Fuel Tanks and ethanol....

[Accurate twrs]

I"ve been giving some thought to the ethanol problem in fuel tanks... Seems if you could separate out the water from your gas you may have a better chance at improved performance and hopefully not damage you boats motor.

By fabricating a separator box in the bottom of a fuel tank you can drain out the water from the gas and reduce water from ever running through your fuel system.

Does this sound doable... Your thoughts and ideas...!!!

[rasorinc]

We always had tank drains on single engine aircraft at the lowest point. Good idea if you have the room. The drain tank has to sit lower then the main tank but only has to hold a gallon maybe but it is a manual operation. Real easy when the tanks are in the wings.

[marshmat]

A sump drain of some kind would seem to be a prudent precaution in tanks of all sorts. It would help with all sorts of crud that builds up in there.

"Southeast" - as in southeast USA? Something like half of all ethanol complaints seem to come from there. I'd be really curious to see a chemical analysis of your gasoline- our 87 octane here in Ontario is up to 10% ethanol, and many folks leave it sitting around in the tank for eight months of winter with no ill effects come springtime. Something about the additive packages, perhaps?

[TollyWally]

I'm as far from Southeast as you can be in the continental US and they put some damn thing in there around my neighborhood. Additive packages or Satan's octane booster, what ever the stuff is it raises pure hell with older tanks. I ended up rigging together a homemade fuel polishing set up and ran my fuel from tank to tank for a day. Now I run my fuel through a double set of Racor diesel filters before it runs the gauntlet of stock filters. So far it's been working but I've only really ran a couple hundred gallons through the motor. So far so good but it's cost me hundreds of dollars in filters and carb repair. The gov't. is so smart, buy off the corn belt vote and poison my boat. Idiots!

I was under the impression the Coasties frowned on drainable gasoline sumps. I may have to have a new tank fabricated, a sump would be a good thing.

[marshmat]

They frown on drains coming out the bottom, but I'm not aware of anything against a sump with a pump-out. In other words: have a small sump built into the tank, with a pickup line running to the bottom of the sump, and some way (a cheap hand pump, perhaps) to suck the crud out this line. Then have the real fuel pickup mounted a few inches higher.

[TollyWally]

That sounds like it woud work real well Matt. I know how I'd prefer to do it but your way is safer and will keep me from all sorts of trouble with all the various powers that be.

[gonzo]

Gasohol has a short shelf life. It starts separating in about a month to six weeks. Ethanol alone is corrosive (because of the water content, it's hygroscopic) and also disolves hoses, gaskets and seals when it is in a high concentration. Henry Ford first started using ethanol on fuel in the Ford Gas he sold at his fuel stations. When lead became available, it was better and cheaper so they all switched to that. All tanks have a sump; the pickup tube is at a distance from the bottom.

[CDK]

Let's not mix facts and fiction.

Jack Daniels nr 7 used to be 43% ethanol, Wild Turkey even 54%. I've never heard of glass corrosion and even the 1 cent cap and seal are never affected by ethanol.

Yes it is a solvent, but a poor one compared to nearly all other hydrocarbons in gasoline. If fact the only distinction (besides taste and smell) between alcohol and the other HC's is its ability to mix with water.
Some fuel system manufacturers have used cheap materials in the past because they assumed there would be no water present, but they all use neoprene seals, brass fittings and PVF fuel lines for more than a decade.

The hygroscopic property of alcohol must not be exaggerated and can also be regarded as an advantage because it avoids engine starting problems from water filled carbs.
If you feel really unhappy about the invisible presence of water in fuel, unscrew the now useless water separator from under the fuel filter and fill that with silica-gel pellets.
Keeping the tanks topped up after a trip also helps to reduce moisture contaminating your fuel.

[gonzo]

With glass engines I would say you are right. With aluminum for example, ethanol produces a lot of corrosion. Pure etanol will destroy a carburetor. I worked in Brazil where 100% ethanol or 90% is the common fuel, and older engines had to get new carburetors with special coatings or be in cast iron. Aluminum tanks have problems too. Most fuel lines, unless they are specially formulated, specifically say not to use fuel with more than 10% ethanol. The same goes for the rest of the fuel system. I am refering to USA systems and materials, which I assume is what he has.

[Bigfoot1]

I"ve been giving some thought to the ethanol problem in fuel tanks... Seems if you could separate out the water from your gas you may have a better chance at improved performance and hopefully not damage you boats motor.

By fabricating a separator box in the bottom of a fuel tank you can drain out the water from the gas and reduce water from ever running through your fuel system.

Does this sound doable... Your thoughts and ideas...!!!

You can build a tank with a catch but you cannot by AYBC rules, have an open drain or valve below the top of the tank Instead make the sump and put in a draw line, into the sump with a valve and fitting on top. I think, but not sure that this valve requires a lock on it so it cannot be inadvertantly opened

[gonzo]

If you make the draw line with a threaded end and put in a cap it would be legal.

[TollyWally]

If that is true that is the way to go.

[CDK]

Can somebody please clarify with at least some credibility how alcohol interacts with aluminum?

I am not a chemist, but technical chemistry was one of my favorite college topics: I cannot understand what sort of reaction could take place.

Gonzo claims first hand experience with ruined carburetors, but my wife prepares Coque-au-vin or Boeuf Bourguignon and never complains the boiling wine ruins her aluminum pans.

Could it be that these stories are kept alive for commercial reasons?

[Bigfoot1]

Re Gonzo remark about putting a threaded end and putting a cap on it.
I would stay away from this without putting a buffer in place. Aluminum fittings on aluminum fittings will often gall the theads. The result is could be a poor seal when you put the cap on and off a few times.
Remember on an aluminum tank you cannot cannot use brass or bronze fittings only 300 series stainless or aluminum.

but if you want to use a cap, put in some stainless buffer into onto the draw line that will stay attached to the drawline thread, then put a stainless cap on a stainless nipple.

When we build diesel or gas tanks in aluminum, for even regular draw lines, this is the procedure that we use. If you dont believe me, try on a bench tightening an aluminum fitting into another aluminun pipe fitting leave it a year, then undo it.
I would say the survival rate of the the thread would be about 50%
Additionally if you decide to use a thread sealant ONLY FOR LUBRICATION , as fuel vapor will dilute it, ensure that it is aluminum compatible. Not a copper based sealant.

copper and aluminum are not galvanically compatible

[CDN-CUCV]

Can somebody please clarify with at least some credibility how alcohol interacts with aluminum?

I am not a chemist either, however, I hope this can shed some light on the subject: For in the case of aluminum tanks, aluminum is a highly conductive metal that relies on an oxide layer for its corrosion protection properties. Low levels of ethanol, such as E10 (10%), are usually not a problem in aluminum tanks because the oxide layer provides a good measure of protection. The problem occurs when the ethanol content is increased.

There are two mechanisms that occur with ethanol. Both mechanisms are a result of the hydroscopic property of ethanol which was mentioned. The more ethanol in the fuel, the more water there will be in the fuel tank. Water not only causes the tank to corrode, it also causes the corrosion particles to clog fuel filters, fuel systems, and damage engine components. The corrosion rate can be accelerated under a number of conditions if other contaminating metals are present such as copper which may be picked up from brass fittings or as a low level contaminant in the aluminum alloy. Chloride, which is a chemical found in salt water, will also accelerate corrosion. In the long term, corrosion can perforate the aluminum to produce leaks that would cause fuel to spill into the bilge and end up in the environment. In the worse case it could cause a fire and/or explosion hazard. Boat fuel tanks are often located under the deck next to the engine where the operator might not be aware of a leak until it was too late. .

The second mechanism that can occurs with the increased use of ethanol based fuel in aluminum tanks is galvanic corrosion. Gasoline fuel is not conductive, but the presence of ethanol or ethanol and water will conduct electricity. The galvanic process that occurs to aluminum trim tabs, stern drives, shaft couplings, etc. will occur within the aluminum fuel tank. Boat builders are able to protect exterior aluminum boat equipment with sacrificial anodes known as zincs. Sacrificial anodes are not a feasible option for the interior of a fuel tank.

I, personally, have known one welder to lose his life to an explosion resulting from hydrogen gas build-up in an aluminum fuel tank. Recently, another local shop had a fire as a result of a enclosed buoyancy tank exploding that had hydrogen gas inside from use a certain bilge cleaner which reacted with the aluminum. This happened in both cases, after extensive flushing of the tanks.

[CDK]

Thanks for your effort CDN-CUCV.

The 1th mechanism cannot be present in an Al tank. As you stated in your opening line, the oxide layer (Al2O3) completely protects the metal so there is no further corrosion, even if water were present. The bond between metal and its oxide is very strong; in fact that is the reason why Al is a useful construction material.

To make Al2O3 in its pure form - a white powder - aluminum must be ground into very small particles so all metal is converted into its oxide and there is no bond left.

The presence of chlorine is another matter entirely. In water it ionizes and dissolves the Al2O3 and forms aluminum chloride which is water soluble. If enough water is present the whole tank will be eaten away.
But this takes place whenever seawater is allowed to enter the tank and is not related to the presence of ethanol.

The 2nd mechanism you mentioned is something I didn't think about: you may have a good point there. A requirement would be that the gasoline-ethanol mixture becomes conductive enough to act as an electrolyte.
I will do some quick tests with different mixtures and post the results here.

[gonzo]

I think the brass jets in the carb bowls and the steel shafts probably cause the electrolysis.

[CDK]

I think the brass jets in the carb bowls and the steel shafts probably cause the electrolysis.

No they don't.

I did the following tests:
A whiskey glass, two new tungsten welding electrodes, 1" apart and a digital multimeter with range up to 200 M-ohm.

-Pure gasoline-98: infinite resistance.
-A mix with 10, 25 and 50% ethanol (95% pure): infinite resistance.
-Only ethanol: 80-90 M-ohm.
-Ethanol with 60% water (also known as Wodka): 1.8 M-ohm.
-Same, but a knife point NaCl (salt) added: 260 Ohm.

Conclusion:

Adding ethanol to gasoline in any quantity cannot cause electrolytic corrosion, not even when pure ethanol with 60% water is used. Only salt can reduce the resistance enough to start electrolysis.

The amount of water in a gasoline-ethanol mixture must not be overstated. In a 50-50 mixture is was possible to add approx 3 vol.% of water, more was separated immediately after stirring. With 10-90 like available in the US, that would mean 0.6% if you try very hard.

Water in fuel can corrode the shafts in the throttles, especially if that is sea water.

[Bigfoot1]

I would contradict your comment that there is galvanic corrosion caused by either gasoline, or enthonal water in an aluminum tank.
Galvanic corrosion is the result of two dissimilar metals in contact with each other in an electrolyte, ie a free ion liquid, like salt water,
Your comment that this could happen the same as trim tabs as trim tabs are in sea water, an electrolyte, so you can get GALVANIC corrosion here, same with stern drives which will have dissimilar metals throughout the assembly is not correct. Corrosion yes, but not galvanic corrosion
If the boat tank is built and installed to ABYC standards, the aluminum tank will not be in contact with any other dissimilar metal that is far apart on the nobility scale to cause significant galvanic corrosion and certainly it would not be in contact with salt water to create this type of corrosion.

Your comment that you have had an explosion in an aluminum tank due to hydrogen build up. Where would the hydrogen come from if the tanks were flushed? Hydrogen cannot, nor other gases, permeate aluminum and secrete out with time, cannot happen,
We have repaired probably about 100 tanks in the last 30 years of building both steel and aluminum tanks, fuel tanks, gas and diesel, we steam them, then weld any areas that need it and have never had an issue.
So your statement that there was a hydrogen build up seem erroneous.
I would have to suspect that some hydrocarbon fuel was available as the source of an explosive vapor.

[CDN-CUCV]

I'm only basing my statement on the hydrogen gas from what the shop owner had told me. Apparently, pink bilge cleaner may have seeped into cracking along welds, cold-cracking , stress cracks I don't know. The tank was a buoyancy tank and not for fuel and it was possible that flushing didn't reach that space so hydrogen may have still been present. I'm not writing off hydrocarbons though, that to me makes more sense considering it was a gas-powered, open boat. I could have explained that better. apologies...

Regardless, boat exploded through the hull and started a fire which caused extensive damage to the shop.

you're are right about the galvanic corrosion. Freudian slip, my bad. I guess electrolytic corrosion would be the correct term perhaps?

[Frosty]

The quote earlier that brass or bronze plugs should not be used in Alluminium but instead stainless is surely the wrong way round?

I cant see anyone fitting ally to ally plugs with out teflon tape or some sealant which would stop galling.

[CDN-CUCV]

PVC caps plugs can work. I've seen brass as well with a little liquid or tape teflon, no big issues. Correct me if I'm wrong ;)

[Bigfoot1]

the teflon tape will not stay in place on the thread faces, The idea around tape sealants is to seal the voids that are at the locatioin of the very tip of each thread. Pipe threads as well as parallel threads are machined to percentage parameters, ie not really tolerance but a designed clearance between the tips to the roots of the opposing thread. So when you tape a joint, it appears that the thread face is covered, and it is until you tighten the joint at which time the plastic deforms into the available space and leaves the thread face, try it sometime, tape a pipe joint, tighten it and untighten it and see where the teflon tape is. My statement was to use an aluminum compatible ( not copper based) thread sealant for lubrication if you were going aluminum to aluminum joint but better to use a stainless pipe fitting that when tightened into the tank is going to be attached to the tank pretty much forever. and then use a cap, or locking valve than can be removed. Of course, stainless on stainless can also gall if over tightened

Someone mentioned PVC caps, not legal by ABYC rules, cracking, embrittlement over time etc.

Frosty, 300 series stainless or aluminum fittings are the only approved fittings for marine fuel tanks in Canada and the US and one would assume the world as galvanic corrosion is not constrained by international boundaries
Just trying to be helpful,

[gonzo]

The brass jets in a carburator are in direct contact with each other. The test is valid for other purposes.

[Accurate twrs]

I like the idea of the sump with a tube at the bottom of it, fitting on top for vacume. Occasionaly i have customers who ask to put a drain valve on the bottom of the tank to which i say NO...!!! In the fitting department i use brass all the time on top of the tank not submersed with no problems at all.. On occasion i will make a brass and copper pick up tube thas's completely removable from the tank. Never had any problems. Anybody know what tank cleaner was used that took the life of the welder..?

[Bigfoot1]

while you may not have had problems, why risk the liability with using brass fittings in an aluminum tank. a small leak in a GAS tank and you can have problems. If ABYC say that brass fitting are not allowed, then why use them.
why???

[Accurate twrs]

Bigfoot... I've been useing brass and copper for nearly 25 yrs now and have never had cause to change. Never have i had a leak in my tanks either.. however I make sure my customers use the ground tab i weld on the tank...
I was surprised how many customers had no ground on their tanks.. Many a customer brought in tanks looking for just a repair, rather then replacement. I would refuse to repair them for the liability. As in no way Jose, not
when my tail is on the line. Currently im chargeing $9.50 a gallon. A certified tank is more. They buy the sending unit if they want one. If a tank has many facets there's a degree of diffaculty charge too.
If i'm missing something here let me know about the copper and brass...
thank you tom

[CDN-CUCV]

Anybody know what tank cleaner was used that took the life of the welder..?

Tank cleaner didn't take the life of the welder. A pink bilge cleaner being was suspect in an explosion that started a shop fire, may have been hydrocarbons too, just going on what the shop owner told me at the time.

The fatality that occured, was another incident where there was welding being done on a boat and the fuel tank exploded. There was a plaque dedicated to that welder at my school.

[PDQAltair]

I have found this EPA memo enlightening. It explains the chemistry of phase separation.

http://www.epa.gov/otaq/regs/fuels/rfg/waterphs.pdf

It makes 2 things clear:
* That a drop in temperature is the main trigger for water drop out.
* The EPA was well aware of the problem.

I always had trouble in the fall, with the first cold snap. Without re-telling a long story...
* Full tanks prevent breathing. Fill after sail.
* Close the vents on small outboard tanks, if provided only.
* Small fill leaks cause BIG problems. ANY deck leak is fatal, since it takes a lot of ethanol to the bottom with it.
* Tanks that are protected from the sun or that are in a cool space have many fewer problems.

This also explains why some say "no problem" and other say "the sky is falling." They may both be correct. It depends on the system design.

[TollyWally]

"The EPA was well aware of the problem."

And the reason those bastards shouldn't beheld accountable?

[Ike]

Why does aluminum corrode when phase separation occurs?

A quote form an article on my web site:
What about other types of tanks? It has been known for years that aluminum tanks can corrode from the inside out due to alcohol in the fuel. If the tank is left in storage for many months phase separation can occur, resulting in separate layers of fuel, alcohol and water in the tank. Acidic compounds form at the boundary between the water and alcohol
and this corrodes the tank. I have been trying to find the source of that info in the last sentence, but I do recall it was in a research paper on alcohol problems in aluminum tanks. Give me a few days and I'll find it.

Also, yes, drains are not permitted in gasoline fuel tanks but nothing in the USCG regulations, ABYC standards, or ISO prohibits a secondary pickup and a means to pump out the water in the bottom of the tank. Tank pickups generally do not go all the way to the bottom of the tank just for that reason. You would pick up all the misc. crude that collects, as well as water. But you can pump it out if you want to. The fitting would have to be on top of the tank and the pump would have to suck the fluid out. It would have to be an ignition protected pump if it is electrical, unless it was outside the fuel tank compartment or the engine space, and the pump was not exposed to fumes.

And in spite of what that EPA paper says the people at the EPA who were dealing with boats didn't have a clue. I was the USCG liaison to the EPA on this issue and they didn't know squat about the effects of alcohol on fuel systems in boats and didn't even believe that it could damage the engines. I, and quite a few other people, quickly acquainted them with the realities of it. But it took a while for it to sink in. As far as the people in the EPA who deal with clean air, they never did get the picture. However NMMA and others are keeping after them on the E-15 and E-85 proposals.

[Bigfoot1]

To accurate twrs, Tom
I was trying to find my most recent copy of the ABYC standards but must have put lent them out.
They specifically state that fittings that are to be used in contact with an aluminum tanks must be aluminum or 300 series stainless due to galvanic corrosion that can take place between dissimilar metals.
If I find my book in the next few weeks, I will forward you the exact wording of the standards.

[Ike]

Actually it doesn't say that anymore.

here's the text of H-24 Gasoline fuel systems;

24.18.1 Tank Materials
24.18.1.1 Material thickness shall be at least the minimum thickness as listed in H-24 TABLE IV.
24.18.1.1.1 Materials not listed in H-24 TABLE IV shall be tested to demonstrate corrosion resistance in a marine
environment equivalent to those materials listed.
24.18.1.2 Steel sheet tanks, when constructed for gasoline, shall be galvanized on the inside and outside by the
hot dip process.
24.18.1.3 Fuel tanks shall not be constructed of terneplate steel.
24.18.1.4 Non-metallic materials are considered acceptable for corrosion resistance; however, all other
requirements of this standard must be met.
24.18.1.5 The copper-base alloys normally used for fuel fittings and lines are considered acceptable for direct
coupling with all fuel tank materials listed in H-24 TABLE IV, except aluminum.
24.18.1.6 Copper base alloy components shall be separated from contact with aluminum tanks or fitting plates by
means of a galvanic barrier such as 300 series stainless steel.
24.18.1.7 Fastenings used to couple fittings, such as fuel senders, to aluminum tanks shall be of 300 series
stainless steel or its equivalent in corrosion resistance.


H-33 - Diesel Fuel Systems, is almost identical wording..

[Bigfoot1]

Ike
24.18.1.6
says that you cannot screw a copper, brass fitting into an aluminum tank, (without a galvanic de-coupler) so I dont understand your comment, that it "actually does not say that any more"
as well as 24.18.1.5 copper is acceptible for fittings to fuel tanks EXCEPT ALUMINUM,
Bottom line, copper or brass based fittings are not allowed for direct connection with aluminum tanks

[Ike]

You said ;
specifically state that fittings that are to be used in contact with an aluminum tanks must be aluminum or 300 series stainless


What I meant is that the standard is a bit broader, allowing for other galvanic barriers. It's still a good idea to use stainless.

[TollyWally]

How do the plastic pipe bushings etc. fare?

[Ike]

I haven't actually observed them in use. Almost everything I've seen is metal usually Stainless steel, even on plastic tanks.

[Bigfoot1]

TollyWally, ( must be a tollycraft owner ha ha)
It appears that non metallic fittings are allowed as per the specs that IKE put in his response. We have seen the plastic caps used on the 5 gallon gerry cans, crack due to embrittlement which can be caused by UV light, maybe ethanol in the gas etc. The strength of plastic cannot equate to stainless or aluminum. On the other side, in the boats that we build, we often use an aluminum fitting that has a plastic draw tube attached to the fitting and we have never had an issue with these. Mind you the plastic is spec'd for this application, where as an ABS or
PVC plastic fitting may not be resistant to embrittlement from the marine environment.
I would expect that if you bought plastic fittings from a marine supplier that had the fitting specified as a plastic fuel fitting, then they might be ok.
Again for the price of a $2.00 fitting, why take the risk.

[CDK]

Glass filled PVC is an acceptable fitting material, although it slowly deteriorates in bright sunlight. It is not harmed by gasoline or alcohol. It is used on a large scale for all kinds of small industrial products. Carbon filled polyethylene is the material black jerrycans are made of, it is very durable in any environment, even with aggressive acids. Without the carbon (from recycled tires) it rapidly gets brittle in UV.
Polyethylene terephtalate (PET) is probably the best choice, both for a marine environment, Coca Cola and beer!

[TollyWally]

Thanks for the input guys. Bigfoot, Not much gets by you. CDK, talk about harsh environment.