scope:

General

CRAs and other alloys shall be selected for their resistance to SSC, SCC and/or GHSC as required by the intended service.

Compliance of a CRA or other alloy with this part of ANSI/NACE MR0175/ISO 15156 implies cracking resistance within defined environmental service limits. These limits are dependent on the material type or the individual alloy.

To enable qualification and/or selection of CRAs and other alloys, the equipment purchaser can be required to provide information on the proposed conditions of exposure to the equipment supplier.

In defining the severity of H2S-containing environments, exposures that can occur during system upsets or shutdowns, etc., shall also be considered. Such exposures can include unbuffered, low pH condensed water. The limits given in the tables in Annex A are for production environments and do not cover conditions occurring during injection or flowback of chemicals that may reduce the in situ pH.

CRAs and other alloys shall be selected using Annex A or following qualification by successful laboratory testing in accordance with Annex B. Qualification based on satisfactory field experience is also acceptable. Such qualification shall comply with ANSI/NACE MR0175/ISO 15156-1.

In Annex A, materials are identified by materials groups. Within each group, alloys are identified by materials type (within compositional limits) or as individual alloys. Acceptable metallurgical conditions and environmental limits are given for which alloys are expected to resist cracking. Environmental limits are given for H2S partial pressure, temperature, chloride concentration and elemental sulfur.

A CRA or other alloy may be qualified by testing for use under operating conditions that are more severe than the environmental limits given in Annex A. Similarly, a CRA or other alloy may be qualified for use in different metallurgical conditions (higher strength, alternative heat treatment, etc.) to those given in Annex A.

The documentation of qualifications performed in accordance with Annex B shall meet the requirements in ANSI/NACE MR0175/ISO 15156-1:2009, Clause 9.

The equipment user shall verify qualifications (see B.2.2) and retain documentation supporting the materials selections made.