My family possesses a propane heater, which we use to provide some semblance of warmth when we go tailgating in the cold months. Often it happens that the propane tank frosts up and the gas stops flowing, and my dad’s reaction is to move the tank closer to the heater when we see the first signs of this happening.
Once, he put the tank on top of the heater–which, for those who are unfamiliar with these things, is basically an enclosed metal drum with a fire inside it. He then proceeded to laugh at me when I decided I didn’t really want to be near the set-up, saying that there was no way the tank would explode. While my dad’s a smart guy and knows a lot about many technical things, physics is not his strong point and I couldn’t stop thinking about shrapnel slicing through me and my loved ones at close range.
So, who was right? Is there something special about propane tanks that would make it okay to do this, or was it just as dumb as placing any other container of compressed gas on top of a fire?
The tank is so cold that it’s getting icy, and then he heats it up VERY quickly over fire. Propane tanks have seams, and it’s not hard to imagine the tank busting a seam from the sudden temperature change. Seam ruptures, gas escapes, kablooie!
It’s much safer to put the tank in a bucket of water, even cool water. Propane evaporates at about -39F, just like R-12 refrigerant. A bucket of water, straight out of the spigot, would be warm enough to make things go again. Putting fire to it is extreme and stupid, Darwinism at work. It probably wouldn’t make it explode, though, the safety disk would rupture first, but there would be a LOT more fire.
Positive feedback loops, like the one your dad set up, can get very nasty. Have you ever set a live microphone down within inches of your speaker system, or applied the brakes in your car while attempting to adjust the seat position? In both cases, bad things happen.
He actually moved it off the heater when I told him I was going to go find some new friends across the parking lot, though he was still bitching at me about it. I really don’t know what got into his head that day. Maybe he was just thinking with his desire to stay warm instead of with his brain.
Anyway, thanks for the info; now if he ever does it again I am armed with information.
(The bucket of water is interesting, and good for home use, but in the particular situation I’m talking about probably wouldn’t have been available.)
I live up in the forest and off the grid, and propane tanks are a fact of life here. Everyone in my community uses them and inevitably there have been accidents. And deaths.
I don’t know the numbers, but those tanks are under a LOT of pressure. When they rupture, because of accident, idiocy, a failed seam or a weak spot due to rust or abrasion, the explosive force is hard to imagine for someone who hasn’t seen it. We had one go up here a few years ago and the scream of escaping gas could be heard for several miles; the column of flame shot 30 feet in the air, the house burned to the ground and two people died. This was a FIVE GALLON tank I’m talking about, just like the one on most barbecues.
People take for granted that because these things are readily available, they’re harmless. While they ARE safe if used with caution and common sense, they are very dangerous if the user gets careless or foolish. You were right to move your family away from your Dad’s ill-considered move; you would have been even more right to clear the entire parking lot and leave stubborn Daddy sitting there on his time bomb!
Holy crap! In my new house they are installing a 500-gallon propane tank instead of the standard 275-gallon oil tank in the basement. However, the propane tank will be buried in the back yard.
Propane by itself is perfectly safe. Even the tankers rolling down the highway and rails need a human to do something stupid before any incidents occur.
Normally foot pressure on the brake is just from leg muscles. If the seat is unlocked then your body weaight is added in proportion to decelleration of the car. More pressure on the pedal can result in an out of control skidding stop.
Put your foot on the brake, press down, release the seat slider. Deceleration will drive the seat forward, increasing the pressure of your foot on the brake, which will increase the rate of deceleration, which will increase the pressure of your foot on the brake… The cycle will stop when the car stops, or you knock yourself unconcious on the steering wheel.
There is a slight chance that your father’s actions could cause a bleve: a Boiling Liquid Expanding Vapor Explosion. If you google it, you’ll quickly see that it would better to just be cold.