Cutting a Propane Tank - Best Gas Detector?

[rayra]

I have a decommissioned 250 gallon propane tank I'm planning to cut into to make a Texas-style offset BBQ smoker. I have read lots of forums on methods to do it safely, and it seems the only 100% fool proof method is to use a gas detector/monitor. My plan is to fill the tank with soapy water several times until the gas detector reads zero. That leads to my question for those who have cut into an empty propane tank using a gas detector/monitor:

Which monitor/detector did you use? How did you do it? Since propane is heavier than air, did you need to drop the monitor into the bottom of the tank?

Laughably silly and excessive. Removed the plumbing. Flood it with water. Dump it out. Get busy cutting.

 

[rayra]

That's one way, but as the tank drains out any vapors trapped in the walls could still ignite once they come into contact with air.... at least that's my understanding. I'd rather flush it completely until a monitor reads zero.

It's a steel tank. How do you imagine "vapors trapped in the walls" is happening?

 

[rayra]

I'd let someone else do it. I once had a 20 gallon tank I wanted to get rid of, so I kept rinsing it with water. When I set it out for the G-man, I could still smell propane.

Mercaptin is a pungent odorant that is ADDED to natural gas / propane as a cautionary measure. The gasses themselves have no odor. The residue of the mercaptin - particularly after venting and flushing - does NOT strictly mean the presence of gas.

 

[Walkers]

That's one way, but as the tank drains out any vapors trapped in the walls could still ignite once they come into contact with air.... at least that's my understanding. I'd rather flush it completely until a monitor reads zero.

Your understanding is wrong. Once the gas is displaced it does not magically reappear. You could simply turn the tank bungs fown to drain, then add a bit of water to the tank. The water is to keep the oily mess on the nottom of the tank from igniting.

 

[Zeke]

FWIW, I have emptied plenty of 1 gallon cans of solvents to the last drop. If I want to have some fun I can count on any of those empty cans to blow inside out with a spark. I'm sure water would take care of it but it's not going to be me cutting a steel tank that was used for propane. I'd sell it in part for an already cut tank of the size needed for whatever the smoker is intended to cook. In fact, if I found such a person to take it in part trade, I'd buy the rest of the kit needed and set to welding it up.

I like to get things done. Safely.

 

[metalmagpie]

Propane is explosive in air but only at a certain mix. If the mixture has much more air than that, the propane will not ignite. I have opened a propane tank and let it completely empty, then fastened an air fitting to the valve and filled the tank up with air, then let that air blow out and equalize, then do that blow out and vent step as many more times as you like. After that, you don't need any water. But if you're worried, drill a really small hole somewhere and put a flame up near it. The worst that will happen is you will get a little flame like a candle.

Never knew about orange stuff breaking down mercaptan. I always used bleach.

Opening the tank up for a long time and then building a big fire under it sure ought to work too, like all those east Texas guys do.

metalmagpie

 

[jsaw]

Kind of an aside, but when the gas company had to extend a gas line in My cel!ar, they shut off the gas off and used a reciprocating saw to cut the pipe. The guy said that in order to ignite the the ratio of air to propane had to be at a very specific ratio and even then would need more heat than would be produced by the saw blade.