FAQ's

What are the NACE MR0175 requirements for API 5CT C110?

Designation of C110 Grade Steel in Mild Sour Service Conditions

Introduction

This page addresses a common question regarding the designation of C110 grade steel in mild sour service conditions in accordance with NACE MR0175/ISO15156. The question asks about the steel’s qualification and region placement based on the temperature constraints in Table A.3 of Section A.2.2.3 and whether any steel listed in Annex A can be selected for Region 1.

Temperature Constraints and Steel Qualification

The answer clarifies that Table A.3’s temperature constraints apply to Section A.2.2.3.2 for downhole casing, tubing, and tubular components. Section A.4 can be used to qualify steels not compliant with Sections A.2 or A.3 using UT tests as specified in Section B.1 for each test batch.

Higher Strength Steels

Figure 1 addresses pH and H₂S partial pressure without limitations on minimum temperatures for higher strength steels.

References and Support

This page cites ISO 15156 Maintenance Panel Inquiry #2015-07 as a reference for this question. Additionally, the page offers the support of oilfield metallurgists for API 5CT materials selection.

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