The HAZOP technique was originally developed almost 40 years ago and is now the most popular method to identify and manage hazards on process plants worldwide. Even though hazard identification is the key focus, operability problems should be identified to understand if they have the possibility to result in process hazards.
HAZOP is applied to identify:
- Hazards – the ways in which a system can fail leading to injury or damage
- Operability – the ways in which a system can fail to perform its intended function
The success or failure of the HAZOP study depends on several factors:
HAZOP study emphases on specific sections of the process named “nodes”. Usually the nodes are identified from the P&ID of the process before the HAZOP commences. A process parameter is taken into consideration and an intention is generated for the associated node. Then a sequence of guidewords is used with the parameter to form a deviation. The procedure is repeated for the subsequent deviations and it continues until the particular node is finished. The focus is then changed to the following node and the procedure is repeated.
The HAZOP study should preferably be carried out as early in the design phase as possible – to have inﬂuence on the design. However, HAZOP Study is undertaken at various stages of project with specific purposes. These are summarized in the following table:
|HAZOP Methodology||Purpose of HAZOP Study|
|FEED Stage||Identify major hazards and check for availability of key hazard data.||To plan for mitigation right from the design stage.|
|During Basic Engineering||HAZOP using flow sheet and block diagram.|
|Before Commissioning||Full HAZOP on frozen P&I diagram.||To fine tune process control methodologies. To define Safe Operating Procedures. To define safe operating limits.|
|During Operation||HAZOP on P & I diagram, SOPs, safety features and control methodology. Check that all intended actions have been implemented, including hardware and software.||To identify existing operational deviation which may lead to potential HSE hazard. To assess the adequacy and efficacy of existing safeguards to prevent unwanted consequences.|
|Major Change in a Process||As Above.||As Above.|