Fuel Tank Stainless or Alum
Fuel Tank Stainless or Alum
(OP)
Hi All. We have to fabricate a 200 litre (50 gallon) fuel tank that will be underslung a trailer. This fuel is not for the truck, it is for a generator mounted on the trailer. Someone told me that it is better to fabricate it from alum sheet, because they said stainless steel sheet will crack. Can someone please validate this and explain why stainless steel sheet will crack but not aluminium sheet when used for a tank on a trailer?
RE: Fuel Tank Stainless or Alum
Metals (and other materials) crack when the load exceeds the strength, or when cumulative fatigue damage exceeds the fatigue tolerance of the design. You need to understand this before you start fabricating things. Especially things filled with inflammable liquids used on public roads.
Many fuel tanks are made of aluminum.
Many fuel tanks are made of stainless steel.
Many fuel tanks are made of steel with various coatings inside and out.
Many fuel tanks are made of aluminized steel (which I guess counts as a "various coating").
Many fuel tanks are made of plastic.
Fuel tanks are cheap and easy to buy in many different shapes. It seems unlikely that you "have to fabricate" one.
There are probably laws and regulations about fuel tanks that you need to comply with.
RE: Fuel Tank Stainless or Alum
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RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
Stainless steel also has issues with road salts and dirt. It requires frequent washing to maintain it's "stainless" properties. High concentrations of salt on the surface can initiate stress corrosion cracking. Aluminum has similar sensitivities to dirt but is not as severely affected by salt.
RE: Fuel Tank Stainless or Alum
Buy, if at all possible. Don't make.
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
I would think that you can find a pre-manufactured Al tank that will work fine.
Providing very good support is critical.
The dynamics of liquid sloshing inside of a tank while being moved can impart some very high forces.
I am a SS guy but the risks of external corrosion on SS concern me.
I have used SS tanks in past, and the outsides were always coated with very good products.
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RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
Chris, CSWP
SolidWorks
ctophers home
RE: Fuel Tank Stainless or Alum
Are you forming the sheet into a rectangular tank with some sharp edges?
Aluminium is "softer" than Stl steel, I.e. has a lower yield, but doesn't work harden as much which is where you might get "cracking"
The radius of any bent shape will be crucial as well. Make it 10 to 15mm and you shouldn't have an issue with either.
Make it sharp edged or <5mm then you might.
So much depends on details you haven't told us....
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Fuel Tank Stainless or Alum
As requested, I have added a typical cross section of the tank, see link below. Bottom section is bent from 5052-h32 bendable marine sheet. Internal radius is 9 mm. End plates are tig welded from outside and mig welded from inside. Will have baffles every +- 400 mm. Top sheet is only welded form outside.
LittleInch, thank you very much for your feedback. I do have some questions regarding the following you said:
"Aluminium is "softer" than Stl steel, I.e. has a lower yield, but doesn't work harden as much which is where you might get "cracking""
I don't understand how this can be true if the ultimate strain of alum sheet is less than stainless sheet? This was actually the original reason why I made this post, because in my mind it doesn't add up why st steel would crack before alum. I think I might be missing something?
5052-h32 ultimate strain: roughly 10%
5052-0 ultimate strain: roughly 25%
316 st steel ultimate strain: roughly 40%
So doesn't this imply that 316 can be bent (strained) much more than al before cracking.
As TugboatEng and EdStainless have suggested, maybe this relates to corrosion cracking.
I also don't think fatigue could be the culprit? Does anyone have any insights?
I really do appreciate the feedback.
RE: Fuel Tank Stainless or Alum
You are trying to understand why someone told you that. You need to ask them.
Every suitable metal will crack if used improperly. Fatigue cracks are independent of plastic strain capability as they occur in the elastic region.
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
I believe that he is correct. However, I would like to understand WHY this is true. Because if I understand the underlying scientific principles I can apply it elsewhere.
RE: Fuel Tank Stainless or Alum
Plenty of companies make stainless steel fuel tanks. If your fabrication manager doesn't have confidence in stainless steel, don't use it.
In a brief search I see the US Coast Guard recommends 316 and care taken in making welds; a number of of comments like monel for boat tanks over stainless and aluminum.
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
But you really to talk to a metallurgist or welding engineer.
There is also mention of SCC which may be more prevalent in bent sections.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Fuel Tank Stainless or Alum
In the weld?
At the bent sections?
Somewhere else?
That will give you something to go on at least.
3mm is not very thick so will heat up and cool down rapidly and my be harder to weld without cracking as a thin sheet than maybe pipe or thicker plate
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Fuel Tank Stainless or Alum
So without understanding the why, he just declares stainless bad - never to be used.
It's commendable that you are trying to understand.
RE: Fuel Tank Stainless or Alum
But do you need those properties in a tank?
SS is easier to weld than Al in my book (I can't weld Al for crap).
It wouldn't surprise me if you couldn't fins SS tanks that were deep drawn and then the two halves welded together.
SS forms easily (think kitchen sinks).
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RE: Fuel Tank Stainless or Alum
https://www.tti.com.au/product-category/poly-diese...
RE: Fuel Tank Stainless or Alum
Note that road tankers are made of carbon steel coated with oil-proof paint. Note that in the past wood was used extensively for this purpose.
RE: Fuel Tank Stainless or Alum
But I would have thought some standard tank could be made to fit.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Fuel Tank Stainless or Alum
https://www.ebay.com/itm/394406762244?_trkparms=am...
John R. Baker, P.E. (ret)
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RE: Fuel Tank Stainless or Alum
Most plastic tanks are not intended for road travel when full.
Ask friends of yours with RVs.
Plastic tanks require a lot of support, like fully supported.
There are options out there in steel, Al, plastic, and SS.
Google
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P.E. Metallurgy, consulting work welcomed
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
https://www.shapesbyhydro.com/en/expert-thoughts/i...
--
Mitch
RE: Fuel Tank Stainless or Alum
A) Based in Australia
B) So interested in the discussion that he or she hasn't bothered to look at any responses since 6th Sept.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Fuel Tank Stainless or Alum
PS my question was only regarding why st/st would crack and alum won't but I appreciate all the extra info regarding tanks, very informative.
RE: Fuel Tank Stainless or Alum
The salt dries.
You get a hot humid day.
The salt rehydrates and the SS surface temp reaches 140F.
You get pitting, chloride stress corrosion cracking, or both.
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P.E. Metallurgy, consulting work welcomed
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
A tank in a lean duplex SS (2101) would work great.
Very strong and more corrosion (esp SCC) resistant.
Not just where roads are salted.
Near a coast has chlorides, and many arid climates have lots of Cl (think salt flats).
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P.E. Metallurgy, consulting work welcomed
RE: Fuel Tank Stainless or Alum
https://www.kencoracing.com.au/index.php/component...
RE: Fuel Tank Stainless or Alum
https://www.americanmobilepower.com/products/reefe...
RE: Fuel Tank Stainless or Alum
for ship use we also manufactured mounting brackets for above deck mounting of cupboards and panels etc.
Also for ship use we built these massive toolboxes with these lids that were bolted down and sealed against water penetration.
while i was with that company we also got truck fuel tanks in sometimes that had sprung a leak and then we did welding repairs on them. that was diesel as well though
the impression that i got was that aluminium is typically seen as a cheaper alternative to stainless steel, but it still gives reasonably good corrosion resistance. the fact that it doesnt spark when struck probably helps too.
RE: Fuel Tank Stainless or Alum
RE: Fuel Tank Stainless or Alum
This is may be off topic but I was under the impression that ULSD (with water present) was actually more conducive to microbial growth than previous diesel with higher sulphur concentrations.
Or perhaps that’s only due to the addition of biofuel?
Link
RE: Fuel Tank Stainless or Alum
Who mixes diesel with ethanol? Microbes don't digest ethanol, they produce it. Ethanol in excess of 10% is quite deadly to microbes which limits microbial growth.
Meanwhile, sulfate reducing bacteria are a well known cause of corrosion in tanks.
The article also goes on about lubricity issues. I've never seen any evidence that a reduction in lubricity has ever caused problems. Sandia National Labs analysed some pumps run on low lubricity fuel and none of the pumps failed due to fuel lubricity.
https://apps.dtic.mil/sti/pdfs/ADA234930.pdf