Welding on gas tank

hey all,
i have some cosmetic mods i'd like to apply to my stock gas tank but need some advice before i start mig welding and blow myself up.
besides dismounting and emptying the tank, are there other issues to address?
thanks.

 

Emtying a tank makes it a lot more dangerous. It is not the liquid that can cause an explosive reaction but rather the vapors of the gasoline. I knew a welder who swears that you can weld on a full container of gas simply by dropping so dry ice into it. The dry ice takes out all of the oxygen or something like that.

 

The way I have always done it (building chopper tanks) is to empty fuel, rinse twice with water, run a hose from a running vehicle into the tank and let it pump exhaust through there until completely dry.

Then weld away.

 

In the past I have removed all gas. Rinsed with soapy water then rinsed with water untill all suds are gone. Removed anything that is removable from the tank ie: cap, petcock , fuel level sender. i have a small space heater that id place in front of the tank and let it slowly warm it up untill bone dry then just go to town. Realistically if you were to drain the tank and remove anything removable then let it sit for a few days in a well ventilated area you would be just as well off, but the tank would still stink.

 

You need to remove everything from the tank and rinse it throughly and pump carbon dioxide in the tank while welding it to remove the oxygen so no flame can get started and if you are not 100 percent sure of what you are doing I would not try it I have seen to many old welders all scared up from gas tanks blowing up in there faces BE CAREFULL!!!!!!

 

thanks guys for all the advice!
i'll post a follow-up either from my garage or the emergency room.
kidding of course. i'm gonna talk to my local welding supply shop also. if i can't do it safely, i won't do it.
thanks!

 

Empty tank. Fill with water. Drain and weld. It's the gas fumes you need to worry about. Filling with water pushes the fumes out.

 

makes good sense, thanks!

 

Don't empty tank, don't fill with water. You end up causing more problems than it's worth that way. Purge the tank with Argon, prep the tank and get your welding done while the purge is still flowing. My rule of thumb is let the purge flow at 5 cfh during welding with everything capped except a small vent. You can initially purge using 20 cfh until whole tank is purged. I time it so that each gallon the tank can hold = 3minutes of initial purge at 20 cfm. A gallon doesn't take up one cubic foot, but I do that to be on the safe side. I've done countless tank repairs that say, on everything from bikes to trucks with never so much as a pop or sputter. No oxygen=no fire. Just make sure you don't ignite fumes OUTSIDE the tank that were displaced my the Argon. I'm sure I'll get tons of negative responses from this post, but it'll be from people who either haven't ever done it themselves, or did it wrong and got a bad story to tell. I've heard all the stories too, and when you start asking questions, they all swear they did everything right. No one likes to admit they screwed up.

Even if you decide to go with the washing and rinsing method, purge the tank. It's usually the guys who wash out the tank that have the horror stories. It gives you a false sense of security so then you're much more tempted to forgo the purging process.

 

That's a sure-fire way to end-up lying horribly disfigured and possibly charred to a crisp, on a bed in a Burn Ward, having morphine pouring into your blood stream to keep you in a comatose state so you don't spend the little time it will take to die of infection screaming in excruciating pain.

I do know that anything short of draining, washing and rinsing the tank and purging it with a constant volume of fresh air until there are no explosive gases present is NOT recommended.

Drain the tank.
Wash and Rinse using a strong detergent.
Remove the Petcock.
Rinse. Drain.
Attach the Vacuum Cleaner Hose to the Exhaust Port on the Vacuum Cleaner.
Tape the other end to the Gas Tank Filler Neck.
Blow Fresh Air through the Tank >> In the Filler >> Out the Petcock Mount for a minimum of 45 Minutes.
Sniff test.
>> Safe for Body Work.

 

purging with argon is much safer than just pushing air through with a vacuum. i weld pipelines on a regular basis and not a single spark gets goin until that line is full of an inert gas (we usually use nitrogen, but argon is just as good)

 

SO you think pumping MORE oxygen into the tank makes it safer than purging with argon. I rest my case. Like I said, I don't know anything except from EXPERIENCE. I've probably repaired more tanks than any body here, and that's the way I do it. Still have all my skin too, imagine that, no disfigurement. Your way of doing it is actually MORE LIKELY to cause an explosion. Water and soap will not clear out all the gas, period. When you get gas on your hands, you wash with whatever soap you like. Do they still smell like gas? You betcha. Gas has a way of filming and sticking very well to just about anything. Then you'll have outgassing of the film (fumes from residual gas). I've even heard stories of guys welding on tanks that have been empty and washed out and left out to set for months that still flame out when welded on. Why? because there are still fumes and oxygen and an ignition source. For fire to exist, you need

Fuel

Oxygen

Heat (ignition)




Ever hear of the fire triangle. You method of prepping the tank does not remove any leg of the triangle. Purging with Argon DOES! I'm not against somebody washing out their tank as part of their prep, but it DOES NOT replace purging with an inert gas. That is the only sure way to remove one of those legs. Like I said though, I probably only repaired just under triple digits so what do I know.......

 

The VAST Majority of Members wouldn't have Argon and wouldn't buy it.

The Body Shop where I have done work refinishing dented tanks required that the Tank get:
Drained
Washed and Rinsed
Dried. Purged with Compressed Air.
Checked by the Foreman BEFORE it got cleared for any "Hot Work".

The "Audience" we write suggestions for, are NOT all Professional Welders -- On-the-clock ... needing to turn-around a piece of work for somebody who brought-in the Tank, and is waiting outside in the back of a Cab with the Meter Running.

Most are "Hobbyists" ... some with enough skill to attempt welding a tank.

What do we tell the guy who doesn't have a tank of Argon but needs to Solder a Penny on a Pinhole leak?

 

i'd tell him use a old fashion soldering iron and lots of flux

 

Wizard should chime in here and tell us how he does it.

 

I would tell him to use PC11 on it. That OR take it to someone who can do it right. The method you mention the body shop using probably wouldn't kill someone, but there's still the potential for some eyebrow loss, if ya catch my drift. Other than that, I think Polock might be on to something with the old school lead paddle idea.

The dry ice idea mentioned earlier would also work, but the problem I have with that is that you can't know when all the oxygen has been displaced because you have no numbers to go by (flow rates vs internal volume). But I suppose you could just load it up and wait until the vent line can extinguish a match (at the risk of flash back).

Basically what it comes down to is this.....If you don't have the materials and tools to do it safe, that kind of work is best left to someone who DOES have the goods. For a pinhole, I only charge $15-$20 bucks if the tank is already off the bike. When people hear that, they usually realize pretty quick that the risk isn't worth $20 and leave it to a professional.

 

Members:

You need to exercise Extreme Caution before you engage in any repair or fabrication to a Fuel Tank.

BEFORE doing any work on a Fuel Tank; you MUST be assured that there are no EXPLOSIVE FUMES which the slightest spark could ignite.

For your Safety and others around you; treat working on a Fuel Tank with the same precaution you would when handling a Fire Arm.

Presume it is loaded ... Until you have checked and KNOW, for certain, it is not.

 

Weld? How? arc, mig, gas or what. Old timers that used gas will tell you that any unburnt acetlyine that can accumulate in the tank, will, and will blow when it reaches a volitile level weather the tank ever had any gasoline in it or not.
In absence of having any nitrogen, helium or some way of keeping the tank safely evacuated, I'd probably go with a hot wash, & hot rinse and soldering it with propane. There are epoxies out there that will work fine too, (unless you want to have it chrome plated) or just maybe buy another better tank. thats my 2c.

 

i stated in my original post i will be using mig for the alterations. i'm not repairing a damaged tank, i'm adding features to it. the local welding shop said they'd supply me with a co2 tank to purge it while welding or i could simply fill it with water while working on it.
hmmmmm.......

 

if they'll supply co2 use that, water would suck a lot of heat out of your weld.

 

good point, thanks!

 

I can see why someone fibreglassed a repair into my spare tank now...

After reading this thread I'm going to have a closer look at it and see if it will stay after a tank lining kit goes in.

 

Last time I wanted to weld a tank, I blew compressed air through it to force evaporate as much fuel vapor as possible, then put the tank behind a brick wall ind ignited the contents. One small whoomp and a few flames for less than 10 seconds. All fumes gone.

No bloody worries !

 

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Cmon be honest now... how many beers?

 

When i first started working on cars we would rinse the tank attach a radiator hose to the exhaust of a running car and stick it into the tank until it was dry then it was ready to braze weld. Would I do that today, F*** no. I know now to use a running purge of inert gas no ifs ands or buts its the ONLY safe way to do it.

 

Found you, AH HA!! ^^^^^^^^^