Swiss Cheese and Plant Safety

By Paul Miller

Industry Trends

PRACTICAL SAILOR magazine, the “Consumer Reports” of the sailing world, recently published an online article on fatal safety accidents during recent long-distance ocean races. These largely preventable accidents involved inexperienced crewmembers who had no business being on serious ocean-racing sailboats. The article, Risk Management and Renting Adventure: Applying the ‘Swiss Cheese Safety Analogy’ to bluewater sailing, has an obvious parallel in the industrial plant safety world.

Lessons in Plant Safety from the Aeronautics World

Interestingly enough, just as the FACE (Future Airborne Capability Environment) approach from the aeronautics world provides a model for the current Open Process Automation (OPA) initiative that continues to attract so much attention at ARC Industry Forums, the “swiss cheese” safety analogy also has its roots in aeronautics.

As explained in this article, Charlie Pucciariello, a former top Navy F-14 pilot and one of the three safety experts highlighted in the PRACTICAL SAILOR article, “…swapped his F-14 for an Airbus and become a commercial airline pilot with smooth rides and soft landings replacing top-gun maneuvers. His second career introduced him to what’s euphemistically known as the ‘Swiss cheese safety analogy.’ It’s an internationally recognized theory and a part of Cockpit Resource Management for pilots.”

As we learned, “The cheese theory looks at accident prevention in the context of a stack of sliced Swiss cheese. Each slice has randomly located holes, and these holes represent a shortfall that can lead to a failure. When slices are stacked, there’s a good chance that the holes are covered by other slices. In the case of sailing, we could label each slice of cheese with names such as design, engineering, manufacture, maintenance, crew skill, decision-making, safety gear, etc. The premise is that only when a hole is contiguous with other holes, and a tunnel extends from one side of the stack to the other, will an accident occur.”

It doesn’t take much of a leap of faith to also extend this analogy to industrial safety, where “design, engineering, manufacture, maintenance, crew skill, decision-making, safety gear, etc.” also play a major (and interactive) role in how and why industrial accidents occur.

“It’s the contributory factors that really need to be scrutinized. There’s often a domino effect in play. It may be either a series of omissions, commissions, or a combination of both that leads to the incident. In some cases, it may be as simple as the right piece of hardware mounted incorrectly that puts the crew at risk. Or it may be a design flaw that affects boat [plant] stability… Stability and strength are two key assets of an offshore racer or cruiser, and the implications of vessel design and material specifications show up in slices of our nautical Swiss Cheese—the fewer and smaller the holes, the better.”

Layers of Protection Can Overcome the Swiss Cheese Effect to Help Avoid Industrial Accidents

In well-designed, well-constructed, and well-instrumented industrial facilities, established “layers of protection” (process design, basic process control, alarms and manual intervention, safety integrated systems, pressure relieve valves, physical containment, etc.) should make it difficult, if not impossible for those “swiss cheese holes” to line up and thus avoid serious industrial accidents. But since industrial accidents continue to occur (consider the combinations of events that created the Deepwater Horizon or Fukushima disasters, for example), it’s obvious that industry as a whole has to pay more attention to those layers of protection, including ensuring that the “crew members” that staff our facilities have the appropriate training, mentorship, and technology tools.

Layers of Protection in Process Plant Safety

In industrial facilities, well-established Layers of Protection (LOP) should ideally keep the “Swiss Cheese Holes” from lining up to prevent serious industrial accidents

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