welding a gas tank

[Crusty320]

Oh boy this is a fun problem I’ve found. So there’s a pipe that is loose and needs to be welded back to the tank the obvious problem here is that it’s a gas tank and gas+fire=boom I’ve looked into a couple options and I want a second option I was thinking that I rinse it out with water and flush it with air then bring it to my buddy to weld it after it’s done then flush any left over water put with gas. Just for context the tank is the original one on the 320 and is lined. Here’s a pic of where the pipe needs to be tac’d back on 

[datzenmike]

Clean it, sand and wire brush it. Tin the pipe and the hole while pipe is out. Fill tank with water with a bubble of air at the work site. (no air... no fire) You should be able to solder it up with MAP gas. I patched a 620 tank at the seam with a brass patch from a radiator.

[thisismatt]

It's soldered like Mike said.  I imagine you'll need an acid core solder/flux, not your typical electrical solder

[datzenmike]

Get the good stuff. Preparation is 99.9%

[Crashtd420]

10 hours ago, Crusty320 said:

Oh boy this is a fun problem I’ve found. So there’s a pipe that is loose and needs to be welded back to the tank the obvious problem here is that it’s a gas tank and gas+fire=boom I’ve looked into a couple options and I want a second option I was thinking that I rinse it out with water and flush it with air then bring it to my buddy to weld it after it’s done then flush any left over water put with gas. Just for context the tank is the original one on the 320 and is lined. Here’s a pic of where the pipe needs to be tac’d back on 

Is that the fuel pickup line or just a vent line? 

 

If it's the pickup I'd make sure it's not all crusty or full of holes.....

 

I used one of these to repair my 521 tank pickup tube....

You need a npt bung welded in place then a nipple to connect the fuel hose.... 

 

Just a quick search... they have various sizes so you'd need to get what suits your needs.... 

[datzenmike]

Also the pick up line is about a half inch above the bottom.

[Crusty320]

2 hours ago, Crashtd420 said:

Is that the fuel pickup line or just a vent line? 

 

If it's the pickup I'd make sure it's not all crusty or full of holes.....

 

I used one of these to repair my 521 tank pickup tube....

You need a npt bung welded in place then a nipple to connect the fuel hose.... 

 

Just a quick search... they have various sizes so you'd need to get what suits your needs.... 

it is the pick up line and seems to be in pretty good shape

[Stoffregen Motorsports]

It goes without saying that the area being soldered needs to be very clean.

 

Sand, wire wheel and soak in metal etch/cleaner to get the area clean enough to weld on and then preheat it with the torch, but careful not to overheat other areas of the tank, otherwise you'll melt the solder from those joints. A wet towel helps cool surrounding areas.

[Z23T]

Back in the late 80's GM had a recall/repair for fuel tank vents on large school buses. We would drain and clean out the fuel tanks, then fill them almost full of water and dump in several pounds of dry ice. The idea being the the CO2 gas released from the dry ice would replace the oxygen in the tank and reduce the chance of an explosion. We repaired a lot of these tanks this way and never had any issues.

[Duncan]

I'll just leave this here.  A little common sense will get you pretty far.

 

This was the gas tank I modified for the wagon I restored.

 

 

 

 

 

Edited January 7 by Duncan

[ttyR2]

I did a solder repair on a small sheetmetal tank for an antique stationary engine (think early part of last century). I washed the tank out multiple times. Dried, it, and could still smell gas. It gets into the pores of the metal. I filled it most of the way with water and started heating with a propane torch. There was still enough vapor in the tank to blow the filler cap off with a small 'pop'. The next tank I did, I plugged all holes but one with tape, and hooked up the argon tank from my MIG welder to the tank, let it flow for about 10 minutes, kept the gas flowing, and had zero problems with a torch. Propane is fine if you're soldering. If you're brazing, MAPP might work, but it has such a wide flame, I'd be more in the realm of oxy-acetylene turned down really low to control distortion.

 

No matter how much cleaning you do, don't EVER take gas vapors for granted. IMHO, purging with inert gas is the way to go.

 

Purging:

 

Finished patch, and the ridiculous amount of fasteners the PO had "glued" to the tank

Edited January 7 by ttyR2

[BZT8FS]

Lots of great advice! My $0.02, I've soldered, brazed, and welded gas tanks.

ttyR2 & Z23T, excellent advice. I've used the dry ice method mostly. Filling with inert gas is best, but I didn't have ready access.

I've found that soldering & welding are the most demanding, brazing has been my go-to as it seems more forgiving, not as sensitive to vibration as soldering and not as demanding as welding, particularly if you're wanting to correct a leak around one of the fittings. If you're just patching a hole whatever you have access to works.

I sent my last tank (510 tank) to Orozcos Auto in Bellflower, CA where I had them weld in an AN fitting and completely coat the inside and leak check it. It's pricey ~$200 - $250 by the time you cover all the shipping but it's the only place I've found that will leak check.

But if it's a situation where you need the lowest cost method dry ice and brazing would be my choice.

[Crusty320]

So I’ve been struggling to solder the pickup line down, it hasn’t been sticking to the tank.this is the first time I have had done any solder work I’m using a weller 140w 120v solder gun with I messaged metal solder paste with 60-40 tin solder and it’s just not sticking. I’m thinking this is better than welding but if I can’t get this to stick might just have to weld it. Anyone know how to get it to stick?

[datzenmike]

I don't think a soldering gun will apply enough heat over a large enough surface.

 

The two surfaces need to be 'tinned' first. This is began by thoroughly cleaning the metal surfaces to bare metal and acid etching the metal with a solder paste and heat, preferably a propane torch. A small amount of solder is applied and excess wiped off with a damp cloth. The parts are now coated with a thin layer of solder. The parts are assembled together and heat applied to the joint and solder applied. It will immediately melt and bond to the solder already applied and flow like liquid around the seam. Follow around with the heat and keep applying solder as needed. When done avoid parts movement till solder sets.

[thisismatt]

You have to use a torch, there's too much mass for a soldering gun to transfer heat to without the heat dissipating too quickly

[Icehouse]

I've TIG welded a ton of gas tanks.  I've never back purged it or filled it with water. I've always just take them empty to a car wash with hot water and sprayed them out with purple power.  Let them dry and weld on them.  I had one catch on fire, when I was impatient and started cutting on it before I cleaned and dried it enough.  That one I just ran my shop vac hose into in flowing clean air in to the tank get the fumes out.  Also if you need a few piece of tube getting it from a metal store online.  The hard line at the auto parts store is coated and super hard to weld without it leaking.  Our race car we added a filter sock.  I've also added baffles before, that was on my Z.