I was ask to fix another fuel tank its a square tank that is used to haul fuel in a pickup i think it is 100 gallons. Both had angle iron that some one had weld on to bolt it down and thats were they crack at the welds. I welded one earlyer this summer that had the same problem i havent ask how it was doing. I wonder if i am wasting my time and they will crack agin in the same spot?
It's funny you ask. A buddy has a Fecon mulcher that's got a stress crack leak. My normal procedure for crack has always been drill a hole in each end to stop it. Clean it out and weld it up. Can the angle be removed? Relocated? Done in a different way? Some of those tanks are so thin it's a wonder they last very long at all. I reckon they way they use it, where they drive and how often crap hits it or falls on it may have an impact on the life of the weld. Also, I wonder if the vacuum affect while pumping fuel has any affect on them? I always crack the filler before I start pumping.
What we used to do was either a heavy chunk of rubber as an insulator, or long bolts with exhaust flange springs. This would allow the tank to settle and sway . We rarely had tanks fail when mounted like this.
These tanks for some reason were set up to bolt down and never bolted to any thing. It would be alot of work to remove the welded on iron and some more welding that i think may cause some new problems. They are owned by freinds or i wouldnt have worked on them.
If the tank is thin you could make metal straps like they use on truck fuel tanks to hold it down.
I preferred to set them with strapping, less convenient but easier modified for a replacement tank/box rather than drilling new holes.
I had the exact same problem with a Fecon mulcher I had leased a few years ago. Fecon had to fix a bunch of those machines under warranty due to fuel tanks cracking. The tank was incorporated into the frame and repeated stressing caused them to fail. The mechanic drilled a hole at each end of the crack, had me fill the tank with fuel, then welded the crack. I had the machine another year, and the crack never reappeared.
Interesting to know there were warranty issues with that. If my friend ever slows down I bet it comes to me for repair.