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PT Notes

Process Safety Incidents, Safety Goals, and Risk Tolerance Criteria

PT Notes is a series of topical technical notes on process safety provided periodically by Primatech for your benefit. Please feel free to provide feedback.

A recent analysis of 68 incidents investigated by the Chemical Safety Board (CSB) identified lack of attention to safety goals and risk tolerance criteria as a key contributor to incident causation. Most companies do not really know what risk their process facilities pose because they do not evaluate risk as there are no requirements to do so under the current US federal process safety regulatory regime. Indeed, it is possible that similar facilities may pose quite different risks because the regulations do not contain any safety goals or risk tolerance criteria.

The goal of process safety programs is to ensure safety and control risks. Consequently, some form of safety goals or risk tolerance criteria are needed. Measures are needed to determine achievement of goals and criteria. In the absence of process safety goals and measures to determine their achievement, resources may be allocated inappropriately. There is a current precedent for the use of numerical risk tolerance criteria provided by the New Jersey Toxic Catastrophe Prevention Act (TCPA). Although the particular approach used is erroneous, companies in the state have accepted the use of numerical criteria.

Many jurisdictions around the world employ the tolerability of risk framework developed by the UK HSE including the As Low As Reasonably Practicable (ALARP) principle. Its use should be incorporated into US regulations. Although the ALARP principle usually employs numerical criteria, it can be used without specifying such criteria but using its essential element that risk should be reduced until the incremental expenditures of resources is grossly disproportionate to the value of the incremental risk reduction achieved. This is a performance-based requirement that is consistent with the current philosophy of US process safety regulations. Use of the ALARP principle would help to accommodate improved process safety practices without the need for periodic modification of regulations.

This topic is addressed in the articles:

Insights into process safety incidents from an analysis of CSB investigations, Journal of Loss Prevention in the Process Industries, Volume 43, pages 537–548, September, 2016.

The ALARP principle in process safety, Process Safety Progress, Vol. 33, Issue 1, pages: 36–40, March 2014.

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