Moving fuel tank

[zellerj]

Russ's information about cross linked poly tanks being permeable was new information to me. I always figured I'd go poly if my aluminum tanks ever developed leaks but pending further research, tank permeability on my gasoline powered boat is a deal breaker.

Time for some research and testing
This news reinforces the importance of keeping water out of metallic fuel tanks, even stainless that undergoes metallurgic changes at the welds. Avoidance of corrosion driven pinhole leaks will prolong the life of metallic tanks indefinitely. Despite our best efforts water often finds its way in so how can we mitigate that easily and efficiently? I'm brainstorming a periodic pure ethanol rinse. The knock on ethanol is that it combines and holds water, why not take advantage of that property? Pump out all the gas possible, pour in a gallon of pure ethanol and then pump that out. Whatever water may have been in the tank will be removed with the ethanol and I believe whatever residual ethanol remains would be insignificant and certainly a better residue for the tank than water.

It looks like pure ethanol is available at roughly $20/gallon but if it's shown to be effective it's seems like chump change compared to tank replacement.

When my aluminum tank (Catalina 30) developed pin holes and leaked, I had a local fabricator put a new aluminum bottom on my tank, that ran up the sides a few inches. the old tank bottom was not removed. Cost me about $80. Should be be good for another 30 years. But Neil, you are absolutely right - without water, I would not have had pin holes in the first place.

An ethanol rinse is a good thought, however acetone would be similar to ethanol at removing water, but would be better at removing organic junk (tars, etc) and cleaning the tank. The solubilizing ability of acetone is pretty amazing. Blowing air through your tank for a while would remove all of the acetone, but probably not necessary to remove it all before adding gas.

[GregH]

New tank arrives today but have to wait until this 48hrs of rain you East Coasters sent us to leave before I can get the tools out!

[tac]

“48hrs of rain”....That’s just a down payment on the sleezy weather (no body to it) you inflict on us every winter.

[joe_db]

IMHO a very likely way for aluminum tanks to corrode is from the outside in. My tank sits on drydeck squares that sit on a starboard (plastic) shelf. The routine systems of a tank on a wood shelf will corrode the tank AND rot the wood. Not sure about inside, but temperature cycling around here in colder months leaves a lot of water collecting on the outside.
* probably the ONE benefit of our horrible alco-gas is that small amounts of water are just absorbed and burned and do not collect on the bottom.

[lat 64]

Just to add to the story of my experience; It was a portable plastic tank that gave me gas odors in my Cat 22. Gas odors, not gas fumes.

The Moeller tank in my columbia has been great. No odors.
we must not throw out the baby on just my one story.

My boat is plastic and so is my tank. All good.

[ndutton]

Russ, I'm appreciative of what you uncovered in Moeller's literature. It's not your information that bothers me, it's the manufacturer's. I'm also glad those of us who have the Moeller tanks are not having permeability problems . . . but a gas tank that the manufacturer warns is naturally permeable? I don't think so.

[joe_db]

PERMEATION

Permeation is a natural phenomenon of gasoline in a cross-linked polyethylene fuel tank.
Permeation is the result of gasoline fumes escaping from the fuel tank, not the loss of liquid fuel.
Several precautions need to be addressed when using a cross-linked polyethylene fuel tank:
• Fuel (gasoline) vapors settle to the lowest point in the compartment, therefore, a means for removing the fumes is required. See ABYC Standards Section H-2 for specifics.
• A covered boat will not allow these fumes to escape, so build up of these fumes is inevitable. Caution should be taken when a boats fuel tank contains fuel and is covered for an extended period of time. A boat cover should never cover the fuel tanks exterior vent fitting(s).
• Fuel vapors will migrate to any compartment open to the fuel tank. The smell of fuel vapors does not necessarily mean that there is a leak in the fuel tank, but a closer inspection should be performed.
• Fuel vapors may be absorbed by other objects located in compartments where fuel vapor may migrate. Following the above precautions, a cross-linked polyethylene fuel tank will provide years of service.


Hmmmm- I guess the same could be said of any kind of flexible hose too, but are we talking 3 molecules a year or 3000 a second

[ndutton]

To me it’s not a matter of an acceptable level of permeation. I look at it much like a Vetus blow molded waterlift or that plastic Boater Bits raw water strainer I had.

Had, past tense.

[sastanley]

To me it’s not a matter of an acceptable level of permeation. I look at it much like a Vetus blow molded waterlift or that plastic Boater Bits raw water strainer I had.

Had, past tense.

Oh boy, I have a Moeller tank, with the plastic Perko fill, a plastic Vetus muffler, and the Boaterbits plastic strainer. All of mine are holding together OK, but certainly there are risks with each..however, I've had no trouble with the Moeller tank which I installed in 2009. (or any of the other things, either.)

[GregH]

Just got the new tank. Can't say I smell any gas fumes at all!

[sastanley]

Greg, Will you be able to incorporate their integrated hold down clamps into your design ? ?

[GregH]

Greg, Will you be able to incorporate their integrated hold down clamps into your design ? ?

Short answer is no.

On each end are two 1/4"-20 threaded inserts. The company told me they were just for bracket position adjustments and not designed as hold down positions. I don't know how strong they are but I would assume strong enough to prevent lateral movement. Not being a Moeller tank they don't have the moulded ledges for that brand's hold downs.

I will be building wooden corner blocks to prevent lateral movement and two 1" webbing rated at 1200 lbs each to strap it down. Under the tank will be three 3" wide rubber strips and between the strips the plywood will have holes drilled for any potential moisture to drain off.

That's where my thoughts are at the moment.


The adjustment threads are the two dark spots on the lower left where a slotted angle bracket attaches. There are another two at the other end.

[sastanley]

Greg, I understand...that sounds Ok to me, but I am not a mech. engineer.. I glassed in PVC boards in the bow for my 25 gal. holding tank with straps over the top and it hasn't moved yet..

[GregH]

yep. Of course all the wood will be slathered in epoxy for sealing the lumber. If the weather cooperates this weekend, will get the table saw out and get it done!

[GregH]

Almost there. Platform and hold downs all built, just have to drill drain holes between the rubber strips and paint the wood. Hope weather holds over next few weekends to get it installed.