Stainless fuel lines prohibited?

Discussion in 'Diesel Engines' started by Stumble, Dec 9, 2013.

  1. Stumble
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    Stumble Senior Member

    Good catch, but it leaves the same question. The new rules state.

    33.14.6 Metallic fuel lines shall be aluminum or copper alloy pipe of no less than schedule 40, or
    33.14.6.1 copper alloy tubing with a nominal wall thickness of at least .032 inches (.81mm).
    33.14.7 Rigid fuel distribution lines secured to hull members shall be connected to the engine by a flexible section.

    So stainless is still prohibited, but aluminum is now allowed. Any idea why?
     
  2. daiquiri
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    daiquiri Engineering and Design

    No idea why, and guess what? I have quickly checked the ISO standards and, contrary to what I wrote previously, seems that even there the stainless is not on the list. :confused:
    I have never noticed it before because had always used the Type-A hoses for this purpose.

    P.S. - Correction to the above: The ISO 10088 - "Small craft. Permanently installed fuel systems and fixed fuel tanks" - DOES allow the stainless steel for rigid fuel lines, as well as mild steel tubes (for diesels only).
     
  3. gonzo
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    gonzo Senior Member

    I suppose that the lines are Monel (copper-nickel) which looks similar.
     
  4. Stumble
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    Stumble Senior Member

    Could you quote the section or provide a link? This has got me very curious.
     
  5. powerabout
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    powerabout Senior Member

    copper nickel makes cupronickle I thought, looks like brass but very corrosion resistent
    monel looks like stainless and also corrosion resistent BUT dies with electrolysis - great for shafting
    WWII soldier dog tags are monel ( I didnt know that either)

    My guess is aluminim pipe was allowed due to all the commercial aluminium vessels, isolating any other piping would be a more expensive issue possibly?
     
  6. michael pierzga
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    michael pierzga Senior Member

    Hmm..aluminium fuel lines...


    When i open my aluminum fuel tanks i can see the effects of microbial corrosion on the tank walls. Pitting.

    Dont think i would like alumium fuel lines

    Evidently stainless does not suffer from microbial corrosion
     
  7. powerabout
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    powerabout Senior Member

    aluminium boats are disposable also arent they..
     
  8. jonr
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    jonr Senior Member

    My understanding is that aircraft allow copper, aluminum or stainless steel fuel lines. Plus some flexible ones. Aluminum is most common.
     
  9. powerabout
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    powerabout Senior Member

    wow
    my experience with stainless is never trust it...
     
  10. Adler
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    Adler Senior Member

    Fuel Pipes

    The use of flexible pipe as intermediate is against to transmit vibration and stresses because of dimensional expansion as temp effect.
    The use of copper alloys is against fire. The new Al alloys can be used safely too.
    In any case when a steel or stainless steel pipe fails to receipt a shear stress
    then the crack process making ignition spark as friction effect.
     
  11. Ike
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    Ike Senior Member

    To shed a bit of light on this. The USCG regulation for recreational boats reads as follows:
    Title 33 Code of Federal Regulations Subpart J Fuel Systems
    Sec. 183.538 Metallic fuel line materials. Each metallic fuel line connecting the fuel tank with the fuel inlet connection on the engine must:
    (a) Be made of seamless annealed copper, nickel copper, or copper-nickel; and
    (b) Except for corrugated flexible fuel line, have a minimum wall thickness of 0.029 inches.

    This applies solely to recreation boats with permanently installed gasoline engines. That can be engines for propulsion or for electrical generation. None of this applies to commercial vessels or diesel powered recreational boats. There are separate regulations for commercial vessels.

    ABYC cannot permit something that is prohibited. So the ABYC Standard reads virtually the same as the law with the exception of the shall be vs must.

    Reasoning was simple. At the time (the 1980's) the regulation was adopted, it was adopted from the ABYC standard and has not changed since. The ABYC Standard is a consensus standard developed by volunteer committees made up of boat builders repairers, surveyors, naval architects and designers, and other interested parties, all of which are in the boating industry. They felt that stainless steel was problematic, prone to crevice corrosion, galvanic corrosion, and cracking at the fittings and should not be used in gasoline systems. Once the USCG adopts it and it becomes a regulation (a long difficult process) then ABYC can't change it.

    I was not on the Fuel Systems committee at that time but was for many years in the 90's up to 2004, and the subject was visited many times. But as long as the USCG doesn't amend the regulation that's the way it will stay. And let me tell from intimate experience with changing regulations that getting that done would be arduous. Not impossible but it would take some time, probably any where from 3 to 5 years, and would have to be justified by ample evidence that SS is not a problem.

    By the way, note: This says "fuel inlet connection on the engine". The fuel inlet is considered to be the fuel pump inlet. So between the fuel pump and the carburetor or fuel injectors you can use what you want. For years Mercury used steel. So SS can be used as well. But in 20 years with the USCG I did not hear a single manufacturer ask if they could use SS as fuel line.
     
  12. Stumble
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    Stumble Senior Member

    Thanks Ike, good to know.
     
  13. powerabout
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    powerabout Senior Member

    i'm fine with that, SS is problematic no secret there and steel is reliable
     
  14. daiquiri
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    daiquiri Engineering and Design

    Found this clarification at the USCG site: http://www.uscgboating.org/assets/pdf/recalls/bscscan68b.pdf
    Guess that, together with Ike's explanation, it ends the question. No stainless.

    Regarding this:
    I cannot because it seems that the stainless is indeed forbidden in ISO too. I was tricked into believing otherwise by a couple of check-lists for surveying which include stainless among the allowed materials for fuel lines, but I just cannot find the support for that claim in the ISO standards I have (which have not been updated to the latest edition, however).

    It is also logical to have ISO and USCG standards require (and forbid) the same materials, since there is an agreement between US and EU on a mutual recognition of certification procedures.

    Cheers
     

  15. Ad Hoc
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    Ad Hoc Naval Architect

    Interesting.

    We've used SS316L for all our fuel system piping for almost 30years on a vast range of boats operating all over the world. Never ever had a problem. All vessels built to DNV/LR class.
     
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