How Long between Cause and Consequence in a PHA? | AIChE

How Long between Cause and Consequence in a PHA?


Conference Presentation

Conference Type

AIChE Spring Meeting and Global Congress on Process Safety

Presentation Date

April 21, 2021


20 minutes

Skill Level




How much time should a Process Hazard Analysis (PHA) team consider between a discrete cause and a credible consequence? OSHA 1910.119(e) requires that all Process Hazard Analyses (PHAs) review and document the “consequences of failure of engineering and administrative controls.” The generally accepted best practice for fulfilling this is to document scenario consequences without safeguards.

The problem is that we know that even a small deviation can result in a major change in a process given enough time. Because of that, in almost every PHA there is an assumption made (documented or otherwise) about the timeframe for a cause to lead to a consequence. Are PHA teams consistent in the assumptions they make? What do regulators and industry groups have to say? How long has elapsed between causes and consequences in real incidents? How can you make sure your PHA teams are consistently following your guidelines and best practices?

In this presentation, the presenter will review industry publications, data, and real process safety incidents to compare how PHAs compare to reality. Finally, we will examine ways to make your PHAs more consistent in a way that reflects likely issues which could occur in your process.


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