Welding On 100 lb Propane Tank Questions

[excelagator]

I am looking to building a lawn roller from a 100 lb propane tank. I have read the threads on this and I will be purging the tank with water 3 times, let air day upside down for a day after that. I have heard filling the tank with CO2 also.

1. One post said to leave the water in tank while welding on the tank, but how the heck do you weld in a plug with that set-up? Scratching my head here.

2. Ideas/hand tools removing the valve?

3. Ideas finding center on the ends for shafts?

4. Any other cool useful projects from propane tanks?

I have a co-worker that has "10-20" of these and I can have them all! I figured if I can build my roller/aerator first, I could build some to sell.

Dan

 

[BigE_]

The danger is that some gases can get "trapped" in the metal of the tank, and as the tank heats up, they can be released, ignite and explode.

Filling the tank with water is generally a safe way to prevent this. Make sure you have a vent hole for the steam to escape! That being said, I would never try it myself -- lawn rollers aren't that expensive at the big box stores (much less $$ than a trip to the emergency room).

Might I suggest reading "Welding Skills" by R. T. Miller?

 

[BigE_]

A cool use for the propane tanks is an axillary tank for an air compressor.

 

[Skyco]

Filling the tank with water is generally a safe way to prevent this. Make sure you have a vent hole for the steam to escape! That being said, I would never try it myself -- lawn rollers aren't that expensive at the big box stores (much less $$ than a trip to the emergency room).

Or a one way trip to the morgue and a nomination for a Darwin Award, neither of which will cost anything to the subject. May cost his survivors though

 

[DonT-B7500]

I knew somebody that used to do gas tank repairs and what he did to purge all gasses from the tanks was to use a rubber exhaust hose, the type service garages use to vent out the hole in the door. He would run the hose into the filler tube and let it escape through the sending unit and let a car idle for about an hour. Supposedly the carbon monoxide purges all the flamable gasses. He never had problems with this method

 

[AlanB]

First I would say, "is it worth it?"

Only you can decide, myself, I would probably opt for a water tank.

That said I find myself doing several things which I reccomend to others not to do

To dehead tanks and such, I made a socket out of two spring hangers welded together to form a rectangle, reinforced the back of it with 1/2" bar stock, and welded on a 1" drive socket. I then put this on my 1" impact gun to remove heads. As dad say's, come or bleed. (ie, something will happen when you get this lashed up)

As to how to weld tanks that have held combustible and flamable products, AGAIN, I would tell you not to do it. What you are trying to build / do is not worth the risk. Professionals, with all the monitoring equipment, and with proper purging etc. etc. still get injured and killed every year when things go wrong.

My latest (I wish I could say only) was reworking a BMW fuel tank, after cutting it half way apart, yes I said half way, and then it blew............ enough of the metal had gotten hot enough, enough of my purging gas had been released, I got the materials between their LEL and UEL and that is what you get. (LEL is Lower Explosive Limit, and UEL is Upper Explosive Limit, expressed in a percentage of that gas to atmosphere)

On to the dry Ice, CO2, purging, inert gas, Water etc. Usually the idea behind most of these is that you are removing part of the fire triangle, or tetrahedron depending on what school of fire fighting you listen too

Short version, you are removing the air. (oxygen in particular) that is neccessary to have a fire or explosion. Unfortunately, usually in the process of doing what you are doing, you can also be adding some atmosphere in there (usually containing oxygen) which can be a very bad thing.

So, when doing this properly, you are constantly monitoring (with a meter) the air inside the chamber you are doing, and monitoring that it remains outside the UEL, LEL. Usually not something most home shops are equipped to handle.

As to the purging, that is usually a rinsing or bathing of the tank, and then removing the rinsate. Often this is done with water, fill it empty it three times, dance around counterclockwise three times and wave chicken bones over it while saying the holy mantra, "thou will not blow up"..... often effective, and particularly with something like a propane tank where by nature it stays pretty clean inside. Now a gas tank with crud in corners, seams etc. It is pretty terrible. That crud, tends to hold residual product. Then when you heat it, it releases that product till you hit the point between UEL and LEL and uh,, did I mention that last Beemer tank I did?

So, section 5, from here you may want to read a bit. I like to look at evac distances tells me how bad wrong the writer thinks things will go

added on edit I forgot to put in this MSDS link

http://www.cenex.com/downloads/propaneMSDS.pdf

So, my reccomendation is to go find a different tank, it would not be worth the hassle and expense to do it right, and the cost of doing it wrong could be your life.

 

[SPYDERLK]

I didnt see the following mentioned in the thread, and agree that the situation can go critical if you dont do this. --
-- You do need some rudimentary cleaning, but, the only way to do the welding and be safe is to ensure no chance for buildup of fumes that may be released by heating. A continuous air purge will do this. If the container has a large hole you can do this with a vacuum cleaner exhaust - if small, compressed air. The hose outlet must be well inside the tank to ensure air exchange and dilution. In a big tank a partial water fill will concentrate the purge in the area you are welding.
larry

 

[firedog]

My first recommendation is to say, don't.

While there are methods we use to hottap, stopple and otherwise cut into piping and vessels containing flammable products, it is not something to be taken lightly or attempted by non-professionals. There numerous check-offs we would make before hottapping a LPG tankcar, and even then, it a last resort option (next a vent & burn).
A few years ago, a collegue & friend was killed while cutting up a deinventoried & water filled tankcar. He had more than thiry years in the railroad & emergency response business.

Also, CO (carbon monoxide) is a flammable as well as poisonous gas, with a autoignition temperature of about 1300 degree F. I strongly advise against using this method.
When deciding to do a hottap, these things weigh heavily: charicteristics & properties of the product involved, vessel construction & metalurgy, ability of the vessel & product to dissipate heat. With a tank as small as 100 gallons, the ability to dissipate the heat is extremely limited, and as AlanB stated, without proper O2 or CGI meters, you're flying blind as to the oxygen content of the tank.

 

[Pete Milley]

I vote for don't do it! However, if you are determined.......let me make a suggestion. When I worked on the ranch we did a number of repairs that I wouldn't ordinarily do. One of which was welding gas tanks. After rinsing the tank atleast 3 times, we would purge the tank with diesel exhaust for atleast an hour, depending on the size of the tank and continue to purge while welding. DO NOT use gasoline engine exhaust! Unburned fumes will collect in the tank and you know what happens next! I'm sure there is a place in the afterlife for those who welded tanks 100 times before, and then.............!

 

[Egon]

Ahh, pull the bung, fill it with water and build a fire under it. When the water boils drain the sucker and start work!