Hazop Analysis:
During Hazop analysis an interdisciplinary team uses a systematic approach to identify hazards and operability problems occurring as a result of deviations from the intended range of process conditions in a particular scenario and in a particular node. An experienced team leader systematically guides the team through the plant design, using a fixed set of guidewords, which are applied to specific process parameters at discrete locations or study nodes in the process system. The study node may be either a discrete point of the process system or it may be a particular run of piping or particular procedure or action.
The team analyses the effect of any deviations at the point of question and determines the possible causes for the deviation (operator error, blockage in outflow, malfunction of control system etc.).The consequence of deviations (e.g. spillage of liquid/solid, pollution etc.) and the safeguards in place or required, are analyzed to prevent the deviation. If the causes and consequences are significant and the safeguards are inadequate the details of recommendations are recorded so that follow-up action can be taken. Recommendations for changes are for design, procedures etc. to improve the system for each node studied.
Process node and its characteristics:
Hazop is done on a discrete part of the process called nodes (part of the process/equipment/action/procedure) which have some design intents and normal operating parameters ;and deviations therein due to some u/s, d/s or within causes actualize the deviation and ultimately the consequence. Node has following characteristics:
- Shares the same design intent.
- Single process operation
- Involves critical parameter
- Contains an active component which causes deviations.
- Contains significant amount of hazardous materials
Deviation:
A process or procedure does not work as intended.
Hazop Study/Analysis Steps:
Are shown in the following diagram
Inputs/ information needed for HAZOP
- Process Description
- Process flow diagrams
- Piping and instrumentation diagrams (P&IDs)
- Heat and material balances
- Isolation, Venting/Flaring/Draining Philosophies
- Material Selection Diagrams
- Layout diagrams
- Material safety data sheets
- Provisional operating instructions
- Equipment data sheets Start-up and emergency shut-down procedures
Modes of operation to be considered:
- Normal operation (Mandatory)
- Reduced throughput operation(Optional)
- Routine start-up(Optional)
- Routine shutdown(Optional)
- Emergency shutdown(Mandatory)
- Commissioning(Optional)
- Special operating modes viz. Catalyst Regeneration, Coker Furnace Decoking etc. (Optional)
Parameters of Node to be studied:
•Flow
–It is the easiest parameter to visualize and determine the effects of changes
•Pressure
–Pressure leads to many of the most common hazards.
•Temperature
–High temperatures may cause fire.
–Low temperature may lead to operational and safety issues
•Level
–Level is only relevant inside vessels.
•Phase
•Composition
Guide words
•No:
–the intention can fail completely
–No flow when there should be
•More
–quantitative increase
–More of any parameter than there should be
•Less
–quantitative decrease
•As Well As
–qualitative increase.
•Part of
–qualitative decrease
•Reverse
–logical opposite of intention
•Other than
–Identify something completely different (substitution)
•Early
–something happens earlier in time than intended
•Late
–something happens later in time than intended
•Before
–something happens earlier in a sequence than intended
•After
–something happens later in a sequence than intended
•Faster
–The step is done in less time
•Slower
–The step is done in more time
Following premises are not considered in HAZOP study:
- Hazop is not a design review.
- Simultaneous occurring of two unrelated incidents (unrelated electrical, mechanical or large time gap between two events) is not considered due to very low probability.
- Natural Calamity (e.g. Earthquake, Flood, Cyclones etc.) .In some countries it is also part of Hazop.
- Sabotage is analyzed in some countries
Hazop Sample Worksheet
| Project Name: | |||||||||
| Process Unit | |||||||||
| P&ID No. | |||||||||
| Node No. and Brief Description of Node | |||||||||
| Sl No. | Parameter | Deviation | Cause | Consequence | S | L | R | Recommendation | Responsibility |
| 1 | Flow | No | |||||||
| High | |||||||||
| Low | |||||||||
| Reverse | |||||||||
| 2. | Pressure | No | |||||||
| High | |||||||||
| Low | |||||||||
| 3. | Temp | No | |||||||
| High | |||||||||
| Low | |||||||||
| 4 | Level | No | |||||||
| High | |||||||||
| Low | |||||||||
| Low | |||||||||
| 5. | Startup | Early Action | |||||||
| Late action | |||||||||
| No Action | |||||||||
| 6. | Shutdown | Early Action | |||||||
| Late action | |||||||||
| No Action | |||||||||
| Emergency shutdown | |||||||||
| 7. | Procedures | Operating Procedures/Instructions | |||||||
| Standard Operating Procedures/Instructions | |||||||||
| 8. | Draining | ||||||||
| 9. | Purging | ||||||||
| 10 | Isolation | ||||||||
| 11. | Venting | ||||||||
| 12. | Emergency Depressurisation | ||||||||
| 13. | Asset Integrity management | ||||||||
| 14. | Inherent Safety in Design | ||||||||
| 15. | Inter unit and inter equipment distances | ||||||||
| 16. | Fire Fighting | ||||||||