How dangerous is it to weld on propane tanks? At one point they did containe an explosive/flammable liquid. Couldn't residual gases go "BOOM" when you started welding fittings to these vessels. How are people getting away with this?

Rinse several times, open every vent possible, blow compressed air through it overnight. When you get ready for your first arc, keep your tounge in your mouth just in case!

WOW!! Sounds like a fun ride. Is propane soluble in H2O? Or is there going to be like some H2O vapor left in the tank that will keep it from exploding? I had an "old timer" tell me that he could weld a leaky gas tank by filling it with H2O and this would make the head space small enough that there wouldn't be insufficient air to explode. Knowing what I think I know now. Wouldn't the H2O keep the metal from getting hot enough to make a good weld?

fabricator talks about some testing he did with rocket engines

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/91960555...971093232#3971093232

Purge it with argon or fill it with water. If you use water, just remember that steel melts near 2000 deg C, so if you are welding a whole bunch, hot water and steam may get rowdy suddenly. Be on guard, or you might get scalded.

There was at tragic biodiesel explosion where a young welder (23 I think) was told to do some welding on a drum previously used for methanol. He told his supervisor it was used for methanol, but his boss insisted it was safe. Boom...

Never let someone else bully you into a dangerous situation.

I take risks daily, but I know what they are, I know what warning signs to watch for and I know the remedy if things start to go sideways on me.

Work Safe!!

Thanx for the info. Sorry I missed the post from 1-17 -08 that pretty much answered all this stuff!!!

Totaly off topic...but when I see "Welding on propane tanks", this video always comes to mind...awwwwwe, FUN!

I would like to know how much are the large propane tanks being sold for over there? Something in the size of 500 gallons or so.

I have been lucky enough to get all mine for no cost....but its usually around $100 for a 500 gallon tank.

i welded on several 250 and 300 gal propane tanks and had no problem i just filled with water first then drain several times and i a well vented area.

quote:

Originally posted by welder:
Purge it with argon or fill it with water. If you use water, just remember that steel melts near 2000 deg C, so if you are welding a whole bunch, hot water and steam may get rowdy suddenly. Be on guard, or you might get scalded.

So you weld on them with the water inside? Seems like that would take a while to get up to a good weld temperature, to me, but I don't know much.

Or do you mean residual water after draining it out? I could see that being hot steam very quickly!

All flammable gasses are rated with an LEL (lower explosive limit) and UEL (upper explosive limit)

For Propane, the LEL is 2.2%, and the UEL is 9.5%

Essentially this is a measurement of the ability for the flames to propagate from the source.

If you are significantly below the LEL, you are relatively safe. OSHA recommends being below 10% of the LEL if you are working inside of the environment.

Since Propane is heavier than air.

Work in an "open" area.

Open a bottom valve in the tank when you are purging.

Propane tank walls should be sturdy, but you still should have valves / vents open.

Search both the biodiesel and SVO forums for "propane tanks" this has been discussed many times.

I use salvaged 20 pound propane tanks to make my barrel collection funnels, probably cut and welded on a few hundred propane tanks over the years without one tiny incident. Make sure you have an opening at the very top of the tank, fill tank with water past overflowing using this opening (3/4 inch valve fitting usually), if the opening is at the highest point any residual light oil that was in the tank will float out with the flowing water (there is ALWAYS a tiny bit of kerosine-weight oil in the bottom of a used tank, it will have a VERY STRONG propane smell as it adsorbes the chemical deliberatly added to propane to make the tel-tale odor). Keep the tank absolutely full of water, as long as there is NO air space in the tank no flamable fumes can collect. I use an electric hand grinder with an 1/8 inch thick cutoff disk to cut the tank, any water seeping from the cut quenches the sparks from the grinder, a bit messy but safe, others say they use a plasma torch with the same technique, the plasma works fine even though there is water on the back side of the steel. Drill bits or hole saws also work fine.

Welding with water in tank - Not a problem, I use a stick welder, it makes extremely high localized heat and welds just fine even with water behind the steel, as long as there is an opening in the tank there won't be any pressure built up due to expansion from the welding heat. Once I cut the end off a 20 pound tank I dump the water, once the tank has a good size opening in it it won't explode, any vapors will simply flash off through the opening, it will get your attention for sure, but it won't rupture the tank, just make it a habit to not stand in front of the opening. I have never had even this happen but others have posted about it happening with an empty tank, even after being flushed with water. The thin liquid oil seeps into the rust and pores in the steel, this can be vaporized from the welding heat, this vapor can ignite if the tank is not filled with water.

Filling with sand works but is a pain to get in and out.

I just recently cut a 100 pound propane bottle in half, and I used a jig saw with a metal cutting blade, I should say it worked really well no sparks and no heat, just layed the bottle on side and rolled it as I cut it.

quote:

Originally posted by JCBIO:
I have been lucky enough to get all mine for no cost....but its usually around $100 for a 500 gallon tank.

You guys are so lucky over there. No propane tanks of any size larger than 100 liters being sold here.

Guess I'm stuck with s.s. tanks.

Steam cleaning is one accepted method to remove flammable residue, but it's probably beyond the average hobbiest' ability. My solution has been to fill with water, then heat the whole tank to boiling, then drain the water. This gets out any hidden residue in crevices.
Even recip saws/jig saws can create sparks.

I have read on the welding forums that some people will use an oxy acetylene torch to cut it which is very bad! Unburnt acetylene gets through and can fill the space and create a big boom! I've cut up a few tanks with a cutting blade on an angle grinder with no problems, just filled the tanks up with water and cut away!

[QUOTE]Originally posted by keithszoo:
How dangerous is it to weld on propane tanks?

Also a point to remember is that the propane cylinders are post heated to stress relieve the metal containers so if you weld on them you not allowing the metal to flex as it has been designed to & therefore creating hardening of the shell at the HAZ if you use it pressured again!

quote:

Originally posted by empirehorn:
I have read on the welding forums that some people will use an oxy acetylene torch to cut it which is very bad! Unburnt acetylene gets through and can fill the space and create a big boom! I've cut up a few tanks with a cutting blade on an angle grinder with no problems, just filled the tanks up with water and cut away!

The people who are posting that are FOS, I routinely cut 500 pounders in half with a torch, do you know how much acetylene it would take to blow up a 500 lb propane tank? And as far as that is concerned in the first place, where is all this unburned acetylene coming from?