Welding fuel tank question

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Welding fuel tank question

March 01, 2021, 06:33:26 pm

Our fuel tank has a hairline crack in it and is leaking fuel, the weld shop wants to fill the tank with water to weld on it but that doesn't sound like a good idea to me. With the baffles and piping inside the fuel tank I don't know how we could get all of the water out afterwards. I'm hoping get some insight on the subject, if anyone has experience with this I'd like to hear about it. Thanks in advance.

Tyler

Re: Welding fuel tank question

Reply #1 – March 01, 2021, 06:50:54 pm

Quote from: wolfe10 – March 01, 2021, 06:40:38 pm

Doubt you will fine anyone to weld a diesel tank that is NOT filled with water.

If you do, do NOT be in the shop when they do it!

When I was in the Operating Engineers as a Heavy Equipment mechanic, we put dry ice in almost full fuel tanks waited 10 minutes then capped the tank and stick welded the cracks on the outside. I am sure OSHA was not informed of this practice. Lots of tanks cracked on scrapers and bulldozers. With my crane I used a JB weld product made especially for gas and diesel repair. Didn't want to press my luck on the dry ice any more.

Re: Welding fuel tank question

Reply #2 – March 01, 2021, 06:57:03 pm

The JB Weld stuff for tank repair works fairly good.......might be worth a try.

Re: Welding fuel tank question

Reply #3 – March 01, 2021, 06:59:08 pm

I was recommended a fuel tank patch kit from napa that I'm going to pick up and try.

If we have it welded, How do we get all of the water out if they fill it up?

Re: Welding fuel tank question

Reply #4 – March 01, 2021, 07:04:01 pm

I have welded fuel tanks before and I like to do it on a cool day. If they fill it with water, where it is being welded should be free of
water as the water will cool the weld to quickly which weakens the weld. Getting the water out shouldn't be a problem.

Re: Welding fuel tank question

Reply #5 – March 01, 2021, 07:21:54 pm

Drain the tank after welding, then turn it upside down. Let it sit for an hour on a warm day and it will be dry. If its not warm enough use a heat gun.
Turning it upside down means you don't have to worry about baffles and the water will drain out of the fill holes (one at each end), and the generator and engine hose connections.

My dad always filled up gas tanks before welding back in the 50's, then took an acetylene torch to the fill hole to ensure there was no fume buildup...

Re: Welding fuel tank question

Reply #6 – March 01, 2021, 07:47:03 pm

Quote from: The Soft Boulders – March 01, 2021, 06:33:26 pm

With the baffles and piping inside the fuel tank I don't know how we could get all of the water out afterwards.
Tyler

Alcohol. A couple of rinses, maybe three and push it through all the outlets with a little air pressure. Water all gone.

Dry ice? Excellent idea. Make the cap the high spot and when the CO2 pouring out extinguishes a flame you're ready to weld. The shielding gas is for welding aluminum is argon and if tank were full of argon there's nothing to support combustion.

Water? BTDT after washing with detergent and triple rinsing the tank with water. The fill with water everywhere but where the heat needs to be. There may be a whoosh but it'll be a small one.

Re: Welding fuel tank question

Reply #7 – March 01, 2021, 07:48:49 pm

I had a cracked tank in our previous coach. JB Weld didn't work. Fancy aircraft fuel tank sealer didn't work. I removed the tank and took it to a shop. They welded a patch over the leaking area, and did not say anything about filling the tank with water.

Wouldn't a small amount of water just be separated by the water-separating filter?

If I were worried, I would put the hose on my shop vac on the air outlet, tape it on to the fuel neck, remove the level sender, and let it run for a few hours.

Re: Welding fuel tank question

Reply #8 – March 01, 2021, 07:59:03 pm

Fill the tank with water leaving the area to be welded above the water. Put a little dry ice in and after a few minutes, weld it. Dump the water followed by Matt B's advise with the shop vac/fuel sender method. Good to have the sun shining on the tank while drying it.

Pierce

Re: Welding fuel tank question

Reply #9 – March 01, 2021, 08:42:35 pm

Tyler, You may want to take a look at this:
https://www.amazon.com/Versachem-90180-Heavy-Duty-Fuel-Repair/dp/B002N5JAO2?th=1

I used it about 18 months ago on my Skid Steer tank(diesel) and its been holding strong ever since.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Welding fuel tank question

Reply #10 – March 01, 2021, 11:57:47 pm

I don't know if we're going to be able to find anyone close by that is going to purge the tank with argon like I would prefer. I'm going to call another place tomorrow and see how they would go about welding it, but if they are going to fill it with water as well then that might be the way it has to get done. Although I don't really like the idea of filling our fuel tank with water, that is the most common solution I've heard from talking with people. There are pros and cons to any method it sounds like and if the residual water isn't a major issue to most people, then maybe I'm worrying about it unnecessarily.

Re: Welding fuel tank question

Reply #11 – March 02, 2021, 09:03:50 am

What about fastening one of those cheap heat guns from Harbor Freight to blow heat into the tank?
Cheap enough when on sale at about $9.95

Re: Welding fuel tank question

Reply #12 – March 02, 2021, 09:11:48 am

Quote from: The Soft Boulders – March 01, 2021, 11:57:47 pm

I don't know if we're going to be able to find anyone close by that is going to purge the tank with argon like I would prefer.

A qualified repairman is going to use argon gas to shield the weld, it's part of the GTAW, Gas Tungsten Arc Welding process. Also known as TIG welding, and when used on aluminum HeliArc sometimes with a mixture of Argon and Helium as the shielding gas.

Besides, you can also use a CO2 fire extinguisher to purge the tank of oxygen.

Re: Welding fuel tank question

Reply #13 – March 02, 2021, 09:30:06 am

There's probably a lot of different ways to purge the tank, but finding a welder here in the area that is going to use those methods might be a challenge. I've read and been told that running a hose from the exhaust pipe on a vehicle into the tank will also work well to purge it, but again, I don't know if I'm going to find anyone that will do that. I would much prefer someone to properly TIG weld the tank but haven't found anyone that can do it.

Re: Welding fuel tank question

Reply #14 – March 02, 2021, 09:33:21 am

I would mig weld it.

Re: Welding fuel tank question

Reply #15 – March 02, 2021, 09:48:22 am

After they fill the tank they weld it up then they pressure test it.. If all is well they put it in the oven to get the water out .. depending on whats inside the tank as fillers.. some have foam and others do not.. They call it burning the water off or out.

Re: Welding fuel tank question

Reply #16 – March 02, 2021, 10:13:30 am

Quote from: The Soft Boulders – March 02, 2021, 09:30:06 am

I would much prefer someone to properly TIG weld the tank but haven't found anyone that can do it.

Oldguy is correct, it can be GMAW aka MIG welded, but at the end of the day you need a qualified aluminum welder, not a guy with a torch and some cadmium rods. And all aluminum welders will use a shielding gas.

Re: Welding fuel tank question

Reply #17 – March 02, 2021, 10:24:59 am

For getting the water out, alcohol mixes with water so the resulting liquid evaporates much quicker than water alone.

Re: Welding fuel tank question

Reply #18 – March 02, 2021, 10:35:38 am

So if the the crack is in a corner it is very likely to re-crack again in the future. I last month built a 30 gallon aux tank for my diesel truck I left the top cap off and internally welded all the lower internal welds. Truck is much harder on weld corners than than your coach. Many more "G" forces while driving. Crack needs to have almost all material removed opening up a V that is to be filled. Do not let them use 4043 , should be 5356 filler. Tig repair or Mig is purely up to what the welder is set up to do. Let him judge what he prefers. I generally Tig for repairs and Mig for initial production. Argon filling is preferred, but washing with soap, water and forced air during welding is fine. No possible way to weld properly full of water in my world. May be doable but I've never attempted
Scott

Re: Welding fuel tank question

Reply #19 – March 02, 2021, 10:47:17 am

Quote from: JohnFitz – March 02, 2021, 10:24:59 am

For getting the water out, alcohol mixes with water so the resulting liquid evaporates much quicker than water alone.

It attaches really well with water and can be poured out. I use distilled water to remove the alcohol out of fuel. Pour it it, shake it up, let it separate and drain off bottom. Alcohol free fuel. Doesn't get rotten as fast.
Scott

Re: Welding fuel tank question

Reply #20 – March 02, 2021, 11:34:58 am

Got a phone call from the weld shop saying they're not interested in doing the repair due to the risk involved. Apparently the last tank they did, some 20 years ago, they blew up and don't want to do another one even if it's filled with water. I don't know how many people we've had do that to us, say they can or will do something and then call later, or not at all, and say they didn't want to do the work...

Re: Welding fuel tank question

Reply #21 – March 02, 2021, 11:57:36 am

Wash the tank with soap and water. Blow out, let it sit inthe sun , .
Fill 96% with water, leaving the welding area high and dry. Leave the tank open vented so that the remaining fumes wont explode the tank further.
Drill the crack ends, V grind the problem area, weld as required.
Empty tank , blow out , run hair dryer into filler neck for an hour or so.

Re: Welding fuel tank question

Reply #22 – March 02, 2021, 01:24:32 pm

Is it that difficult to weld a tank that has held diesel fuel? You know how hard it is to get it to burn let alone explode? Or maybe I'm off my rocker.

Re: Welding fuel tank question

Reply #23 – March 02, 2021, 01:52:32 pm

Welded, GAS tank used argon to purge tank-- don't trust the label on the argon tank put paper towels in a bucket light them then turn the argon into the bucket, if fire goes out you are good if not find another bottle. One tank labelled argon turned out to be oxygen--would have made for a bad day.
We don't use MIG we use TIG each to their own
Chris

Re: Welding fuel tank question

Reply #24 – March 02, 2021, 01:55:29 pm

Go down to Wally world and get a jug of the cheapest cooking oil, pour it into the tank, swirl. Weld tank. done. If you're lucky it'll smell like french fries:).

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