[TheForge] old propane tanks

[Jerry Frost]

Freon can be VERY dangerous heated or in moderately high concentrations.

When we did something with a propane tank we'd pull the valve and fill it 
with warm water and a little chlorox, about 1 cup for a 20 lb tank and so 
on. The clorox clears the mercaptins so it stops stinking. then we drained 
it and did whatever. Unlike gasoline or diesel fuel, propane doesn't leave a 
residue in the tank, the only residue is the waxy mercaptins and that's just 
an odorant.

Heck, as kids we used to try to get propane tanks to explode to no avail. 
Even putting a full tank in a fire didn't do much of anything, it just 
spurted a largish flame from the pressure relief. We got tired of pulling 
the valve and lighting the residual propane, all it ever did was go whoosh, 
not even a thud. Propane can be really dangerous in uncontrolled conditions 
like say your basement.

Cutting an empty tank is pretty low risk but by all means do NOT do 
something that makes you uneasy, especially not on MY say so.

Whatever you do, do NOT cut an empty fuel oil tank, diesel or heating oil. 
As Bruce pointed out there MUST be a flammable mixture of tuel and air to 
result in an explosion. With many fuels, gasoline for instance, it's a 
little hard to get a flammable ratio. Gasoline's saturation level is well 
above the flammable range. Meaning the point where gasoline can't evaoprate 
any more because the air is holding as much as it can is well above the 
flammable ratio and gas is very volatile so it's going to reach it's 
saturation level quickly.

Fuel oils on the other hand have a saturation level smack in the middle of 
the flammable range. This means that unless a fuel tank is absolutely full, 
NO bubble of air at all, the air bubble is a fuel air bomb. Fuel oils reach 
their saturation level more slowly but not very. Fuel oils also leave a 
flammable residue behind that can be ignited. I don't know the mechanics or 
chemistry of it but washing the residue out is nearly impossible. When we 
welded on a used fuel tank all but one guy left the shop though one guy 
stayed across the road to call  EMS if neccessary. A welding shop about 3 
miles from where I was living at the time was working on a fuel truck and 
had been steamming it for three days when an old hand (NOT the guy who was 
doing the job) got impatient and just struck an ark on the cracked fitting. 
The explosion killed the guy adjusting a steam line on top of the tank, the 
"old hand" was blown through a wall into the office  and survived. The other 
guys in the shop escaped with injuries and burns. There were two steam lines 
in the tank and after three days there was still a flammable mix. It 
destroyed a 30,000 sq/ft shop, injured a bunch of people and killed one.

Welding or cutting fuel oil tanks give me the willies big time but it was 
part of the job.

Jer
----- Original Message ----- 
From: "Paul Novorolsky" <crosspein at sbcglobal.net>
To: "Blacksmithing List Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Tuesday, September 27, 2011 2:09 PM
Subject: Re: [TheForge] old propane tanks


> Just for the record: from what I've read, freon decomposes to phosgene
> at high temps. So while freon tanks are less likely to go boom, they
> aren't completely "safe" either. So they too need to be handled
> appropriately.
>
> Information can be found on many welding safety sites.
> Search= phosgene freon
>
>
> **paul
>