Stainless fuel lines prohibited?

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

  1. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    I recently came across ABYC H33.10 b 1, which prohibits stainless tubing from being used as fuel lines. For the life of me I can't figure out what the justification is for this. Any insights?
     
    1 person likes this.
  2. pdwiley
    Joined: Jun 2008
    Posts: 1,002
    Likes: 86, Points: 48, Legacy Rep: 933
    Location: Hobart

    pdwiley Senior Member

    WAG - work hardening and fracturing from vibration. But that's strictly a guess.

    PDW
     
  3. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 146, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    In such cases I imagine an official who pulled his necktie too tight: it restricts the blood flow and impairs brain functions.
    I have a long welded steel tube on my property that connects the propane tank to my house because local rules prohibit the use of copper tubes for propane.....
     
  4. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Im stainles pipe all the way to the engine bed, then a flex link to the engine.

    This is a very common setup for diesel fuel

    Im not sure how to interpret that rule
     
  5. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 246, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    I have to agree here. Also because (just for the sake of comparison) the NFPA standards for motor pumps explicitly require the fuel lines to be made of either black or stainless steel, and explicitly forbid the use of galvanized steel and copper. The trouble-maker is the sulphur, which is contained in the diesel fuel in various concentrations - depending on the local regulations. In the EU and the US, the sulphur content is tightly regulated and is typically less than 10-15 ppm. But in other areas of the world, the situation is much worse.
    This chart tells it all: http://www.unep.org/transport/pcfv/PDF/Maps_Matrices/world/sulphur/MapWorldSulphur_December2012.pdf

    The sulphur reacts with the water condensated from the air, and forms the sulphuric acid. This acid in turn strongly reacts with the zinc, which is contained in the galvanized steels and in several types of copper alloys. The 316 and 316L stainless steels are both fairly resistant to low concentrations of sulphuric acid, so should not give corrosion problems.

    Cheers
     
  6. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 146, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Sulphur in fuels is always present as an organic compound like dibenzothiophene , two or more benzene rings where a carbon atom is substituted by sulphur. It is the preferred food for several bacteria strains and it is the cause of the typical smell, but as long as the sulphur is bound to carbohydrates it does little harm.

    Only when the fuel burns, the atoms loose their CnHn partners and grab the nearest oxygen atom(s) and form SO and/or SO2. In the presence of water that turns into H2SO3 and H2SO4, both strong acids that attack many metals forming sulphites and sulphates. For reasons not completely understood, stainless steels are remarkably resistant.

    A possible reason to ban stainless tubing could be that the fuel line usually ends in a fitting that is made from a less noble metal, so there may be galvanic corrosion if moisture is present. I witnessed the effect on moorings where a heavy galvanized chain is extended with a stainless one. There is severe corrosion near the contact area unless a short piece of rope separates them.
    In my opinion the ABYC should not prohibit stainless fuel lines but require the use of stainless fittings.
     
  7. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 246, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Correct. I didn't want to get too much into chemistry, but the way you wrote it is definitely more informative. Cheers.
     
  8. gonzo
    Joined: Aug 2002
    Posts: 14,275
    Likes: 584, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Interestingly, all gas engines have stainless pipe between the fuel filter, the pump and the injection system.
     
  9. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Can someone post a copy of the rule ?

    What is a fuel line ?
     
  10. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    b. Fuel Supply Line
    (1) Metallic fuel distribution lines shall be seamless copper, nickel copper or copper nickel. The normal wall thickness of these metallic fuel lines shall be a minimum of .032 in. (.81 mm). Nonmetallic fuel hose shall be identified as USCG Type AI.
    (2) Rigid fuel distribution lines secured to hull members shall be connected to the engine by a flexible section. The rigid line shall be supported within 4 inches (lOI.6mm) of this connection.

    The rule doesn't prohibit stainless, it just requires they be copper, nickle copper, or copper nickle.
     
  11. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 115, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Hmmmmmm....

    My observation with aluminium boats is always...aluminium tank to ..steel pipe... to stainless valve..then stainless pipe to machine room..then flex to engine..then steel pipe on the engine itself

    There may be short copper nickel links on the engine fuel distribution circuit.
     
  12. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 246, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    The English language is not my mother tongue, but as far as I know (and please correct me if I'm wrong) the verbal construction "shall be" in legal documents indicate the imperative, as opposed to the construction "may be" which is permissive.
    So if the rules say that fuel line "shall be" either copper, nickle copper, or copper nickle, it means that no materials other than these three are allowed.

    Cheers
     
  13. powerabout
    Joined: Nov 2007
    Posts: 2,906
    Likes: 61, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    surprised black steel isnt allowed as its the most trouble free ( assuming you paint it) and there are plenty of commercial vessels out there using it
    I guess ABYC and USCG are not talking commercial but for pleasure boats they do have a great many good rules
     
  14. Stumble
    Joined: Oct 2008
    Posts: 1,896
    Likes: 71, Points: 48, Legacy Rep: 739
    Location: New Orleans

    Stumble Senior Member

    Correct. The effect is the same as if they had prohibited stainless, but the wording is different. In that this wording also prohibits all other metal fuel lines.
     

  15. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 246, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    This is the 1989 version of the H-33:
    https://law.resource.org/pub/us/cfr/ibr/001/abyc.H-33.1989.pdf

    and this is the 2005 draft version I have found in internet: http://newboatbuilders.com/docs/H-33_Diesel_2005.pdf

    The current H-33 version is dated 2010 and is available for purchase at the ABYC site. But, considering that ISO standards already cover all the topics of the H-33 and are being adopted worldwide as a reference, buying the ABYC standards would imo be pretty much a waste of money.

    Cheers
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.