NACE MR0175/ISO 15156 Part 2, Annex A: Manufacturer’s Query on Hardness Limits for Sour Gas Service

Introduction

This page provides a question and answer related to NACE MR0175/ISO 15156 Part 2, Annex A. The question is about a clarification needed for a manufacturer of temporary pipe work, flow lines, etc. for sour gas service in well testing and process use in a surface application.

The Query

The manufacturer believes that Paragraphs A.2.1 through A.2.4 and Table A.1 with a hardness limit of 22 HRC are applicable in their circumstance, but pipe suppliers in their region inform them that 26 HRC is acceptable in such applications. The question is whether the 26 HRC limit is only applicable to material used in a downhole application, not a surface application.

The Answer

The answer states that ISO 15156-2, A.2.2.1 indicates that carbon and low alloy steels used in any product form must comply with the requirements of A.2.1, which include the hardness limit of maximum 22 HRC for the parent material. Exceptions to this rule are specifically named in other paragraphs of Annex A.

Welds and Hardness Requirements

Welds in such materials must also comply with the requirements of A.2.1.4 that refers to Table A.1 which sets hardness requirements for welds. Sub-clause A.2.2.2 provides examples of materials that can comply with A.2.1, including some examples of tubular products in Table A.2. Sub-clause A.2.2.3 addresses downhole components only.

Qualification of Materials

The standard allows materials, such as AISI 4130, to be qualified at higher hardness than 22 HRC for possible use as pipe in sour service by laboratory testing in accordance with Annex B and Table B.1 or on the basis of field experience as described in ISO 15156-1, 8.2. Welds must also comply with the requirements of A.2.1.4.