Re: Fuel Tank Leak
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My tank had what looked like a gooey brownish tar like deposit in the lower part of the tank. The upper parts of the tank looked pretty clean. I found that Acetone would cut the deposits so I added some Acetone (a liter or so) and rocked the tank back and forth. I then removed the shut off valve and drained as much of the solvent out as possible. Then working through the shutoff valve hole I swished around a pc. of cloth on the end of a flexible wire to help remove the deposits and soak up the remaining Acetone. I probably repeated this process at least 10 times at which point the drainage was coming out clean and the inside of the tank that I could see looked shiny so I this method seemed to work pretty well. I was able to dry out almost all of the Acetone using dry rags poked into the shutoff hole. Acetone wants to evaporate quite quickly so I just left the fill, vent and shut off valve hole open for a couple of days until the Acetone smell was essentially gone based on the smell test. I then placed a wet dry vac on the ground well away from the boat and using a long hose drew fresh air through the tank for an hour or so to be really sure that all fumes were removed before the welding. Recognize that a wet dry vac is an ignition source so if you use this method be sure that essentially all of the fumes are gone and that you place the vacuum well away from anything important just in case! I was confident that the Acetone was gone at that point but if something bad was going to happen I wanted it to happen away from the boat and not during the welding.
All of the cracks were located on the forward end of the tank and the tank fits up pretty close to the bulkhead. I used a dental mirror initially to find the cracks. In retrospect and given that removal of the tank is really not that hard to do, I think that I could have saved time just moving the tank into the pass thru area so that I could fully inspect the tank directly. I was actually able to inspect every surface of the tank, even the bottom. The crack that was seeping was not very obvious, quite fine. I will try to attach a photo to this post. The other cracks that I found were even less obvious.
The welder was naturally concerned about possible fumes in the tank. I explained the process I used to clean the tank and then he smelled the fuel fill pipe and was happy with the lack of fumes. I spent a few hours going over the whole tank ahead of the welding process, cleaning and polishing areas to locate all of the cracks. I marked everything that I was able to find. The welding only took about 2 hours and the tech welded a lot of spots that we not leaking.
Best of luck and if you have additional questions that I can help with let me know.
From: Dennis Johns <sbmesasailor@...>
To: main@AmelYachtOwners.groups.io Group Moderators <firstname.lastname@example.org>
Sent: Tue, Dec 29, 2020 12:54 pm
Subject: Re: [AmelYachtOwners] Fuel Tank Leak
Thanks for your response, sorry that you had to resolve this problem before me but glad I have an alternative to cutting through the deck. Yes, I know the tank fits in the companionway to the aft berth, I've had it out before....Some questions:
1) Did you do the cleaning yourself or if not what type of person did you hire?
2) How did you find the crack(s)? Were they obvious or is there a special method?
3) Wasn't the welder concerned about residual fumes?
3) How long did the process take?