Stainless coupling in gas lines

[Sneaks]

I need a brass barb adapter that adapts 5/16" to 3/8" fuel hose. I've not discovered any in auto parts stores, plumbing stores or West Marine. Internet searches have thus far been fruitless.

I have, however, discovered a nifty stainless steel version at the local homebrew beer supply house. Does anyone know of some obscure rule that precludes using anything but brass fittings in marine fuel applications?

Don

 

[journey on]

One thing comes to mind:
The price factor. I'll bet it costs more that a 5/15 to pipe plus coupling plus pipe to 3/8 fitting from West Marine. ~$6 total

Otherwise, you'll have the snappiest looking fitting around.

Another thought might be sparking, but the fuel will be inside the line ( I hope.)

journey on

 

[Sneaks]

One thing comes to mind:
The price factor. I'll bet it costs more that a 5/16 to pipe plus coupling plus pipe to 3/8 fitting from West Marine. ~$6 total

Actually, the beer makers sell them for $1.50 :shock: and it's a lot neater installation.

 

[gljjr]

On my sled I have a nifty Stainless quick release fitting mounted on the back of the boat for my kicker. It looks just like the air hose fittings you would use with an air compressor but smaller. It sure is a slick way to plumb in the kicker to the main tank.

I don't see any reason you would have a problem with the Stainless fitting. Sparking problems are not going to be any different with Stainless over Brass.

 

[JeffC]

Digging back into the grey cells from the few years I'd worked as a corrosion engineer ....(a few years ago, I'm afraid.)

Among the most common type of stainless alloys are of a type known as Austenitic Stainless Steels. (This is defined by the grain structure). I think of 'generic' stainless steel as being "316 stainless" which is an austenitic stainless.

The Austenitic alloys are not generally recommended for applications in seawater environments because of the potential for chloride stress corrosion cracking.

Having said this, the stress corrosion cracking mechanism requires that the presence of tensile stress (a 316 alloy bolt would be bad news in a seawater environment). A barb fitting should be ok (unless it has a portion with a threaded compression fitting on one half (?). I can check with a neighbor of mine who happens to be a PhD metallurgist if you want me to follow up further.

My memory is a little hazy, as I really work in a different field of engineering (although my first two years of college I did major in metallurgy)

Oh... one more thing. You can confirm if your fitting is of an austenitic alloy by checking it with a magnet... austenitic stainless steels are unique in that they are non magnetic.

Yes... it is a pity that I don't have a C-Dory... one day, one day

 

[Larry H]

One solution would be: one fitting with male 5/16 barb with a 1/4 in male pipe thread and another with male 3/8 barb and female 1/4 pipe thread. Screw them together and you have an adapter.

 

[Pete in NY]

As a manufacturer of OEM parts in Asia, I have supplied stainless steel fittings to the semi-conductor industry. They use lots of corrosive gasses and acids when computer chips are etched on silicone wafers. Stainless is misunderstood by many since it does rust. In semiconductor tubing the material used is 316L VimVar (Vacuum Induction Melt, Vacuum Arc Remelt) high purity material. The inside of fittings are highly polished to mirror finishes and passivated to remove any stray iron atoms that can spoil a batch of chips. Passivation is a splecialized process nitric acid bath or more environmentaly friendly citric acid bath that removes the iron on the surface and leaves more of the chrome and nickel "stainless" steel is made from. I'm sure if you spent time around boats you have seen rust on stainless steel fittings or bolts. Thats because the material was not passivated (cheaper to not passivate and a lot of buyers aren't engineers who know what they are doing). Depending on the stainless type, I would use caution in using on a boat's fuel system. A cheap unpassivated 18-8, 302 or 303 stainless may not be the best. 304 is used for a lot in food industry fittings since it machines better than 316, however, 316 is also widely used since 316 will rust less due to higher chrome content. A little rust in my beer may not hurt me, but I woudn't want it getting into my engine, since I really don't know what it may do. There must be a reason they usually use brass. Any jet engine mechanics around? What are Jet fuel systems made from?

Regards,
Pete in NY

 

[Sea Wolf]

Don-Good Question! Most wouldn't have bothered to think twice or ask!

Pete- Great answer / information! The classroom is OPEN. This is starting to get fun!

Larry H- Now why did you have to go and spoil all the fun with a simple, practical, ingenious answer like that!

Good thinking all!!! Joe.

 

[Sneaks]

I agree, Joe. It's certainly becoming educational. My tendency so far is to just go with the stainless adapter since it's much lighter than Larry's solution and doesn't require mounting or vibration considerations while lying on the starboard tank. Besides, fuel isn't supposed to have water in it! :shock:

My diesel truck has Bosch injectors which are much more contaminant sensitive than this FI Yamaha, yet the fuel passes through a mixture of aluminum, steel, and some sort of high density plastic as well as whatever passes for rubber fuel hoses nowadays on it's way from the tank to the injector pump.

I've seen steel and aluminum used in inboard installations but brass seems to be the preferred material in marine store fuel fittings areas, hence the question.

An interesting side note; many manufacturers are using plastic wire tie wraps to cinch down fuel hoses onto fuel fittings rather than the "traditional" stainless bands. Since there's no real pressure in outboard fuel lines from the tank to the engine, it's certainly cost effective. I always carry a few in my emergency tool kit along with duct tape, and the combination of those two really come in handy.


Don


.

 

[CAVU]

Don,
At the risk of spoiling all the fun, would a few feet of new fuel hose, all the same size solve your problem? Sorry I couldn't offer any metallurgical insights.

 

[dogon dory]

Sorry, Folks - Post Deleted By Author

 

[Pat Anderson]

Actually, you must burn a $20 bill if you normally obtain these sorts of items from West Marine. It is permissible to burn a $10 bill only if you normally obtain your marine hardware at commercial marine suppliers rather than consumer outlets...

There are indeed restrictions on using the stainless steel beer hose fitting in the fuel system of a C-Dory. If you purchased the fitting from a vendor who sells beer equipment or any other equipment intended for the food industry or for any other industry not intended for marine applications and if you did indeed pay $1.50 for the fitting, then it is permissible to use it on your boat if you also burn a $10 bill immediately after installation and testing of the system.

 

[Pete in NY]

Rust may be a non issue. I think the reason that brass and aluminum are commonly used in fuel systems is because they don't spark. If you put a piece of stainless steel on a grinding wheel in the garage, you get sparks. Sparks and fuel equal you know what!!

I suppose if someone had the time to look up the Coast Guard Regs, I'm sure there must be some Fed regulation about this.

Have a nice day burning money guys.

Pete in NY

 

[Sneaks]

Dan, indeed it was $1.50 here. Shipping would have added $6.50 but they're just a few miles from me so a visit saved shipping. You'll notice the URL shows brass splices but I guess if you're in the beer making industry for any length of time, everything looks brassy because they're actually food grade stainless.

Fascinating place, the Beverage Factory. This beer making business as a hobby looks to be a bigger money pit than boating! Especially outfitting a home bar. Thankfully the Admiral was along and had a death grip on the checkbook.

I suppose if someone had the time to look up the Coast Guard Regs, I'm sure there must be some Fed regulation about this.

Yup Pete, a certified marine surveyor prolly knows chapter and verse, but of all the professions associated with C-Dory ownership on here, none have outed themselves yet.

Pat/Dan, it is indeed fitted and tested. Though I doubt it will appease the Gods of Watsonville, CA, home of West Marine, I promise to faithfully burn $20 worth of steak on the barbecue this very weekend.

Don