Can someone suggest a good source to guide in the design of a gas control valve trim (plug and seat) set? I must comply with NACE MR0175.

Some of my questions are...

> What are my material options?
> What should I specify for hardness requirements (plug versus seat)?

Usually this is a company know how and trade secrets. If you are trying to do it yourself then you should be willing to invest time, money and a lot of frustration until you succeed.

In a previous life I used a piping "NACE" specification that called for plug valves to have A216 WCB bodies, 316 SS trim, and teflon sleeve material.  Sorry, no information on hardness criteria. I haven't broused MR0175 in some time but I'd expect it to address that to some degree.

Assuming you are a user of valves I recommend you talk to the valve supplier and get their recommendation. Some of the preliminary questions I have are 1) what is the gas?,2)what type of valve is this?, and 3) how big is the valve?

Typical valve trim materials are:
316 SS - ASTM A351,CF8M (cast)--- Notes 1,2
316 SS - ASTM A479,GR316,A (bar)--- Notes 1,2,3
416 SS - ASTM A487,CA6NM,CLB (cast)--- Notes 1,4
416 SS - ASTM A582,Type 416,A (bar)--- Notes 1,4
Note 1 - Any weld must be done to NACE welding procedures. Avoid this at all costs.
Note 2 - Material hardness HRC 22 Maximum, no cold working allowed.
Note 3 - Must be in the solution annealed condition per supplimentary requirement S5.
Note 4 - Material hardness HRC 23 Maximum, no cold working allowed.
Hope this helps.

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