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PW 2348 Study on the relative impact of human factors on layers of protection in a process safety review
  1. Sivasubramanian Ramasamy
  1. Farabi Petrochemicals Company, Jubail Industrial City, Eastern Province, Saudi Arabia


Human life is priceless. Hence, any loss of human life, either single or multiple fatalities or injuries shall be prevented by all means.

In the past, Chemical Hazards in the work places had resulted in multiple fatalities and affected the community. SVESO, CHORNOBYL, 3 MILE ISLAND, TEXAS CITY and BHOPAL DISASTER are a few to remember forever. They all had one thing in common – Human Error, either as root cause or as a contributing cause.

While best engineering practices aim at better and reliable safety systems derived from the recommendations of Process Safety Review (PSR) with Layers of Protection (LoP), we should remember that a Plant Operator or a Supervisor could override the protection thus breaking the chain, as no human is perfect.

This article is focusing on the inevitable inter-relationship between Human Factors (HF), LoP and PSR, entwined in a crystal lattice of Safety Performance.

The requirement of each LoP is ascertained by the PSR. While the Safe Operating Envelop is an active protection layer, it depends on human decision making skills. Whereas the Safe Design Envelop is a passive protection system depending on Safety Instrument Systems. When both layers fail, Emergency Response is the final layer, effective unless the manpower is trained, ready and willing to take the risk. Anything beyond this is a disaster.

From the above, it is evident that in every Layers of Protection, there is human involvement/interference to some extent. This influence will determine the success of a Safety System’s performance and therefore need more reliable and robust methods to identify the possible Human Failure Factors in a PSR.

This paper will deal with the relative impact of Human Factors on Layers of Protection in detail and would look for a possible solution to sustain/enhance the performance of Safety Systems.

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