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PREN of TP304/304L in NACE MR0175/ISO 15156-3

PREN of TP304/304L in NACE MR0175/ISO 15156-3

PREN of TP304/304L in NACE MR0175/ISO 15156-3

Hi guys,

For LNG project, 304/304L welded pipe need comply with the Sour service of NACE MR0175 / ISO 15156-3.

In my opinion, generally the hardness test is required for stainless steel pipe in sour service, but the client ask us to provide the PREN and Ni+2Mo in the MTC which is a guidance information specified Table D.1 of Annex D in ISO 15156-3 2015.

So anyone could give me suggestions about the PREN requirement, is it mandatory for pipes?
Thanks so much.

RE: PREN of TP304/304L in NACE MR0175/ISO 15156-3

It's mandatory if the purchaser specifies it. Are they asking for information, or have they set the stated values as an acceptance criterion?

Steve Jones
Corrosion Management Consultant


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

RE: PREN of TP304/304L in NACE MR0175/ISO 15156-3

I agree with SJones if they set the stated values as an acceptance criterion in the purchase order you have to comply with it.


RE: PREN of TP304/304L in NACE MR0175/ISO 15156-3

And if they have not stated the acceptable value in the contract specs, they are only seeking information contractually.

RE: PREN of TP304/304L in NACE MR0175/ISO 15156-3

I can't read the attached file for some reason.
PREn isn't Cr+2Mo, bit that is another issue.
If what they are asking for meets the standard alloy then do the paperwork for them.
If it would require something special then tell them the cost.

PREn is nearly worthless for an alloy like 304L.
According to the specs the min value would be 18.0, just the min Cr.
Of course you can add up to 0.10%N and still be in spec, and the residual Mo is often 0.2-0.4% but just as often it is 0.02%.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: PREN of TP304/304L in NACE MR0175/ISO 15156-3

As in Table A.2 of ANSI/NACE MR0175/ISO 15156-3:2015(E), PREN requirement is NOT indicated, the same is NOT mandatory.

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