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NACE MR0175 - Allowable Low Alloy Steel Grade

NACE MR0175 - Allowable Low Alloy Steel Grade

NACE MR0175 - Allowable Low Alloy Steel Grade

Good morning to everyone,
i'm new on this Forum.
I'm a mechanical engineer and i'm working in the upstream Oil & Gas industry.
I have a question obout choosing a low alloy steel grade according to NACE MR0175.
The purchaser request a valve body and bonnet in AISI 4130 indicating API6A material class EE-1.5.
Since there isn't this material grade addressed in NACE, i'm sure that I can't choose this grade marking "-1.5" H2S partial pressure limit.

But my question is:
- According to NACE MR0175, wich low alloy steel material grade (or Carbon steel) I can choose to satisfy the customer request "EE-1.5" Mat.Calss??
- Or I can choose any grade respecting NACE hardness requirement and I shall mark EE, without any H2S Partial Pressure Limit (equal to mark "EE-NL")?
- Or I may suggest to the customer for example AISI 4130 Body&Bonnet with fully cladded inlay, with stem i.e. in AISI 410 (limited to 1.5 H2S partial pressure in NACE?

Someone knows any grade of low alloy steel that listed with H2S partial pressure limit, that are in accordance with NACE?

Thank you in advance for the answer.


RE: NACE MR0175 - Allowable Low Alloy Steel Grade

Check with the purchaser. It could be that they have based their requirement on a valve with internals in a material with the 1.5 limit, and are applying the designation to the whole assembly. You are right to be puzzled, as there are no H2S partial pressure limits for low alloy steel.

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.

RE: NACE MR0175 - Allowable Low Alloy Steel Grade

4130 has an NL rating for bonnet and bodies. The EE-1.5 also applies to the trim. Would need to know the temp rating to choose the correct trim material.

Petrotrim Services, LLC

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