16 HAZOP

A hazard and operability study (HAZOP) is a systematic examination of a process to assess the hazard potential of off normal operation or malfunction of individual items of equipment and the consequential effects on the facility. HAZOP is only one of the tools used in a PRA and should be seen as complementary to other techniques, such as FMEA. The HAZOP is qualitative and aims to stimulate the imagination of participants to identify potential hazards and operability problems. Structure and completeness are given by using guideword prompts.

General HAZOP procedure

  1. Select component
  2. Take note of the Design Intention
  3. Select a process parameter
  4. Combine with a guideword to form possible deviation to normal operation
  5. For each deviation, identify possible causes and consequences
  6. Evaluate existing protections for adequacy
  7. Suggest suitable action to improve operability
  8. Continue with other guidewords and repeat
  9. Select new process parameter and repeat
  10. Select next parameter and repeat

General HAZOP

HAZOP common guideword combinations

Parameter/Guideword More Less None Reverse As well as Part of Other than
Flow high flow low flow no flow reverse flow deviating concentration contamination deviating material
Pressure high pressure low pressure vacuum delta p explosion
Temperature high temperature low temperature
Level high level low level no level different (wrong) level
Time too long/too late too short/too soon sequence step skipped backwards missing actions extra actions wrong time
Agitation fast mixing slow mixing no mixing
Reaction fast reaction/runaway slow reaction no reaction unwanted reaction
Startup/Shutdown too fast too slow actions missed wrong recipe
Draining/Venting too long too short none deviating pressure wrong timing
Inertising high pressure low pressure none contamination wrong material
Utility failure (instrument air, power) failure
Maintenance none
Vibrations too high too low none wrong frequency

License

Icon for the Creative Commons Attribution 4.0 International License

Risk Assessment Copyright © 2015 by R.A. Borrelli is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book