We provide chairpersons and scribes to HAZOP and LOPA/SIL studies. Many companies prefer to hire these from outside their organisations for reasons of independence and specific expertise. The rest of the team – consisting of domain experts – is provided by the client.
In a HAZOP (Hazard and Operability) study, the plant design is broken up in sections or nodes. Of these, the normal operating mode is defined. HAZOP identifies deviations with the aid of guidewords, and potential consequences and safeguards. If necessary, recommendations are defined by the team. If required by Client, the risks of the identified scenarios can be rated against a companies’ Risk Matrix.
A LOPA (Layer of Protection) study is a semi-quantitative appraisal of scenario risks, usually carried out on unacceptable risk scenario’s identified in the HAZOP study. All layers of protection – that prevent the final outcome of a scenario, e.g. an instrumented safety system – are identified and their Probability of Failure on Demand (PFD) estimated. The result is an estimation of the residual risk after application of the available layers of protection. If the residual risk is still above companies’ standards, extra measures are needed. A LOPA study can also be used to determine the required Safety Integrity Level (SIL) of instrumented safeguards to arrive at a risk level acceptable to the company..