Diesel Tank Cleaning?

[sartorst]

Originally Posted by sartorst

DONT use silicone on fuel tank applications, oil yes, fuel NO!!

IT will turn to soft useless jelly

[nitpik]

OK, Delancy, since nobody else has asked, I will ask what will probably turn out to be the stupid question of the day:
How did you get the 7" OD backing plates into the tank through the 5"ID inspection holes? I am guessing you had to bend them, then straighten them out once inside?

[Roy M]

Sorry, I thought the picture with the label, Form-A-Gasket Sealant said everything. Next time I'll try to be clearer. Rebel Heart described perfectly how to apply and renovate it.

On the backing plates, you can cut the backer in half, insert and glue in place with Permatex using the machine screws to register, then let it set up. It will then always be in place when you remove the lid.

Since my tank is built of plywood, coated in epoxy, I was able to use tee-nuts on the underside of the tank top to secure the lids.

[rebel heart]

Originally Posted by sartorst

DONT use silicone on fuel tank applications, oil yes, fuel NO!!

I've always operated under the rules that diesel works more like oil than "fuel". And the permatex isn't just "silicone".

Regardless, it's used as the sole gasket material for my iron inspection ports on my iron tank. No jelly found.

[Delancey]

Nitpik- +1 what Roy M said. If you look at the 'parts' picture I posted you can see the backer ring is two pieces.

After I had all the holes drilled and tapped in the backer ring, fuel tank, and cover plate, I cut the backer ring in half with a jig saw. When the gasket is glued on it acts as sort of a hinge so you can fold the assembly and fit it in the 5" hole.

If I did it again I might cut the backer ring in two pieces so they butt nicely together before drilling and tapping holes. As it is there is a small gap between the backer ring pieces when they are installed because of the saw kerf from making the cut.

Probably not a big deal, the gasket is doing it's job and I think I have a good seal, but if I did it again it's a small detail I wouldn't miss.

[DeepFrz]

I wouldn't worry about the small gap between pieces. After all the whole center part of the bottom ring is open. The ring is basically to hold the bolts in place and to help seal the bolt holes, both of which it does very nicely. Nice job.

[rebel heart]

I emailed Permatex about the diesel thing on Friday and got this response. For what it's worth my inspection ports still aren't weeping, but I guess with this reply I'll probably cut the gunk out and use the product they're recommending.


Many Thanks for your interest in Permatex products . . . . The Ultra Blue P/N 81724 ).. RTV ( Silicone Gasket Makers are not fuel resistant ) .. Permatex makes a product called "MotoSeal #1 ".. it is Impervious...To fuel (Diesel or gasoline )..it is a Polyethylene Rubber ... cures to a rubbery texture. It is recommended for 2 & 4 cycle engines ,especially for motorcycles and chainsaws , and generators (can be added ). Click on Link .........

http://www.permatex.com/products/Aut...Maker_Grey.htm

[DeepFrz]

I think Delancy got it right with the Buna N.

[Jbaffoh]

There is no need for sealant--the buna-n compresses and seals nicely. Also, 16 bolts is overkill (and double the potential for leaks). Finally, tapping the backing plates is also overkill. The internal gasket holds the bolts in place.

I mimicked the seabuilt system, using custom sizes and an 8-bolt pattern instead of 6. After more than a year, everything works perfectly.

[Delancey]

I would be interested to learn that microbes influence corrosion of aluminum, never heard of such a thing.

I recently opened up my fuel pump and was surprised to see a significant quantity of rusty crud attached to a magnet inside, I think a more likely culprit for the minor pitting at the bottom of the tank but I could be wrong.

Presumably, the rusty crud came from wherever the PO sourced his fuel for the past thirty years. Another reason to pre-filter your fuel before it goes in the tank! At least if you have an aluminum one.

The ports I installed allowed me to do a thorough inspection of the interior. All of the welded seams look fine, including the area of corrosion on the outside of the tank I fixed with a blob of weld.

[gonesail]

the tank is almost 30 years old? mine developed pinhole leaks at that age. i like the seabuilt inspection ports too.

[Roy M]

In a bar room discussion with other like-minded boat tinkerers, we came up with the following possible scenario: water, from either the raw fuel or condensation from humidity from the vent line, collects and falls to the bottom of the tank. Then, "critters" from somewhere else (air, contaminated fuel, an advance team from Planet Splorgg) take up residence in the water and devour the rich hydrocarbons at the boundary layer. They poop, adding CO2 to the ambient liquid world, which raises the acid level. The aluminum tanks, when originally welded, were fused under a protective shield of an inert gas, but the side of the weld that encounters the "critters" and the acidic solution, wasn't protected from oxygen's reach. After years of steady attack by the acidic solution, vulnerable points of the inner weld begin to fall victim to the host environment and they develop pathways to the outside world. It doesn't happen to my epoxy sheathed plywood tanks, only the welded metal ones. Anyways, "in vino veritas", so we are probably right (alcohol bespeaks the truth, at least to the drinkers). Works for me.

[Aloha_float]

@Roy

Good theory ... A bit derived from Mork and Mindy though

Bacteria in diesel fuel interfaces with water and develop complex bacteria colonies that we know as sludge. Anaerobic bacteria actually excrete acid that acts as an electrolyte to form galvanic cells or anodic corrosion sites. Facultative bacteria interfere with passivation so corrosion can accelerate and result in putting corrosion or in some cases tank failure.

This process is known as MIC and is well known in the water treatment and fuel industry.

DOW has written one of the better articles in this.

There is a ton of info on the web if you google microbially influenced corrosion in diesel fuel.

[Roy M]

Thank you Aloha_float! Now I have a cool acronym to toss about: MIC, microbially influenced corrosion. It flows smoothly. You appear knowledgeable in this area. Can you tell me if mitochondria are alien beings sent here to make things work? I love this forum.

[Aloha_float]

energetic buggers....not a Doc, that's my wife's role. I work in the fuel industry specifically related to diesel fuels so. Metallurgy is one of my few areas of study...