Keeping Acetylene cylinders in the house?

dunno about the 1/7th rule being violated in your case: pressure being directly related to volume am just guessing that 4~7 #'s vs the max of 250# or min of 28# you'll be all right. i think that rule comes into play when/if you try to fill another tank/exceed the alleged flash point of 15#

as far as storing next to the water heater, wellllll.... something about a brick wall between the O² & fuel bottles comes to mind, but hey!!; if they don't leak....

good luck,

Your gas guy is dangerously stupid. The 1/7 rule comes about because the acetylene is dissolved in acetone in the tank, with very little gas space at the top. Acetylene will spontaneously, without any oxygen, decompose at room temperature if the pressure is high enough. about 15PSI above atmospheric is considered the highest safe operating pressure. The acetone stabilizes the gas.

There are a couple of factors that come into play wit the 1/7 rule: As you withdraw gas, more comes out of the soution, similarly to the CO2 in carbonated soda. The pressure is temperature dependant, as wel as dependant on the remaining dissolved acetylene. If you draw the gas slowly, the pressure at the head of the tank drops slightly, and more gas comes out of solution (LeChatliers principle, if oyu took chemisry) to reestablidh the equilirium at the surface. As you draw the gas at a higher rate, the fresh gas must come out of solution faster, and at a high enough rate of withdrawal, it begins to form bubbles at the surface, and possiby in the solid media (a porus filler used to help stabilize the dissolved acetylene) which will, just like a well shaken soda, carry liquid out. The liquid acetone cause spitting at the torch, damage to hoses, damage to the regulator, and other troubles. As the rate of withdrawl is increased, some fillers can be damaged, supposedly even to the point of having solid material being lifted into the valve and to the regulator.

The Tanks are designed so that if the acetylene is withdrawn at a rate of 1/7 of the tank capacity per hour at most (7 hours to use the tank, constant flow, no more than that rate for any sustained draw, even a few seconds.), under the worst expected service case, the acetone won't be carried out. Keep in mind that this is worst service case. Might you get away with higher draws just fine under some conditions, and in fact probably would, but the higher the rate, and the worse the conditions, the more risk. What are worst ase conditions? I don't know. And I don't want to find out.

Thanks for the link and the very lucid explanation. Much more useful than the warning in the manual.

I sort of figured he was a buffoon. This was the same guy who sold me the welding set last year and advised me that I didn't need to purchase the #2 victor torch tip to do 1/8" material. He said I could just crank up the gas and oxygen pressure and use the #0 tip that came with the kit. When I showed him the recommendation from the manual, he told me I shouldn't pay attention to manuals. I didn't have a reply to that, but bought the #2 from another store much further from home.

This guy is the reason I am considering buy my new gear online. I really don't get very good service at the local welding store.

I wouldn't keep the cylinders near an ignition source. If there were a leak, the results could be catastrophic.

The person at Airgas is an idiot. The reason for the 1/7th capacity rule is to prevent pulling acetone over with the acetylene. At minimum that'll contaminate the weld, or worse it can damage the regulator, hoses, and even the tank filler material. Don't pay any attention to that guy.

Gary

Not to be argumentative, but, actually there is quite a bit of it in the engine rebuilding industry. O/A welding is arguably the best way to repair cracks and other damage to cast iron heads. Arc welding works...but has other issues that make it a problem. Dave Mundt