- 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
Management/Process Safety Information and Knowledge/Process Design