Can I weld a used oil tank?

[johmue]

My question is whether or not it is safe to weld a used oil tank. I have read several methods that have been used to do this but almost all of them sound like back woods style and unsafe. Any suggestions on how this can be accomplished safely? Are there any published codes and/or documentaion on safe methods?

Thanks for the help

 

[MikeMilburn]

Most anything is safe if done properly. The way I've done welding on gas and diesel tanks is to have the tank steamed out and then checked with a sniffer for flammable gas.
Even then, if you're like me when you first strike the arc you're waiting for the big bang. What I usually do for a bit of extra insurance is to flood the inside of the tank with a C02 extinguisher, this will displace the oxygen. I've also heard of people using dry ice (C02), put a piece of it inside the tank for awhile and it will also dissipate the oxygen.
You said a used oil tank, granted oil is not as flammable as gas but who says noone didn't dump a little in there, plan for the worst case, my opinions only, take them for what they're worth....Mike

 

[Leviticus49]

I agree wholeheartedly with Mike Milburn as to the fear in the back of your mind as you strike up.

A method I have used in the past is to fill the vessel COMPLETELY with water, turning it so where the cutting or welding has to be done is at the very top. As you cut into the vessel as small amount of water would run away(meaning the vessel was full) I believe this is now not allowed. As Mike says the only sure way is to have the vessel purged completely of all residues AND then checked by a competent technician.

 

[edellison]

depending on the size of the tank purging with argon or other inert gas is an option. another sucessful "back woods" method would be to use a hose and run a line frmo the exhust of a car/truck into the tank. i've made or been involved in repars on many fuel/oil tanks with these methods and no problems

 

[ledon]

API (American Petroleum Institue) 653 is the standard used to govern repairs and alterations of petroleum tanks of all varietes. Depending on the tanks size, Inerting may not be an option. If the tank is large enough to allow entry, cleaning and ventilation along with Gas free services would be you most economical solution. If it is small, (a few 100 gallons) then an inert atmosphere would be the best way to go.

 

[snowlotus]

yes, i agree with this method that it depends on the tanks size. but if the tank is big enough with some flammable gas, and it is on use (it means that we have to repair it while it is working), how to repair and keep it safety?