Propane
By Richard Wolfe
Not all liquefied petroleum gas (LPG) is propane, but all propane is LPG.
Sounds confusing, doesn’t it? Butane is an LPG. There are others, but we are not concerned with that right now.
Propane is everywhere. All your travel trailers and most motor homes have a propane tank or two with them, ranging in size from five gallons to 50 or more. Some construction trucks have them for the heaters that they use to keep tar melted. So the chance that you will get a call on a vehicle that is carrying propane is fairly good.
Of course, do not confuse it with natural gas. That is one of the new earth-friendly fuels that are supposed to be low emissions. You will find a lot of utility companies with natural gas as the main fuel for the vehicle. This is also popular in Canada.
If a vehicle has been wrecked, or you hook up wrong and get a gas line, you will have a BIG PROBLEM because propane is extremely flammable.
Propane is colorless, and in some applications is odorless, so it might be hard to notice. The vapor density is 1.6 so it is heavier than air, which means that it will seek out and hide in low places, like ditches. Its boiling point is -44 degrees F, so it is producing vapors all the time (unless you happen to be in Coldfoot, Alaska; then you might be safe).
The expansion rate is 270 times the volume that it is contained in. Figure out what the 2,000 gallon tanker would produce. Oh boy, that is a lot of gas.
The flammable limits are 2.2% to 9.5%. It is so flammable that flames will progress at 15 feet per second though a large cloud, which is about half the speed of a desperate man running. Don’t try to drive though a cloud or you will provide the ignition source. You cannot even use your flashlight or radio near the leak, as you might cause it to go bang.
A new term for you to learn is BLEVE, which means “Boiling Liquid Expanding Vapor Explosion,” but when I was taught, I learned it as “Blast Leveling Everything Very Effectively.”
If you happen on a tank that is on fire or real near a fire, run very far and very fast, because the tank will explode with devastating results. And be sure not to run near the ends.
In Memphis, Tennessee, on December 28, 1988 a tanker containing 9,511 gallons overturned and caught fire, then exploded sending parts of the tank over 400 feet, and flattening a house.
In Seaford, New York, on May 24, 1988, a 2,500 gallon tanker overturned and caught fire, burning for over 45 hours before it finally burned itself out.
I can imagine the hassles of recovery and towing of these accidents. These are real work because of the extreme heat weakening everything. I handled a gas tanker accident and we had to trailer it, as every time we lifted it, it bent due to the weakened frames.
Even though propane is low in toxicity, it is a asphyxiate, by excluding (displacing) oxygen. It is a cryogenic, and can cause frostbite. In high concentrations, it may cause central nervous system depression with symptoms including lightheadedness, drowsiness, unconsciousness, and possibly death. A 1% concentration can cause dizziness in 10 minutes.
REMEMBER, keep upwind and uphill from any leaks that you find. A cloud in the area of a propane tank means you have a leak. A leak vaporizes almost immediately, chilling the air and making the water vapor visible. If you see a cloud and smell something, then you are really in trouble. A strong smelling chemical called "Mercaptan” is added to propane to help with leak detection. This is a material you want to be real cautious around.
(Article was retyped and posted with permission from Towing and Recovery Phootnotes Magazine, and appeared in the January 2000 issue on page 24.)
