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Galvanized steel for high pressure fittings?

Discussion in 'Compressors, Boosters and Blending Systems' started by ThePimp, Jan 5, 2021.

  1. ThePimp

    ThePimp Angel Fish

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    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:

    H8vpjG8.png

    y9XtI5E.png




    Chrome plated brass:

    wWHPduM.png



    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!
     
  2. Ichebasje

    Ichebasje Angel Fish

    # of Dives: 200 - 499
    Location: Sittard, The Netherlands
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    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.
     
  3. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    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.
     
    RayfromTX likes this.
  4. ThePimp

    ThePimp Angel Fish

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    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?
     
  5. broncobowsher

    broncobowsher Solo Diver

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    Brass + SS = no problem.
     
  6. ThePimp

    ThePimp Angel Fish

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    And aluminium + SS?

    Blocks are of aluminium, filter housings and such...
     
  7. happy-diver

    happy-diver Skindiver Just feelin it

    # of Dives: 1,000 - 2,499
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  8. ThePimp

    ThePimp Angel Fish

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    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.
     
  9. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    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.
     
  10. ThePimp

    ThePimp Angel Fish

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    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)?
     

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