NACE - Ball valve
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Question: If the following modifications are made to a ball valve that meets the standards NACE MR0103/MR0175 (2002 version), can it still be considered to comply with NACE standards? The stem material is to be replaced with 17-4PH. Please advise. Thank you.
Yes, the material allows using a higher grade in place of a lower one
Thank you. Does that hardness meet NACE requirements?
I asked my supervisor and would like to share the response with everyone. Laboratory tests on sulfuride stress cracking conducted in synthetic sour well solutions (5% sodium chloride + 1/2% acetic acid saturated with hydrogen sulfide), in accordance with NACE Test Method TM-01-77, show that, to achieve the best resistance to this aggressive medium, the alloy should either be in Condition H 1150-M or aged at 1150°F (620°C) for two 4-hour periods. Under either of these heat-treated conditions, AK Steel 17-4 PH Stainless Steel is considered by NACE to be suitable for use in sour (sulfide) environments, and it is listed in MR-01-75.
For specific information on NACE SSC HIC, please contact me; materials are available in both Chinese and English. Engineer Zheng from Zhonghai Testing is an expert in this field
Theoretically, precipitation-hardened martensitic steel 17-4PH is capable of resisting H2S, but its effectiveness is much lower than that of the 3-series steels such as S20910. It can be used in situations where H2S corrosion is not severe or where there are no other types of combined corrosion effects. However, in cases of severe corrosion or complex conditions, S20910 should be used at the very least; for low-pressure valves, 316L is suitable, and for conditions requiring higher strength levels than CL900, nickel-based alloy 718 is necessary