NACE MR0175 limits for UNS N06975 and UNS N10276

Question:

(a) NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14 permits sulfur at 300°F in any H2S partial pressure, but not at 425°F. Where, if anywhere, between 425°F and 300°F are alloys in this category sulfur-resistant? If an oil-company client has a well with bottom-hole temperature of 350°F with produced brine that contains sulfur, will an alloy like 2550 (UNS N06975) be sufficiently resistant,

(b) must C-276 (UNS N10276) be deployed?

Answer

(a) In some cases the comparisons you make are not strictly valid because the data sets for the materials considered vary in the H2S limits, in the temperature limits, and in the metallurgical limits that are imposed. It is thought that the limits given are conservative and further testing could demonstrate that the true limits are less restrictive than those shown.

(b) UNS N10276 would be acceptable.

This question is in relation to NACE MR0175/ISO 15156-3 A.4.2, Table A.14 and A.33

Reference: ISO 15156 Maintenance Panel Inquiry #2003-13 Q4