Use Elegant Design to Bolster Inherent Safety

Embrace a variety of strategies that can eliminate hazards from operations

By Kelly K. Keim and Scott W. Ostrowski, ExxonMobil Research and Engineering

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You could try training your personnel on the proper location for the lock. You could put a sign on the cabinet to indicate where the lock goes. Then you could realize operators will hang the lock in the wrong location before they look for a sign that would tell them the right location — and put another sign on the wrong location that says: “Lockout lock does not go here!” However, eventually even that sign becomes just background noise.

We tried all these things before happening upon a solution that worked — cutting off the hasp on the door handle!

An operator knows a lock must be placed on the switchgear. Now, if the operator forgets exactly where the lock should go, the person will think about it and either come up with the right — and only — solution or ask. The possibility of making a mistake no longer exists.

Is this an inherently safer switchgear? Yes.

Does it fall into one of the four basic inherent safety strategies? Not really, although it may be a form of mistake proofing.

The Key To Success

Application of inherent safety principles is just one aspect of making safety second nature. For each situation, other approaches may be equally effective as the basic four and may be economically feasible when none of the four are. Moreover, it’s important to realize that mandating the use of inherent safety is like placing signs throughout the workplace that say: “Be Safe.” Each has little benefit until you have translated the mindset into practical application.

You achieve expertise in the practical application of inherent safety principles through the diligent and repeated search for and application of inherently safer solutions. This experience is what makes a safety engineer effective and a process plant a safer place to earn a living. You train your brain to spot applications for solutions you’ve seen before and you apply principles you’ve used before to solve new problems. The end result is a mindset that makes safety second nature.

KELLY K. KEIM is chief process safety engineer for ExxonMobil Research and Engineering, Baytown, Texas. SCOTT W. OSTROWSKI is a senior process safety engineering associate for ExxonMobil Research and Engineering in Baytown. E-mail them at and

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  • <p>One of the flaws in the scrubber solution may be the need for a high-pressure spray nozzle to provide semi-atomized droplets to the face of the scrubber packing. I've tried troughs in this application but they are quickly plugged and replaced by spray nozzles. </p> <p>Typically, these spray nozzles operate at about 7.5 psig up to 12-15 psig. Much beyond 10 psig the typical nozzle produces atomized spray. The spray can carry over bring dissolved or partially dissolved chemicals. You would need to include a 17-23 ft elevation in the location of the water trough to compensate for the (unplugged) drop through the spray nozzle. This is quite do-able but it is something to be aware of.</p>


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