Layers of Protection Analysis (LOPA) is a method applied to determine the adequacy of independent protection layers and the required integrity level for an instrumented function for safety (LOPA SIL), environmental (LOPA EIL), or commercial (LOPA CIL) hazards.
It is a multi-disciplinary workshop-based methodology where the participants validate the hazard scenario from the hazard analysis; assess the consequences of the hazard scenario, its initiating causes, their likelihood, the independent protection layers, and other risk modifying factors. LOPA is similarly structured to other workshop-based methodologies such as HAZOP, HAZID, FMECA, etc. However, LOPA requires more effort from all involved parties during the preparation period prior to the workshop. The main concerns regarding the outcome of a Layers of Protection Analysis are:
Too low SIL, EIL, CIL (or no IL required) for hazard scenarios where additional risk reduction is required. It leads to the insufficient design of safety barriers increasing the risk of major accidents;
Too high SIL, EIL, and CIL which, in turn, leads to overdesigned systems with consequent increase of CAPEX and/or OPEX;
Independent protection layers (IPLs) not conforming to specificity, independence, dependability, and auditability requirements;
IPLs are not properly evaluated in terms of effectiveness in achieving the targeted risk reduction.
ORS performs Layers of Protection Analysis continuously for multiple clients around the world. Our experience is that, when preparation activities are given sufficient time and importance, the quality of a LOPA increases remarkably. More specifically, successful LOPAs usually have the following similarities:
Process hazard analysis (typically a HAZOP), conducted prior to the LOPA, where hazard scenarios have been clearly identified and risk-ranked based on consequence and applicable risk acceptance criteria;
Layers of Protection Analysis facilitator and scribe are competent and well prepared for their roles;
A detailed terms of reference document is prepared, prior to the Layers of Protection Analysis, listing all required documentation, and hazard scenarios, and including relevant information to assess the validity of initiating causes and adequacy of IPLs;
A competent, experienced, and well-prepared multidisciplinary team not exceeding eight full-time participants in order to enable accurate assessment and decision-making.
You are welcome to contact one of our specialists to discuss how we can help you carry out successful Layers of Protection Analysis.
Read also our article about: "Quantifying uncertainties in LOPA"