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