Stainless steel (feul)tank

Preacherman

If my memory serves me well, it has something to do about orgamic or bacterial growth with diesel oil reaction to stainless steel tanks of some sorts. I read this a very long time ago and cannot recall the excact detail anymore.
Anyone with more info?

 

Where did you get this????

 

Tanks according to Calder:
Stainless steel is considered by many to be the ultimate fuel tank material, but in fact it can be worse than other metals! First, a good grade of low carbon content stainless is needed (high in nickel--preferably 316L, although 304L is far more common), which must be properly welde using correct welding wire(stainless welds are far more prone to stress failure than either steel or aluminum welds). Secondly, to avoid crevice corrosion the tank must be installed in such a way as to keep it dry and ensure a god airflow over it ( the points at which a tank rests on its bearrers are notorious for developing pinholes).

Regardless of the material used, to slow corrosion all metal tanks should be:
1. Designed so that there are no external dips or hollows that can acumulate water;
2. Installed away from bilge water, with nonmetallic, non-moisture-absorbant, nonabrasive strips separating the tank from its supports, retaining straps, or tie-downs.
3. So placed that there is an air space around the entire tank ( unless the tank is weled into the hull of a steel or aluminum boat--integral tanks are acceptable with diesel but not with gasoline)

He also says that:
A steel tank that is properly primed and painted with a two-part epoxy will be as resistant to corrosion as most aluminum and stainless steel tanks, but at far less cost.

 

Tanks according to Gerr:
Stainless steel has been used successfully for fuel tanks, but for many years it was not recommended by ABYC. Dr. Harry Lipsttt, a proffessor of materials science says the reason is corrosion at the welds, or "weld decay." Most common marine-grade stainless, 304 or 18-8, contain both chromium and carbon. When the metal is heated to over 1,000 Degrees F (538 deg C) for welding, the carbon is driven away and regions of chromium carbide form, with chromium-depleted areas immediately adjacent. These two "alloys" form a galvanic couple and can cause serious corrosion quickly.
Control the problem by using a stainless steel with carbide-forming material added---titanium. This is avilable as Type 321 stainless. Another altenative is to use a low-carbon alloy, with less than 0.03% carbon content. Type 316L ("L" for lowcarbon) or 317L meet this requirment. ABYC has recently accepted 316L and 317L tanks--provided welding is done according to very rigid specifications (see ABYC's section H-33).

 

Yeah Dutch Peter I noticed that about the condensation being lower. I can't quite work out why it would be way. Considering that the thermal conductivity of austenitic stainless steel is much lower than that of normal low alloy steel, I can't fathom how that is possible! But I don't really understand fully how that fact would effect condensation? Would that cause stainless to be slower in reaching ambient temp, therefore being more likely to condense water? I think it would depend on the exchange rate of the internal air and the number and rate of temp changes.
I am betting different materials would work better in different climates.
I bet engineers that deal with chemical plants, cracking plants, gas turbines and the like, know this stuff off the cuff.

 

Just put an air drier in the vent line and condensation won't be a problem. Silica gel in a cartridge type water filter. Install the filter element first and fill the rest of the housing with silica gel and assemble it. It isn't rocket science!

 

Ssor
Then you shouldn't have any problem designing, manufacturing and selling such an item.

Well, no wait a minute, what happens when Diesel burps up the vent, swells the silica and plugs your vent? Maybe it is rocket science?

 

Hi all of you guys,

Fo me case is closed I wnt from I316 to GRP now I did find a company who makes them custom in HDPE this at a resonable price.

Can have a look at: http://www.kemeling.nl/constructies/product.php?nr=5
It is in Dutch, bur for some of us this is not a problem

Greetz,

 

Dgreenwood, To avoid the problem of spilling fuel overboard I installed an overflow trap with a manual drain cock on the bottom that return any overflow back to the tank when I refill the tank.

 

Yup
Same setup I use...I have couple designs I have tried and they are improving. With the environmental police watching you, you can't be too careful these days.

 

Mr. Greenwood,

I'd like to change this statement in "can be created by welding". And still fracturing and porosity has nothing to do with hardspots. Has more to do with inadequate welder performance, bad weld design, wrong working environment, etc.

Correct, as crevice corrosion has all to do with oxygen depletion. Stainless steel needs oxygen to form a protective layer!! The inside of the tank is therefor the least of your problem as it is also protected by oil! On the outside you have to keep your bilges clean and dry, this has always been good advice.

Ofcourse you need a good welder, otherwise you'll have a leaking tank!
You also need an experienced welder for your mild steel boat!!!

Can you specify the standard used, as far as I know the only one available for CE is EN ISO 10088 and that has no special requirements for stainless steel tanks!!!!

Don't know where you get the impression that I think water in a fuel tank is not a problem. If properly designed a tank should have a drain to get ride of water, and if not possible one should think of using a daytank which allows for drainage!!!

 

Mr Greenwood,

My statement of "where did you get this" was related to the GRP tanks not permited by CE. As for condensation, every tank will fill up with condensation. When you warm up the surrounding air (return line fuel) and then let it cool down, stuff like that happens. The amount of air is a factor, humidity, as is available surface. I think these factors weigh more than type of material.