Kumar Bhimavarapu, Factory Mutual Research


Machine Safety February 1, 2000

Use Layer of Protection Analysis (LOPA) to Comply with Performance-based Standards

T he performance-based standards ANSI/ISA S84.01, IEC 61508, and IEC d61511 mandate the use of risk assessment techniques to meet the established target risk level(s) for a process. Different risk assessment techniques that are quantitative, qualitative or semi-quantitative in approach are used to evaluate the process risk and identify the safety systems needed to meet the target risk levels. Such an analysis of process safety requirements is called Safety Integrity Level (SIL) analysis. Semi-quantitative risk assessment techniques are used to derive most of the benefits of the quantitative techniques, and to minimize the resources necessary for a rigorous quantification of risk.

By Kumar Bhimavarapu, Factory Mutual Research