Layer of Protection Analysis (LOPA) is a tried and tested technique for determining the effectiveness (or otherwise) of safeguards, protection layers and safety instrumented functions for providing risk reduction as protection from the hazards identified for a given process. The hazard identification would often be as a result of an earlier Hazard and Operability Study (HazOp).
A LOPA meeting would normally be chaired by an experienced chair who is an expert in the application of the technique. The LOPA also relies on the experience and expertise of others present in the meeting – and the success of the LOPA relies heavily on the team assembled to work through the process, under the guidance of the LOPA chair. In large meetings, a LOPA scribe may also be appointed to record the decisions and reasoning behind them – as it can be difficult for the LKOPA chair to run the meeting and also keep the notes, hence the need for the scribe.
During a LOPA (based on a particular approach, agreed in advance of the meeting and recorded and approved in the “Terms of Reference”), the various safeguards which might provide risk reduction for the various hazard scenarios are analysed to determine their effectiveness in providing protection. They are also analysed to determine their independence from other safeguards and from the event which triggers (or initiates) the hazardous event – as safeguards which are not independent cannot be relied upon. Once the effectiveness of existing safeguards has been established, it is a simple step to determine if further risk reduction is needed to achieve a “tolerable” risk and – if so – how much additional risk reduction is required.
As with HazOp, while LOPA may be considered to be part of the “Process Safety” of a particular application, it would normally form one of the early stages of the Functional Safety Lifecycle (as defined by IEC 61511), so the approach to LOPA must recognise the need for verification, functional safety assessment and traceability to earlier and later lifecycle phases. The LOPA must be structured so as to allow for (and facilitate) these elements. The LOPA is not an end itself, but part of a broader approach and this must be recognised in the design and documentation of the LOPA.
=Method can provide expert LOPA chairs and scribes, who will use our tools and templates to deliver a LOPA that is effective, efficient and (as far as is possible) enjoyable. Our approach ensures that the tasks that follow the LOPA (the verification, the functional safety assessment and writing of the Safety Requirement Specification) are recognised and supported. =Method can also deliver those follow on tasks if required.
Or if you wish to develop your own expertise in this area, =Method can train and coach you to take on roles in the LOPA yourself.
If you have any enquiries about our Process Safety Consultancy services please call us on 01462 713313 or contact us online.
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