Precipitation hardened stainless steel NACE complinace

[metboss]

Hi all,

We placed the order to vendor a year ago for the procurement of Sub-surface safety valve (Drilling) which has 17-4 Precipitation Hardened stainless steel as a trim material (Disc + seat) compliance to NACE MR-0175 (2009 Ed). Recently, we received partial quantity with 17-4 PH trim with NACE compliance.
Now for remaining quantity, vendor is come up with a query mentioning that as per new NACE guidelines, 17-4 PH SS cannot be used for trim & can’t be complied with NACE MR-0175 requirements.
Instead, now, they are proposing Inco 925 material with NACE compliance for trim in place of 17-4 PH SS with cost impact (high cost).

My questions are:

1)Did NACE issue a new guidelines that prohibits the usage of 17-4 PH SS for trim ? If so, as per which edition/circular and when it was issued ?
Is there any grace period for manufacturer so that 17-4 PH SS can still be certified to NACE MR-0175. Please give clause/table reference for such grace period provision.

2)Can we still use 17-4 PH SS for trim and is there any risk if we use old NACE reference?
(Our service fluid H2S partial pressure is below 200 ppm and other factors are okay with NACE MR-0175(2009 ed) table A.27)

Regards

 

[SJones]

The 2015 versions of the three parts of ISO 15156 are at the printer

http://www.iso.org/iso/home/search.htm?qt=15156&sort=rel&type=simple&published=on

NACE are having, or have had, a ballot of "invited experts" to accept the new ISO standard as NACE MR0175/ISO15156

Thus, the restrictions could be in these imminent documents.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[SJones]

Missed the answer to 2)

2) If you are the end user of the item, you can use what you like. The risk will come from the lawyers if it all goes horribly wrong and cognisance of the new standard has not been made.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[metboss]

Thanks S.Jones for your feedback.

 

[JHWC]

Hi Metboss,

What is the trim that you are looking at?

Thanks,
Jeffrey

 

[metboss]

Hi Jeff,

The currently specified is 17-4 PH SS whereas vendor is proposing Inco 925.

 

[SJones]

1) The 2015 version of ISO 15156 is now published; so, you can check in Part 3 to see what is causing the vendor to baulk at supplying the specified material.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[JHWC]

Hi Metboss,

I just glanced through the new version of ISO 15156, there isn't any changes to 17-4 PH. It was proposed but was not implemented in the latest edition.

Let me know if you need evidence. I can provide one if you need.

Thanks,
Jeffrey

 

[SJones]

Notwithstanding that there is no such thing as "NACE compliance" when using Table A.27, is the specific application within the H2S partial pressure limitation of the same table?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[JHWC]

The reason why people tend to say "NACE COMPLIANCE" is because of the hardness being controlled and specified.

To achieve the hardness (22 HRC max) for stainless steel (for example, 410), one has to comply with the recommended heat treatment process.

The partial pressure of H2S for 17-4 pH is 0.5 psi (max). Higher than that, the material will result in SCC.

Thanks,
Jeffrey

 

[SJones]

There are a few other things to control and specify as well. Apart from that, I'm trying to point out that simply saying "NACE compliance" is not technically correct because there are limitations on partial pressure of H2S that only the end user can warrant as being compliant.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[JHWC]

Thanks Steve,

You are correct and I definitely agree with you.

Cheers,
Jeffrey

 

[jmec87]

NACE MR0175 lists the H2S limit as partial pressure of H2S, not ppm. The higher the pressure, the lower the concentration of H2S required to exceed the 0.5 psi H2S partial pressure limit for 17-4 PH. For example, if the working pressure is 20 000 psi and an H2S concentration of 30 ppm, then based on the ideal gas law the partial pressure of H2S is 20 000 * 0.00003 = 0.6 psi.

For 2500 psi working pressure and 200 ppm H2S concentration, the partial pressure of H2S is calculated to be 2500 * 0.0002 = 0.5 psi. If you're running around or over 2500 psi with about 200 ppm H2S, you're probably exceeding the NACE limit and may be at risk of failure.