On Tue, 02 Dec 2003 01:55:24 GMT, David A. Webb
wrote:

On Tue, 02 Dec 2003 00:30:55 GMT, Kent Fowler
wrote:

The reason I pointed you toward bleve is to see the result of a
vapor explosion.

As I said before, you can't have a vapor explosion without a proper
fuel/air mixture. The gas inside the tank is far from explosive,
hence a vapor explosion is far from possible.

And what happens if you just happen to burn a little bitty
hole in the tank with your torch?

Okay, for the sake of argument, lets assume for a second that my
Bernz-O-Matic propane torch could somehow burn a hole in the propane
tank. Now I have a spot where gas could exit, or flame could enter.

We are right back to where I stated the fact that 100% propane gas is
not explosive. Heck, it isn't even flammable if there is no oxygen
present. If the flame tried to travel inside the tank, it would
extinguish as soon as it ran out of oxygen. The smaller the hole, the
faster this would occur. The flame would never reach the inside of
the tank, because there is no oxygen to support combustion.

Since I am very slightly heating the tank, it is more likely that some
of the gas would be forced out of this pinhole. If it caught on fire,
it would burn. But with very little pressure and gas flow, it would
be pretty uneventful.

If it was a pinhole, the flow of gas *could* be pretty fast coming
out of the hole, in which case it is unlikely the gas could even
ignite. Ever try to light a propane torch with too much gas flow?
Can't do it.

The vapor inside my tank isn't going to spontaneously ignite.
It can't, without oxygen. So again, where is the risk

The little bitty hole and a heat source such as
your torch will sure do it.

Do you honestly think a tiny hole in the tank is going to instantly
allow enough air into the tank to replace 90% of the internal volume?
That is what would have to happen in order to have the gas inside
explode.

Or, are you concerned with the tiny hole allowing gas to escape and
catch fire? It isn't going to be much gas, since I said there was no
pressure in the tank.

The torch and the vapor is the risk


Are you one of these people who believe lighting hair spray on fire as
it exits a can is dangerous, because the flame can travel through the
nozzle, and inside the can, causing the contents to explode?
You have the pinhole (nozzle being depressed), you have the fuel, you
have the fire..... but the flame can't travel into the nozzle.

Lighting hair spray on fire as it exits the can is dangerous for many
reasons, but not that one.

Dave
Dave, let me put it this way and then I am ending my part in this
thread. . I hate to see folks get hurt/burned/killed by taking
chances they did not have have to. I have known people who were maimed
or killed by doing just that. And in my opinion, you took a pretty
scary chance and I think you were lucky the conditions weren't right
to have an accident. They could have been real easily. As I said, I
would have gotten a big wrench or if push came to shove and I could
not have taken the valve out. I would have filled the tank with water
through the valve to eliminate the vapor space then used the torch. I
wouldn't have stuck even a match to it until that vapor space was
gone. Why take the chance????
As far as the hairspray thing. I'll say this. I work with
hydrocarbon reactions using super high pressures and elevated
temperatures every day. I know the physics. I know the math. I also
know what can happen if one little thing goes wrong.

Regards, Kent