NACE MR0175 (sour service)

NACE MR0175 / ISO 15156 sets the materials requirements for equipment in oil and gas production environments containing wet hydrogen sulfide, called sour service. The standard applies once the H2S partial pressure in the gas phase reaches 0.3 kPa (0.05 psia); above that, components must resist sulfide stress cracking, hydrogen-induced cracking, and stress-oriented HIC. For carbon and low-alloy steels (Part 2) the core control is a hardness cap of 22 HRC; corrosion-resistant alloys are covered in Part 3. The standard governs material selection for FPSO process plant, wellheads, and gas-handling equipment retrofitted aboard offshore production vessels.