Fuel tank install

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fallguy1000
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Fuel tank install

Post by fallguy1000 » Fri Aug 24, 2018 8:42 am

Getting closer to install time for the two 64 gallon crosslinked Moeller tanks.

A few questions.

1. If you have a two foot drop and a two foot run to the tank; how do you avoid filling the line when you fill?

2. If there are permeation vapors inside the tank compartment; how do you avoid compartment odors and is venting the compartment itself wise or useful? Is the venting of a compartment regulated? Moeller says permeation vapors are normal, but why then are tank compartments not required venting?

3. The tank has four bracket hold down pockets. Moeller's website says to only hold the tank on the aft holddowns (2) to allow for expansion. Has anyone installed a four bracket tank using only the two aft brackets? I have one inch of play for n aft on 46" tank length. A 3% expansion is 1.38". Any worries about the tank being too big? Is the for and aft void just an opening then? If the tank is allowed a 3% expansion on its width; it is about 3/4". So no neoprene on the sides either? And short the brackets 1/2" from each pocket edge?

4. Moeller says to allow 2-3% expansion in all directions. The tank is roughly like ?12" high, so 3% expansion would be 0.36" or like 3/8". Do you put foam shims under the tank and under the bracket both? How do you shim 1/8" neoprene for 3/8" expansion?

5. My fuel fill and venting locations are relatively close to a door to a habitable space. If I move the venting of the tank and the compartment; the vent would end up below the fill which is a major no-no. I can move the fuel fill and vent a little further away from the door. The door would serve as a cabin ventilation and possibly be open, but the cabin ventilation is designed to have air moving through the cabin and past the fuel venting; not past the fuel vent and through the space. If I move the fill n vent farther away; does that make sense or am I hairsplitting?

6. How do you pressure test! Do you test without the cap? Plug and shrader the fill and gauge the vent?
Last edited by fallguy1000 on Fri Aug 24, 2018 2:20 pm, edited 1 time in total.


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pee wee
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Re: Fuel tank install

Post by pee wee » Fri Aug 24, 2018 9:25 am

don't have any advice for you, but #4: 12" x 3% would be .36" or close to 3/8".
Hank

fallguy1000
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Re: Fuel tank install

Post by fallguy1000 » Fri Aug 24, 2018 12:20 pm

Yes on the math error. So my neoprene ain't gonna give 3/8" when top n bottom is 1/4" total
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TomW1
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Re: Fuel tank install

Post by TomW1 » Fri Aug 24, 2018 6:24 pm

Fallguy I don't know if it is possible but you have made some major mistakes in the location of your fuel fills and vents. They need to be as far as possible from living quarters.

Cracker Larry and I went through the new rules when they came out in 2007-8 and explained it here on the forum. All tanks must be impermeable to fumes, by USCG and ABYC rules, and A1 fuel fill hoses and vent hoses are required to prevent fumes from them. You also need to use joint fuel, vent fill and they should be mounted on the most outward part of the hull if possible. You can use separate ones but the vent must be outside the boat. There is also a shut off indicator that you can mount that will let you know when the tank is full.

Moeller made there tanks Impermeable shortly after this came out with a coating on the inside so your okay there. You just need to move your fill and vents. Use the right parts and you don't need to vent the compartments.

Use all four tie downs. Have never heard of Moeller recommending only two especially in a boat your size. Hate to see a tank come loose if you hit rough water. If you use the brackets and allow room around the tank you don't have any problem with expansion.

I hope I have answered most of your questions. If not please let me know.

Tom
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fallguy1000
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Re: Fuel tank install

Post by fallguy1000 » Fri Aug 24, 2018 10:11 pm

Nothing is located, yet. Asking the wheres, so no major mistakes and hoping for some tom help!

I can take some pics of the tank location and mockup the surrounding structure.

I am limited by the design, of course.

Watch for some pictures sometime tomorrow.

I will mock up in cardboard.
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BarraMan
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Re: Fuel tank install

Post by BarraMan » Sat Aug 25, 2018 3:04 am

fallguy1000 wrote:
Fri Aug 24, 2018 8:42 am
Getting closer to install time for the two 64 gallon crosslinked Moeller tanks.

A few questions.

1. If you have a two foot drop and a two foot run to the tank; how do you avoid filling the line when you fill?
I don't!
2. If there are permeation vapors inside the tank compartment; how do you avoid compartment odors and is venting the compartment itself wise or useful? Is the venting of a compartment regulated? Moeller says permeation vapors are normal, but why then are tank compartments not required venting?
I have 2 x Sant Marine (Aussie company) and 1 x Moeller plastic tanks. Sant Marine say the compartment that contains the tank must be vented - so mine are all vented.
3. The tank has four bracket hold down pockets. Moeller's website says to only hold the tank on the aft holddowns (2) to allow for expansion. Has anyone installed a four bracket tank using only the two aft brackets? I have one inch of play for n aft on 46" tank length. A 3% expansion is 1.38". Any worries about the tank being too big? Is the for and aft void just an opening then? If the tank is allowed a 3% expansion on its width; it is about 3/4". So no neoprene on the sides either? And short the brackets 1/2" from each pocket edge?
My Moeller tank only has 1 x bracket fitting on each end - so I just sat it on neoprene strips with calculated required clearance for expansion on each side and end.
4. Moeller says to allow 2-3% expansion in all directions. The tank is roughly like ?12" high, so 3% expansion would be 0.36" or like 3/8". Do you put foam shims under the tank and under the bracket both? How do you shim 1/8" neoprene for 3/8" expansion?

5. My fuel fill and venting locations are relatively close to a door to a habitable space. If I move the venting of the tank and the compartment; the vent would end up below the fill which is a major no-no. I can move the fuel fill and vent a little further away from the door. The door would serve as a cabin ventilation and possibly be open, but the cabin ventilation is designed to have air moving through the cabin and past the fuel venting; not past the fuel vent and through the space. If I move the fill n vent farther away; does that make sense or am I hairsplitting?
I would move the fill and vent as far away from the door as I could get it.
6. How do you pressure test! Do you test without the cap? Plug and shrader the fill and gauge the vent?

I pondered that for a long time, but in the end I just put my faith in the quality of manufacture and didn't pressure test the tanks. All good - no leaks! :D

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Re: Fuel tank install

Post by piperdown » Sat Aug 25, 2018 1:24 pm

All the other questions are waaayyyy beyond me but if I was pressure testing (and I've done a few on various devices) I make sure to plug everything.

Attach a threaded air port on one opening and a threaded gauge on another one. Seal all the other openings. Hit with 5 psi and see how it holds for 20 mins. You shouldn't have a pressure drop if everything is sealed/welded correctly. For tanks and other items like that you are testing the container, not the fittings, for leaks.

I don't know if there is an allowable drop in pressure on a boat fuel tank like there is on some equipment I test. Some equipment, if it's very leaky, I end up using helium tracer gas to track down where the leak is at for repair.
Eric (aka, piperdown)

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fallguy1000
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Re: Fuel tank install

Post by fallguy1000 » Sat Aug 25, 2018 9:34 pm

Youtube video about tank fill and vent locating.

https://m.youtube.com/watch?v=8W06CdQnBFk
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Jeff
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Re: Fuel tank install

Post by Jeff » Sun Aug 26, 2018 7:31 am

Fallguy, where will the actual fill cap go or did I miss this point on the video?? Jeff

fallguy1000
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Re: Fuel tank install

Post by fallguy1000 » Sun Aug 26, 2018 10:51 am

The vent would go on the outwale versus on top of the gunwale. That way fuel vent odors would be less likely to sink into the cockpit or doorway to the cabin.

The fill could still go on top of the gunwale to make it less likely to lose the fuel cap. I realize they can come with chains, but I could avoid the odd angled fill as well then and the stop thingy Tom mentioned?

By the way, what is that called?
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