The Stovebolt Site Forums The Shop Area Engine Shop Brass fittings on stainless tubing

The engineering data I can find recommend against brass compression fittings on stainless tubing. However, a search of this site shows stainless fuel and oil lines connected with brass fittings. I assume this is acceptable due to the low pressures involved. Has anyone had problems with leaks while using brass fittings?

Joe D.

I have experienced no problems, Joe. However, my trucks are garaged and not driving around a lot.

Any metal-to-metal contact between different metals can result in corrosion (galvanic reaction/corrosion), to differing degrees and depending on the "environment".

I do not have metal corrosion charts, but, I dimly recall that SS against brass was far less reactive than brass against most other metals?

http://www.engineersedge.com/galvanic_capatability.htm

In regards to running a fuel line- personally, I would never use a compression fitting with stainless steel - flare only. In fact, I wouldn't use a compression fitting anywhere in a fuel line setup.... compression fittings aren't rated for fuel. Fuel leaks create fires.

You will see every kind of setup imaginable, including installing those really cool clear glass fuel bowl filters right above the exhaust manifold. Those always make me cringe.

Maybe I'm paranoid, but you'd never, ever see those things in a modern aircraft engine compartment (and for good reason).

I would use compression fittings for oil & vacuum, however.

I always go back to the NHRA rule books. They made safety top priority and really stressed fuel system safety. Compression fittings have no place on a car, Period!

Our School bus lot has CNG fuel lines run above ground for 400 feet or more with a compression fitting every 10 or 12 feet. There are hundreds of them in the fueling system all holding 3600-3800 psi. They are stainless on stainless and made for the job, but I still wouldn't run them on a gasoline system.

I know stainless fittings on stainless tubing will withstand 10,000 psi. I tested my fuel line to 100 psi, so I feel pretty good about that.

This is interesting in that different guys have different ideas on what they will or will not put on a fuel system. This discussion is as bad as one where someone says he would never paint a car black and has personal data to back it up.
Why doesn't a mechanical engineer jump in here and tell us what the SAE standard is regarding compression fittings on fuel lines. If the SAE standard says they are ok for use in fuel delivery systems in vehicles, and one knows how to install them correctly(an issue we often miss), then where's the problem?
There is a discussion going on over on the AACA forum on crimp connectors vs soldered connections. Guys with aircraft maintenance experience to shade tree wrenches are giving their opinions as to what is right or wrong. No one seems to give a hoot as to what the standards are. Heck guys, someone here is going to state that a 1/4" x 19tpi bolt works better than a 1/4" x 20tpi and can prove it. He will not care that 1/4"x 20tpi is a standard we all work with.

It comes down to the right fitting for the job it was intended to do and, this is the big one, installed correctly!

It's the last one that can get you in trouble.

Joe

When I was on Okinawa during my USAF days, it was not uncommon to see some of the local shade tree shops use brass compression fittings and COPPER TUBING on brake lines! Since the island was only 5 miles wide at its widest point, there was no getting away from salt spray and corrosion. On a quiet night you could probably hear cars rust!
Jerry

I assume all references here are to inverted flares as opposed to 45 or 37 degree flares.

Joe D.