Brass fittings for high pressure hydraulic system

[aircraftengr]

Is it advisable to use brass fittings/connectors/adaptors for a marginally high pressured hydraulic system such as an autopilot which can go up to 1000psi?

I am convinced that it is a wrong move, but have been overruled by higher authority due to cost issues - brass is cheap, while stainless steel costs a bomb!

Yet, I am determined not to remain silent about this. Most brass fittings are rated at about 670psi even though they have a safety factor of 4. I still feel this is dangerous. How about forged brass? I was looking through the Parker catalog and found that their forged brass has a rating for up to 3250psi.

However, they do not produce the brass fittings that I need as those are irregular and seldom used. I cannot resort to steel because the fittings are to be in the lazarette and they will definitely rust - steel is out of the question.

Unless someone can prove to me that grease-wrap and painting effectively avoids rusting.

HELP!!

 

[sreid]

One ploy is to ask that the instruction to use the brass fittings be put in writing. This will sometimes make managers reconsider but it can have employment consequences.

Any chance that there are alternate sources for the SS fitings that can be purchased at a lower price?

 

[desertfox]

Hi aircraftengr

On a similar vane to sreids post, I would be tempted to write a memo to your higher authority pointing out that
these brass fittings are not suitable for the system rating
and that you are sure that they (the higher authority) would not use them if they realised this.
Hopefully this will put you in the clear and maybe not create the employment issues that sreid mentions.


regards desertfox

 

[aircraftengr]

Thanks for your response, guys.

However, I'd like to have very solid proof before I even consider going to higher authority. As a structural/material engineer, I know that it is impossible to rate a certain fitting, due to the lack of knowledge of the process that goes on like extrusion, machining or annealing.

So I'd have to depend on the manufacturer's ratings. Obviously, for forged metal, the rating is higher, but that would be an unreasonable assumption to apply on all brass fittings.

How do I make my estimation and put forward my argument?