I've pulled both gas tanks out of my 24' Grady White to replace the stringers and was wondering how can i test the tank for leaks. Actually, it has two tanks, both 100 gallons. One is a factory aluminum but the other is a "custom" stainless steel. I' ve never run the boat, so before i fuel in it, i thought it might be a good idea to check. I've thought of putting them on one at a time on sawhorses or blocks and filling it with water or, pressurizing it with my compressor and use soapy water on the outside. However, i'm not sure what pressure those tanks will withstand. Any ideas or suggestions are appreciated.
IMO those tanks should never be pressurized beyond 25 psig. the best way to check is to fill with water and then put 25 psig and look for leaks. fluid will find a hole faster than air and it seems to find all the pinholes that could be in there. also get some food colouring to add to the water to help ID the possible leaks
thanks for the quick reply starrider. I should be able to fill them up and test them this week. If i should find a leak, i'll be posting again on this topic.
STOP!!! 4-psi MAXUMIUM!!! 25-psi (about 1-2/3 bar) can blow the tank apart!!!Safety specs put new tank testing at 4-psi. Used tanks are often tested at 2 to 3-psi.To do the testing properly, remove all fluid and test with air pressure only. Use a manometer to measure any drop in air pressure.
I've had good luck doing it on the bench or sawhorses. Cap the vent/outlet- or even connect them with a rubber hose. Hold a rag wrapped around a air hose and presurize the tank. You won't be able to build up more than a couple psi that way. Even a shop vac. hose on the vac's exhaust side will work.Have a assistant go around with a spray bottle of soapy water generously spraying any suspect seams or whatever. After it's sprayed, if it leaks, you'll see it in a second or two.
Air presure and very soapy water. It's the pinhole leaks that you will have to look carefully for. The pinholes wont put out any large bubbles, just a very tiny sream of tiny bubbles.I used to weld alum. and steel diesel fuel tanks on a production line. The pinholes on the alum. ones we "sealed" by punching them with a hammer and punch. That would stop the leak. I have always wondered if that was a perminant fix? It's not how I whould seal my own tank.
Okstate, I don't know if you got this problem fixed, but I'll give you another solution that you might want to try, for two reasons. I'll cover the reasons after the method. Go to any weld supplier and ask for a can of liquid penetrant and another of developer. The instructions are on the can, but I can lead you through it very easily. The process is simple enough. Spray the penetrant onto all of your welds. It will draw into any openings in your welds. Wait 7 to 10 minutes, clean the surface penetrant off, and spray developer on. The developer is like flour, and will draw penetrant back up out of the cracks. Depending on the indications you get, you'll know how deep the holes are. The hardest part of it is interpretation, but if you go with this, I'll tell you what I need and I'll interpret it for you. This is what I do for the Navy. Now, the advantages of this. 1st, it's very simple. No air pressure worries. It's cheap, and it's accurate in reading what's below the surface. If you have porosity, laps, seams, etc... in the surface of your weld, it would be best to know how deep they are. This way, you can fix it right now and avoid a leak in the future. Anyway, I was doing a search for something else and saw this. I thought it might help, if you haven't finished your work yet, or maybe it will help someone else.
thanks alot swimmin'. I always welcome suggestions, especially novel ones like that one. I'll try and pick some up this week and post the pics by early next week. thanks for the idea.
Good for you. You're going to need some help reading the indications. I'll help you with this, if you'd like. Email me directly. foster.james@lincoln.navy.mil The size and shape of your indications will tell us what may need to be repaired. The deal is, though, that you'll need to test 1" on each side of the weld, and the area you best should be clear of dirt, paint, etc...You can use acetone to clean it, but no wire brushing. They'll show up as indications later, and make true indications hard to read. Still, this is fairly simple but email me if you have any questions at all. I love this process for how accurate it is, and it's worth the peace of mind.
I pressurized both of my 100 gallon gas tanks today with the discharge end of my wet/dry vac. I duct taped up the fill,vent and one of the discharge nozzles and then taped the vacuum hose to the other discharge nozzle and let her rip. I sprayed all welds with soapy water and found no bubbles. I then followed up with swimmin's suggestion using the penetrant/developer technique. I'll post pic's tomorrow.
Here's the pix of my aluminum gas tank after using the developer/penetrant technique. It looks worse than it reall is 'cause i put a little too much penetrant. I circled the areas of concern with a pencil. my welder was concerned with welding the spot on the bottom due to the age and condition of the aluminum...afraid of blowout. Anyway, i'm pleased with the new (to me) technique. It appears to show more porosity and possible future leaks that couldn't have been detected with soap and bubbles. http://152.20.76.250/iboats/boat/alu...bottomrear.jpg
HI Okstate. You did a good job on the penetrant test. Being as how I've spent the weekend on a native island, surrounded by beautiful women, I'd have to say you've done a better job than me incidentally. Now, to serious business. The bleedout only needs to be read on your deepest spots here. There are other possible discontinuities, but I don't see any of them in your tank. What I do see is those heaviest spots, and I'm sure you saw them beforehand. I measure by the width of that bleedout at it's widest places. Quite honestly, even with just a picture, I'd tell you that that tank wouldn't pass an inspection as a sprinkler system. With respect for safety, please, PLEASE look at replacing that tank. Another aluminum tank might cost a bit. An alternative is plastic, of course. You'll find a lot of discussion on that. I'm glad you were successful with the test. You're right about it showing a lot that a regular soap test won't show. Though you didn't have them, it will also show a lot of other discontinuities common to aluminum if you do it on other applications. For anyone else who ever wants to try, this test is good for any fairly non-porous material. Stainless, aluminum, even porcelain in case you ever want to have some fun when you're drinking.
Thanks for your input Swimmin. So basically, one or two holes that you can see is indicative of much finer pores that cannot be successfully repaired. Honestly, i thought worst case scenario, drill out the visible holes, clean and prep the area and weld a plug into it. Clean the entire tank and cover with epoxy. I never even dreamed of having to replace the entire tank. Ain't boating fun. I do have a 100 gallon stainless steel tank that didn't show any deep bleedout. Trouble is, its only about roughly 1/8" thick material. In fact, if i push down with my hands, i can deflect the top...not permanently though, it returns to its original position with a boom sound. I think it has a baffle in it, but need i even consider using this?
I had exactly same problem, corroded pinholes, caused by saltwater in bilge.Ended up sanding tank on outside and laying up 2 layers of thin mat and a special epoxy. Held up beautifully. Just get a priming acid for aluminium to prime tank first. Easy fix and cheap compared to new tanks. I think gas resistant epoxy is available from west.
Sure. If you can clean up the holes and weld them, then do it. If epoxy is compatible with aluminum, do it (I don't know). I'd do either one of those things. They're both long-term fixes. I'd just be sure to do something. Your aluminum is in bad shape, and the middle of the water is a bad place to start smelling gas.
okstatefan, what type of 24 foot Grady do you have?I have a 24 offshore that probably needs stringers because my floor is soft in a few spots and I am sure there is more rot under the floor. if you have any pictures or advice it would be greatly appreciated.
It's an '87 Offshore Pro 24 walkaround cabin. Stringers, particularly the inner ones (that line the gas tank compartments), the bulkhead (that separates the bilge and rear gas tank compartment) and gas tank failure are common among the 24's. If your soft spots are underneath the gas tank compartment lids, the bracing underneath (on top of the gas tanks) may be comprompised. That's relatively easy. If your soft spots are outside of the gas tank compartment lids....ask for forgiveness for the words you'll be saying later. I'll post pix of my stringer replacement project this weekend.
If you don't haave a manometer I have used a balloon on a piece of rubber tubing. Pressurize till the balloon is quite full. Close air source valve. measure balloon circumfirence, let it sit for a while 20 minutes and remeasure. Should be the same.
okstatefan,I have started asking for that forgivness. I know this project will be involved, but also totally possible. I do have an enclosed shop to work in. were your stringers under the cuddy walkaround ok?that is my main concern because that seems like it would be hard to get to. please post pictures or you can e mail to markwest@charter.netthanks
test aluminum gas tank for leaks
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