A series of tests were conducted on commercially produced bar stock for three commonly used alloys in the size range 2.0 to 2.5 inch (51 to 64 mm) to evaluate serviceability limits in sour (H2S containing) production environments with the goal to extend these limits in NACE MR0175/ISO15156. UNS S17400 was found to be highly susceptible to SSC. SSC was observed under all three environmental conditions used in this project to a minimum severity condition of 0.15 psia (1 kPa) H2S, 30,000 ppm chloride, and pH 5.0 at 75 F (23 C). Serviceability limits were identified for UNS S31600. In the initial test series the maximum use limits were 1.5 psia (10 kPa) H2S, 5,000 ppm chloride, pH 5.0, 200 F (93 C). In a second set of tests, additional limits were defined that consisted of 1.5 (10 kPa) psia H2S, 1,000 ppm chloride, pH 4.0, and 300 F (149 C). Serviceability limits were identified for UNS N05500. Based on the three test conditions used in this project, No failures were observed at 100 psia (689 kPa) H2S, 50,000 ppm chloride, pH 3.5, 75, with steel couple. No ballot was prepared for UNS S17400. Two ballot items for UNS S31600 were prepared and ratified for NACE MR0175/ISO15156 for service up to 1.5 psia (10 kPa) H2S, 5,000 ppm chloride, pH 5.0, 200 F (93 C) and for 300 F (149 C) at 1.5 psia (10 kPa) H2S, 1,000 ppm chloride, and pH 4.0. A 2006 ballot item was prepared for NACE MR0175/ISO15156 for UNS N05500 but was unsuccessful. An additional test with notched C-rings of this material at 225 F (107 C) and a steel couple followed by ambient temperature exposure with the test environments of 15 psia (103 kPa) H2S, 50,000 ppm chloride, pH 3.5 (initial) to 4.6 (final) showed no failure. A new ballot item for this material is in progress.

Subject
Materials failure, Materials, Autoclaves, Partial pressures, Acidity, Serviceability, C ring stress corrosion testing, Test environments, Heat, Steel, Sulfide stress cracking, Chlorides, Chloride stress corrosion cracking
Keywords:
Sulfide Stress Cracking, Stress Corrosion Cracking, Hydrogen Sulfide, Deep Water, Materials Selection
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2008
Association for Materials Protection and Performance (AMPP)
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