Welding a fuel tank

[Willy]

Welding a vessel that has previously contained a product that can produce an explosive mixture of vapors and air should never be a "you never know" situation.
If one doubts his ability to ascertain his capacity to do the job safely or to assess the situation then he is wise in turning the job down. Trouble occurs when ignorance of the process is allowed to take charge, and unfortunately it does happen all too often. Such is the cost of a free society.

Can I safely weld a 2-5 thousand gallon tank that has previously contained gasoline or diesel for example? NO!
I'm simply not equipped to perform such a job, I'll walk away from that one thanks. After spending about a quarter century in the fuel, oil, and chemical distribution world I have been given enough exposure to a wealth of training and experience to at least assess the validity of such an attempt. I've safely handled many millions of gallons of the stuff without incident to know it's characteristics and safe handling guidelines very well.

Although there are a number of different ways to repair/weld a small fuel tank safely, knowledge is always the key ingredient to a safe repair. Knowing what is required to initiate an explosion and how to control those factors is the first step in being safe.

As an example, take the common brush type fuel pump motor in millions of fuel tanks. Although most times the motor is completely submerged in fuel, the motor does produce sparks inside the pumps motor when it is running out of fuel.
The reason this is an uneventful occurrence is that the air/fuel ratio is simply too rich to burn.
Personally the the thing that scares me the most about handling fuel is static discharge in the presence of vapors, I've personally witnessed a number of fatalities associated with this phenomena that is generally not recognized.

[Old School]

Back in the day !!! we soldered gas tanks on many cars. We never used a torch or welder but used a soldering iron instead. Of course the area had to be cleaned really good and of course the iron needed to be heated but was done away from the tank. This always seemed to work out well without the problem of the BIG BANG. Years ago I remember a few auto repair shops up in smoke because of welding fuel tanks.

[ironmonger]

Most of the mentioned methods of "safeing" the tank are well-tested and accepted for preventing explosions, it's not "this might work". My personal favorite is using the mig welding gas, either argon or argon/CO2. It doesn't have to be blasting away, especially in a M/C tank, just put the hose in there and let it bleed in for a few minutes, then go to work.

+1
This is the only response that makes any sense whatsoever. Steam, soap, water, time or monkey poo won't solve the problem. Without measuring the O2 levels, any other method is witchcraft.

Displacing the oxygen will absolutely prevent any explosions. If you don't know how to test for O2 content or whether the argon or CO2/argon mix has filled the tank, prudence would preclude you from proceeding...

[Carm]

"Personally the the thing that scares me the most about handling fuel is static discharge in the presence of vapors, I've personally witnessed a number of fatalities associated with this phenomena that is generally not recognized. "

Willy
U.S. fuel industry began enforcing drain up/transfer procedures related to that around 1985. No plastic in contact, ground clips etc.
Easy to facilitate, savvy contractors had no problem, especially considering incinerated employees/lawsuits.
"There are NO accidents" may sound harsh or unattainable but causes thereof are usually related to ignorance (unknowing) and sometimes ego.

[vpt]

The only way I would ever weld any fuel/gas tank is if it is filled with water. I can physically see water, see that the tank is full, know it is safe. You can keep your invisible magical gasses.

[ironmonger]

The only way I would ever weld any fuel/gas tank is if it is filled with water. I can physically see water, see that the tank is full, know it is safe. You can keep your magic gasses

Did you use magic gasses to weld that?
If you leave residual hydrocarbons in the tank what are you going to use to dry the tank? You may need the magic gasses to dry it.
Remember our previous thread about welding gas lines... would you fill those with water as well?

[CalM]

Some folks are just so safe, one has to wonder if they will ever die.

Wouldn't that be nice ;-)

[GNM109]

Welding or cutting on fuel tanks often causes serious injuries and fatalities. It is inherently unsafe.

https://www.osha.gov/pls/imis/Accide...eyword_list=on

[Carm]

Some folks are just so safe, one has to wonder if they will ever die.

Wouldn't that be nice ;-)

Not sure how to read that.
1. It would be nice to never die
2. It would be nice if folk who think they are so safe die.

Gonna guess #1, since so far nobody got there.

As to the OP, there are people who weld on flammable containing tanks, pipes and vessels every day. There are safe ways to do it. If they didn't you wouldn't be able to drive a car, truck, heat your home without chopping wood, lube your lathe, fly anywhere, have the military defend you, solder your pipes, grill your dinner or in some places, have an electrical supply.

[CalM]

ambiguity is it's own reward ;-)

[GNM109]

ambiguity is it's own reward ;-)

+1.............

[LKeithR]

+1
This is the only response that makes any sense whatsoever. Steam, soap, water, time or monkey poo won't solve the problem. Without measuring the O2 levels, any other method is witchcraft.

Displacing the oxygen will absolutely prevent any explosions. If you don't know how to test for O2 content or whether the argon or CO2/argon mix has filled the tank, prudence would preclude you from proceeding...

Now you're talking! I find these threads--on welding or cutting fuel tanks--to be both sad and frustrating. Every idiot who ever cut or welded a live tank and "got away with it" spouts off about how safe and easy it was to do the job with their particular form of witchcraft or voodoo. This only misleads other, less experienced people, giving them a false sense of security and opening the door for them to injure or kill themselves or others.

Let's be clear...welding or cutting on a tank that has held flammable liquids of any kind is not safe. There are only two methods that I know of to make the tanks safe: One is to do a complete hot boil out. The other is to completely purge the tank with an inert gas--in both cases a test should be made to verify the results. Anything else is a gamble. If you want to kill or injure yourself--as long as you do it on your dime--I guess that's OK; but please don't spread your BS about unsafe methods and put other people at risk.

I've been welding since 1969 and I've seen my share of "bad endings"--one resulting in death and a couple that left people badly injured and burned. Even had a couple close calls myself--back when I was young and dumb--so I know how easy it is to be influenced by what someone else says or does...

[vpt]

Did you use magic gasses to weld that?
If you leave residual hydrocarbons in the tank what are you going to use to dry the tank? You may need the magic gasses to dry it.
Remember our previous thread about welding gas lines... would you fill those with water as well?

Yes, argon, don't know where it comes from or how they collect it but I use it to weld. They say it is inert.

Gas tanks get a wash of gas/diesel after welding to get rid of any residue water.

I faintly remember the gas line talk. That is a different deal, there is no oxygen in a live line so there should be no risk of a 4th of july show.

[Carm]

(snip) Every idiot who ever cut or welded a live tank and "got away with it" spouts off about how safe and easy it was to do the job with their particular form of witchcraft or voodoo. This only misleads other, less experienced people, giving them a false sense of security and opening the door for them to injure or kill themselves or others.

Let's be clear...welding or cutting on a tank that has held flammable liquids of any kind is not safe. There are only two methods that I know of to make the tanks safe: One is to do a complete hot boil out. The other is to completely purge the tank with an inert gas--in both cases a test should be made to verify the results. Anything else is a gamble. If you want to kill or injure yourself--as long as you do it on your dime--I guess that's OK; but please don't spread your BS about unsafe methods and put other people at risk.

Yes, sometimes I qualify as an idiot, to this day even.
But never did I spout off about "safe and easy". Idiot or no, you do what it takes to be safe, and that might not be "easy", meaning that time and procedures are adhered to regardless of anyone's financial bottom line.

As GNM said, "Welding or cutting on fuel tanks often causes serious injuries and fatalities. It is inherently unsafe."

An inarguable statement. If it is your employment, and you wish to live another day, you do what must be done.

"Driving a two ton vehicle at 70 MPH on a highway full of other two ton vehicles moving at different speeds often causes serious injuries and fatalities. It is inherently unsafe."

The analogy being nobody drives a car without prior knowledge and degree of control. Drivers are always at risk. Sometimes the hazard is other drivers.

Hot work in a professional setting doesn't have "other drivers".

Working in your own shop shouldn't have "other drivers" either. It is your responsibility to police the area, safe off, and verify conditions that lead to safety. Many a building burned down from cutting/welding, no fuel tanks involved.

[Magicniner]

The tank should either be steamed clean or have an inert gas piped in whilst working to maintain a non flammable mixture, a very easy way to achieve the second is to pipe the exhaust from an internal combustion engine into the tank, clean breathing air for the welder should be a consideration ;-)
Filling with water and just leaving the area to be welded unfilled doesn't make a tank safe, it confines the potential explosion with an incompressible liquid - very un-smart and well documented bad practice for tank welding!

- Nick