API Trim 10 instead of Trim 12 2

[curtis2004]

Hello all,

I am working on a small 2" drain line replacement project in NGL facility. I am using company spec to specify valves and come across with a problem. The 2" line material is 304 SST with design temperature of -100C/50C. The main reason for -100C temperature - during draining ethane can flash and cool the line. The service is sweet.

A valve vendor have 2" swing check valve ASTM A351 CF8M body, trim #10. My spec calls for ASTM A351 CF8 trim #12. 316 seems better material than 304, but how about trim? I think since this is 2" drain line and used only when the line is drained (once a 6 months) we can substitute trim #12 with trim # 10.

Do I need to check anything else before filling up request for deviation?

Thanks,
Curtis

 

[TD2K]

Since the piping is 304 SS and this isn't used much, I wouldn't see a concern with it.

 

[curtis2004]

TD2K,

Thanks for your input.
When trim #12 usually preferred over trim #10? Do you know as an example when people should order trim #12?

Regards,
Curtis

 

[TD2K]

316 generally has better corrosion resistance than 304 in many services but for a clean, sweet service like ethane it's a moot point between the two.

 

[reverman]

Trim 10 is 316 stainless on both seat surfaces and 316 stem

Trim 12 is 316 stem, one seat surface 316 and one seat stellite #6 (hard faced)

Neither trim allows 304 stainless.

Typically people want the "upgrade" to trim 12 due to wear concerns and wanting to avoid galling by having dissimilar metals in seating contact. I would not assume somebody will accept trim 10 over trim 12.


Most likely a CF8 (304) valve will have API trim 2 (Not trim 10) which is 304 stainless on both seat surfaces and 304 stem.

API does not have a trim number for 304 with half stellite so often customers may say "trim 12" when what they really want is a all 304 stainless valve with one side hardfaced seat.

I usually go back in these cases and clarify what they want each seat surface to be and the stem material (in the case of swing check valves the hinge pin material)

 

[niteshgargeck]

There should not be any big concern by using trim 12. the difference between both is only in trim 12 seat is stellite.
now the thing is where the difference lies. yes with stellite you can have some problem because in practices, hard-facing of seat through stellite can negatively affect the valve tightness at very low (and high temperatures), as a consequence of different thermal expansion coefficients of austenitic stainless steel and stellite.
So better to go on your original spec.