Galvanized steel for high pressure fittings?

[ThePimp]

Hi everyone,

What would be the suggested material for fittings and valves?

I see galvanized steel, brass, nickel plated brass, stainless steel...however I'm finding the fittings I need mostly in galvanized steel or chrome plated brass.

As you've previously seen probably, I'm building my own external compressor filter, so its a 200 bar installation (not going to 300 bar).

I see most of the valves/connections as chrome plated brass, and fittings (1/4 BSP to JIC, or 1/4 BSP 90 degree and such) as galvanized steel.

Galvanized steel example:

Chrome plated brass:

Is this a good choice?

I'm aiming to make a Hyper filter which will not see pure Oxygen go through it, but should help put out from compressor the OCA air.


Also is it important what goes into what...galvanized steel male fitting be screwed into chrome plated brass and vice versa due to brass being the softer material?


Thnx!

 

[Capt. Bas]

To be honest, everything rated for the pressure should be sufficient.
Try not to mix the different types of metal to prevent galvanic corrosion otherwise I don't see a lot of problems.

Looking at your top picture it looks like Stainless steel to me, galvanized is rougher on the average without the nice surfaces on the mating area's.

 

[rjack321]

Looking at your top picture it looks like Stainless steel to me, galvanized is rougher on the average without the nice surfaces on the mating area's.

Those are zinc plated and they are fairly common in air systems. There are no "hot dipped" fittings in 1/4 NPT kinds of sizes because obviously the zinc will clog up the threads.

@ThePimp
In an OCA scenario you WILL get corrosion in there eventually which can lead to very fine flakes or particles of zinc or steel potentially in your gas. So upstream of your final filter, they are fine. Downstream no. High velocity particulates can lead to something called impingement at bends or in your valves which can lead to an o2 fire.

Brass (unchromed) is the ideal material and least likely to create a spark but also rarely available in >200bar working pressures. Female NPT brass fittings can get overtorqued and fail so be cautious and only tighten as much as needed to create a seal.

 

[ThePimp]

Thanks rjack!

But then SS is the only way to go?

Which is fine, only I'm not sure how to combine it with mostly brass valves? Won't they corrode together?

 

[broncobowsher]

Brass + SS = no problem.

 

[ThePimp]

And aluminium + SS?

Blocks are of aluminium, filter housings and such...

 

[happy-diver]

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[ThePimp]

How good is this Weicon?

Do you need to change it every some time or as you assemble it, it's good if it's a fixed connection?

Good thing about Weicon is that it's available in my hometown.

 

[rjack321]

And aluminium + SS?

Blocks are of aluminium, filter housings and such...

Are you keeping it wet? Dissimilar corrosion requires an electrolyte or nothing happens. And even if they did corrode together, NPT threads are not the kinds of things to assemble and disassemble more than once or twice anyway.

 

[ThePimp]

Are you keeping it wet? Dissimilar corrosion requires an electrolyte or nothing happens. And even if they did corrode together, NPT threads are not the kinds of things to assemble and disassemble more than once or twice anyway.

Not more than residual dampness.

I'm asking this for different purposes, but one of them being additional Filter for my compressor.

I suppose it will get wet with condensate.

And what about other kinds of threads? JIC, BSP (G)?