Ingenuity Can Help Handle Flammable Liquid Fires
departments
The Volunteers Corner
Fortunately, most flammable liquid incidents—fires or spills—are small. We say “fortunately” because responses to my questioning of fire fighters in several score departments indicate that the amount of foam concentrate carried on pumpers is four or five cans—20 to 25 gallons.
This means that unless the flaming area is relatively small, the first thing you have to concede is that your foam capability—protein or AFFF—is inadequate for the problem. Remember, unless a flammable liquid fire is extinguished, the residual flame will begin breaking down the foam and the fire will expand—eventually to the entire flammable liquid surface while you are looking to the horizon for the arrival of more foam. When more foam finally arrives you may have as much fire as before, but you now lack the original foam supply.
So what can you do when you arrive at a flammable liquid fire with less foam than you need? The first thing is to recognize this situation and the next thing is to radio for an adequate supply of foam. Incidentally, you won’t get a large supply of foam out of the thin blue—you have to have arrangements right now for obtaining more foam at those rare times when you desperately need it.
Size up the situation: When we talk of inadequate foam capability on the initial response, obviously we are talking about spills and fires involving highway tankers, railroad tank cars and small bulk plants for retail distribution. We will keep the comments that follow within these limitations.
Inasmuch as extinguishing the fire minimizes all other problems associated with the incident, you must evaluate your extinguishing capability. A rule of thumb to remember is that petroleum products with Hash points above 100°F can be extinguished with water fog. Conversely, petroleum products with flash points below 100°F cannot be extinguished with fog. Note that this rule of thumb applies only to petroleum products.
If water fog can be used, you have to determine whether your water supply will allow you to apply fog at a high enough rate of application for a long enough time to extinguish the fire. If the answer is yes, extinguish the fire. If the answer is no, then you must look at alternatives.
Kxplosion possibility: If you can’t extinguish the fire immediately, then your most serious problem is the possibility of an explosion of the tanker or tank. This raises the question of whether you have a large enough water supply to cool the flammable liquid container. A highway tanker or a railroad tank car requires a water application rate of at least 500 gpm to sustain the hope of adequate cooling to prevent an explosion. If other railroad tank cars or bulk plant tanks are exposed to the fire, then the required water supply will be greater.
If your water supply is inadequate, then you must turn to evacuation of the area. This means removing everyone within 3000 feet of the fire—in all directions. This can be relatively simple if the tanker is burning in the countryside with a population per square mile that you can count on your hand. However, evacuation can be a horrendous problem in a heavily populated city area. You will need all the help you can get. Use all available fire apparatus and police cars and get them to move out and use their sirens and FA systems to alert people.
If time is still on your side—although running out—and you have a deluge set, put it in operation to cool the tank, even though you may not be able to supply it with more than 400 gpm. Then withdraw fire fighters from the area. Looking at the fire won’t do anything to extinguish it.
If most of the flame at a highway tanker fire comes from a spill that isn’t too large, sometimes an aggressive attack with fog lines can wash much of the burning spill from beneath the tanker. In this way, you can remove a significant portion of flame that was heating the tank and leading to an explosion.
Spill fires: When your problem is a spill fire and you don’t have enough foam to extinguish it, you have some alternatives. Unfortunately, the alternatives also have inherent problems that you have to evaluate. But remember, we are operating in desperation alley.
If the flaming spill is not too large and if you have sufficient water available, the fire can be “extinguished” by dilution. Note that we used “if” twice in that last sentence. If the liquid from a couple of drums ruptured in a truck crash was burning, dilution could be an alternative in the absence of foam.
When you consider dilution, you also must evaluate what will be endangered as dilution increases the liquid volume and causes the fire to flow before it is controlled. You have to decide whether the benefits exceed the dangers. If the flaming spill is quite small and is not receiving additional liquid from a leaking tank, a couple of shovels and roadside loose earth can end the fire.
In those rare incidents where there is no exposure problem in a spill fire, letting the fire consume all the fuel is an alternative.
An important thing to remember at any flammable liquid spill fire is that the application of water for cooling the leaking tank or tanker is going to increase the spill flow problem. This is something you have to consider from the start of your size-up. Where is the burning spill going to go and what will it endanger? Can you contain it with sand, dirt—or even a charged hose laid on the ground—or can you divert the spill to a safe area?
Consider your alternatives and select the ones that minimize your problem.
