to vulnerabilities
a willingness on the part of the organization to direct resources for addressing safety concerns (3)

References: S2S (safety to safety website)

Roberts KH. Managing high reliability organizations. Calif. Manage Rev. 1990;32:101-113.
Weick KE. Organizational culture as a source of high reliability. Calif. Manage Rev. 1987;29:112-127.
From website: HSTAT: Health Services Technology Assessment Text
From website: Patient Safety Network, PsNet)

Safety Climate: An indication of how well safety culture is embraced in an organization.

1.2 Process Safety Information and Knowledge

1.2.1 Hazards Management

Management>Process Safety Information and Knowledge>Hazards Management

(Keywords: Management>Process Safety Information>Harzards Management)

Hazards Management: Hazards management is a procedure that outlines the requirements for the management of hazards and provides a standard model. It fulfills the employer’s duty under the OHS&W regulations 1995 to identify the hazards associated with the activities, the working environment, the use of plant and equipment and also to assess levels of risk and implement appropriate risk control measures.

Reference: 1. D.Crowl and J. Louvar, Chemical Process Safety: Fundamentals with Applications, Prentice Hall (2002) Chapter 2; 2. MSDS sheet from online; 3. http://www.unisa.edu.au/ohsw/procedures/hazard.asp

Toxicity Information

Toxicology was defined as the science of poisons. A fundamental principle of toxicology is “ There is no harmless substances, only harmless ways of using substances”. Today toxicology is more adequately defined as the qualitative and quantitative study of the adverse effects of toxicants on biological organisms. A toxicant can be a chemical or physical agent, including dusts, fibers, noise and radiation. The toxicity of a chemical or physical agent is a property of the agent describing its effect on biological organisms. Toxic hazard is the likelihood of damage to biological organisms based on exposure resulting from transport and other physical factors of usage. The toxic hazard of a substance can be reduced by the application of appropriate industrial hygiene techniques. The toxicity, however, cannot be changed. The toxicity information of chemicals can be found or calculated by Dose versus Response, Hodge-Sterner Table for Degree of Toxicity and Threshold Limit Values.

Permissible Exposure Limits

OSHA sets enforceable permissible exposure limits (PELs) to protect workers against the health effects of exposure to hazardous substances. PELs are regulatory limits on the amount or concentration of a substance in the air. They may also contain a skin designation. OSHA PELs are based on an 8-hour time weighted average (TWA) exposure. Permissible exposure limits (PELs) are addressed in specific standards for the general industry, shipyard employment, and the construction industry.PEL values are not as numerous and are not updated frequently.

The lowest value on the response versus dose curve is called the threshold dose. Below this dose the body is able to detoxify and eliminate the agent without any detectable effects. In reality the response is only identically zero when the dose is zero, but for small doses the response is not detectable. The American Conference of Govt. Industrical Hygienists (ACGIH) has established threshold doses, called threshold limit values (TLVs), for a large number of chemical agents. The TLV refers to airborne concentrations that correspond to conditions under which no adverse effects are normally expected during a worker’s lifetime. The exposure occurs only during normal working hours, eight hours per day and five days per week. The TLV was formerly called the maximum allowable concentration (MAC). There are three different types of TLVs (TLV-TWA, TTLV-STEL and TLV-C).

Physical Data: When describing the physical data of a chemical the following properties should be given: Physical state and appearance , Odor, Taste, Molecular weight, Color, pH, Boiling Point, Melting Point, Critical Temperature, Specific Gravity, Vapor Pressure, Vapor Density, Volatility, Odor Threshold, Water/Oil Dist Coefficient, Iconicity (in water), Dispersion Properties, and Solubility.

Reactivity Data: The following properties of a chemical altogether represent reactivity data of a chemical: Special remarks on Reactivity Polymerization, Flammability, Auto-Ignition Temperature, Flash Point, Flammable Limits, Products of Combustion and Fire and Explosion Hazards.

Corrosivity Data: The following two properties provide corrosivity data of a chemical; Corrosivity and Special remarks on Corrosivity.; Reference: 1. D.Crowl and J. Louvar, Chemical Process Safety: Fundamentals with Applications, Prentice Hall (2002) Chapter 2; 2. MSDS sheet from online; 3. http://www.unisa.edu.au/ohsw/procedures/hazard.asp

Thermal and Chemical Stability Data: The following properties of a chemical represent thermal and chemical stability data: Stability, Instability Temperature, Conditions of Instability, Incompatibility with various substances and Thermal Conductivity.

Mixing Effects: Various effects can happen when mixing substances. These include precipitation of a new substance, evolution of heat, absorption of heat, and evolution of gas (if one of the products is a gaseous substance). Of course, change in the color of the mixture is an apparent indication of a reaction happening. The matter with combination of two or more substances is that toxic chemicals or gases may be the products of the formerly inert substances. In other cases, some chemicals could react vigorously with the production of enormous heat, which in uncontrolled instances can set nearby objects on fire. One of the most hazardous effects of crude mixing of certain substances is that a rapid evolution of toxic fumes may result. Doing such procedure without proper gears and instruments could expose one to hazardous substance.

Flammability Diagram: A general way to represent the flammability of a gas or vapor is by a triangle diagram shown below. Concentrations of fuel, oxygen and inert material are plotted on the three axes. Each apex of the triangle represents either 100% fuel, oxygen or nitrogen. The air line in the figure represents all possible combinations of fuel plus air. The air line intersects the nitrogen axis at 79% nitrogen and 21% oxygen which is the composition of pure air. The UFL and LFL are shown

As the intersection of the flammability zone boundary with the air line.

The stoichiometric line represents all stoichiometric combinations of fuel plus oxygen. The combustion reaction can be written in the form,

Fuel + z O2 ? combustion products

Here, ‘z’ represents the stoichiometric coefficient for oxygen.

The intersection of the stoichiometric line with the oxygen axis is given by

100 (z/1+z)

The stoichiometric line is drawn from this point to the pure nitrogen apex. The LOC is the line that shows any gas mixture containing oxygen below the LOC is not flammable. The shape and size of the flammability zone on a flammability diagram change with a number of parameters, including fuel type, temperature, pressure and inert species. Thus the flammability limits and the LOC also change with these parameters.

1.2.2 Process Design

Management>Process Safety Information and Knowledge>Process Design

(Keywords: Management>Process Safety Information>Process Design)

Block Diagram: The block diagram consists of a series of blocks representing different equipment or unit operations that were connected by input and output streams. Important information such as operating temperatures, pressures, conversions and yield was included on the diagram along with flowrates and some chemical composition. However, the diagram did not include any details of equipment within any of the blocks.

The block flow diagram can take one of two forms. First, a block flow diagram may be drawn for a single process, which is known as Block Flow Process Diagram. Alternatively, a block flow diagram may be drawn for a complete chemical complex involving many different chemical processes, which is also known as a Block Flow Plant Diagram.

Block Flow Process Diagram represents a process function and consists of several pieces of equipment. Block Flow Plant Diagram consists of several block flow process diagram representing complete plant. Each block in this diagram represents a complete chemical process. It allows to get a complete picture of what this plant does and how all the different processes interact.

Both types of diagrams are useful or explaining the overall operation of chemical plants. They are used to convey information necessary to make early comparisons and eliminate competing alternatives without having to make detailed and costly comparisons.

Reference: Wikipedia

Process Flow Diagram

A process flow diagram (PFD) is a diagram commonly used in engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations. Another commonly-used term for a PFD is a flowsheet.

Typically, process flow diagrams of a single unit process will include the following:

Process piping
Major bypass and recirculation lines
Major equipment symbols, names and identification numbers
Flow directions
Control loops that affect operation of the system
Interconnection with other systems
System ratings and operational values as minimum, normal and maximum flow, temperature and pressure
Composition of fluids

Process flow diagrams generally do not include:

Pipe classes or piping line numbers
Process control instrumentation (sensors and final elements)
Minor bypass lines
Isolation and shutoff valves
Maintenance vents and drains
Relief and safety valves
Flanges

Reference: Wikipedia

Process Chemistry: Process chemistry involves single or series of chemical reactions that lead to a variety of products. Process chemistry describes and explains mechanism of chemical reaction. The operating temperature and pressure of the process, effect of changing temperature and pressure, optimum process conditions are also described by Process Chemistry. Process Chemistry also gives information on catalyst of the process.

Reference: Wikipedia

Piping and Instrumentation Diagram (P&ID): It shows all of piping including the physical sequence of branches, reducers, valves, equipment, instrumentation and control interlocks. The P&ID are used to operate the process system.

A P&ID should include:

Instrumentation and designations
Mechanical equipment with names and numbers
All valves and their identifications
Process piping, sizes and identification
Miscellaneous – vents, drains, special fittings, sampling lines, reducers, increasers and swagers
Permanent start-up and flush lines
Flow directions
Interconnections references
Control inputs and outputs, interlocks
Interfaces for class changes
Seismic category
Quality level
Annunciation inputs
Computer control system input
Vendor and contractor interfaces
Identification of components and subsystems delivered by others
Intended physical sequence of the equipment

A P&ID should not include:

Instrument root valves
control relays
manual switches
equipment rating or capacity
primary instrument tubing and valves
pressure temperature and flow data
elbow, tees and similar standard fittings
extensive explanatory notes

Reference: Wikipedia

An annotated line diagram showing the process equipment and its process interconnections and control instrumentation links.

Codes & Standards Involved: For existing equipment designed and constructed in accordance with codes, standards, or practices that are no longer in general use, the employer shall determine and document that the equipment is designed, maintained, inspected, tested, and operating in a safe manner.

Reference: Wikipedia

Material and Energy Balance

Material balances are the basis of process design. A material balance taken over the complete process will determine the quantities of raw materials required and products produced. Balances over individual process units set the process stream flows and composition. It is an useful tool for the study of plant operation and trouble shooting. They can be used to check performance against design, to extend the often limited data available from the plant instrumentation, to check instrument calibrations and to locate sources of material loss.

As with mass, energy can be considered to be separately conserved in all but nuclear processes. The conservation of energy, however, differs from that of mass in that energy can be generated in a chemical process. Materials can change form, new molecular species can be formed by chemical reaction, but the total mass flow into a process unit must be equal to the flow out at the steady state. The same is not true of energy. The total enthalpy of the outlet streams will not equal that of the inlet streams if energy is generated or consumed in the processes; such as that de to heat of reaction. Energy can exist in several forms; heat, mechanical energy, electrical energy and it is the total energy that is conserved. In process design, energy balances are made to determine the energy requirements of the process: the heating, cooling and power required. In plant operation, an energy balance on the plant will show the pattern of energy usage and suggest areas for conservation and savings.

Reference: Wikipedia

Process Control Design: The operation of the plant according to specified conditions is an important aspect of loss prevention. This is very largely a matter of keeping the system under control and preventing deviations. The control system, which includes both the process instrumentation and the process operator, therefore has a crucial part to play.

The control system required depends very much on the process characteristics. Important characteristics include those relating to the disturbances and the feedback and sequential control features. A review of the process characteristics under these heads assists understanding of the nature of the control problem on a particular process and of the control system required to handle it. Processes are subject to disturbances due to unavailable fluctuations and to management decisions. The disturbances include those in: (1) raw materials quality and availability; (2) services quality and availability; (3) product quality and throughput; (4) plant equipment availability and (5) environmental conditions and due to (60 links with other plants; (7) drifting and decaying factors; (8) process materials behavior; (9) plant equipment malfunction and (10) control system malfunction.

Reference: Wikipedia

1.2.3 Equipment

Management>Process Safety Information and Knowledge>Equipment

(Keywords: Management>Process Safety Information>Equipment)

Design Data: Data of equipment parameters, material of construction, costs and the physical properties of process materials are needed at all stages of design, from the initial screening of possible processes to the plant startup and production.

1.2.4 Operations

Management>Process Safety Information and Knowledge>Operations

(Keywords: Management>Process Safety Information>Operations)

Upper and Lower Safe Limits: In the course of operation, all process plants will experience upsets because of control malfunction, pump outage, power outage and the like. During such upsets, process conditions may deviate from the normal operating range. It is important that the safe operating limits for critical operating parameters for hazardous operations is known to the operators. These should be established and incorporated into the operating procedures.

Upper and Lower Operating Limits: It is very much important to identify the critical operating parameters. The operator should know the implications of operating outside allowable limits. It helps operator during upset conditions. It also alerts the maintenance staff to instruments that require regular checking to ensure proper operation. Operator and maintenance team must know the safety concern of operating beyond the safe limits of the critical operating parameters. The distinction between alarm levels needs to be addressed as well. It is also helpful to know the corrective and emergency actions that are needed to prevent a hazardous situation from escalating.

Critical Alarms: It is very much important to identify the critical operating parameters and critical instruments in the process by reference to control instrumentation and alarms.

1.2.5 Instrumentation

Management>Process Safety Information and Knowledge>Instrumentation

(Keywords: Management>Process Safety Information>Instrumentation)

Instrumentation: Instrumentation is needed in process plants to obtain data that are essential to perform several activities. Among the most important are control, the assessment of the quality of products, production accounting and the detection of failures related to safety. In addition, certain parameters that cannot be measured directly, such as heat exchanger fouling or column efficiencies, are of interest. Finally, new techniques, such as on-line optimization, require the construction of reliable computer models for which the estimation of process parameters is essential.

There are different types of instrumentation used in process plants. They are flow rate, level, temperature, pressure, density, concentration, pH measurements instruments. It is also customary to include valves as part of instrumentation.

Reference: Miguel J. Bagajewicz, Process Plant Instrumentation: Design and Upgrade, Technomic Publishing Company (2001)

Safety Instrumented Systems (SIS): Systems of hardware and software which are designed to detect a hazardous out of control condition and return them to a safe state. By definition they must be automatic and independent of other protective or control systems.; A combination of sensors, logic solver and final elements that performs one or more safety instrumented functions.; Reference: Layer of Protection Analysis – Simplified Process Risk Assessment, 2001, CCPS, ISBN 0-8168-0811-7

1.2.6 Facility

Management>Process Safety Information and Knowledge>Facility

(Keywords: Management>Process Safety Information>Facility)

Facility: Facility refers to the chemical/petrochemical plant, reservoirs or storage tanks, pipelines. A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials Chemical plants use special equipment, units, and technology in the processes. Other kinds of plants, such as polymer, pharmaceutical, food, and some beverage production facilities, power plants, oil refineries or other refineries, natural gas processing and biochemical plants, water and wastewater treatment, and pollution control equipment use many technologies which have similarities to chemical plant technology such as fluid systems. Some would consider an oil refinery or a pharmaceutical or polymer manufacturer to be effectively a chemical plant.

Petrochemical plants (plants using petroleum as a raw material) are usually located adjacent to an oil refinery to minimize transportation costs for the feedstocks produced by the refinery. Specialty chemical plants are usually much smaller and not as sensitive to location.

Reference: Wikipedia

1.2.7 Codes and Standards

Management>Process Safety Information and Knowledge>Codes and Standards

(Keywords: Management>Process Safety Information>Codes and Standards)

Codes and Standards: The goal of company standards, codes, and regulation is (1) to communicate the firm’s intentions regarding minimum acceptable safe practice, and (2) to assure that all operating locations within the firm share a common approach to process safety. Codifying such expectations in internal standards helps produce consistent performance among operating locations.

Proper management of standards, codes and regulations is a necessary part of chemical process safety activities. All U.S. chemical plants, now and in the future, will e subject to Federal Govt. regulations, such as OSHA 1910 and EPA SARA title III. Depending on plant locations, state environmental and toxic hazard legislation will also apply. Similarly, plant design engineers need to have access to up-to-date standards and codes to perform their duties in a responsible manner.

In addition to governmental and other external standards, many companies develop and implement their own internal standards or guidelines. These internal standards assure a consistency in decision-making by design engineers and plant personnel.

The more widely accepted design practices are contained in various national and industry standards. They form a valuable source of reference material and are extensively used as a basis for design. In general, they

promote industry-wide uniformity of standards
allow sharing of wider experience base
provide a means for development of consensus
give legally defensible criteria on which to base designs

There are several types of external standards:

Legal, for example-effluent disposal and pollution laws, personnel protection laws, planning laws
Industry wide standards, for example- API codes, ASME standards
Professional technical bodies, for example – CCPS, AIChE design groups, Chemical Manufacturing Association, Chlorine Institute
National/international codes

The following are list of some external codes/regulations:

Organization	Codes/Standards
American Society of Mechanical Engineers	Boiler and Pressure Vessel Code
American Petroleum Institute	STd. 650 Welded Steel Storage Tanks
American National Standards Institute	B31 Pressure Piping

Many companies also develop standards and codes that form the cornerstone of the procedures necessary to perform most technical functions. Development of such procedures requires the allocation of valuable resources over many years but the benefits can be substantial. These procedures promote uniformity in design and overall philosophy. They allow company memory to be widely used and they provide a vehicle for dissemination of policy.

Types of Internal Standards/Procedures

General-maintenance practices, reporting procedures, behavior in plant areas
Process specific-special construction procedures or materials, unique operating methodology, chemistry, design principles, problem areas
Design specific- design of equipment, selection of equipment,

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.3 Project Management

Management>Project Management

(Keywords: Management>Project Management)

Project Management ^*: Project management is the discipline of planning, organizing, securing and managing resources to bring about the successful completion of specific project goals and objectives.

The components of project management are: project entry, scoping, planning and approvals, procurement and contracting, quality assurance, health, safety and environment (HSE), pre-commissioning and start-up, wrap-up and evaluation and implementation.

Professional project management is the key to the safety, quality, cost and schedules of all engineering tasks.

Reference: 1. B. Peachey, R. Evitts and G. Hill, Project Management for Chemical Engineers , Education for Chemical Engineers, Volume 2, Issue 1, 2007, Pages 14-19; 2. Guidelines for Performing Effective Pre-startup Safety Review

Project management is fundamental to the way the group works across the full array of technical, organisation, commercial, environmental and political aspects

Reference: Accreditation Case Study, Shell, APM (Association for Project Management) Corporate

Ajay Malhan, senior vice-president of project and development services for Jones Lang LaSalle, the global real estate services ?rm, says “Good project management is about managing the schedule, budget, quality and safety on a project, and there are risks associated with all of that,”

Reference: “The link between project management excellence and long-term success”: A report from the Economist Intelligence Unit Sponsored by Oracle. Economist Intelligence, Economist.

Project Management Procedures and Controls: There are two types of managers. Functional managers take care of a dedicated department and normally have direct authority over a budget and personnel. Project managers fill temporary positions established to accomplish a specific task, the project.

The project manager performs the task of project management. He needs to be clear who the clients are, what problems need to be solved and why. At the project entry stage, the project manager must realize project tasks will always include: planning the work, communicating clearly and motivating those who will work with him or her to solve the problem, monitoring the timeline, quality and expenses of the project, ensuring health, safety and environment issues are clearly addresses, and responding quickly to solve deviations from the proposed work plan. There is never a time that problems will not occur during an engineering task.

In the next phase of the engineering project, the project manager begins by itemizing in writing all the information gathered in the project entry phase in order to confirm the true scope of the work. This is followed by the preparation of preliminary plans, and finally approval of the plans by the client. No work should commence until the plans are approved. After accepting the project, the initial task for the project manager in this phase is gathering data. Most projects involve a physical structure to be modified or build and an important task for the project manager is to determine soil properties, geology of the area and ecological issues that may affect the work.

Since, these are typically technical tasks that are beyond the expertise of chemical engineering, it is important that assistance is available either within the company or in the form of external consultants. Thus the project manager must assemble a project management team with participants that have a variety of skills to assist in completing project tasks. The project manager must realize that dye to his or her limited expertise and usually even more limited time, he or she cannot possibly complete engineering project on their own. So it is important that access to personnel and equipment needed to successfully complete the design task is readily available.

Once planning and approval are completed, a project comes to life with the acquisition of workers, materials and equipment needed to do the work. The project manager needed to be aware of the proper procurement procedures used in the company. In this phase, selection of contractors is very much important.

Quality assurance is the main focus of the project manager. It includes ensuring that all aspects of the project meet expected performance standards, meet all safety criteria, comply with all government regulations and the project work is performed in a balanced, cost effective manner. Performance measure include ensuring equipment meets all the technical specifications developed in design stage and set out in detail in the contacts issued to the contractors. To meet this goal, appropriate manpower with appropriate skill seta must be available to work directly with the project managers.

The project manager must make sure that HSE issues are stipulated in all contracts and that appropriate safety equipment and emergency response services are on hand at all times during construction and startup. Each contractor must accept responsibility for HSE compliance during their phase of work. Procedures for HSE and reporting requirements must be followed and appropriate penalties must be in place for violations of these issues. Safety personnel must be on hand to check procedures, materials, alarms and equipment as well as to respond to emergencies such as fires or spills during all stages of construction and operation.

Before contractors are paid and released from their obligations, it is imperative that after each work stage equipment is tested to ensure it works to expected performance levels. Each contractor must leave the site in a pristine so that following work units are not impeded in meeting their scheduled activities. The project management team should meet one last time to provide design feedback, vendor, and contractor assessments and overall project feedback. The report will be a vital piece of information to project management teams in the future or if any new problems show up after project completion.

Quality-assurance Processes: Quality assurance is the main focus of the project manager. It includes ensuring that all aspects of the project meet expected performance standards, meet all safety criteria, comply with all government regulations and the project work is performed in a balanced, cost effective manner. Performance measures include ensuring equipment meets all the technical specifications developed in the design stage and set out in detail in the contracts issued to the contractors. To meet this goal, appropriate manpower with appropriate skill sets must be available to work directly with the project manager. During the design work, issues to be reviewed include schedule, costs, specifications, drawings, safety, maintainability, operability and reliability. During construction the quality assurance personnel check the credentials of vendors and contractors review the materials handling and control procedures, record and verify construction changes and ensure all contractor work is completed to the company’s satisfaction, before payments are made. Finally, before operations begin, the quality assurance personnel ensure units have been tested, operating and maintenance manuals are readily available, safety and emergency systems are in place and working and finally that appropriately trained operating personnel are on hand.

Pre-startup Review: PSSR is a formal review of a manufacturing process to verify that critical areas of the affected process have been assessed and addressed prior to using the process. Using the process could include: commissioning, introducing hazardous chemicals, or introducing energy.

There are eight basic steps to be considered for every type of pre-startup safety review program. Each facility can choose the best way to achieve their method of accomplishing the end goals of these steps. Those end goals may be – • higher levels of process safety performance, • better environmental risk management performance, and • total manufacturing quality enhancements. Consider how the steps offered below and the description.

Step 1 – Train the entire workforce on PSSR as related to their PSSR duties

Step 2 – Identify trigger events and determine if PSSR is to be performed

Step 3 – Determine the type of PSSR to performing – Simple/Short Form or Complex/Long Form.

Step 4 – Build the PSSR team.

Step 5 – Conduct the PSSR.

Step 6 – Complete the PSSR Documentation.

Step 7 – Track any post-startup PSSR action items.

Step 8 – Seek continuous improvement in your PSSR program.

Inherently Safer Design (ISD): Development of a process using the principle that safety is a permanent and inseparable attribute of the process.

1.4 Risk Management

Management>Risk Management

(Keywords: Management>Risk Management)

Risk Management: Process risk management involves the systematic identification, evaluation and control of potential losses that may arise in existing operating facilities from future events such as fires, explosions, toxic releases, runaway reactions, or natural disasters. Whether resulting losses are measured in terms of direct costs, impacts on employees and/or the public, property and/or environmental damage, lost business, penalties or liabilities, the possibility of experiencing such losses is considered a risk. Even when effective capital project review systems have been used to design out many risks, there will still be a residual risk. Corporate managers must inevitably face these residual risks in dealing successfully with the everyday operation of their businesses and with the long-term planning of new ventures.

The practice of process risk management anticipates the possibility of process safety-related losses and evaluates their potential impacts so they can be managed effectively. Process risk management requires recognition of possible risks, evaluation of the likelihood of hazardous events, the magnitude of their consequences, and determination of appropriate measures for reduction of these risks. Thus process risk management is a practical instrument that can assist in business decision-making in the face of uncertainty.

A company should put in place management systems that will assure appropriate process risk management. These systems might include review and approval programs, risk acceptability guidelines, business-area risk reviews, pre-acruisition risk reviews and residual risk management.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Systematic application of management policies, procedures and practices to the tasks of analyzing, evaluating and controlling risk.

Reference: IEC-60300-3-9

Hazard Identification

Hazard identification is the process of determining what hazards are associated with a given operation or design, as it is operating. In existing operations, hazard identification is performed periodically to determine the implications of changes to process knowledge, and new guidelines and standards, and to recognize changes to processes, procedures, equipment and materials.

The role of hazard identification in process risk management at existing operations is to establish the foundation upon which many of the other process safety management components build.

The responsibility for initiating and assuring completion of a hazard identification activity should be explicitly assigned; frequently it will rest with the facility manager. Before beginning hazard identification, a key planning step is to determine what types of consequences are of concern:

Fatalities or injuries to employees and/or to the public
Release of hazardous material
Business interruption
Environmental damage and
Property damage

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

The process of recognizing that a hazard exists and defining its characteristics.

Reference: IEC 60300-3-9

Risk Assessment: After performing hazard identification in existing operations, the next component of a successful process risk management program is evaluation and interpretation of the hazards. This activity usually entails an evaluation of both the potential consequences of a hazard and its likelihood of occurrence. These evaluations may be either qualitative or quantitative. The goals of such evaluations are to determine the significance of a given hazard, to prioritize the hazard for the most cost-effective application of risk—mitigation measures, to help develop risk reduction measures, and to help identify residual risk requiring management attention.

Risk analyses are site specific and should consider and reflect local meteorological conditions and surrounding populations. If they are qualitative, the output of such studies is usually a prioritized or grouped listing of hazard scenarios. If they are quantitative, they can be used to produce overall measures of risk, such as risk profiles, risk contours and/or individual risk levels.

Management systems designed to support this component must assure that many technical issues are handled consistently and in a manner appropriate to the issue under study. The management system should offer guidance as to the frequency with which such evaluations should be carried out. Frequency may be influenced by many factors, such as the inherent hazards of chemicals involved and the proximity of vulnerable populations and facilities. In implementing risk analysis program, the management system should specify the internal review procedures to employ, and when to use qualitative vs. quantitative analysis.

Control of risk analysis is often achieved through a requirement for management and staff signoffs, the establishment of schedules for individual studies, and specification of reporting requirements.

The management system should indicate where the responsibility for risk analysis lies. The responsibility for carrying out such studies may initially be at the corporate level as a few trial or benchmark studies are done. In some cases, these studies are introduced through the engineering department. Ultimately, however, the responsibility is usually at the facility level.

If an organization is using detailed quantitative analyses, then ongoing support from trained specialists will be required.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Risk Management: Risk can never be completely eliminated, but risks can be reduced. The purpose of this component of risk management is to manage the risks that remain after implementation of risk controls.

Process risk management involves analyzing risks, determining their acceptability, and implementing risk mitigation measures where appropriate. However, risk analysis is based upon a series of assumptions and uncertainties. For example, risk analysis is likely to assume a given plant layout and design as well as certain operating procedures and certain neighboring facilities. The analysis may be based on current understanding of chemical hazards and hazard modeling methodologies, both of which are evolving.

Managing residual risks should involve ongoing review and reconsideration of the underlying assumptions and uncertainties. Changes in these assumptions and uncertainties may chance the acceptability of the risks.

Management systems should assure thorough documentation of the uncertainties and assumptions, and assign responsibility for both maintaining on-going awareness of changes and for periodically initiating ac active search for new information in relevant technical fields. In addition, the process safety audit program, should periodically confirm the assumptions made in the risk analysis.

Residual risk management should also include periodic review of the identified risks to assure that they have not grown to unacceptable levels. Through the introduction of new neighboring units or the development of property adjacent to the plant site or other factors external to a specific unit, the level of risk presented by the unit may increase. The management system should prompt periodic risk analysis to confirm that residual risks are not surpassing corporate guidelines for acceptability.

Assumptions made in the scoping of earlier risk analysis should also be reviewed periodically. For example, there may be incident scenarios that were not analyzed in earlier studies since facility design or other factors compromised their credibility. Subsequent changes may require reconsideration of such exclusions. Alternatively, a subsequent review may identify scenarios not considered previously, either because the scenarios went unidentified or because subsequent incidents raised new issues.

The assumptions made regarding failure frequencies should also be examined during periodic reviews. As operating history is gained, it may be necessary to modify the assumptions used in earlier risk analyses. Review of maintenance history may also suggest areas needing further study.

Formal documentation of periodic reviews and communication of the results of risk analysis are also critical. A technique used by some companies is to require the formal recertification of process risk reviews on a regularly scheduled basis. Periodic auditing of the results by an established internal review group is important to assure that hazard identification and risk review procedures are being properly and consistently applied across the entire organization.

Results of all such studies should be circulated in a timely manner through an established communication channel that includes all key reviewers, decision-makers and authorizations. Follow-up examination of action items is essential for effective management control.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Process Hazard Analysis ^*: The primary objective of a hazard analysis is to identify all possible hazards, then it must categorize the hazards in terms of severity of consequences and then it must evaluate the probability of the hazard occurring. Preliminary hazard analysis is the initial hazard assessment conducted on the system. It identifies safety critical areas within the system and starts evaluating hazards and identifying safety design criteria and applicable safety requirements. Also subsystem hazard analysis examines each major subsystem and identifies specific hazards and safety concerns including failures, faults, processes or procedures and human errors. The SSHA also should address hazard controls and how those controls are verified.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

A systematic effort designed to identify and analyze hazards associated with the processing or handling of highly hazardous materials and a method to provide information which will help workers and employers in making decisions that will improve safety.

Reference: Occupational safety and health administration (OSHA)

PHA is a thorough, orderly, and systematic approach for identifying, evaluating, and controlling the hazards of processes involving highly hazardous chemicals. The facility shall perform a process hazard analysis on all processes covered by the EPA RMP rule or OSHA PSM standard.

Reference: United States Environmental Protection Agency

Reduction of Risk: Once process risks in ongoing operations have been both identified and evaluated, the acceptability of the risks and the need for risk reduction must be considered. Some examples of potential risk-reducing measures include increasing operator training, substituting less hazardous materials, reducing inventories, modifying equipment, upgrading protective systems, installing additional or improved process control, increasing separation distances, improving monitoring and testing and changing materials of constructions. These various measures would reduce process risk either by reducing the likelihood of occurrence, reducing the consequences of a release or eliminating some risk altogether. Planning a risk reduction program requires establishment of philosophies or criteria for evaluating the acceptability of process risks.

From a management perspective, it is not sufficient to identify potential process risk-reduction measures. Effective implementation of risk-reduction measures is imperative. This may require quality assurance, supervision, support for ongoing efforts and the continuous updating of drawings and procedures. A commitment of resources to the overall program is required for the implementation of the appropriate measures.

Communication channels should be established to allow engineering; maintenance and operations staff to give their input on perceived hazards and recommended risk reduction on an ongoing basis. These comments can be reviewed at a suitable level and subsequent recommendations examined at plant level. Procedures that recognize the value of operator intervention in to a potentially unsafe situation should also be implemented. Management should create an environment in which operators will not hesitate to provide input on process safety.

In addition to risk reduction actions that are taken in response to specific risk and hazard studies, many companies also have specific design standards intended to control risks.

Controlling the risk reduction process is very important. Once a process risk has been identified and evaluated, it is important to maintain detailed records of subsequent decisions and actions, regardless of the course of action that is followed.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Residual Risk Management: Through risk reduction procedures, risk can be reduced but can never be completely eliminated. The purpose of this component of risk management is to manage the risks that remain after implementation of risk control (i.e., the residual risks).

Management systems should assure through documentation of the uncertainties and assumptions, and assign responsibility for both maintaining on-going awareness of changes and for periodically initiating an active search for new information in relevant technical fields. In addition, the process safety audit program should periodically confirm the assumptions made in the risk analysis.

Residual risk management should also include periodic review of the identified risks to assure that they have not grown to unacceptable levels. Through the introduction of new neighboring units or the development of property adjacent to the plant sire or other factors external to a specific unit, the level of risk presented by the unit may increase. The management system should prompt periodic risk analysis to confirm that residual risks are not surpassing corporate guidelines for acceptability.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Process Management during Emergencies: An important component of process risk management is the management and control processes during emergencies. The purpose is to control all relevant processes such that consequences are minimized. There are two parts to this component: (1) management of the particular process that had experienced the emergency incident and (2) management of other processes that interact with, or are near to, that particular process.

Organizing for emergency response must occur long before an emergency situation arises. Emergency response planning should indicate who will be responsible for process management during emergencies. Process control rooms should be designed to offer protection from process hazards or remote process control locations should be provided. Emergency plans should be practiced through periodic drills.

In some situations, a response team may have to take corrective action, such as manually shutting valves. Members of the team, including the team leader and emergency coordinator, should be knowledgeable of the various processes in the facility. In large facilities, this responsibility can be spread among several individuals who must be kept informed of significant process changes through management of change procedures.

Implementation of emergency process management programs requires more that just staff preparedness. Early detection and assessment of an impending emergency can contribute to successful control and mitigation. Process control systems should be designed to provide rapid feedback of key information on the cause of each emergency and operators should be knowledgeable and training in emergency response procedures. Such procedures should be fully documented and readily available for reference. Appropriate shutdown switches or kill buttons should be provided, but it is also important that staff know when other courses of action may be more suitable. In computer controlled processes, emergency shutdown sequences should be programmed-in; however, operators should also know how to respond in case of computer failure.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Encouraging Client and Supplier Companies to Adopt Similar Risk: The components of risk management discussed thus far deal mainly with the management of risk at one’s own facility or plant. However, a comprehensive program also addresses systems that can be put into place to encourage customers, supplier companies and hazardous waste disposal companies to practice similar levels of risk management. Included among the target organizations for this effort are the transportation companies that carry feed materials from suppliers, product materials to customers and contract manufacturers, and hazardous wastes to disposal firms. The overall purpose of the component is to create a level of risk management that is suitable and consistent among all industry players. The underlying philosophy for all companies to understand is that serious incidents affect the viability of the entire companies to understand is that serious incidents affect the viability of the entire industry. Not just their own company. It is important, therefore, to encourage and persuade others to adopt similar high standards of risk management.

These programs require commitment from management and an organized coordinated effort among many functions in a firm. Because these programs can directly affect intercompany relationships, they cannot be undertaken without strong senior management support.

Various strategies can be used to encourage good risk management in other firms. Strict contractual arrangements, memoranda of understanding, inspections and cooperative agreements can all be satisfactory, depending upon one company’s knowledge of the other company’s operations. When implementing a program of this kind, marketing and sales personnel and buyers should be aware of such strategies so that communication with customers and suppliers can occur early in the process. Business managers should also be involved in the process to demonstrate the overall commitment to this philosophy.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Selection of Business with Acceptable Risk: When process risks have been analyzed, there will be some situations where the risk is too great to be acceptable. In some such cases, the feasible risk mitigation measures will not be sufficient to make the risk acceptable. It may be necessary to leave a business when this situation occurs.

Another area that needs proper process safety management consideration is that of acquisitions. Although the tight timing involved and the desire to minimize the number of people with knowledge of the pending acquisition can cause complications, process safety is becoming increasingly recognized as an area that needs pre-acquisition review.

The current position of many companies is to obtain information on significant process risks and potential liabilities, sometimes using outside consultants who may be more acceptable to the target facility. So long as the checklist used to identify risks or liabilities of concern is periodically updated to reflect new regulatory hurdles and the finding of past reviews, this may suffice as a first level screening process.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.5 Management of Change

Management>Management of Change

(Keywords: Management>MOC)

Management of change (MOC): MOC is a systematic way to identify, review and approve all modifications to equipment, procedures, raw materials and processing conditions, other than replacement in kind, prior to implementation.; MOC encompasses the proper control of changes in hardware, software, procedures, raw materials, materials of construction, packaging, etc. which is not ‘like for like’ and may change the hazards of a process. It involves many aspects; how to recognize change is taking place or has taken place and (proactively) when change is needed, how to request, review, approve, provide training and safe implementation of the change.

Change of Process Technology

Six major reasons for need to make process changes are listed below:

Maintain process continuity
Compensation for equipment unavailability
Startup or eng-of-run shutdown
Experimentation
Change in production rate
New equipment

A management system for process changes should incorporate planning for each of these situations, and should consider the unique circumstances of each. During normal operation, it is the prime responsibility of the operating personnel to maintain smooth operation. In traditional plants, it is not unusual for a process operator to make numerous changes per shift to maintain optimum operating conditions. Some process parameters may be varied over a wide range and still remain within safe operating limits, while others may require tight control. Establishing safe operating limits is a means of controlling the process operator’s activities ad should be implemented by incorporating them in the operating manual or procedures. In computer controlled plants, much of this activity is performed by the computer system. However, operators still must monitor operations and respond to alarms. In emergency situations, where there is no time for review and approval, the established procedure should be to shut down rather than operate outside of established safe operating limits.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Change of Facility: When an equipment change is being contemplated, there should be careful consideration of the process safety implications. The organizational responsibility for approving such changes should be clearly defined, and approval only should occur after an appropriate review has been completed. The implementation of the change should be limited to the specific equipments changes that have been reviewed and approved. There should be control over the equipment change process, achieved through mechanisms such as requiring documentation of all work performed, and having both operating and maintenance personal sign off on the agreement of the work done with the approved work orders.

Many equipment changes will require a corresponding change in process conditions. Major new equipment should be included in capital appropriation requests and be reviewed as part of any new capital project. There are however, certain types of equipment changes made in the field that are not included in a capital project review: Some are process improvements, piping rearrangements, experimental equipment, temporary equipment, decommissioning, change in materials of construction, change in computer programs and change in instrumentation.

Although many changes may appear harmless, without proper review process hazards can be created. Equipment changes not covered by capital project reviews must still be controlled by a review and approval procedure. There should be systems for assuring that these changes are identified in advance so that a review will be scheduled. Appropriate personnel should be involved in the review. A checklist of issues to be considered helps assure appropriate review. Completion of the review should be documented to assure accountability and facilitate subsequent audit.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Organizational Changes: Within an operating firm, personnel changes may be more frequent than hardware or process change. Arrivals and departures will occur at both the operating and management levels.

Personnel changes present challenges for the process safety management. New staff must learn both process characteristics and their roles in the process safety management systems. Both documentation and training are key elements in this transaction.

Similarly, changes in organizational responsibilities may require careful review of process safety management systems to assure that all process safety responsibilities are appropriately assigned.

The departure of experienced staff creates special challenges. Every facility seems to have a certain individual who has worked at the site since startup and has been involved with all major expansions. This individual knows where all the underground piping runs, why equipment is operated in a certain manner, what major accidents have occurred, and many other valuable pieces of information that may never have been documented. Even if a site has implemented review and documentation programs for new projects, the documentation for changes made to older facilities may not be available except in the minds of select individuals. When these individuals leave, this part of the “Company Memory” is lost.

When organizational changes cause these historians to leave, it is important to have them document as much of the facility’s technical history as possible before they leave. In particular, any unique operating knowledge or characteristics should be documented. The rationale behind design decisions and operating practices should also be captured.

The lost of multiple personnel can be even more significant. As companies continue to streamline staffing, there comes a point beyond which any further reductions can have serious safety implications. This may not be apparent under normal operation, but in an emergency, if staffing levels and/or staff experience levels are too low, a minor problem could easily escalate to become a major incident. Staff organization should be tested for consistency with the operational demand of all difference circumstances, including both normal operations and emergencies. This can be managed by planning a minimum staffing and experience level for each project unit. Any change in staff would require a review to ensure that these minimum levels are not violated. When staffing experience in a unit becomes too low, certain measures should be initiated, such as increased training, the temporary retention of transferees, or the engaging of retirees as temporary consultants.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.6 Mechanical Integrity

Management>Mechanical Integrity

(Keywords: Management>Mechanical Integrity)

Reliability Engineering: Reliability engineering is the process of evaluating how long a system and its individual components can be operated safely before they must be taken out of service for maintenance or replacement. Knowing the reliability of a piece of equipment is important in planning its installation and maintenance. For Example, a piece of equipment that will require frequent maintenance should be readily accessible, both to operating personnel who may be responsible for isolating and preparing the equipment for maintenance, and to maintenance personnel and their equipment. High or frequent maintenance requirement might suggest the need or substitution of equipment better suited to the operating conditions. High maintenance equipment may also need to have standby units or bypasses installed to maintain continuity of operations, an call for an adequate stock of spare parts to allow timely repair. The same reasoning applies to equipment that must be taken out of service for inspections or testing as part of a preventive maintenance program.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Materials of Constructions: Use of improper materials of construction, during both initial installation and subsequent maintenance of operating facilities, can have catastrophic consequences. To assure that appropriate materials are used, a facility should adopt piping and vessel standards that are appropriate to the hazards present. Responsibility for the adoption of vessel and piping standards should be clearly designated. In many cases, available industry standards can be adopted; however, the process safety management system should address the organizational issue of who will identify the standards to be followed, who will monitor changes in the industry standards used, and who will communicate these standards and changes within the firm, vessel and piping specifications should be supplemented by systems to assure that the materials actually installed are the correct ones.

When severity of risks is high, it may also be appropriate to adopt a tracking system-especially one for tracking materials of construction from the mills until the pipe, vessel, or other component is installed in the facility. A material tracking program can serve a control function in the process safety management system. Implementation of an effective material tracking program requires a considerable amount of planning, as well as an evaluation of potential suppliers who are willing to provide the necessary documentation with the finished products. At the plant level, considerable planning need to be expended in establishing a materials tracking program for some higher risk operations, while using more conventional methods for other operations. One effective mechanism is to establish separate accounts for ordering materials under the materials tracking program. Thus when an order is received by a pre-approved supplier, it is clear that special documentation requirement will be followed.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Fabrication and Inspection Procedures: Vessel and piping fabrication requirements should be clearly specified in the mechanical design package. During fabrication, a quality assurance program should be in place to ensure that equipment is built according to design and meets all applicable codes and standards.

The process safety management system should include mechanisms to assure that appropriately qualified craftsman are used. Since vessel and piping fabrication are frequently performed by vendors, management controls may have to extend into the vendor’s shop.

The management system should also ensure that all vendors’ standards and work practices meet requirements. It is useful to have a set of standards for all vendors to follow. This presents organizational issues, both in designating responsibility for standards development and in managing the contractual relationship with vendors to enforce the standards. In addition, some level of auditing is a useful control mechanism.

Documentation of tests and inspections performed during fabrication provides another control mechanism, and also generates important baseline data for comparison with future in-service tests and inspections conducted as part of a preventive maintenance program. For vessels built according to the ASME code, code certificated should be retained. As built drawings, along with all other documentation, materials of construction verification should be placed in an accessible equipment file. All documentation should be signed and dated by the person responsible for verifying the data.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Maintenance Procedures: In a performing repair or preventive maintenance work, hazardous conditions may result if the equipment has not been prepared for the job or if the job is not performed properly. There must be assurance that the equipment is safe to work on. A management system is needed to control the implementation of required maintenance safety procedures.

Any maintenance, whether an actual repair or preventive in nature, should be initiated through a formal system. A written order system is often used to document the work to be done and to facilitate management control of maintenance work. A system for organizing the priority of work requests should be adopted, with work requests that have safety implications given special priority.

Where special precautions are needed to perform the work safely, they should be identified on the work order. Certain types of work may require special work permits such as: line break, hot work, confined space and excavation.

Each permit should have a set of procedures that defines the requirements under which the permit is issued. The permit should be issued by authorized, qualified personnel with this responsibility clearly assigned. The authorizing person should sign the permits to promote accountability. The management system should address how responsibility will be transferred between shifts when the work extends beyond the time when the original maintenance crew leaves.

A set of safe work practices should be developed to support the work request system. These practices should include: equipment isolation or locking and tagging; plugging or capping open-ended valves; lifting of equipment over active process lines and confined space entry procedures.

After maintenance has completed the work, a final check should be required by qualified operations personnel as a control to ensure that the work requested has been satisfactorily completed, and that all equipment has been returned to an operable condition. Assurance of quality should include ensuring that the proper spare parts are used and that the work performed meets applicable standards and codes.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Inspections

The field inspection provides insights into the design and operation of the equipment that may not be apparent from a review of the drawings. To assure that all issues are considered, a checklist should be used during the field inspection. The checklist should cover such issues as:

Protection of small-bore lines and fittings from external impact
Adequate support of piping
Location and identification of critical safety systems and equipment, emergency shutdowns, fire protection equipment, safety showers and breathing apparatus
Location of vents and drains
Means of safe egress from an area in case of emergency
Means of access to valves
Proper electrical classification
Proper operation of critical alarm, interlock and emergency shutdown systems
Test and test results from pre-startup checks

The inspection should be made by staff familiar with the design as well as staff familiar with operations. During the inspection, one individual should be assigned to document all items found by the inspection team. The resulting list of items should be prioritized to identify which items must be corrected prior to commissioning, prior to starup, or those that can be corrected at a later time. Appropriate controls should be in place to verify that all items are completed at the required times, and may include another field inspection.

There should be procedures for the testing of key pieces of equipment prior to the introduction of hazardous materials into the process. Testing requirement should be described in startup procedures, and responsibility for completing these tests should be assigned. Completion of equipment tests should be documented with records of the startup.

Upon completion of the review, the tam should issue a report identifying any deficiencies that must be corrected prior to startup. Based on this report, a team of plant management staff should be made responsible for approving the facilities for startup. A completed sign-off sheet by all these individuals should be the final document to allow hazardous materials into the process.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

A deliberate, systematic scrutiny or examination of an activity or project; a thorough, close, critical examination, checking or testing against established standards.

Reference: Human Factors in Process Operations, 1992, Robert C Mill, IChemE, ISBN 0 85295 294 5

Preventive Maintenance: Within the process safety management system, preventive maintenance (PM) consists of a program of test and inspections conducted on equipment to detect impending or minor failures and to mitigate their potential before they can develop into more serious failures. From a process safety point of view, a PM program consists of a number of activities, including:

Identification of equipment and instrumentation critical to process safety
Determination of required tests or inspections
Determination of test or inspection frequency
Establishment of maintenance procedures
Training of maintenance personnel
Development of acceptable limits or criteria for passing
Documentation of results
Analysis of results

The first planning step is to compile a list of equipment for which some form of preventive maintenance is desirable .Items may be put on PM because of legal or insurance underwriter requirement, recommended practices by trade organization, manufacturers’ recommendations, company policy or the facility’s determination that the equipment or instrumentation is critical to maintaining the safety of the facility.

A procedure should also be developed to ensure that new or modified equipment is added to the PM program as appropriate. The next step is to select the required test of inspection method; it can range from a simple visual inspection to use of sophisticated tools. Because selection of a method may involve complex technical issues, appropriate expertise should be employed in program development.

Testing should be performed at an established frequency based on known failure history, manufacturer’s recommendations, and/or legal requirements. Where data are not available, engineering judgment must be used to set the initial frequency; this rate is adjusted on the basis of actual test data. The management system should also include mechanisms for initiating PM actions at the scheduled frequency and documenting the results.

Control mechanisms should be established to ensure that the required PM has been properly performed. Appropriate maintenance procedures must be developed and approved to ensure that tests and inspections are carried out properly and consistently between individuals. For detailed procedures, checklists should be developed. At the same time, appropriate training must be provided maintenance personnel, so that they fully understand the PM procedures and are qualified to use any special tools or equipment. Coordination with purchasing personnel is also important to ensure an adequate supply of spare parts and the availability contractors.

The final steps in a PM program include data review and analysis. For each piece of equipment or instrument undergoing PM, a set of criteria should be established to determine if the component has passed or failed the test. If it fails, then appropriate corrective action needs to be specified, including possible replacement. Finally, based on the results of the PM program, testing and inspection frequencies may need to be adjusted.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Process, Hardware, and Systems Inspections and Testing: Prior to commissioning a new process, replacing equipment or restarting after a shutdown, a pre-startup safety review should be conducted. The pre-startup review is a final check of both the equipment and operating procedures to assure that all elements are in place and functional. The review team should verify that all safety items identified in prior design and hazard reviews have been adequately addressed; that operating, maintenance and emergency procedures have been written; that operator training is complete; that a PM program is in place; that all equipment falling under the PM program has been identified and that a system for managing change is in place. The latest revision of the piping and instrumentation drawings should be reviewed, followed y a field inspection. The review team should consist of representatives from design, production, construction, maintenance and any others as appropriate.

Protection of small-bore lines and fittings from external impact
Adequate support of piping
Location and identification of critical safety systems and equipment, emergency shutdowns, fire protection equipment, safety showers and breathing apparatus
Location of vents and drains
Means of safe egress from an area in case of emergency
Means of access to valves
Proper electrical classification
Proper operation of critical alarm, interlock and emergency shutdown systems
Test and test results from pre-startup checks

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Installation Procedures: Codes and standards are generally not specific in addressing the field installation of equipment. Planning on the part of construction management personnel is necessary to develop adequate quality control systems to ensure that equipment is installed according to design specifications and equipment manufacturers’ instructions. According to Kletz, a majority of piping failures are caused by a combination of unsatisfactory design, construction not according to design, or poor execution of work not covered by standards and left to the discretion of the constructor.

Equipment installation jobs should be planned, and all critical steps and important verifications identified. Construction and maintenance personnel should be responsible for assuring that planning is done, and that workers assigned to the job understand its critical elements.

Typical construction project will have a number of field inspectors who check for such items as proper documentation. For projects involving PMI requirements, additional control of materials of construction is necessary.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Alarm and Instrument Management: Instruments and alarms are vital components to communicate to the operator whether the process is in or out of control. During normal operation, many instruments and alarms are in service and their functionality can be easily verified. Other alarm systems, however, such as a high-level alarm or any emergency shutdown system, may infrequently or never be activated under normal operation, so there is no assurance that it is still functional.

The process safety management system should also assure that other fixed or portable safety related instruments are regularly tested. Such equipment should be calibrated at regular intervals, with management controls in place to initiate the work. Where these instruments and/or alarms are deemed critical to safe operation, they should be included in the preventive maintenance program. Similarly, any instruments or systems containing sensors that are safety critical and that provide input to computerized control equipment should be included in preventive maintenance program. Also any changes to such instrument or alarm setting outside of acceptable ranges should first be reviewed and approved.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Demolition Procedures: Once a piece of equipment is no longer required, appropriate means of isolating and ultimately removing the equipment should be developed. Frequently, a piece of equipment is removed from service for a prolonged period of time prior to demolition. When this occurs, appropriate reviews through process change procedures should be performed. If the equipment is definitely no longer needed or usable, it should be scheduled for demolition. Prior to demolition, the equipment must first be isolated from any active equipment in such a way as to minimize piping deadlegs subjected to process pressure. The equipment should be marked in a manner that leaves no question that it is no longer to be used. In such cases, elements of the work request, work permit, and safe work practices should be followed as appropriate.

Decontamination procedures should be developed with consideration for the hazards involved, and these procedures should be thoroughly reviewed. The procedure should address both the decontamination of equipment to be demolished and the related waste disposal issues.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.7 Human Factors

Management>Human Factors

(Keywords: Management>Human Factors)

Human Factors (or Human Factors Engineering): The term Human factors refers to technical systems and equipment so designed that they can be used safely and efficiently by humans.; Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Refers to the study of human abilities and characteristics as they affect the design and smooth operation of equipment, systems, and jobs. The field concerns itself with considerations of the strengths and weaknesses of human physical and mental abilities and how these affect the systems design. In general, human factors engineering examines a particular activity in terms of its component tasks and then considers each task in terms of: physical demands, skill demands, mental workload, and other such factors, along with their interactions with aspects of the work environment (e.g., adequate lighting, limited noise, or other distractions), device design, and team dynamics.

Reference: S2S (safety to safety website: Patient Safety Network, PSNet)

Administrative Controls vs. Hardware Engineering Controls: Administrative controls are the procedural mechanisms that are used for hazard control. Hardware controls are the controls that are physically built into process systems. In many situations where risk mitigation is desired, a choice can be made among administrative control, hardware controls, or a combination of administrative and hardware controls.

Some of the basic process safety issues involved in the choice are:

Increased automation may simplify the operator’s role, but may increase the complexity and frequency of maintenance
Operators may rely on alarms to warn of upset potentials and relax their tracking of operations if a system is overly automated
Reliance on the operator to take certain actions in emergency situations may not take completely into account fatigue, time to respond, background noise levels obscuring alarms, inadequate numbers or types of communications channels and the like

The company should assure that hardware/procedure tradeoffs made by designers and hazard reviewers are based on risk analysis results, and that these decisions are predicated upon past company practice. To encourage consistency and equivalency of risk levels, the management system should encourage communication within the organization of hardware/procedure design practices.

Whenever risk mitigation measures are being recommended or selected, company practice on administrative vs. hardware controls should be considered. This will require a management system in which staff involved in risk control measure selection are familiar with past practice, and in which selections are reviewed by the level of management that approves risk-mitigation measure implementation.

The documentation of risk-mitigation measures selection should record the choices made between administrative and hardware controls. Such documentation will help assure that human factors were considered in selecting mitigating measures, and that there is an audit trail for later verification that human factors were considered.

The process safety management system should assure the availability of human factors knowledge. In some firms, human factors specialists are made available to process safety review teams to bring this expertise to the review. In other cases, human factors training is given to staff involved in process safety review work so they will better understand the issues. Either approach requires the commitment of appropriate resources.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Ergonomics: Ergonomics is about ‘fit’: the fit between people, the things they do, the objects they use and the environments they work, travel and play in. If good fit is achieved, the stresses on people are reduced.; References: S2S(from the UK Ergonomics Society website: The Ergonomics Society. Proper attention to ergonomics will improve usability, comfort, productivity, reliability and well-being.)

Human Error: An act of commission (doing something wrong) or omission (failing to do the right thing) that leads to an undesirable outcome or significant potential for such an outcome. For instance, installation of relief device with an incorrect set pressure would be an act of commission. Failing to notify an incoming shift team of recent process problems would be an error of omission.; Errors of omission are more difficult to recognize than errors of commission but likely represent a larger problem. In other words, there are likely many more instances in which the provision of additional information would have prevented an incident than there are instances in which the information provided quite literally should not have been given.; In addition to commission vs. omission, three other dichotomies commonly appear in the literature on errors: active failures vs. latent conditions, errors at the “sharp end” vs. errors at the “blunt end,” and slips vs. mistakes.; References: S2S(safety to safety website: Patient Safety Network, PSNet)

Human Error Assessment: Even in a perfectly designed situation, operators will still make occasional errors, just as equipment will have failures. Operator errors may be introduced by poor system/equipment design or by the complexity of operations. Human error assessment refers to the determination of human reliability or performance. As such, it can be used in conjunction with other reliability analyses to determine whether administrative controls to enhance operator performance or hardware changes will provide the greatest improvement in overall reliability/safety.

By conducting human error assessments, one can also obtain a better understanding of whether the human element is performing about as optimally as can be expected, or whether specific design or procedural changes would enhance performance. This evaluation will also make it clearer in reviewing incidents as to whether an operator was negligent or conforming to the standards for the job.

Since formal human error assessment is a complex undertaking, it may be useful to have a company guideline indicating hen it is to be performed. The initiation of human error assessment should be the responsibility of operating management. However, the conduct of the assessment will require the involvement of specialized experts, or other appropriately trained staff, to fully understand and address the human factors issues.

Various detailed sources are available on conducting human error assessments, as are more generalized data bases on human error rates. While the generalized sources may be adequate for overall reliability analyses, key operations and operator vs. automation decisions may warrant or necessitate a human error assessment specific to that particular operation.

In conducting a human error assessment, human factors specialists should be heavily involved. Their analyses should be documented and retained after results are shared with appropriate engineering and operations personnel.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Man Machine Interface: Process industry requires good man-machine interface in order to enhance the stability of system operation, in which the sense of tension and mental load of operators is an important indicator measuring human-machine optimization.; Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Maintenance: The procedure of keeping a system in optimal operating conditions.; Maintenance can range from being predictive, and preventive, to reactive

1.8 Training and Performance

Management>Training and Performance

(Keywords: Management>Training)

Selection and Development of Training Program: The process safety management system should ensure selection or development of training programs that will meet specific training plans and objectives. This is most easily done when the training objectives are well defined and explicitly stated. When a program consistent with training objectives is considered, its administrative characteristics should be reviewed relative to the firm’s requirement. Issues such as program length, time structure, pre-requisite knowledge, audio-visual or computer requirements, costs and instruction method should all be considered. The acceptability of the program should be judged by a group that includes training professions, technical specialists and operations personnel.

When a curriculum design is established and decisions have been made to develop all or parts of the training program, the next step is to begin the implementation of the program by developing the course materials needed to support the learning objectives. This will include such things as:

Instructor lesson plans
Visual aids
Special or modified equipment for demonstrations
Student texts
Simulators
Test
Administrative and record-keeping aids

Requiring the use of a written lesson plan for a training program is a commonly used control mechanism that helps assure quality and consistency. Without a formal plan, important information may be skipped or extraneous information may be introduced. The lesson plan serves as a guide to the trainer and assures covering all the critical points.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Refresher Training & Initial Training: Information showing on-the-job performance is most conveniently obtained from incident reports and from employee performance evaluations. Systems should be established to share this information with training program planners. Changes to equipment and systems, changes in procedures and plant rules, and changes in regulations all affect training requirements. The management system should provide links between performance of current procedures and training program planners.

Deficiencies in training objectives may be identified as the result of student feedback during retraining, or feedback from supervisors who may detect a pattern to performance deficiencies in their department. Since the least desirable way to identify the need for revising a training program is through the occurrence of an incident, great care should be taken in planning and organizing the program.

When a revision is necessary, specific recommendations for the change, including how the need was identified, the significance of the correction, and a specific action plan, should be prepared. Documented follow-up is essential to ensure that changes are implemented and prove to be effective.

To help ensure that the documentation is complete and that the program is being administered properly, annual auditing of the program is important. The audit should determine whether:

Training was timely
Any students were missed
Training was appropriate
The students accomplished the learning objectives
Related job performance is satisfactory
The program has been adequately documented
Any deficiencies requiring revisions exist

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Records Management: Documentation of a training program can be important for several reasons. In some cases, various regulatory requirements regarding training may apply. However, the most important reason for documentation is to control the program. Documentation facilitates verification of who has been trained and in some cases, how effective that training has been. In addition, documentation is the key to obtaining and analyzing the feedback that comes from measuring performance.

Documentation of a training program can be split into five distinct areas:

Information related to conducting the training
Information showing on-the-job performance
Information about external factors
Identified deficiencies in training objectives
Recommendations for revision and follow-up on their implementation

With regard to the actual instruction process, the following information should be maintained:

Who was instructed
What training were they given
Who was the instructor
When did the training take place
What standards were met
What regulations if any were satisfied
How did the student perform before and after training
When is the student to receive retraining

This information should be compiled by the instruction and retained by a single responsible person at the facility.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.9 Incident Investigation

Management>Incident Investigation

(Keywords: Management>Incident Investigation)

Incident Recording, Reporting & Analysis: Creating an historical record of incidents that is widely available and in a usable form is an important part of a process safety management system. This record could include not only information about major incidents, but all incidents, including near misses. The record should be in a usable form so that commonalities between past events and potential future events can be brought to light. Relevant categories should be established so that searches can focus on commonalities. Examples of such categories could include specific management system deficiencies, hazard sources, immediate causes, process information and short incident descriptions. The information should be general enough to ensure that an incident is not regarded as an isolated phenomenon, and specific enough to ensure that information is not regarded as too vague and broad to be useful.

Historical incident recording in useful form can allow precautions to be taken at other facilities, allow lessons learned to be taken into account in future design, and help identify trends not apparent from single incidents. Because incidents have many causes, some causes may not be identified in the investigation of a single incident For example, if an incident occurs on a Saturday, this may simply be coincidence or it may be a symptom of deficiencies in management systems on weekend shifts. If a pattern of weekend incidents develops, then management can take appropriate action. Without incident recording and analysis of the record, such patterns may go unnoticed and lessons from which to improve process safety management may go unlearned.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Incident Classifications: Incidents can be defined an unplanned events with undesirable consequences. In the context of process safety, incidents include fires, explosions, release of toxic or hazardous substances, or sudden release of energy that result in death, injury, adverse human health effects or environmental or property damage.

Near misses can be defined as extraordinary events that could have reasonably resulted in an accident or incident. To some the definition of incidents includes near misses. Because there are many similarities between “incidents” and “near misses” for the purpose of process safety, incidents refer to both types of events.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Near Miss Reporting: It is important to note that the same causes and modes of failure are present in both major incidents and near-misses. This means that as many lessons can be learned from near-misses as any other kind of incidents. The circumstances surrounding all near-misses should be reported and recorded. While it may not be feasible to investigate every near-miss in the same depth as major incidents, at least some near-misses merit substantial investigation.

Reporting of near misses is necessary so that a decision can be made as to the depth of investigation needed. As in the case of incident reporting, management should create an atmosphere in which near-miss reporting is encouraged, rather than seen as an opportunity to assign blame. Near-misses should then be analyzed to explore ways in which process safety management systems can b improved. Recording of near0mmisses allows lessons learned to be preserved for future benefit.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

Company Memory-Lessons Learned: Company, every member of investigation team learns about problems that precipitate accidents. This new knowledge helps every team member avoid similar situations in the future. In the investigation is appropriately reported, many others will also benefit.

This concept is also important for reporting minor accidents or near misses. Minor accidents and near misses are excellent opportunities to obtain “free chances” to prevent larger accidents from occurring in the future. It is much easier to correct minor problems before serious accidents occur than to correct them after they are manifested in major losses.

Accident investigations are designed to enhance learning. The fundamental steps in an investigation include –

Developing a detailed description of the accident
Accumulating relevant facts
Analyzing the facts and developing potential causes of the accident
Studying the system and operating methods relevant to the potential causes of the accident
Developing the most likely causes
Developing recommendations to eliminate recurrence of this type of accident
Using an investigation style that is fact finding and not faultfinding; fault finding creates an environment that is not conducive to learning

Good investigations help organizations use every accident as an opportunity to learn how to prevent future accidents. Investigation results are used to change hazardous practices and procedures and to develop management systems to use this new knowledge on a long-term and continuous basis.

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.10 Emergency Planning and Response

Management>Emergency Planning and Response

(Keywords: Management>Emergency)

Emergency Planning & Response (Emergency response plan): Process safety of a chemical plant encompasses several layers of protection. Control measures, shut-down systems, release absorption, accumulation of releases by dikes and protection by barriers. These layers of protection are intended to prevent an event from propagating into severe consequences because of deviations from normal operation conditions. Emergency response is the last layer of protection that is intended to control an event if possible or to reduce consequences in cases of loss of control. However, a reliable response to an emergency event requires planning.

The three components of emergency planning are : preparedness, response and recovery. Also, there are two main types of emergencies with which the chemical industry is concerned. These are the works emergency and the transport emergency. They are some what different and require separate treatment. Whatever the type of emergency plan, the overall message is that it should be kept simple and flexible, but capable of being scaled up or down as circumstances demand.

Reference: Occupational Safety and Health Standard. Process Safety Management of Highly Hazardous Chemicals. Alaska Department of Labor and Workforce Development

A response plan which allows for all predicted ‘out of control’ events to be described and response laid down to eliminate or mitigate the consequences. Its attributes should allow local and external responders to act effectively if such events occur.

Emergency response: Action based on an emergency.

On-site Emergency Planning: Unanticipated circumstances may yield emergency events. Emergency planning adds an additional layer of protection to circumstances where all of the other layers of protection failed to prevent the incident.

Reference: Occupational Safety and Health Standard. Process Safety Management of Highly Hazardous Chemicals. Alaska Department of Labor and Workforce Development

Emergency Preparedness: Emergency preparedness process begins with identification of credible scenarios for which appropriate response strategies are developed. The analysis of resources and capabilities of facilities to respond to the emergency scenarios is part of the preparedness stage. This analysis examines the resources and the capabilities at the facilities, at neighbor sites, and the resources that are available at the local community. The development of resources is conducted according to the resources assessment and the potential of cooperation among site emergency responders, neighboring facilities, and neighboring communities.

At least three separate parties are involved in emergency situations, in addition to the network within the facility. Therefore, communication systems are crucial to successful execution of emergency plans in real time situations as well as in drills. The complex nature of emergency events requires a very clear hierarchy of command, and a procedure without any ambiguities. It is extremely important that every position in the hierarchy is assigned to personnel with the appropriate skills and personality. Training and assessment of the potential collaboration among these three groups is also extremely important. It is not uncommon for preparedness programs to be revised based on assessments of drill results.

Emergency systems are developed in parallel with the development of physical facilities. The list below consists of typical items in emergency systems; however, it can vary according to special circumstances:

Emergency power supply
Emergency water supply
Communication systems
Emergency management computer support system
Site and community alert systems
Adequate incident command transportation
Appropriate control room protection measures

Reference: Occupational Safety and Health Standard. Process Safety Management of Highly Hazardous Chemicals. Alaska Department of Labor and Workforce Development

Drills: The planning of cooperation and the development of understanding with the offsite services is vital to the success of response to emergency. The first step is obviously establishment of agreements to cooperate in emergencies. These agreements are established mainly by the senior managers of the organizations involved. But this needs to be followed up by active planning and drills by plant personnel.

The activities should be seen not as two disjoint activities, but as a single operation in which a growing weight of resources is brought to bear on the incident. The planning should aim to clarify not only what is to be done but also who is to do it.

Cooperation benefits greatly if there is a full-time liaison officer, and this can be justified in an area where there is large potential for emergencies. What is known in advance is the general location and nature of possible emergencies. Other factors will not be so well defined: time, weather and number of people. Excessive detail in the planning should be avoided. The aim should be to plan broad areas of responsibility, chains of command and systems of communication.

Off-site services will require their own communications. On-site, the practice has been for the police, fire and medical services to be linked by radio to their own communications systems. The EOC should be available to them. Alternatively, they may wish to set up their own mobile control centers.

The off-site services will also normally need to tap into the on-site emergency internal communication. This should be allowed through the EOC. An alternative is to provide for their use portable radios as used by the emergency teams.

Emergency drills are effective in familiarizing personnel with their functions. While drills with on-site personnel can be dictated by a routine, real-time simulation that involves all forces, on-and off-site are much more complicated to perform. However, the effectiveness of the plan, as well as the performance of each of the entities in the response stage can be assessed only in full scale drills. It is common that full-scale emergency drill resulted in major changes in the plan, and sometimes it required conducting process hazard analysis in order to better understand the hazards, and the risks associated. In any case, the emergency plan should consist of a procedure for implementation of change of management.

Reference: Occupational Safety and Health Standard. Process Safety Management of Highly Hazardous Chemicals. Alaska Department of Labor and Workforce Development

1.11 Auditing

auditing”>

Management>Auditing

(Keywords: Management>Audits)

Audits: Audit is defined as methodical, independent, and typically periodic examinations, involving analyses, tests and confirmation of local procedures and practices. Audits provide management with a tool for measuring facility performance. The general goal of most process safety audit programs is to verify whether a facility’s procedures and practices comply with legal requirements, internal policies, company standards and guidelines, and accepted practices. An audit tells a company whether its procedures and practices are adequate and whether they are being followed.

Resource Management: Managing the resources available to the program, including the budget, the personnel, and the other resources available from other parts of the organization

Staff Selection and Training: Selecting, orienting, training and continually developing the audit team staff

Program Development: Continuing to develop, refine and advance the audit program

Keeping Current: Keeping up to date on current activities

When staffing a process safety management system audit team, it is desirable to have members with expertise in the following areas:

Facility Operations
Safety Disciplines
Management Systems
Peer Facilities

Reference: CCPS(1989) Guidelines for Technical Management of Chemical Process Safety

1.12 Operational Integrity

Management>Operational Integrity

(Keywords: Management>Operations)

Standard Operating Procedures: A Standard Operating Procedure (SOP) is a set of written instructions that document a routine or repetitive activity followed by an organization. The development and use of SOPs are an integral part of a successful quality system as it provides individuals with the information to perform a job properly, and facilitates consistency in the quality and integrity o a product or end-result. The term SOP may not always be appropriate and terms such as protocols, instructions, worksheets, and laboratory operating procedures may also be used.

SOPs detail the regularly recurring work processes that are to be conducted or followed within an organization. They document the way activities are to be performed to facilitate consistent conformance to technical and quality system requirements and to support data quality. SOPs are intended to be specific to the organization or facility whose activities are described and assist that organization to maintain their quality control and quality assurance processes and ensure compliance with governmental regulations.

If not written correctly, SOPs are of limited value. In addition, the best written SOPs will fail if they are not followed. Therefore, the use of SOPs needs to be reviewed and re-enforced by management, preferably the direct supervisor.

The development and use of SOPs minimizes variation and promotes quality through consistent implementation of a process or procedure within the organization, even if there are temporary or permanent personnel changes. SOPs can indicate compliance with organizational and governmental requirements and can be used as a part of a personnel training program, since they should provide detailed work instructions. It minimizes opportunities for miscommunication and can address safety concerns. When historical data are being evaluated for current use, SOPs can also be valuable for reconstructing project activities when no other references are available. In addition, SOPs are frequently used as checklists by inspectors when auditing procedures. Ultimately, the benefits of a valid SOP are reduced work effort, along with improved comparability, credibility and legal defensibility.

The operating procedures needed carry out normal work effectively and safely. Usually applied to production facilities and laboratories.

Safe Work Practices: OSHA’s Process Safety Management standard requires employers to develop and implement safe work practices to control hazards during operations such as lockout/tagout, confined space entry, opening process equipment or piping, and entrance into a facility by maintenance, contractor, laboratory or other support personnel. Safe work practices often apply to hazardous work. For example, a permit is required for hot work by the PSM standard. The use of permits is governed by a set of procedures, called a permit-to-work system. OSHA regulations exist for other types of hazardous work such as confined space entry and lockout/tagout.

Many accidents have occurred during the performance of hazardous work. Worker fatalities and injuries have occurred when confined spaces containing unsafe atmospheres were entered, piping containing hazardous chemicals was opened, and work was performed on equipment while still energized. Such accidents can often be attributed to human factors issues.

2 Technical Tools

2.1 Hazards Identification

2.1.1 Non-Scenario-Based Hazard Evaluation Procedures

Technical Tools>Hazards Identification>Non-Scenario-Based Hazard Evaluation Procedures

(Keywords: Technical Tools>Hazards Identification>Non-Scenario-Based Hazard Evaluation Procedures)

Preliminary Hazard Analysis (PreHA): Preliminary Hazard Analysis (PreHA) is a method for the identification of hazards at an early stage in the design process, and it is a term normally used to describe a qualitative technique for identifying hazards relatively early in the design process. PHA is a requirement of the MILSTD-882D Standard Practice for System Safety. The CCPS Guidelines state that PHA is intended for use only in the preliminary stage of plant development, in cases where past experience provides little insight into the potential hazards, as with a new process. The information required for the study is the design criteria, the material and equipment specification, and so on.; Reference: Lees’ Loss Prevention in the Process Industries

A quick identification of any threatening event in a plant.

Preliminary Hazard Analysis (PHA) is an inductive method of analysis whose objective is to identify the hazards, hazardous situations and events that can cause harm for a given activity, facility or system. It is most commonly carried out early in the development of a project when there is little information on design details or operating procedures and can often be a precursor to further studies. It can also be useful when analyzing existing systems or prioritizing hazards where circumstances prevent a more extensive technique from being used.

A PHA formulates a list of hazards and generic hazardous situations by considering characteristics such as:

a) Materials used or produced and their reactivity;

b) Equipment employed;

c) Operating environment;

d) Layout;

e) Interfaces among system components, etc.

The method is completed with the identification of the possibilities that the accident happens, the quantitative evaluation of the extent of possible or damage to health that could result and the identification of possible injury or damage to health that could result and the identification of possible remedial measures. PHA should be updated during the phases of design, construction and testing to detect any new hazards and make corrections, if necessary. The results obtained may be presented in different ways such as tables and trees.

Reference: IEC 60300-3-9

Hazard analysis (HAZAN): Is the identification of undesired events that lead to the materialization of a hazard, the analysis of the mechanisms by which these undesired events could occur, and, usually, the estimation of the consequences.

Every Hazard analysis consists of three steps: i) Estimating how often the incident will occur. ii) Estimating the consequences to: employees; the public and the environment; plant and profits.

Reference: S2S (safety to safety website: Process Equipment Reliability Data. Chemical Process Quantitative Risk Analysis; AIChE, 345 East 47th Street, New York, NY 10017; Center for Chemical Process Safety of the American Institute of Chemical Engineers; New York; 1989; pp.150)

Safety Review: Safety Reviews are intended to identify plant conditions or operating procedures that could lead to an incident and result in injuries, significant property damage, or environmental impacts. A typical Safety Review includes interviews with many people in the plant: operators, maintenance staff, engineers, management, safety staff, and others, depending upon the plant organization. Safety Reviews should be viewed as cooperative efforts to improve the overall safety and performance of the plant, rather than interfering with normal operations or as a punitive reaction to a perceived problem.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

Relative Ranking: Relative Ranking is actually an analysis strategy rather than a single, well-defined analysis method. This strategy allows hazard analysts to compare the attributes of several processes or activities to determine whether they possess hazardous characteristics that are significant enough to warrant further study. Relative Ranking can also be used to compare several process siting, generic design, or equipment layout options, and provide information concerning which alternative appears to be the “best” option. These comparisons are based on numerical values that represent the relative level of significance that the analyst gives to each hazard, potential consequence or risk depending on the approach used. Relative ranking studies should normally be performed early in the life of an existing facility’s hazard analysis program. However, the relative ranking method can also be applied to an existing process to pinpoint the hazards of various aspects of process operation.; Reference: CCPS: guidelines for hazard evaluation procedures, third edition

Ordering of risk respectively to its magnitude.

Checklist Analysis: A Checklist Analysis uses a written list of items or procedural steps to verify the status of a system. Traditional checklists vary widely in level of detail and are frequently used to indicate compliance with standards and practices. In some cases, analysts use a more general checklist in combination with another hazard evaluation method to discover common hazards that the checklist alone might miss. The Checklist Analysis approach is easy to use and can be applied at any stage of the process’s lifetime.

A detailed checklist provides the basis for a standard evaluation of process hazards. It can be as extensive as necessary to satisfy the specific situation, but it should be applied conscientiously in order to identify problems that require further attention. Generic hazard checklists are often combined with other hazard evaluation techniques to evaluate hazardous situations. Checklists are limited by their authors’ experience; therefore, they should be developed by authors with varied backgrounds who have extensive experience with the systems they are analyzing. Frequently, checklists are created by simply organizing information from current relevant codes, standards, and regulations. Checklists should be viewed as living documents and should be audited and updated regularly.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

Formalized listing of actions to be performed in a given work setting to ensure that, no matter how often performed by a given practitioner, no step will be forgotten. An analogy is often made to flight preparation in aviation, as pilots and air-traffic controllers follow pre-takeoff checklists regardless of how many times they have carried out the tasks involved. Checklists are an example of positive reporting on safety critical tasks, in other words the affirmation of the safe status of equipment. In contrast a system of negative reporting assumes that all equipment is in a safe state unless explicit warning that it is not- a potential flaw in the system for closing bow doors in the Herald of Free Enterprise sinking.

Reference: S2S (safety to safety website: Patient Safety Network, PSNet)

2.1.2 Scenario-Based Hazard Evaluation Procedures

Technical Tools>Hazards Identification>Scenario-Based Hazard Evaluation Procedures

(Keywords: Technical Tools>Hazards Identification>Scenario-Based Hazard Evaluation Procedures)

What-If Analysis: The What-If Analysis technique is a brainstorming approach in which a group of experienced people familiar with the subject process ask questions or voice concerns about possible undesired events.

What-If Analysis is not as inherently structured as some other techniques such as HAZOP Studies and FMEA. Instead, it requires the analyst to adapt the basic concept to the specific application. Very little information has been published on the What-If Analysis method or its application. However, it is frequently used by industry at nearly every stage of the life cycle of a process and has a good reputation among those skilled in its use.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

What-If Analysis/Checklist Analysis: The What-If/Checklist Analysis technique combines the creative, brainstorming features of the What-If Analysis method with the systematic features of the Checklist Analysis method. The purpose of a What-If/Checklist Analysis is to identify hazards, consider the general types of incidents that can occur in a process or activity, evaluate in a qualitative fashion the effects of these incidents, and determine whether the safeguards against these potential incident situations appear adequate. Frequently, the hazard evaluation team members will suggest ways for reducing the risk of operating the process.

Reference: Lees’ Loss Prevention in the Process Industries & CCPS: guidelines for hazard evaluation procedures, third edition

Hazard and Operability (HAZOP) Studies: HAZOP stands for “Hazards and Operability” and it is a technique or methodology used in Process Hazards Analyses (PHAs) in which a multidisciplinary team uses guide words to systematically study a process to discover whether deviations from the process design intention can occur in equipment, actions or materials, and whether these deviations can create a hazard. In the “knowledge-based HAZOP” approach, the guide words are supplemented or partially replaced by the team’s knowledge and checklists used to compare the design against established design standards.; Common usage: Sometimes the word ‘HAZOP’ is used as a synonym for PHA, where the methodology is implied.

A systematic method for identifying possible hazards and potential operating problems in a plant or process by the application of so called ‘guidewords’ (e.g. more, less, other, etc.) to the plant or process flow sheet to study process deviations.

Reference: HarsNet working group, 2002, HarsBook, A technical guide for the assessment of highly reactive chemical systems, Frankfurt.

A HAZOP study is a form of fault modes and effects analysis (FMEA). HAZOP studies were originally developed for the chemical industry. It is a systematic technique for identifying hazards and operability problems throughout an entire facility. It is particularly useful in identifying unforeseen hazards designed into facilities due to lack of information, or introduced into existing facilities due to changes in process conditions or operating procedures. The basic objectives of the techniques are:

a) to produce a full description of the facility or process, including the intended design conditions;

b) to review systematically every part of the facility or process to discover how deviations from the intention of the design can occur; and

c) to decide whether these deviations can lead to hazards or operability problems.

The principles of HAZOP studies can be applied to process plants in operation or in various stages of design. A HAZOP study carried out during the initial phase of design can frequently provide a guide to safer detailed design.

Reference: IEC 60300-3-9

Failure Mode and Effects Analysis (FMEA): A Failure Modes and Effects Analysis (FMEA) tabulates failure modes of equipment and their effects on a system or plant. The failure mode describes how equipment fails (open, closed, on, off, leaks, etc.). The effect of the failure mode is determined by the system’s response to the equipment failure. An FMEA identifies single failure modes that either directly result in or contribute significantly to an incident. Human operator errors are usually not examined directly in an FMEA; however, the effects of inadequate design, improper installation, lack of maintenance, or improper operation are usually manifested as an equipment failure mode. Failure Modes and Effects Analysis evaluates how equipment can fail (or be improperly operated) and the effects these failures can have on a process. These failure descriptions provide analysts with a basis for determining where changes can be made to improve a system design.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

Qualitative hazard identification method based on the knowledge of each failure mode of the items of a plant.

Reference: Geoff Wells, 1996, HAZARD Identification and risk assessment.

FMEA is a technique, primarily qualitative although it can be quantified, by which the effect or consequences of individual component fault modes are systematically identified. It is an inductive technique which is based on the question “what happens if…?”. The essential feature in any FMEA is the consideration of each major part/component of the system, how it becomes faulty (the fault mode), and what the effect of the fault mode on the system would be (the fault mode effect). Usually, the analysis is descriptive and is organized by creating a table or worksheet for the information. As such, FMEA clearly relates component fault modes, their causative factors and effects on the system, and presents them in an easily readable format.

FMEA is a “bottom-up” approach and considers consequences of component fault modes one at a time. As such, the method is tolerant of a slight amount of redundancy before becoming cumbersome to perform. Also, the results can be readily verified by another person familiar with the system.

The major disadvantages of the technique are the difficulty of dealing with redundancy and the incorporation of repair actions as well as the focus on single component failures.

An FMEA can be extended to perform what is called Failure Mode, Effects and Criticality Analysis (FMECA). In a FMECA, each fault mode identified is ranked according to the combined influence of its probability of occurrence and the severity of its consequences.

Reference: IEC 60300-3-9

Hazard Identification(HAZID) Studies: A Hazard Identification (HAZID) study is an analysis at the early stages of development of a process to uncover hazards that can have an impact on its safety, thus allowing integration of process safety in the initial process design. The study is a team work which needs brainstorming process, using simple hazard analysis techniques. Consequence modeling and risk assessment is not required at this stage.

2.2 Risk Assessment

Risk Assessment (QRA): The overall process of risk analysis and risk evaluation.; Reference: IEC 60300-3-9

The process of identifying the hazards present in any undertaking (whether arising from work activities or other factors) and those likely to be affected by them. Also evaluating the extent of the risks involved, bearing in mind whatever precautions are already being taken.

Reference: HarsNet working group, 2002, HarsBook, A technical guide for the assessment of highly reactive chemical systems, Frankfurt.

2.2.1 Quantitative Risk Assessment

Technical Tools>Risk Assessment>Quantitative Risk Assessment

Quantitative Risk Assessment (QRA): The quantification of risk by the assessment of the numerical probability of occurrence or the numerical frequency.

2.2.1.1 Consequence Techniques

Technical Tools>Risk Assessment>Quantitative Risk Assessment>Consequence Techniques

(Keywords: Technical Tools>Risk Assessment>Quantitative Risk Assessment>Dispersion, Modeling, Effects, Consequences )

Consequence Techniques (Consequence Analysis)

The estimation of loss in the case of an accident.

Consequence analysis is used to estimate the likely impact should the undesired event occur. Consequence analysis should:

be based on the undesirable events selected;
describe any consequences resulting from the undesirable events;
take into consideration existing measures to mitigate the consequences together with all relevant conditions that have an effect on the consequences;
give the criteria used for completing the identification of the consequences;
consider both immediate consequences and those that may arise after a certain time has elapsed, if this is consistent with the scope of the study;
consider secondary consequences, such as those associated with adjacent equipment and systems.

Consequence analysis involves estimating the impact on people, property or environment, should the undesired event occur. Normally, for risk calculations related to safety (of the public or workers), it consists of estimating the number of people located in different environments, at different distances from the source of the event, that may be either killed, injured or seriously affected, given the undesired event has occurred.

The undesired events usually comprise situations such as release of toxic materials, fires, explosions, projectiles from disintegrating equipment, etc. Consequence models are needed for predicting the extent of casualties and other effect. The knowledge of the release mechanism and the subsequent fate of the released material (or energy) enables prediction to be made of the effects of the release at any distance from the source at any time.

There are many methods for estimating such effects ranging from simplified analytical approaches to very complex computer models. Care should be taken to ensure that the methods are appropriate to the problem being considered.

Reference: IEC 60300-3-9

Emission: A failure of plant integrity, but it is important to consider other occurrences, including escape from valves which have been deliberately opened and forced venting in emergencies. But loss of refrigeration with resultant forced venting could also give a large release of vapor. Finally, emissions caused by terrorist acts are of growing concern.

Reference: Lees’ Loss Prevention in the Process Industries

Vaporization: If the fluid that escapes from containment is a liquid, then vaporization must occur before a vapor cloud is formed. The process of vaporization determines the rate at which material enters the cloud. It also determines the amount of air entrained into the cloud.

Reference: Lees’ Loss Prevention in the Process Industries

Source Term: The source term can be critical for the modeling of the subsequent dispersion of a dense gas. It is therefore important that the source model should be realistic and complete. If the model for the source term is poor, the results of the whole dense gas dispersion estimate may be seriously in error.

Reference: Lees’ Loss Prevention in the Process Industries

Gas Dispersion: The account given so far of gas dispersion has been confined to the dispersion of gases of neutral buoyancy, or passive dispersion. A large proportion of industrially important gases exhibit negative buoyancy. It is these gases particularly which are prominent in hazard assessment.

Reference: Lees’ Loss Prevention in the Process Industries

Plumes: The dispersion of material issuing as a leak from a plant is determined by its momentum and buoyancy. If momentum forces predominate, the fluid forms a jet, while if buoyancy forces predominate, it forms a plume.

Reference: Lees’ Loss Prevention in the Process Industries

Jets: If the momentum of the material issuing from an orifice on a plant is high, the dispersion in the initial phase at least is due to the momentum, and the emission is described as a momentum jet.

Reference: Lees’ Loss Prevention in the Process Industries

Fires: Fire (or combustion) is a chemical reaction in which a substance combines with oxygen and heat is released. Usually, fire occurs when a source of heat comes into contact with a combustible material. If a combustible liquid or solid is heated it evolves vapor and if the concentration of vapor is high enough, it forms a flammable mixture with oxygen in the air. If this flammable mixture is then heated further to its ignition point, combustion starts.

Reference: Lees’ Loss Prevention in the Process Industries

Explosions: An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a “high explosive”. Subsonic shock waves are created by low explosives through the slower burning process known as deflagration.; Reference: Lees’ Loss Prevention in the Process Industries

Explosion is a release of energy sufficient to cause a pressure wave.

Reference: S2S (safety to safety website: HarsNet working group, 2002, HarsBook, A technical guide for the assessment of highly reactive chemical systems, Frankfurt.)

2.2.1.2 Frequency Techniques

Technical Tools>Risk Assessment>Quantitative Risk Assessment>Frequency Techniques

(Keywords: Technical Tools>Risk Assessment>Quantitative Risk Assessment>Frequency Techniques)

Frequency Techniques (Frequency Analysis): Used to estimate the likelihood of each undesired event identified at the hazard identification stage.; The purpose of frequency analysis is to determine the frequency of each of the undesired events or accident scenarios identified at the hazard identification stage. Three basic approaches are commonly taken:; a) Use relevant historical data to determine the frequency with which these events have occurred in the past and hence make judgements as to the frequency of their occurrence in the future. The data used should be relevant to the type of system, facility or activity being considered and also to the operational standards of the organization involved;; b) Predict event frequencies using techniques such as fault tree analysis and event tree analysis. When historical data are unavailable or inadequate, it is necessary to derive event frequencies by analysis of the system and its associated fault modes. Numerical data on all relevant events, including equipment failure and human error from operational experience or published data sources are then combined to produce an estimate of the frequency of the undesired events. When using predictive techniques, it is important to ensure that due allowance has been made in the analysis for the possibility of common mode failures involving the co-incidental failure of a number of different parts or components within the system. Simulation techniques may be required to generate frequencies of equipment and structural failures due to ageing and other degradation processes, by calculating the effects of uncertainties;; c) Use expert judgment. There are a number of formal methods for eliciting expert judgment which make the use of judgments visible and explicit and provide an aid to the asking of appropriate questions. Expert judgments should draw upon all relevant available information including historical, system-specific, experimental, design, etc. The methods available include the Delphi approach, paired comparisons, category rating and absolute probability judgments.; Reference: IEC 60300-3-9

Fault Tree Analysis (FTA): Fault Tree Analysis (FTA) is a deductive technique that focuses on one particular incident or main system failure, and provides a method. The fault tree is a graphical model that displays the various combinations of equipment failures and human errors that can result in the main system failure of interest (called the Top event). The strength of FTA as a qualitative tool is its ability to identify the combinations of basic equipment failures and human errors that can lead to an incident. This allows the hazard analyst to focus preventive or mitigative measures on significant basic causes to reduce the likelihood of an incident.; Reference: CCPS: guidelines for hazard evaluation procedures, third edition

A method for representing the logical combinations of various system states which lead to a particular outcome (Top event). With suitable data it can be used to quantify the probability or frequency of an event.

Reference: HarsNet working group, 2002, HarsBook, A technical guide for the assessment of highly reactive chemical systems, Frankfurt.

FTA is a technique, which can be either qualitative or quantitative, by which conditions and factors that can contribute to a specified undesired event (called the top event) are deductively identified, organized in a logical manner and represented pictorially. The faults identified in the tree can be events that are associated with the component hardware failures, human errors or any other pertinent events which lead to the undesired event. Starting with the top event, the possible causes or fault modes of the next lower functional system level are identified. Following stepwise identification of undesirable system operation to successively lower system levels will lead to the desired system level, which is usually the component fault mode.

FTA affords a disciplined approach which is highly systematic, but at the same time sufficiently flexible to allow analysis of a variety of factors, including human interactions and physical phenomena. The application of the “top-down” approach, implicit in the technique, focuses attention on those effects of failure which are directly related to the top event. This is a distinct advantage, although it may also lead to missing effects which are important elsewhere. FTA is especially useful for analyzing systems with many interfaces and interactions. The pictorial representation leads to an easy understanding of the system behavior and the factors included, but as the trees are often large, processing of fault trees may require computer systems. This feature also makes the verification of the fault tree difficult.

FTA may be used for hazard identification, although it is primarily used in risk assessment as a tool to provide an estimate of failure probabilities or frequencies.

Reference: IEC 60300-3-9

Event Tree Analysis (ETA): An event tree is constructed by defining an initial event and the possible consequences that flow from it. An event tree graphically shows all of the possible outcomes following the success or failure of protective systems, given the occurrence of a specific initiating cause (equipment failure or human error). Event trees are also used to study other events, such as starting at a loss event and evaluating mitigation systems.

Event trees are used to identify the various incidents that can occur in a complex process. After these individual event sequences are identified, the specific combinations of failures that can lead to the incidents can then be determined using Fault Tree analysis.

The results of the Event Tree Analysis are event sequences; that is, sets of failures or errors that lead to an incident. An Event Tree Analysis is well suited for analyzing complex processes that have several layers of safety systems or emergency procedures in place to respond to specific initiating events.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

A graphical logical model that identifies possible outcomes following an initiating event. With suitable data it can be used to quantify the occurrence of an event.

Reference: HarsNet working group, 2002, HarsBook, A technical guide for the assessment of highly reactive chemical systems, Frankfurt.

ETA is a technique, either qualitative or quantitative, which is used to identify the possible outcomes and if required, their probabilities, given the occurrence of an initiating event. ETA is widely used for facilities provided with engineered accident mitigating features, to identify the sequence of events which lead to the occurrence of specified consequences, following the occurrence of the initiating event. It is generally assumed that each event in the sequence is either a success or a failure.

ETA is an inductive type of analysis in which the basic question addressed is “what happens if…?”. It provides the relationship between the functioning or failure of various mitigating systems and ultimately the hazardous event following the occurrence of the single initiating event, in a clear way. ETA is very useful in identifying events which require further analysis using FTA (i.e. the top events of the fault trees). In order to be able to do a comprehensive risk assessment, all potential initiating events need to be identified. There is always a potential, however, for missing some important initiating events with this technique. Furthermore, with event trees, only success and fault states of a system are dealt with, and it is difficult to incorporate delayed success or recovery events.

ETA can be used both for hazard identification and for probability estimation of a sequence of events leading to hazardous situations.

Reference: IEC 60300-3-9

Bowtie Analysis: A less formal variation of Cause-Consequence Analysis is the “Bow-Tie” technique. It similarly combines two methodologies presented in earlier sections, Fault Tree Analysis and Event Tree Analysis, and uses the format of an incident investigation and root cause analysis technique known as Causal Factors. The Bow-Tie analysis offers a cost-effective approach for a screening hazard evaluation of processes that are well understood. This approach is a qualitative hazard evaluation technique ideally suited for the initial analysis of an existing process, or application during the middle stages of a process design.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

Common Cause Failure Analysis (CCFA): A Cause-Consequence Analysis (CCA) is a blend of the Fault Tree Analysis and Event Tree Analysis techniques that were discussed in the preceding sections. A major strength of a Cause-Consequence Analysis is its use as a communication tool. The cause-consequence diagram displays the relationships between the incident outcomes (consequences) and their basic causes. This technique is most commonly used when the failure logic of the analyzed incidents is rather simple, since the graphical form, which combines both fault trees and event trees on the same diagram, can become quite detailed.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

Human Reliability Analysis (HRA): A human reliability analysis is a systematic evaluation of the factors that influence the performance of the operators, maintenance staff, technicians, and other plant personnel. It involves one of several types of task analyses; these types of analyses describe a task’s physical and environmental characteristics, along with the skills, knowledge, and capabilities required of those who perform the tasks. A human reliability analysis will identity error-likely situations that can cause or lead to accidents. A human reliability analysis can also be used to trace the cause of human errors. Human reliability analysis is usually performed in conjunction with other hazard evaluation techniques.

Reference: CCPS: guidelines for hazard evaluation procedures, third edition

External Events Analysis: It lists a range of candidate external events for consideration. The hazard intensities of external events can be represented by parameters such as the peak ground acceleration of earthquakes, tornado intensities, and the kinetic energy of aircraft.

Reference: CCPS: guidelines for chemical process quantitative risk analysis, second edition

2.2.2 Semiquantitative Risk Assessment

Technical Tools>Risk Assessment>Semiquantitative Risk Assessment

(Keywords: Technical Tools>Risk Assessment>Semiquantitative Risk Assessment)

Layer of Protection Analysis (LOPA): LOPA is a semi-quantitative tool for analyzing and assessing risk. This method includes simplified methods to characterize the consequences and estimate the frequencies. Various layers of protection are added to a process, for example, to lower the frequency of the undesired consequences. The protection layers may include inherently safer concepts; the basic process control system; safety instrumented functions; passive devices, such as dikes or blast walls, active devices, such as relief valves; and human intervention.; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed.

Containment: A condition in which under no condition reactants or products are exchanged between the chemical system and its environment.; References:S2S (safety to safety website: HarsNet working group, 2002, HarsBook, A technical guide for the assessment of highly reactive chemical systems, Frankfurt.)

Control of the expansion or propagation of accidental loss; commonly used in fire control.

References:S2S (safety to safety website: from Glossary of SSDC terms and acronyms, Oct.1984, US DOE 76-45/28 SSDC-28)

Prevention: All the measures taken to minimize the occurrence probability of an accident.

Isolation: Prevention of an explosion passing to communicating vessels or pipe work by the use of barriers, valves, inerting etc which prevent the passage of flame.

Decontamination: Cleaning of a contaminated site after a major accident.

Safety Management System (SMS): System to administrate safety culture.; An important part of the requirements of the Seveso Directive.; The part of the enterprise’s general management system that includes the organizational structure, responsibilities, practices, procedures, processes, and resources for determining and implementing a chemical accident prevention policy. The safety management system normally addresses a number of issues including, but not limited to: organization and personnel; identification and evaluation of hazards and risks; operational control; management of change; planning for emergencies; monitoring performance; audit and review.; Reference: OECD Environment, Health and Safety Publications Series on Chemical Accidents No. 10, Annex 1, 2nd Ed., 2003.

Fast acting shut off valves: To prevent flame and pressure propagation in pipes and ducts, valves (gate or butterfly) or flaps may be used which close in a sufficiently short time. The closure can be effected by means of an actuating mechanism initiated by detectors or by the explosion pressure wave itself.; References: S2S (safety to safety website)(EN 1127-1: 1998)

Rotary valves: Can be used to prevent flame and pressure propagation. In the case of an explosion, the movement of the rotor shall be stopped automatically by means of a detecting system, to ensure that the discharge of the burning product is prevented.; References: S2S (safety to safety website)(EN 1127-1: 1998)

Flame arrestors: Device fitted to the opening of an enclosure or to the connecting pipe work of a system of enclosures and whose intended function is to allow flow, but prevent the transmission of flame (EN 12874:2001); NOTE : This device should not be confused with a fire barrier, which is ineffective in case of explosion.; References: S2S (safety to safety website)(EN 13237:2003 (E))

Fire extinguishing

Active operation by man or technical installation in purpose to extinguish a fire. There are mainly 4 extinguishing methods based on the Fire Triangle(Triangle made by the three elements that must be present in order to start a fire) and Tetrahedron (tetrahedron made by the three elements of the fire triangle and a fourth element called “chemical chain reaction”, all of them needed in a fire to continue) approaches:

cooling the burning material
excluding oxygen or other combatant
excluding fuel
breaking the chemical chain reaction

Different elements are necessary to extinguish a fire:

Fire extinguishing equipment and hoses
Fire extinguishing equipment and installations (Accessories)
Fire extinguishing installations and systems
Fire extinguishing agents and additions
Smoke control

Reference: S2S (safety to safety website)

Procedure: A stepwise description of a task.; Reference: S2S (safety to safety website: Human Factors in Process Operations, 1992, Robert C Mill, IChemE, ISBN 0 85295 294 5)

Semiquantitative Risk Matrix: semi-quantitative risk matrix approach usually uses a 4 by 4 matrix with broad quantitative bins for the frequency axis, while keeping the purely qualitative descriptions for the consequence axis. Three categories of risk are defined: Acceptable, Marginal, and Unacceptable. Even though the frequency axis is quantitative, the resulting risk for each region in the matrix is a mixed bag product of a numerical range and qualitative description, such as 10-4to 10-6)*Low. Again, there are no direct comparisons possible between the risk of some regions, such as 10-4 to 10-6)*Low and (< 106)*Moderate for example.

Reference: Thomas J. Altenbach, A Comparison of Risk Assessment Techniques from Qualitative to Quantitative, ASME Pressure and Piping Conference, 23-27, 1995

Qualitative Risk Matrix: Qualitative risk matrices provide a pictorial way of determining levels of risk for each part of an ecosystem. A risk matrix is composed of two axes, which describe the overriding factors that would determine the likelihood of each species experiencing a pre-defined undesirable event. The most critical aspect of developing a qualitative risk matrix is choosing appropriate factors for the vertical and horizontal axes. Both the frequency and consequence of each accident scenario are then estimated on simple relative scales, such as Low-Medium-High. The risk for each scenario is the product of the frequency rating and consequence rating.

Reference: K.L. Astles , et al, An ecological method for qualitative risk assessment and its use in the management of fisheries in New South Wales, Australia , Fisheries Research 82 (2006) 290–303

2.3 Facilities

2.3.1 Plant layout

Technical Tools>Facilities>Plant layout

(Keywords: Technical Tools>Facilities>Layout, Siting )

Site and Plant Layout: The most important feature of siting is the distance between the site and build-up areas. Sites range from rural to urban, with population densities varying from virtually zero to high. Separation between a hazard and the public is beneficial in mitigating the effects of a major accident. An area of low population density around the site will help to reduce casualties.

Plant layout is a crucial factor in the economics and safety of process plant. Additional space tends to increase safety, but is expensive in terms of land and also in additional pipework and operating costs. Space needs to be provided where it is necessary for safety, but not wasted.

Reference: Lees’ Loss Prevention in the Process Industries, Third Edition

Equipment Layout: The process safety goals of equipment layout are to design a workplace that will minimize the risk of injuries, environmental damage, overall property damage, and related business interruption resulting from potential toxic releases, fires, and explosions. To design and build the new unit within cost and schedule constraints. Balancing all of the goals: health, safety, environmental, cost, and schedule while keeping in mind the lifecycle of the unit and the operational goals. Typical separation distances between various elements in open-air process facilities. These distances are based on historical and current data from refining, petrochemical, chemical, and insurance sectors. The separation distances cited are based on potential fire consequences.

Reference: CCPS: Guidelines for Facility Sitting and Layout

Temporary Buildings: Temporary housing may also be required during the construction phase to support the surge in manpower requirements. If the temporary housing is to be located on the site, consider the separation distances between temporary facilities, construction activities, and plant start-up.

Reference: CCPS: Guidelines for Facility Sitting and Layout

Permanent Buildings: When a remote site is under consideration, investigate the surrounding area to determine the availability of housing and amenities for permanent personnel. In remote locations where company housing is provided, finding a suitable location for company housing is as important an issue as finding asuitable location for the new site.

Reference: CCPS: Guidelines for Facility Sitting and Layout

Layout Optimization: Laying out a complex, site, plant, or unit can be a challenging exercise. There are safety, environmental, financial, and public concern risks to balance with project cost and schedule goals. There is a large amount of both site and process data to be gathered and considered in the layout and spacing process. This is a cost effective way to manage risk. This minimizes the probability of an incident occurring or escalating because higher risk equipment is located away from lower risk equipment. It also allows risk minimization measures (e.g., fixed protection systems, containment systems, detection systems) to be installed efficiently around the higher risk equipment rather than across the entire site.

Reference: CCPS: Guidelines for Facility Sitting and Layout

2.3.2 Personal Protection

Technical Tools>Facilities>Personnel Protection

(Keywords: Technical Tools>Facilities>Personnel Protection)

Personal Protective Equipment: Personal Protective Equipment, commonly referred to as PPE, is equipment worn to minimize exposure to a variety of hazards. Examples of PPE include such items as gloves, foot and eye protection, protective hearing devices, hard hats, face shields, respirators and full body suits.; Reference: S2S (safety to safety website: Occupational Safety and Health Administration, USA Department of Labor.)

Active fire protection: Generic term for automatic fire protection, e.g. sprinkler or automatic fire alarm. Also used for other interacted systems such as control systems for fire-proof doors.; Reference: S2S (safety to safety website)

Location of Fire Protection: These typical separation distances assume a minimal level of site fire protection such as fire hydrants, manual firefighting capabilities, and adequate drainage to prevent flooding during a major firefighting effort. Distances may be reduced or increased based on risk analysis of site-specific conditions or when additional fire protection, safety measures, or other layers of protection are implemented.

Reference: CCPS: Guidelines for Facility Sitting and Layout

Control Room Protection: A process control building should contain the facilities and offices essential to process control. It should not be located in a structure with unrelated functions such as administration, accounting, engineering, and research laboratories. Where central control buildings include analytical laboratories or kitchens, consider the provision of a firewall to separate these areas from the process control areas. It is advisable to construct a control building with no equipment located above or below the control room. Where central control buildings house the emergency control center, consider the building location and the location of the personnel expected to staff the emergency control center.

Reference: CCPS: Guidelines for Facility Sitting and Layout

2.4 Mechanical Integrity

Technical Tools>Mechanical Integrity>Risk Management Tools

(Keywords: Technical Tools>Mechanical Integrity>Risk Management Tools)

Risk-based Inspection (RBI): RBI is a risk assessment and risk management tool that assesses the likelihood and consequence of a loss of containment in process equipment used as an ongoing part of the MI program. It integrated the traditional RAGAGEP standards with flexibility to focus and optimize the activities on risk reduction by identifying higher risk equipment and failure mechanisms.

Reference: CCPS: guidelines for mechanical integrity systems

Failure Modes and Effects Analysis (FMEA) and Failure Modes, Effects and Criticality Analysis (FMECA): Inductive reasoning approach that evaluates how the equipment can fail and the effect that these failures have on process or system performance, and ensures that appropriate safeguards against the failure(s) are in place. FMECA is an FMEA that assesses the criticality of the failure modes and resulting effects using qualitative, semi-quantitative, or quantitative risk measures.; Reference: CCPS: guidelines for mechanical integrity systems

Semi-quantitative method for hazard assessment. It consists on applying a criticality index to the events studied in a FMEA.

Reference: Geoff Wells, 1996, HAZARD Identification and risk assessment.

Reliability-centered maintenance (RCM): Comprehensive review and analysis of system and their components using(1) an FMEA/FMECA to identify potential equipment failures and their impact on system/process performance and (2) decision tree(or similar tools) to determine appropriate failure management strategies.

Reference: CCPS: guidelines for mechanical integrity systems

Layer of Protection Analysis (LOPA): A semi-quantitative analysis of the risk of a scenario; each scenario has a consequence with its associated severity and one initiating event with its associated frequency; IPLs are evaluated for applicable risk reduction; additional layers, such as SIFs , can be added to meet a risk target.

Reference: CCPS: guidelines for mechanical integrity systems

2.5 Human Factors and Errors

2.5.1 Human Reliability Analysis

2.5.1.1 Task Related

Technical Tools>Human Factors and Errors>Human Reliability Analysis>Task Related

(Keywords: Technical Tools>Human Factors and Errors>Human Reliability Analysis>Task Related)

Technique for Human Error Rate Prediction: The THERP approach is based on the results of a task analysis, which breaks a task into a number of subtasks. Then makes this subtask array into an assembly of discrete HRA subtasks, forming an HRA event tree. To quantify this HRA event tree, one should select the appropriate human error probabilities to match the subtasks in the HRA event tree.

THERP is a task-defined HRA type mode. The elements considered are developed by carrying out a task analysis on the specific HRA task to be modeled and quantified. Within the set of subtasks to consider are series tasks, parallel tasks, and recoveries.

Reference: Human reliability assessment: theory and practice

Cause-based decision tree: A set of subtasks are placed in a decision tree or event tree format. The CBDT structure is more like a conventional event tree, expect there are a number of such trees. CBDT formulation is one of a set of HRA methods included within the current EPRI HRA calculator.

CBDT is a development of THERP constructed by Beare and colleagues acting on a suggestion from the operator reliability experiment (ORE) group to develop a decision tree approach to incorporate results from ORE project.

Reference: Human reliability assessment: theory and practice

Human error assessment and reduction technique: Bring to the process a large amount of experience to human factors effects from different industries. The key elements of HEART are a listing of a number of tasks in tabular form along with an associated mean HEP and a range of values to cover uncertainties in the estimates. The method also covers a number of weighting factors, which are introduced to cover the potential influence of a range of PSFs.

Although the central part of the method is task oriented, the task was defined as something more global rather than the subtask approach taken by Swain and Guttman.

Reference: Human reliability assessment: theory and practice

2.5.1.2 Time Related

Technical Tools>Human Factors and Errors>Human Reliability Analysis>Time Related

(Keywords: Technical Tools>Human Factors and Errors>Human Reliability Analysis>Time Related)

Time Reliability Curve: A crew will eventually respond to an accident given enough time, so the estimated HEP decreases depending on the time available before an accident reaches an irreversible point. TRC uses three curves to predict the HEP median value and distribution (5% and 95%) as a function of time.

Reference: Human reliability assessment: theory and practice

Operator Reliability Experiments: Operator reliability experiments (ORE) study provided a considerable amount of data on the response of crew at a variety of Nuclear Power Plants (NPPs), both pressurized and boiling water reactors. The result from the ORE project have led to a better understanding o the response of crews to accidents and the worth of procedures, training , and good man-machine interface design. The result also indicated that the time response data could indicate that operators were very reliable or that there was uncertainty and outright failure.

Reference: Spurgin, A,J. Human reliability assessment: theory and practice

Operator Reliability Experiments/Human Cognitive Reliability: The human cognitive reliability (HRC) model was developed for quantification of crew success (or failure) probability as a function of time and allowing for various types of human behaviors that can result in significantly different probabilities. The model also allowed for certain selected performance-shaping factors (PSF) that can influence the crew response times. The model was designed to be relatively simple to use, capable of generating insights into crew behavior, compatible with other HRA methods and finally, being able to produce similar estimates when used by different analysts.

Reference: Hannaman, G. W., Spurgin, A. J. & Lukic, Y. D., Human Cognitive Reliability Model for PRA Analysis (EPRI RP 2170-3). Electric Power Research Institute, Palo Alto, CA, USA, 1984

2.5.1.3 Context Related

Technical Tools>Human Factors and Errors>Human Reliability Analysis>Context Related

(Keywords: Technical Tools>Human Factors and Errors>Human Reliability Analysis>Context Related)

Cognitive reliability and error analysis method: CREAM was developed by E.Hollnagel based on his experience in the field of both human factors and human reliability. There are two versions of CREAM in Hollnagel’s book; one is a simplified view of controlling modes and the other is a more detailed view of human errors. Both methods have been applied in NASA study. CREAM I was applied as a screening method in an early HRA study for the International Space Station PRA and later was replaced by the HDT approach. CREAM II was applied for one of the HRA studies for the Orbiter PSA/HRA study.

Reference: Human reliability assessment: theory and practice

Holistic decision tree

The HDT combines a tree structure with anchor values to determine the end state HEPs for a particular accident scenario; this approach has some connection to the SLIM HRA approach. The method is directed toward a holistic approach to the estimation of HEP values for the MCR crew.

Reference: Human reliability assessment: theory and practice

A technique for human error analysis: The ATHEANA method can be broken down into two parts: identification of human errors within an event sequence and quantification of these human errors. The normal HRA methods subsume the errors identified with the event sequence mostly by historical means. The difference is that ATHEANA has search method to identify error forcing conditions (EFCs) exist that can lead to errors.

Reference: Human reliability assessment: theory and practice

Cognitive reliability and error analysis method II: CREAM II is called by its developer extended CREAM. It is based on upon two concepts: a generalized cognitive failure function (CFF), which is divided into four groups: observational errors, interpretational errors, planning errors, and execution errors. Rather than task identification, the method concentrates upon cognitive characteristics associated with a task.

Reference: Human reliability assessment: theory and practice

Standardized plant analysis risk-human reliability: The method was developed by Idaho National Laboratories for use by the USNRC. The method consists of the combination of a simple human reliability represented based on a cognitive part and an action part with HEPs values associated with each and a set of PSFs to be used in combination with HEPs. The user determines the human reliability value and uses expert judgment to select the PSFs and their values.

Reference: Human reliability assessment: theory and practice

3 Science

3.1 Large Scale Chemicals

Science>Large Scale Chemicals

(Keywords: Science>Large Scale Chemicals)

Liquefied natural gas: a temporarily liquefied natural gas, which is mostly methane, for storage or transport purpose, taking up to 1/600 volume of gaseous state

Reference: NOAA’s national ocean service, office of response and restoration, Chemical Reactivity Worksheet (CRW) http://response.restoration.noaa.gov/type_subtopic_entry.php?RECORD_KEY%28entry_subtopic_type%29=entry_id,subtopic_id,type_id&entry_id%28entry_subtopic_type%29=328&subtopic_id%28entry_subtopic_type%29=24&type_id%28entry_subtopic_type%29=3

Vapor cloud explosion: a detonation of flammable vapor cloud resulting in formation of shock wave and fires; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Gas or vapor which, when mixed with air in certain proportions, will form an explosive gas atmosphere (EN 60079-10:1996).

Reference: S2S (safety to safety website: EN 13237:2003 (E))

Fire control by water curtain spray: a system which can spill water from nozzles attached to sprinkler devices while fire control and confinement is needed; mostly the protection of water curtain can block the flammable materials and flame from spreading further out of its restricted area by droplets absorption of heat, spark prevention, and bringing flammable mass down to ground

Plume visualization in atmosphere: a study of simulation to find the LNG plume thermal imaging effects and the influential parameters of the figures; an approach to find out how the LNG plume transport vertically in the open region air

Burning rate and heat transfer rate of pool fire: a study of LNG pool fire and the two-phase flame propagation with energy transfer analysis

Reference: CCPS, AIChE Industry Technology Alliance, Safety Alert 1. Reactive Material Hazards – What you need to know (2001) 2. A Checklist for inherently Safer Chemical Reaction Process Design and Operation (www.aiche.org/ccps/safetyalerts)

Ammonia: a compound of nitrogen and hydrogen with the formula NH3; colorless gas with pungent odor; an important fertilizer and food precursor

Production process science: a study of ammonia production, discussing process of LNG or LPG or petroleum naphtha into gaseous hydrogen

Storage safety: a study of ammonia (usually refers to anhydrous) storage in tanks and vessels, with OSHA regulation 1910.111 compliance analysis

Liquefied petroleum gas: a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, usually contains motor fuel propane with heavier molecular weight products during crude refining

Transport pipeline setting: a study of the LPG transportation with the pressure & temperature limits, and chemical sustainability, and electrostatic accumulation prevention

Storage safety: a study of LPG storage with consideration of OSHA 1910.110 compliance analysis

Chlorine: a toxic chemical compound with atomic number 17; a widely used disinfection material

Production process science: a study of large-scale production of chlorine, involving several steps and many pieces of equipment (The plant also simultaneously produces sodium hydroxide (caustic soda) and hydrogen gas somehow.)

Storage safety: a study of leaking prevention of large scale chlorine with vessel design, pipeline evaluation, and other potential parameters

3.2 Emission Analysis

Research>Emission Analysis

(Keywords: Research>Emission Analysis)

Two phase flow: the emission of two physical phase fluid flow

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Fauske flow: a empirical model of two phase flow, with correlation for the transition from single-phase to two-phase flow in fluid flowing from a vessel through an aperture or short pipe to atmosphere has been given

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Leung models: a model of one-component two-phase flow flashing, with consideration of homogeneous equilibrium model

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Device control phenomena: the study of device control in order to control the phenomena of emission

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Depressurization: a study of reducing pressure within a chamber or confined equipment to avoid structure damage

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Blowdown: removal of liquids or solids from a process vessel or storage vessel or a line by the use of pressure difference

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Rupture: a part of device or the phenomenon describing the damage of device structure due to interior collapse

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Vaporization: the phenomenon of liquid phase material become vapor due to pressure reduction or temperature increasing

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

3.3 Dispersion Analysis

Research>Dispersion Analysis

(Keywords: Research>Dispersion Analysis)

Dispersion influential factors: the parameters affecting the dispersion phenomenon

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Wind speed: the speed of flowing air, which is a significant part of dispersion analysis of hazardous release

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Atmospheric stability: the circumstances stability which is influential to particles or vapor movement, like in turbulent cases the particles in air move in a more chaotic way and ten not to stay in one layer

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Ground conditions: the condition of surrounding/nearby ground, i.e. temperature, wind speed, humidity, etc., which may affect the dispersion of particles

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Height of release above ground level: the vertical distance from the releasing source to ground

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Momentum and buoyancy of initial material: the momentum and buoyancy of the releasing chemicals, which are important factors of the floating ability for suspension and the velocity of movement

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Dispersion models: mathematical models for describing dispersion behaviors

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Neutrally buoyant dispersion models: the models used to estimate the concentrations downwind of a release in which the gas is mixed with fresh air to the point that the resulting mixture is neutrally buoyant (Thus these models apply to gases at low concentrations, typically in the parts per million ranges.)

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Dense gas dispersion models: models that simulate the dispersion of dense gas pollution plumes, such as DEGADIS, SLAB, and HEGADAS

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

3.4 Chemical Reactivity

Science>Chemical Reactivity

(Keywords: Science>Chemical Reactivity)

Reactive materials: the chemicals which has specific extent of tendency to react with other media, such as oxidizer

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Thermodynamic properties: the physical properties of state functions, such as internal energy, evaporation enthalpy, etc.

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Reaction energy: the energy released / absorbed from a chemical reaction

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Adiabatic temperature rise: The increase in temperature of a reacting mixture as a result of exothermic chemical reaction, when there is no heat transfer to or from the environment. ?T = ?H/Cp where ?T is the adiabatic temperature rise (K), ?H is the heat release (J/kg) and Cp is the mean heat capacity (J/kg/K).

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Gas generation: the gaseous product or side product generated during the steps of reaction processes

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Maximum pressure after reaction: As for the phase-changing chemical reactions

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Kinetic properties: the properties emphasizing on continuous, dynamic changes which should relate to the path of process, such as reaction rate; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Reaction rate: The amount of reactants consumption in unit reaction time; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

The rate at which the conversion of reactants takes place. The rate of reaction is a function of concentrations and the reaction rate constant. The heat (q) produced by a reaction is a linear function of the rate of reaction, which makes the rate of reaction a basic parameter in determining the required cooling capacity during all stages of the reaction process.

Reference: S2S (safety to safety website: HarsNet, HarsBook, A technical guide for the assessment of highly reactive chemical systems, DECHEMA e.V., Frankfurt, 2002.)

Rate of heat generation: the amount of heat released in reaction per unit time

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Rate of pressure rise: the amount of pressure increase in reaction per unit time

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Apparent activation energies: the energy that must be overcome in order for a chemical reaction to occur; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

In practice, reaction rates are often determined by physical processes (e.g. mass flow, diffusion, mass transfer area) as well as by chemical processes. The activation energy observed in these cases is called the apparent activation energy.

Reference: S2S (safety to safety website: HarsNet, HarsBook, A technical guide for the assessment of highly reactive chemical systems, DECHEMA e.V., Frankfurt, 2002.)

Decomposition energies: the energy for reactants to decompose into other species, i.e. the energy to break chemical bonds

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Reactive interactions: the interaction of reactive materials, i.e. the species of reactions which may reflect the hazard of chemicals in industry processes

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Instability: the tendency to spontaneously react with air, water, or easily-obtained/contacted media in the surroundings

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Polymerization: a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Pyrophoricity: phenomenon of a substance that will ignite spontaneously in air

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Peroxide formation: Materials that are susceptible to peroxide formation (i.e., auto-oxidation) are ones that typically react with air, moisture or impurities and produce a change in their chemical composition in normal storage. The peroxides that form are less volatile than the solvent itself and thus tend to concentrate. This is particularly dangerous if peroxides are present during a distillation, where the applied heat to the concentrated solution may trigger a violent explosion.

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Water reactivity: A reactivity issue of a group of organic reactions that take place as an emulsion in water and that exhibit unusual reaction rate acceleration compared to the same reaction in an organic solvent or compared to the corresponding dry media reaction; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

A substance presents reaction with water if a clear, intense, and usually very quick, exothermal reaction is observed when the substance is put in contact with water.

Reference: S2S (safety to safety website)

Oxidation: the interaction between oxygen molecules and other substances

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Runaway Reaction: A reaction that is out of control because the rate of heat generation by an exothermic chemical reaction exceeds the rate of cooling available.; References: S2S (safety to safety website: HarsNet, HarsBook, A technical guide for the assessment of highly reactive chemical systems, DECHEMA e.V., Frankfurt, 2002.)

Runaway reaction consequence: The result of a process that reaction rate is seriously increased due to temperature of other factors, causing abnormal acceleration of product formation and making the hazardous materials produced or large amount of heat accumulated; usually causing toxic release and explosion; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Runaway Scenario: The runaway scenario is a useful tool to assess the risks related to runaway reactions. It describes the temperature increase as a function of time after a loss of heat exchange (cooling failure). The construction of the scenario helps to assess both the severity of the consequences and the probability of occurrence of a runaway reaction.; Reference:S2S (safety to safety website:Ullmann’s Encyclopedia of Industrial Chemistry, Vol. B.8, 1995, Plant and Process Safety, VCH Verlagsgesellschaft, Weinheim, Germany)

Gas evolution: A chemical reaction that produces a gas, usually it comes from an aqueous solution

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Temperature: Reflection factor of internal heat change of a material

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Pressure: reflection factor of weight suffering on unit volume

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

3.5 Flammability

Science>Flammability

(Keywords: Science>Flammability)

Fireball: Type of fire in gaseous hydrocarbons or other flammable gas cloud that takes place in the periphery of the cloud.

Flash fire: The combustion of a flammable vapor and air mixture in which flame passes through that mixture at less than sonic velocity, such that negligible damaging overpressure is generated.; Reference: CPR 14E., 1997, Methods for the calculation of physical effects, p 6.11

Jet fire: A jet or spray fire is a turbulent diffusion flame resulting from the combustion of a fuel continuously released with some significant momentum in a particular direction or directions. Jet fires can arise from releases of gaseous, flashing liquid (two phase) and pure liquid inventories.; References: Health & Safety Executive.

Pool fire: A pool fire is a turbulent diffusion fire burning above a horizontal pool of vaporizing hydrocarbon fuel where the fuel has zero or low initial momentum. Fires in the open will be well ventilated (fuel-controlled), but fires within enclosures may become under-ventilated (ventilation-controlled). Pool fires may be static (e.g. where the pool is contained) or running fires. Pool fires represent a significant element of the risk associated with major accidents on offshore installations, particularly for Northern North Sea (NNS) installations that may have large liquid hydrocarbon inventories; References: Health & Safety Executive.

Essential elements of combustion: influential parameters of combustion

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Fuels: any material that stores energy that can later be extracted to perform mechanical work in a controlled manner

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Implosion: Sudden failure and collapse of a vessel or pipe due to an external overpressure causing forces surpassing strength of the vessel wall, ususally initated by a deviation of hull roundness.

Oxidizers: the compound combined by two oxygen atoms, playing the role of all the oxidation reactions in the biological and chemical reaction processes

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Ignition sources: the source that offers heat generation or energy storage medium to raise the temperature of material for the formation of flame

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Flammability parameters: the factors affecting the flammability of material

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Flash point: The lowest temperature at which it can vaporize to form an ignitable mixture in air; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Minimum temperature at which, under specified test conditions, a liquid gives off sufficient combustible gas or vapour to ignite momentarily on application of an effective ignition source.

Reference: S2S (safety to safety website: EN 1127-1: 1998, EN 1127-2:2002 (E), EN 13237:2003 (E))

Flammable limits: the proportion of combustible gases in a mixture, between which limits this mixture is flammable

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Autoignition temperature: the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Fire point: The temperature at which it will continue to burn for at least 5 seconds after ignition by an open flame

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Flammability and physical states: The physical states’ influence on material flammability

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Gas – Pure vapor/Mixture: The fraction of different gas species can affect directly the physical properties of the mixture, which is different from pure substances

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Liquid – Pure/Mixture: The fraction of liquid species can influence the component properties, which can affect the relative evaporation rate so that the according vapor phase flammability will change

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Aerosol: The suspension of droplets system in specific air space, containing more flammable mass than vapor and more flammable volume than liquid; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Aerosols are formed by diffusion of gases and liquids in air.

Reference: S2S (safety to safety website: Sharma 1992)

Aerosol Explosion: Similar to a vapor cloud explosion, but fuel is present as vapor and small droplets. The latter may enhance explosion power.

Solid materials: Usually focus on dusts, ashes, and other solid particles suspending in air space, with the hazard of explosion due to higher reaction surfaces

Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

Explosions: The rapid reactive shock wave releasing with fire balls and further combustion flame

Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

A sudden and violent release of energy, usually accompanied by the production of hot gas causing blast and a bang; the extent of violence depends on the rate at which energy is released.

Shock Wave/Blast: A gasdynamic phenomenon caused by an initial amount of pressurized expanding gas, which while expanding generates compression waves which develop and steepen into a supersonically propagating wave of a jumpwise pressure increase shaped as an abrupt peak followed by a gradual decay. A shock wave is characterized by its peak pressure, the material or wind velocity behind the front and the shape of the pressure decay which integrates to the shock impulse.

Fragments/Debris: Due to high pressure and the violence (brisance) of the explosion a (containment) wall/system may fracture with fragments being propelled and causing damage over a considerable distance.

Flame/Hot Gas: As many explosions involve hot gas often generated by exothermic combustion reactions, damage may be caused in the close vicinity by the associated flame.

Near Miss: An accident that is prevented at the last moment or is narrowly avoided.; Any unplanned event which, but for the mitigation effects of safety systems or procedures, could have caused harm to health, the environment or property, or could have involved a loss of containment possibly giving rise to adverse effects involving hazardous substances.; Reference: OECD Environment, Health and Safety Publications Series on Chemical Accidents No. 10, Annex 1, 2nd Ed., 2003.

Detonation: an explosion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it; usually this happens when there is confinement around the pressure releasing point; Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

Explosion propagating at supersonic velocity and characterized by a shock wave.

Reference: S2S (safety to safety website: ISO 8421-1(1987-03-01, 1.12), EN 1127-1: 1998, EN 1127-2:2002 (E), prEN 14460:2002 (E), EN 13237:2003 (E))

A reactive shock wave: due to the temperature jump associated with the compression of a material of a pure substance or a mixture at the front of a shock wave a reactive substance can decompose exothermally. When reaction is fast enough (reaction zone Chapman-Jouguet condition) the generated energy will in part be used to sustain the shock resulting in a steady state process. Pressure and propagation velocity depend on energy generated, while in condensed substances pressures will be a thousand times higher than in gases.

Deflagration: a subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it); Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

Explosion propagating at subsonic velocity.

Reference: S2S (safety to safety website: ISO 8421-1(1987-03-01, 1.11), EN 1127-1: 1998, EN 1127-2:2002 (E), prEN 14460:2002 (E), EN 13237:2003 (E))

A propagating exothermic decomposition zone which generates hot gases (flame) resulting in pressure build-up. The propagation speed can vary over a wide range depending on substance structure, its phase, and feed-back processes from pressure increase and turbulence causing flame acceleration but the velocity is always subsonic relative to the local sound velocity.

(Exo-)thermal explosion: Accelerating thermal decomposition by self-heating depending on the balance of heat generated and heat loss to the environment. In contrast to detonation and deflagration, reactions take place throughout the substance. In the case of confinement, pressure increase can further accelerate the process. Also typical is the occurrence of auto-catalysis which plays a role at the start of reactions when decomposition products enhance reaction rate.

Confined explosions: explosions happening in congested region, with higher pressure increase and shock wave transport speed; Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

Type of explosion in a liquefied hydrocarbon or other flammable gas cloud in a confined space, such as vessels, pipelines, buildings, etc. The expanding of combustion products inside the container results in a major explosion and possible damage to personnel as well as to the industrial facilities.

Reference: S2S (safety to safety website)

Unconfined explosions: explosions happening in relative open space; Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

Type of explosion in a liquefied hydrocarbons or other flammable gas cloud in a non-confined space.

Reference: S2S (safety to safety website)

Vapor explosions: the explosion occurring with the rapid vapor reaction

Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

Compressed Gas/Vapor Explosion: Failure of containment under internal gas pressure associated with a bang. This will be caused by surpassing the actual strength limit as a result of continual compression, by fatigue resulting from repeatedly depressurizing and pressurizing activities, by wall thinning due to corrsoion, erosion or chemical attack, or by a gas explosion inside. The explosion appears as a rupture of the containment and a blast sometimes with generation of fragments.

Gas Explosion: Similarto a vapor cloud explosion but within a confined space, hence resulting in a constant volume explosion leading to higher pressures within the containment. Oxidizer is often air but may be pure oxygen, nitrous oxide or chlorine and many less common other ones. Fuels are mostly hydrocarbons.

Dust explosions: the fast combustion of dust particles suspended in the air in an enclosed location; Reference: Gexcon Handbook http://www.gexcon.com/handbook/GEXHBchap2.htm

A mixture with air, under atmospheric conditions, of flammable substances in the form of dust or fibers in which, after ignition, combustion spreads throughout the unconsumed mixture.

Reference: S2S (safety to safety website: EN 50281-3:2002 EN 50281-1-2:1998 EN 50281-1-1:1998 and EN 13237:2003 (E).

Similar to a gas explosion but with a fuel in the form of combustible particles. These can be agricultural products, organic powders or finely divided metals.

Condensed Phase Explosion: Deflagration or detonation of a solid or liquid substance or mixture of substances.

Runaway Reaction & Explosion: This is a (exo-)thermal explosion during a chemical process operation such as a batch, semi-batch or continous reactor process, but also possibly during drying, storage, distillation, evaporation, etc. Often part of the substance deflagrates initated by the thermal run-away. Also this phenomenon will often be associated with hot expanding gases fragmenting containment causing a blast, penetration and fire damage. In some cases a violent secondary vapor cloud explosion occurs after mixing of hot gaseous reaction products with air.

Explosions characterization methods: ways of studying the explosion properties, including temperature, pressure raise, and flame scale, shock wave transport…etc

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Explosion energy: the energy release after explosion happens

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Suppressants: the media or device which can eliminate the fire by reducing the heat, combustible materials, and amount of pressure change; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Substance contained in the HRD-Suppressor which, when dispersed into a volume to be protected, can arrest or prevent a developing explosion in that volume. Three categories of suppressants are in general use, separately or in combination (powder, water, chemical suppressants).

Reference: S2S (safety to safety website: prEN 14373:2002 (E))

Effect on flame developments: the suppressant influence on the formation, propagation, and quenching of flame

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Fire protection system: the materials with fire resistance, sprinkler system enclose, or available personnel protection devices to mitigating the unwanted effects of fires

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Prevention design: the design of fire prevention or protection

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Inerting: the concept of “not readily reactive with other elements; forming no chemical compounds or something that is not chemically reactive” being put into application for industry operations; usually used for increasing storage tank safety

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Vacuum purging: a most common inerting procedure for vessels, including drawing a vacuum on the vessel, relieving the vacuum with inert gas, and repeating above steps until desired concentration is reached

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Pressure purging: Vessels can be pressure-purged by adding inert gas under pressure. After this added gas is diffused throughout the vessel, it is vented to the atmosphere, usually down to atmospheric pressure.

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Sweep-through purging: purging process adds purge gas into a vessel at one opening and withdraws the mixed gas from the vessel to the atmosphere (or scrubber) from another opening. This process is generally used when the vessel or equipment is not rated for pressure or vacuum.

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Siphon purging: A modification of sweep-through purging; the purging process start by filling the vessel with liquid (water or other). The purged gas is subsequently added to the vapor space as the liquid drained from the vessel.

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Static electricity: the buildup of electric charge on the surface of objects

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Charge accumulation: the staying charges in the device due to the property of static electricity — remain on an object until they either bleed off to ground or are quickly neutralized by a discharge

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Electrostatic discharge: the sudden and momentary electric current that flows between two objects at different electrical potentials

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Streaming current: an electric current or potential which originates when an electrolyte is driven by a pressure gradient through a channel or porous plug with charged walls

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Voltage drops: the reduction in voltage in the passive elements (not containing sources) of an electrical circuit

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Capacitance of body: the ability of a body to hold an electrical charge

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Explosion-proof equipment: electrical apparatus (such as compressors, motors, and switches) designed to contain explosions or flames produced within them (due to arcs, sparks, or flashes) without igniting the surrounding (external) flammable gases or vapors; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Any electrical equipment designed to be installed, used or introduced in areas where explosive atmosphere can be present. It must have a declaration of conformity adequate to the type of zone and must be properly CE marked.

Reference: S2S (safety to safety website)

Ventilation – Open air plants/Plant inside buildings: the system designed for offering an exit for extra heat or vapor can be released to outside area to prevent overpressure or overheat; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Sprinkler: An active fire protection measure, with perforations through which water issues from a hose to sprinkle.; Reference: S2S (safety to safety website)

Sprinkler systems: an active fire protection measure, consisting of a water supply system, providing adequate pressure and flow rate to a water distribution piping system, onto which fire sprinklers are connected; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Boiling liquid expanding vapor explosion (BLEVE): Is the condition that happens suddenly when a tank containing pressurized liquefied hydrocarbons or other liquefied gas, produces an explosive effect due to its contact with fire or impact. The liquid in the tank rapidly absorbs the energy from the surrounding atmosphere which increases the vaporization rate. When this pressure exceeds the safety limits of the tank, failure occurs and causes a massive explosion. This phenomenon may result in fireballs, blasts, projectiles and possible toxic clouds, or vapor cloud explosions.

Boiling Liquid Expanding Vapor Explosion occurs due to a contained liquid being heated externally above its boiling point at atmospheric pressure. Once a crack in the containment allows the superheated liquid to depressurize it starts suddenly to flash vaporize producing much gas rupturing the vessel and producing a blast and maybe fragments. As many liquids are flammable a BLEVE may result in a rising flame ball with a very high surface emitting power. Radiant heat damage in that case is over a larger area than the that by blast. However non-flammable liquids can also BLEVE. Water in a steam vessel is a notorious example with many associated fatalities.

Rapid Phase Transition Explosion: RPT is an explosive boiling off of a cryogenic liquid such as LNG on a much warmer liquid substrate surface, e.g., water. Threshold limits of accumulating higher boiling components (e.g., ethane and propane) have an influence. Effects of the explosion are weak.

Vapor Cloud Explosion: Due to dispersion of a gaseous fuel in air and ignition a deflagration (flame) propagates through the cloud. Obstacles (congestion) and confinement can generate turbulence in the moving gas resulting in flame acceleration and higher pressures/blast. Most VCEs are deflagrations but a deflagration transition into detonation is certainly possible.

Zoning: The geographical result of an examination of an area in a facility to assess Fire and Explosion risks.; This is usually relevant to the ATEX evaluation.

3.6 Toxicity

Science>Toxicity

(Keywords: Science>Toxicity)

Health hazards: the harm caused by toxic material release or contamination

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Acute toxicity: the adverse toxic effects of a substance which result either from a single exposure or from multiple exposures in a short space of time (usually less than 24 hours)

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Chronic toxicity: a property of a substance that has toxic effects on a living organism, when that organism is exposed to the substance continuously or repeatedly

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Environmental hazards: the harm caused by toxins to the nature

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Aquatic toxicity: the toxins existing in aquatic systems

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Atmospheric toxicity: the toxins existing in atmosphere layers

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Dose and response models: the change in effect on an organism caused by differing levels of exposure (or doses) to a stressor (usually a chemical) after a certain exposure time

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Lethal dose: an indication of the lethality of a given substance or type of radiation

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Effective dose: the amount of drug that produces a therapeutic response in 50% of the subjects taking it, sometimes also called ED-50

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Probit correlations: a popular specification for a binary response model that employs a probit link function, showing maximum likelihood results

Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

Threshold Limit Value (TLV): A level to which it is believed a worker can be exposed day after day for a working lifetime without adverse health effects; Reference: Chemical Process Safety – Fundamentals with Applications, 2nd Ed., Daniel A. Crowl/Joseph F. Louvar

A term to express the airborne concentration of a material to which nearly all persons can be exposed day after day without adverse effects. References: The Center for Chemical Process Safety of the American Institute of Chemical Engineers. Safety Health and Loss Prevention in Chemical Processes. 345 East 47th Street, New York, NY 10017, 1990.

3.7 Other Field of Study

Science>Other Field of Study

(Keywords: Science>Other Field of Study)

Crisis management (Abnormal situation diagnosis): The ensemble of the activities under direct responsibility of the Civil Protection Authorities that cover the following operational phases: emergency planning, emergency control and post-accident assessment.