Valve for CNG

[yoppu]

Hi, did anybody know the common material for CNG exhaust valve.

 

[CoryPad]

I believe the common alloys are stainless steels 21-2N or 21-4N.

 

[yoppu]

Thanks CoryPad, I got the info that 21-4N is normally for diesel engine. but what is really different between 21-4N and INCONEL 751 or Pyromet 31?

 

[CoryPad]

What is really different is the composition, microstructure and properties.

For example, 21-4N has 4 % nickel, Inconel 751 has 70 % nickel and Pyromet 31 has 57 % nickel.

 

[yoppu]

Tq. CoryPad, based on the usage what are the composition should we take attention for example something really can stand high temperature and pressure?

 

[CoryPad]

In general, the higher nickel content should provide higher temperature capability. You can look on the Internet for strength information to compare with stress from pressure.

 

[EdStainless]

The real issue should be high temp corrosion resistance, and Ni does not help with that.
Oxide formers, Cr, Al, Ti Si are what protect at high temp.
High Ni alloys may have better strength, but that isn't the limiting factor in valves.
High Ni alloys will also have better resistance to carborization and sulfidation, neither of which should be factors.

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