The inside of a fuel tank

[capngeo]

Interesting thread! I too lost a tank in my '86 CAL28 about three years ago. My biggest problem is lack of fuel turn over (I'm still burning the fuel from the first fill of the new tank). I only run the aux for 20 mins or so a month for exercise. It is a rare day in Key West that we don't have wind enough to sail.

[Aloha_float]

Originally Posted by thinwater

It can be bacteria, but that is not the only thing. I am and API tank inspector and the corrosion pattern is very common. Much of the time bacteria play no part (tanks that are boiled, for example).

• Stray current.
• Salt in the fuel (fuel station flooded?).
• Condensation that extracts acid from the oil. The acid can exist in the fuel from the supply train, not just bacteria in your tank.

While a biocide can kill bacteria, additives like StarTron and Stabil will inhibit corrosion from a wide range of attacks. These 2 have been independently tested to be particularly effective on aluminum. Several other additives can actually make aluminum corrosion worse.

Polishing can help, but it will not remove dissolved water and the acid and salt in that dissolved water. I have done corrosion testing studies where the fuel was saturated with water containing corrosive elements and then polished. The polishing made less difference than you would think.

(While Star Tron's claims about helping prevent phase separation in e-10 where not supported by testing, it is NOT smoke an mirrors. It is moderately effective as a biocide and quite effective as a corrosion inhibitor. And I don't have a dog in the fight.)

Salt is a good point. If you do dissolve the biofilm and water remains, the salt will create a brine which is very effective as an electrolyte. I go back to my days in engineering school where we tested the resistance of distilled water versus salt water.

The key to an amine coating is the electrical impedence of electron transfer between the base metal and the electrolyte. Even in the presence of an electrolyte, corrosion is prevented as amines impede the set-up of a galvanic corrosion cell.

We have done some testing regarding phase separation in ethanol blended fuels and have found a bacteria layer between phases. Once we dissolve this phase, we clear up the separation issue. This would make sense with the use of enzymes as well. We have not drawn any conclusions on this, we just feel that bacteria may play a role in this case as well.

Grounding tanks is one way of avoiding galvanic corrosion however, MIC is still an issue. Grounding (or cathodic protection systems) are not effective against SRB or MIC. Pipeline professionals can attest to failures due to MIC even with the presence of galvanic cell protection.

[Delfin]

After a few thousand gallons of diesel burned, some of which is a year old once burned, I have never seen a trace of water or contaminants in the Racor bowls. The system I built probably isn't worth it for a sailing vessel, although the cost and bother of replacing a tank might be enough of an offset to warrant a decent polishing system. We take advantage of rough weather, especially when the tanks are low, to polish under the theory that whatever is in them will get stirred up and filtered out at that point. Polishing systems are not that tough to build, IMO, but if you do build one, use a pump that can move the amount of fuel rated for the filter. In my case, that's 3 gpm. Otherwise, it won't be anywhere near as effective. Also highly desirable are 120 vac motors to turn the pumps since the 12/24 vdc pumps are noisy and do not have the duty cycle to polish for a couple of hours without overheating.

Instructions with pump and motor recommendations and optional electronic controls are here:

Polishing System

[Roy M]

Plywood tanks! Coated in West System. Over thirty years old and in perfect condition. Skip the bother of metallurgists and bacteriologists. Put LARGE access ports and clean them out every couple years.

[Emmalina]

I just drain half a litre every month out of both tanks to see how they are... My last steel tank lasted 30 years just rebuilt it in epoxy. Until the other one leaks its good to go. Fuel when cruising is hard to control but I don't believe polishing makes that much difference. Just using other filters before you change your normal ones.

[shorebird]

Plywood tanks, or more specific, epoxy tanks, or any tanks made from resin reinforced strand, are getting a closer look in my industry, and are offered as replacement for home heating tanks. (without the plywood.) I'm not knocking them, but homemade tanks of any kind can lead to problems with surveys, insurance, and liability. I know of one instance recently where a small 80 gallon steel tank was inadvertantly placed onto a small bolt protruding from the tank base, leading to a leak, and emptying of the tank into the ground. The resulting cleanup set him back $80,000, and the cleanup could go far higher if fuel leaks into a waterway.

[Emmalina]

Sorry cant get my head around an 80 gallon tank leak costing 80k.... When my tank leaked and i wasn't there i lost 1200l And i was very upset but 80k for what and where ? Its hardly a volatile liquid/ And considering your average cargo ship sprays a 100l a minute of unburnt fuel into the sea where are you going with this ? Nobody leaks fuel for fun !

[s/v Jedi]

Originally Posted by Delfin

After a few thousand gallons of diesel burned, some of which is a year old once burned, I have never seen a trace of water or contaminants in the Racor bowls. The system I built probably isn't worth it for a sailing vessel, although the cost and bother of replacing a tank might be enough of an offset to warrant a decent polishing system. We take advantage of rough weather, especially when the tanks are low, to polish under the theory that whatever is in them will get stirred up and filtered out at that point. Polishing systems are not that tough to build, IMO, but if you do build one, use a pump that can move the amount of fuel rated for the filter. In my case, that's 3 gpm. Otherwise, it won't be anywhere near as effective. Also highly desirable are 120 vac motors to turn the pumps since the 12/24 vdc pumps are noisy and do not have the duty cycle to polish for a couple of hours without overheating.

Instructions with pump and motor recommendations and optional electronic controls are here:

Polishing System

I agree that polishing is the key. I am still burning 5 year old diesel from Colombia which isn't very clean, without any issue. I polish now and then (using a bottom connection in the sump but you can add a suction pipe all the way into the sump from the top of the tank too if you want to adhere to code) at 10 microns and my primary filters can be 2 microns without ever plugging up. I also use Startron enzyme treatment every 6 months plus when I get new fuel.

The diagram I posted before contains a full polishing system; I used the Nordhavn system as the base for it. For sailboats with Racor 500 class filters, the Walbro 6802 I used is a match with the filter and performs fine; but it has been replaced with an even better pump. Maximum pressure from the pumps should be at or below 7 psi. This is of importance for both the filters and the high pressure pump on the engine in case of the bleed/boost pump.

[Emmalina]

Sorry its a 100l an hour before you all bash me LOL

[ohdrinkboy]

Please explain to a newbie to diesel (I've had an outboard for the past 15 yrs).....what are you using for your manifolds and valves associated?

Thanks.

[thinwater]

Originally Posted by Roy M

Plywood tanks! Coated in West System. Over thirty years old and in perfect condition. Skip the bother of metallurgists and bacteriologists. Put LARGE access ports and clean them out every couple years.

That's what I did on my last boat and it passed the survey. However, some surveyors are very stick about having a code stamp. This is touchy area, triply so for gasoline.

Attention to detail is vital. This is not at all easy if done right, but VERY dependable. Any shape is posible. In my case the tank hung under the bridgedeck in an un-used hollow, hanging from a reinforced flanged lid. No corrosion, inside or out.

• Correct resin. Though you can build with West System, there are better products for diesel and e-10. I will call them "chemical resins" but they are fuel-specific. Even for a diesel tank I would get something e-10 and biodiesel compatible; there is some cross blending, accidents happen, and regulations change. West is not. I built my tank pre-ethanol and was VERY glad that I had chosen an ethanol-compatible resin (I saw the change coming).
• Glass. Add some reinforcement, at least 3 layers plus tape on the seams.
• Smooth. The inside should be what we call "inspectable" after 2 layers of glass. Fair until there are no rough spots that could conceal voids or cracks.
• Veil. Once beautiful, add a coat of chemical resin, a single layer of light cloth or scrim (the lighter the better, 2 oz. is enough), and second chemical resin coat. This is to control cracks in the veil coats.
• Baffles if needed. Add after the veil. More work.
• Fittings. Again, attention to detail. Bring the glass through the fittings if possible.
• Exterior. At least one layer of glass and one layer of chemical resin (yup, fuel is going to get on the outside someday).
• Code. Everything about the installation should be checked.

An advanced project.

[s/v Jedi]

Originally Posted by ohdrinkboy

Please explain to a newbie to diesel (I've had an outboard for the past 15 yrs).....what are you using for your manifolds and valves associated?

Thanks.

1/4" brass/bronze T's, nipples and miniature fuel valves. You find them in the West Marine catalog for sure and when you recognize them after looking at it, you can buy them anywhere

Use approved 5/16" - 3/8" (8-10mm) fuel hose, no smaller. The valves I mean can even be used under the bowls of the Racor 500M (with the metal shields) for easy draining.

Here is my full blog article on this: A new fuel system for Jedi (English) - s/v Jedi

and here a photo of one of the manifolds:


Also: check out the hose clamps on those pictures: that is Monel wire

[shorebird]

Originally Posted by Emmalina

Sorry cant get my head around an 80 gallon tank leak costing 80k.... When my tank leaked and i wasn't there i lost 1200l And i was very upset but 80k for what and where ? Its hardly a volatile liquid/ And considering your average cargo ship sprays a 100l a minute of unburnt fuel into the sea where are you going with this ? Nobody leaks fuel for fun !

Canadian environmental laws are quite draconian, and I could have clarified where the spill took place, here in BC, although my understanding is that some states are as bad, or worse. If you had that spill here, you may be on the hook for as much as a million $ if fuel spills into a fish bearing stream. If a spill occurs under your house, such as from a basement installed furnace oil tank, you could be required to raise the house, dig out the soil from underneath until soil testing indicates no fuel contamination, then have all the removed soil disposed of as hazardous waste. If you are unable to pay, the home can be seized to pay the cleanup. If you declare bankruptcy, your debts can be discharged. Except that one. If your corporation can't pay for a cleanup because of a spill by the company, the directors can be held personally liable, and personal assets seized for cleanup. Its a new day, here, and you do NOT want to spill fuel. Our tanks (I am a steel tank manufacturer) used for bulk storage are virtually all "contained" or double wall, often with an alarm sounding if fuel breaches the tank and spills into the secondary containment.
I hope never to see contained tanks required for the marine industry, since they are heavy, use much more space, and are expensive.
Regards,
David

[zboss]

Originally Posted by s/v Jedi

Here is my diagram again, it has everything needed:

Hi,

What is the purpose of the boost pump in your configuration?

Thanks!

[s/v Jedi]

Originally Posted by zboss

Hi,

What is the purpose of the boost pump in your configuration?

Thanks!

Two-fold: bleeding the filters and line, pump, injectors is one and boosting fuel delivery through dirty filters is two. The latter one is in case you need the engine urgently even though a filter is plugged up. I also use it to run the last bit of fuel out of my tank, as it draws from the very sump.

I am always amazed that people like to draw fuel somewhere up from the bottom of their tanks. This allows crud and water to accumulate in the bottom. It is much better to always draw from the bottom so that any dirt and water accumulates in the filter instead. In my view of-course, but it is the view based on logic