NACE MR0175 has been entirely replaced by the International Standard ISO15156-1 to ISO15156-3 issued in 2003 with subsequent Technical Corrigenda and Technical Circulars issued with updates and modifications. The standard provides guidance on materials selection in oil & gas exploration and production applications based upon cracking resistance in sour service. (Note: For applications in refineries, then NACE MR0103 is the appropriate standard).
The emphasis now is clearly on the end user to determine what is acceptable for their service requirements and it also allows relaxation for some conditions. This is the International Standard that should be used for selection of materials which are crack-resistant in H2S-containing production environments. It includes wider consideration of cracking mechanisms than the earlier standard and requirements to test the hardness of welds with Vickers 5 or 10kg load. It represents a substantial change from the previous document.
Only in the USA is the MR0175 label still carried on the document as well as ISO15156 (the text is identical in all documents issued by individual Standards authorities). This is simply due to the need to retain documents supporting sour service requirements under certain USA State laws, which require facilities to comply with NACE MR0175. NACE fully supported the development and move to harmonise the EFC16 and EFC17 (European Federation of Corrosion publications N°16 and N°17) and NACE MR0175 documents and this has resulted in the production of ISO15156, which is maintained via NACE and ISO. This replaces MR0175 in the just the same way that new versions of MR0175 replaced older versions.
The maintenance under ISO TC67/ Work Group 7 is delegated to the 'Maintenance Panel' which has an international membership and a balance of the equipment manufacturers, users, materials producers etc. To support this document NACE Task Group TG299 'Oversight Committee' comprises about 50 NACE members who can serve for five years to assist in ballot review and changes to the document. Also, any questions or requests for clarification (interpretations) are handled via NACE. So, NACE is very much involved in this new approach.
Full descriptions of the operation of the standard and responses to inquiries for interpretation, plus a discussion forum can be found at the ISO dedicated web site: www.iso.org/iso15156maintenance
Further information about in sour service can be found here.