Layer Of Protection Analysis

By Tabitha Mishra
Last updated: October 31, 2017

What Does Layer Of Protection Analysis Mean?

Layers of protection analysis (LOPA) is a method of risk assessment used in high-risk scenarios. It evaluates the layers of protection for process risks to determine whether they are adequate.

LOPA is a balance approach that falls somewhere between a simplified qualitative process hazard analysis (PHA) and a more detailed and costly quantitative risk analysis.

Safeopedia Explains Layer Of Protection Analysis

LOPA is used by companies that are striving to achieve a specific risk target or to ensure that their risk levels are as low as reasonably practicable (ALARP). It allows companies to ascertain the level of risk associated with hazardous events, based on both the severity of those events and the likelihood that they will take place.

LOPA uses rules and clearly defined criteria to provide more reliable results than those obtained through a process hazard analysis. It helps focus limited resources on the most critical safeguards to identify those that are most essential, such as employee training, operations, and equipment maintenance. This allows companies to avoid implementing more safeguards than are necessary to actually reduce risk.

LOPA Methodology

Prior to beginning a layers of protection analysis, an organization must define their tolerable frequencies for high-consequence events. The analysis is then conducted to for a specific scenario to determine whether its potential outcomes fall within those tolerable frequencies.

The steps for conducting a LOPA are as follows:

  • Identify and define the undesirable impact or consequence
  • Determine what events could initiate the undesirable impact
  • Determine and list available layers of protection for preventing the initiating event from creating an undesirable impact
  • Quantify from existing data and engineering judgment how frequently the initiating events take place
  • Quantify based on existing data and engineering judgment how effective the existing layers of protection are in terms of PFD (probability of failure on demand)
  • Calculate the resulting frequency of the undesirable impact

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