Article Archive
DAVE'S NOTES
No "pre-plan" covers everything
Volume 24, No. 5

"Fool proof," as defined by Wikipedia, describes building, organizing or writing in a way that is usable to someone of low to average intelligence. Variations of the term include idiot proof, Murphy-proof, goof proof, fail-safe and defensive design. Unfortunately, when it comes to fire fighting, some industrial managers think the phrase "pre-plan" should join that list.

For example, in my capacity as a fire protection consultant, I recently drafted standard operating procedures for an LPG facility at a refinery. The area involved bullet tanks, spheres and truck loading racks, everything necessary to spark havoc. Management wanted fire fighting procedures in writing covering every potential contingency, right down to where to connect the hose, how to screw on the nozzle and where to direct the water.

Why would I disagree with this approach? Pre-planning is a valuable tool, establishing in advance the equipment, manpower and other resources available in an emergency. But the best pre-plan remains flexible to adaptation. Dictating an exact and rigid response to every potential mishap is impossible.

The variables in fire fighting are limitless. You can anticipate fires, but you can never predict every scenario. Pre-planning an entire response around a specific flange or vessel only guarantees that something else not included in the pre-plan will be the component that fails. If you pre-plan for a vessel failing at the top, you can be sure it will fail at the bottom.

The success or failure of a major fire operation directly relates to the training and qualifications of the emergency responders, not slavish devotion to a by-the-numbers checklist. The incident commander and the operations chief must have personal knowledge of the techniques available for the endless variety of fires they will face.

More important than operational procedures is understanding why fire behaves the way it does in an industrial setting. Flame from a quarter-inch line impinging on the vapor space of a pressure vessel is relatively manageable. Major flame impingement on that same space merits immediate evacuation of every living thing for a considerable distance. Experience tells us that in about 20 minutes that pressure vessel will become history as violently as possible. (See "Wrong Pasadena," Page 6.)

Our country is littered with monuments to firefighters who did not understand the science behind a BLEVE (boiling liquid expanding vapor explosion). The case that stands out in my mind happened on a turkey farm outside Albert City, IA, in April 1998. Teenagers riding an ATV struck two pipelines carrying liquid propane from an 18,000 gallon capacity LP tank to two vaporizer units. The ensuing cloud of vapor ignited.

According to an NFPA bulletin, the venting gas from the LP tank created a loud noise similar to a jet engine. Firefighters positioned themselves as close as 90 feet from the LP tank. The plan was to protect exposures while the fire burned out.

The department's training officer later told me that firefighters had been taught that such tanks were safe to approach if the relief valve went off. That is not true. A tremendous explosion sent large sections of the LP tank flying in different directions. The largest measured 24 feet long and landed 300 feet away. Another piece struck and killed two firefighters.

Etch this in your memory. A pressure vessel does not fail because of overpressure. It fails because the vessel wall protecting the vapor space blisters, becomes thinner and catastrophically loses its ability to hold pressure. Training and experience teaches this to firefighters. Using a pre-plan as a last minute cheat sheet does not get the job done.

Since experience in industrial fire fighting is harder to come by these days, the only alternative is good realistic training and lots of it. Youngsters taking over from us old codgers need to understand not only why a pressure vessel BLEVEs but what you can do to keep it from BLEVEing.

Many years of experience, knowledge and training are compiled in IFW. Make use of it before the worst happens at your facility.

 
 

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