NACE MR0175 17-4 PH Steel

[Krishnnaa26]

Dear All

Doubts on use of 17-4 PH steel in sour service especially for valve stems.

1) Do the word "valves" mentioned in title text of Table A.27 of NACE MR 0175 is related to the valves in wellheads/Xmas tress/packers/subsurface equipment OR valves anywhere in oil and gas processing plant/equipment?. It is noted from Table A.1 of NACE MR0175 that Table A.27/Table A.28 are not listed under Process plant/any equipment or component.
2) If Table A.27 can be used for any other valves in oil and gas process plant/equipment, do the point (b) [Stress < 50% SMYS or 380 MPa whichever is less] should be specified for the valve stems?
3) The environmental limits for 17-4 PH Steel are specified only in Table A.27 but not in Table A.28 and Table A.30. Any help on the basis or reasons behind this?.
4) For the statement provided in the Remarks Column of Table A.28 (No limits on individual parameters are set, but some combinations of the values of these parameters might not be acceptable), can the limits provided in Table A.27 be acceptable for the items listed in the the title text of Table A.28, in absence of any test data?
5) Do the relatively low %elongation and high %RA of 17-4 PH steel have any role
- on the environmental limits specified in Table A.27 and for the NO LIMITS in Table A.28/Table A.30.
- on the statement at (b) [Stress < 50% SMYS or 380 MPa whichever is less] in Table A.27 which is not available in Table A.30.
- in allowing the use of >33 HRC at 95% AYS in Table A.30.

 

[EdStainless]

First, read the scope of MRO175.
It is related to cracking because of H2S in the environment.
It does not cover CSCC or pitting.
Those are up to you to evaluate.

 

[Krishnnaa26]

EdStainless

Thq for your speedy response and agreed to your points.
However, it is intended to get members opinions/thoughts/previous experiences (if any) in similar situations etc., on use of 17-4 PH Steel usage in sour service conditions.