Leaking Fuel Tank

Northern Spy said:

Rotomolded or blowmolded plastic tanks may not have baffles, but hot gas welded tanks certainly can have them integral to the tank construction. I agree with Peter, plastic tanks certainly deserve consideration. I know I would price out a fabricated plastic tank if I was in the same situation.

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What Spy said. These guys install baffles, inspection ports, CAD design etc. It all comes down to total installed cost, access and schedule.

Water, Fuel & Waste Tanks for Boats & Vehicles. Custom & Standard

I have twin monel saddle tanks 145 gallons each made by Allcraft. They are from 1970.
The tanks metal is still ok.
The one problem I have had, they used brass pickup tubes. One pickup tube rotted off the bottom 6 inches. I replaced using annealed 3/8 copper tube.

Here is a refernece from 1967.
https://books.google.com/books?id=Z...ge&q="seafarer" "monel" "fuel" "tank"&f=false

I was having terrible issues with pumps stopping pumping of fuel.
I was trying new pumps. Finally nothing was working.
So I pulled out the fuel pickup and saw this.
The last 6 inches of tubing is gone, rotted away.



A common brass tube they used on the inside of the monel tank.

This tube fits into a larger tube which is supposed to be attached to top and bottom of the monel tank. However, the bottom attachment of the outer tube has come loose, likely due to corrosion. Likely the internal components, that outer tube the pickup tube fits into is also brass not monel. My guess is monel is only skin deep.

I would not mind silver brazing a monel tank as a repair. But to remove them would require removing the engine. And as far as I can tell, the monel itself is still in excellent condition.

You can see one very green monel tank to right of the engine here.

OK - lost the full response I wrote due to whatever. Starting over -

I really like the plastic tank repalcement option. Talked to TekTanks - between the fab time and the freight - not viable. They did not (or would not) refer me to a US equivelant.

I've found a bunch of info through on line sources. A couple listed below. I'm not interested in getting into a p**ing contest re: these guys. This is like a detective story - read the info and take what seems to be relevant.

Fuel Tank Installation | Steve D'Antonio Marine Consulting

How to Install an Aluminum Fuel Tank : Boats, Yachts - Maintenance Repair and Troubleshooting

Defueling today. Hope to have them pulled next week for inspection.

Just a note for TF potential boat buyers - everything I've read indicates that there are no "lifetime" fuel tanks. Not steel, not plastic, not Al. I have a 40 yo boat. It lasted this long without an issue. I probably have gotten service well beyond the expected lifetime of the vessel. No gripes with Viking.

It seems that installation technique is nearly everything. Not everything, but most everything.

Again, the input is invaluable. Thank you all.

Properly built coated and installed aluminum tanks will last a very long time even in the worst of conditions. I expect mine will easily last over 100 years, with just a little maintenance, which means pulling the plates and looking at them. The key thing is being able to pull plates and look. Its expensive to build them like that so most dont. And building in access in the boat for access to the access plates adds yet another layer to why its not done. And it needs to look good, double difficult. No boat builder would go to those lengths, just no money in it. People wont pay for that. I require it.

http://triplemplastics.us/custom-fabrication/

http://www.barrplastics.com/custom-plastic-fabrication-welding.html

Barr had a nice write up in Pacific Yachting a few years back on a holding tank.

http://www.dura-weld.com/index.htm

http://www.greycoproducts.com/storage-tanks/

http://www.plasticweldingrepairs.ca/plastic-fabrication.php

http://www.customplasticfabrication.com.au/services/marine-plastic-fabrication-applications/ and speaking of tanks, the AUD just tanked a few days ago.

Note: I'm not really advocating plastic tanks, I'm just pointing them out as an awareness exercise. I believe it may be a viable option. I've purchased fabricated plastic tanks for industrial services. I do see that some fabricators shy away from fuel tanks. Liability reasons maybe?

kulas44 said:

I agree that plastic is great, installed properly, For vehicles and small boats, but the problem is that in sizes large enough for most of our purposes they dont work because they cant be baffled.

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They can actually, as Spy says, but another great thing about them is it is often best to use 2-3 smaller tanks a side, interlinked in such a way that when large volumes are not needed excess capacity can just be closed off by taps between them. Makes the installation a breeze because of the smaller size, and doing that make baffles superfluous.
Here are the people I got my water tanks from, as an example - they are out there. The US will have similar, I'm sure.

http://www.atlastanks.com.au/diesel.html
http://www.atlastanks.com.au/marine.html

Peter B said:

They can actually, as Spy says, but another great thing about them is it is often best to use 2-3 smaller tanks a side, interlinked in such a way that when large volumes are not needed excess capacity can just be closed off by taps between them. Makes the installation a breeze because of the smaller size, and doing that make baffles superfluous.
Here are the people I got my water tanks from, as an example - they are out there. The US will have similar, I'm sure.

Atlas Tanks - Diesel Tanks
Atlas Tanks - Marine Tanks

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But, with the Viking having good access to remove the tank and re-install same why monkey around with small interconnected tanks? Just get one cost effective tank properly made and move forward. Most likely Al construction is the price winner, but the OP is getting to the nubbins on the $$ question.

If the OP's vessel were hauling acid instead of diesel then plastic would be the clear winner.

sunchaser said:

But, with the Viking having good access to remove the tank and re-install same why monkey around with small interconnected tanks? Just get one cost effective tank properly made and move forward. Most likely Al construction is the price winner, but the OP is getting to the nubbins on the $$ question.

If the OP's vessel were hauling acid instead of diesel then plastic would be the clear winner.

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Consider though today, all fuel haulers are hauling acid fuel.
All fuels form acids, mostly from biology, stuff grows in tanks, forms acid wastes that eat metal. Used to be gasoline would not, but then they put alcohol in there, and get some moisture from air mixing into fuel, and even gasoline grows acetobacter bacterias.


https://www.dieselnet.com/news/2014/07nist.php

And ethanol may contaminate diesel, diesel grows bacterias regardless.
https://www.dieselnet.com/news/2012/09pmaa.php

sdowney717 said:

Consider though today, all fuel haulers are hauling acid fuel rl]

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Well, when I see metal storage tanks and metal fuel haulers all converting to plastic I will worry. Maybe I'll keep a pair of rubber gloves handy though. The sky is not falling, yet.

sunchaser said:

The sky is not falling, yet.

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Ah...but can you be sure it is not slipping..? These tanks are expected to last 20-30 years. What if biodiesel is mandated in 4 year's time..? Aluminium tanks will slowly dissolve...

My plastic tanks are rated at 58 gallons per tank.

Combined, they have an easy 100 gallons useable as several of my fill ups have been 100 gallons.

I stayed with 2 tanks as a 330 mile to 350 mile cruising range is plenty for my boat...true distance cruisers may want more...I could have added 2 more and doubled...but I prefered the storage space.

These tanks are rotomoulded plastic with a donut hole in the center that acts as a baffle. Being able to see into the tanks when filling or checking fuel is a delight....I believe I can also tell if the fuel is cloudy but haven't had bad fuel yeti the last 600 miles with these tanks.

For single engines trawlers that don't want a big expense, these factory ready Moeller tanks at $300 per tank and easy to fit were the ticket.

And worrying about them and the future? I believe the kind of plastic used holds most chemicals known to man in labs all over....and more and more on the back of trucks riding down rough roads with who knows what in them.

I think I made the best choice for my overall needs. Other boats have other issues...but don't rule out simple and inexpensive because plastic sounds cheap.

SBU22

Fuel tank failures of this sort are a heartache to be sure, I sympathize with you. Sadly, most are completely avoidable too. As you said, saving grace is the tank is removable without major surgery.

"5. Reinstall – what provisions/precautions should I take? Set base on neoprene, provide neoprene “insulating” material between structural elements and tank shell. Anything else?"

While it's exceedingly common, I avoid using neoprene strips for elevation or insulation, the material is too flexible and prone to crushing over time.

The goal with aluminum is to elevate the tank off the shelf on which it rests a minimum of .25", to allow water to flow under the tank and not be trapped.

What ever material shim you use for this elevation, it must be non-hygroscopic and crush-proof, and compatible with aluminum. I use GPO3, which is essentially prefabricated fiberglass. Shim strips should be oriented athwartships to allow water to drain when the vessel rolls.

The shims must be fully bedded to the tank, eliminating any gaps into which water could flow, leading to poultice corrosion. The bedding could be polyurethane, and must have ample squeeze out, the tank surface should be thoroughly cleaned and de-waxed using solvent, and then abraded using a 3M Scotchbrite pad, and then solvent washed again before adhering the shims in place.

The tank should be built with mounting brackets that can be through bolted to the shelf on which the tank rests. This avoids the need for cribbing and for any other potentially poultice-inducing material to make contact with the tank. The entire bottom of the tank should be supported (on the shims), avoid overhangs. Any other supports that are required, which make contact with tank, should use the shim/bedding protocol mentioned earlier.

If you are having a new tank fabricated, the top of the tank should slope, to avoid standing water from a deck leak, preferably inboard.

Any plumbing fittings attached to the tank must be galvanically compatible with aluminum, i.e. not brass or bronze, stainless is acceptable.

Virtually all of the above recommendations, and more, are codified in "ABYC H-33 Diesel Fuel Systems".

Personally, having designed and installed scores of replacement fuel tanks in my career, I avoid exterior coatings on aluminum tanks, I believe they are unnecessary and can be counterproductive. Aluminum remains corrosion resistant when exposed to air. The coatings can actually exacerbate corrosion if breached (scratches and nicks will invariably occur during installation), water enters the breach and migrates under the coating, where there is no air, and corrosion gets a toe hold, I've seen happen. This occurs on painted aluminum hardware on a regular basis, tanks are no different. Hopefully the environment in which tanks are installed is too dry for any of this to occur, but still, if the tank is exposed to air, as it should be, coatings are unnecessary.

Aluminum tanks corrode from both inside and out. Clearly keeping the exterior of the tank dry is paramount. Water inside the tank will ultimately cause pitting, and if it supports biological growth, as it invariably does, the byproduct is hydrogen sulfide, which is corrosive. I've seen aluminum tank bottoms turned into moon-crater like surfaces in less than three years by water and biological contamination. If your primary fuel filters "produce" water regularly, then you have water in your tank.

As others have noted, and in my experience, interior patch coatings are a waste of time, I have yet to see any work long term on a tank that's already been exposed to fuel.

sdowney717 said:

What they need to figure out is an airfree tank with no vent to the air. No air, no water, no bugs, no acids, no bad fuel. Maybe a floating membrane on top of the fuel that moves up and down with changes in fuel level. that is sealed away from the air.
Maybe like a balloon of fuel in a rigid box.

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That's been done in cars - the Toyota Prius had this for at least the first two generations. They have an expandable bladder inside a steel shell. Apparently it was done to reduce vapor emissions as part of the 'green car' effort. It hasn't been prone to failure, but of course is pretty small - 10 gallons or so. I agree that it is likely not scalable and haven't seen anything similar on boats.

Nice write up Steve D. What is your experience with marine diesel tanks say above 150 gallons as an alternative to AL or Fe?

I would be interested to hear as well. I haven't checked, as I don't have my reference material, but I'm pretty sure plastic wouldn't be allowed on an inspected vessel by CFR regulations.

In fact, I doubt it would pass the test fire in H-33.

sunchaser said:

Nice write up Steve D. What is your experience with marine diesel tanks say above 150 gallons as an alternative to AL or Fe?

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Thanks. Given the choice, for diesel, my tank material preference is fiberglass, using a fuel-approved resin. I can't recall the last time I encountered a failed FRP diesel fuel tank. To their credit, Hatteras was using these 30+ years ago. I've cut open (one shortcoming they have no inspection ports), these old tanks to clean them and after hot water pressure washing they look like new. That simply can't be said about virtually any metallic tank I've ever opened. The challenge is they are expensive to manufacture, so they are usually deemed impractical unless it's a high end vessel or production application. Which means the only practical alternative is AL. Done right, and kept free of water, AL will last a very long time.

There are some relatively large roto-molded polyethylene tanks out there now (a British company is making welded poly tanks, which means they can be custom made to virtually any shape or size, however, I don't believe they are selling these in the states, at least not for fuel, but they are available for water and waste), several production builders are using them. They are corrosion proof and can stand in bilge water and get rained on by deck leaks with no problems. They can't be fully baffled, they are prone to distortion, they usually don't have inspection ports, and they undergo hydrocarbon expansion, which means they grow in all directions between 2%-4% the first time they are exposed to fuel, which means the mounts need to take this into account. For smaller applications, center consoles, tenders etc. I believe they are ideal. As far as fire resistance and ABYC H-33 goes, Moeller, which many manufacturers use, says the following, "All Moeller permanent tanks are ABYC and NMMA compliant..." which at least implies it meets the flame resistance standard. I know some builders who use these tanks do participate in the NMMA/ABYC certification program, which, in theory at least, means the tanks would need to comply.

Steve DAntonio (#73) – really appreciate your input. I wrote “5. Reinstal …….. neoprene….” before I read your article that I linked to above. Valuable information.

Sdowney717 (#42) – the concept has been around a long time in the hydrocarbon/chemical bulk storage business. It’s called an Internal Floating Roof – used as a product loss/emission control measure. Good concept as long as the IFR remains floating – once they sink or cock, big trouble in engineering a safe recovery.

Pretty much along the lines of the discussion, I’ve looked at several alternatives:
1. Bladder – Sounds easy until the need to create a baby’s a** smooth containment surface is considered. I am assuming that the existing tank shell is in pretty rasty condition or it wouldn’t be leaking. Additionally – no baffles. Instead there are foam inserts that even the perceived industry leader (ATL) projects have a life expectancy of 7-10 years before they dissolve into the fuel. Finally – yeah the NASCAR and Baja guys use them. How many of those rigs are expected to be in use for a decade (or more than a season, for that matter)?
2. Plastic – All of the above comments, confirmed by Inet “research” seems to indicate relatively high cost, internal baffling tricky, all exacerbated by difficulty finding sources for capacities in the range of 150 usg.
3. Patching/lining compounds – I’m just not willing to bet that the resources I have available are capable of creating the clinically clean surfaces required for the sealer’s bond to work. If I were going that route, I think the CS 3204 would be my leading candidate.

As an update, the tanks were defueled over the weekend. The odor that triggered this exercise disappeared, as well. I have to believe that the pump out rig used left a heel in the tanks (1/2 or 1”). So, guessing that the leak is higher than that. Or, the leak is in the bottom and the reduction in static head was sufficient to stop the oozing.

Question – regarding the use of SS plumbing fittings – Will any SS work or are we talking a particular grade (304 versus 316)? The originals are bronze with what appears to be a fairly substantial tape applied to threaded surfaces. At least from the exterior, no visual indicators of corrosion. Not that I propose to go back that way, but interesting 40 years in.

I to have read and heard advice to not use brass/copper fittings on aluminum tanks. I have also seen lots of aluminum tanks , most in fact, that have had them with no problems as far as I could tell.

sbu22 said:

Steve DAntonio (#73) – really appreciate your input. I wrote “5. Reinstal …….. neoprene….” before I read your article that I linked to above. Valuable information.

Sdowney717 (#42) – the concept has been around a long time in the hydrocarbon/chemical bulk storage business. It’s called an Internal Floating Roof – used as a product loss/emission control measure. Good concept as long as the IFR remains floating – once they sink or cock, big trouble in engineering a safe recovery.

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A supple plastic closed cell foam sheet placed over the fuel floating on top, maybe even bubble wrap type material? It is fuel proof even for gasoline. Actually those who have open clean outs in the tanks could experiment with that idea. fuel will slosh around, but see it has all these built in floats, it will always float on top of the fuel. Such a thing would reduce the air to fuel interface, which for me and gasoline would help preserve the volatiles in a large tank, etc...Whether keeping diesel away from the air is beneficial, I dont know.

Now for a fully sealed tank design--------------

Fuel tanks could have a soft flexible plastic sheet formed like a bag on top of the fuel and the fuel fill would fill the tank below the sheet. The sheet would not have to stretch, it could just wrinkle up with the incoming fuel and straighten out with the outgoing fuel level.

A common HDPE plastic sheet is fuel proof. So design a tank where the entire top is removable, secure the plastic sheet inside on the top edge, then seal on the hard tank top.
Return vents can be on the tank side as well as pickup tubes. The fuel fill could also enter the tank side with fill pipe going down to tank bottom.
Leave enough room for fuel expansion above the plastic sheet and you would not need a tank vent open to the air for fuel, the tank vent would vent the air above the plastic sheet as the fuel level went up or down and also with temperature expansion and contraction, see this tank is 100% sealed away from the atmosphere. So no water to cause fuel degradation.

Tanks could still be fully baffled, each baffled area would have its own plastic sheet (bag) .

Imagine in a long rectangular tank, each bag would fully extend to tank bottom when tank is empty inside of it's own baffled area.

Such a tank would also be easy to clean out the entire tank or repair it simply by removing its entire top.


I had a destroyed fuel level float in an old portable Tempo tank.
I took some of that white closed cell packing foam sheet and used that to create a new fuel tank float, wrapped it around the shaft secured with cotton kite string. It has worked great now for over a year, no degrading in gasoline.

The saga of the tanks continues. Thought it might be helpful to others that may encounter the situation. With a little time to stand back, several notions come to mind.

First, I’m glad I discovered the issue while in the slip and not 300 miles from home.

Second, I guess I always assumed that a leaking tank would be discovered as fuel coursed its way through the bilge and puddled up at a low point – at least not the case here. It’s obvious that this oozing has been going on for a long time. Odor (and not that strong) was the tell.

Third, at least in this case, you can hope that there’s a localized problem that a patch will cure; after a good bit of looking and talking to pretty solid and reliable folks, it seems that localized (barring a mechanical puncture or a stress crack) damage is rare. Corrosion is the likely enemy. More like a disease than an event.

Fourth, although there are many material choices for fuel tanks, the drivers of cost, availability, internal baffles, and tank size favored aluminum, at least in my situation. If wishes were things, I guess they’d be monel.

Fifth, and probably obvious and old news to the experienced hands, aluminum fuel tanks (unlike my statement in the original post) are not bulletproof. In fact, aluminum is quite susceptible to moisture induced corrosion in an oxygen deficient atmosphere.

Sixth, the boat builder (Viking) got 40± good years out of the installation. I really don’t expect they planned that Panache would still be on the water that long when they built her. There were flaws (at least as they are now understood) in the install related to the use of neoprene and other resilient foam material as electrical isolation and shock absorbing material.

If I can figure it out, I’ll post some pictures of the damaged items.

This is pretty much what I was looking at when they were installed. The lower, darker discoloration is from contact with the neoprene surround at the base. The transverse discolored strip is where the steel holdown brackets were installed. Installed and with the sight lines available, they looked pretty good to my eyeball.

Well, that was a failure.

I'm going to give this one more try.

Now, the bad news:

One more time. Patience is a virtue.

Tank bottom in full contact with the well supported (robust full structural shelf) covered with neoprene shock absorbing material. Exactly what all of the sources I've consulted say should not happen. An engineered moisture trap.

If you having new tanks fabricated, perhaps they can place supporting legs on the tank along the stringers/shelf to keep the tank above the moisture trap. You lose a little tankage, but it's worth it if the tank lasts for the next 50 years.

Yeah, new tanks are in fab right now. I took the advice of several local TFrs, kicked around the industrial waterfront and talked to several high quality commercial marine shops that are on their a** due to the offshore oil "slump" and found a good deal.

Good suggestion on the frame, Al, but there are some location specific issues that make that difficult. It's kind of a sight gag, or I'd try to describe it.

I'm going with starboard or GPO3 transverse strips bonded to the tank bottom with the devil's spawn (5200 or similar) at say, 6" intervals with sufficient depth to have at least 1/4" clearance for air circulation. Basically what D'Antonio recomends in the piece I cited above. Will probably bond the lower side of the impermeable strips to same size neoprene (or something) strips to provide a modicum of vibration damping. Still working on details.

Then of course there is Monel.

Or if the tank is being custom made a steel tank with a deep servicable sump will see all the water , and bugs in the sump , (if its serviced) not in the tank.

ONLY a working sump can solve the hassle of a bad (say 50/50 fuel and water) load.

Gravity and a simple hand pump does the trick.