Full Scale SSC Testing of High Hardness 4130 Steel Riser P-line Weldments

摘要

American Petroleum Institute (API) standard 16C, Choke and Kill System, requires that peripheral lines (P-lines) meet the hardness requirements of NACE MR0175/ISO15156-2. This means a maximum hardness of 22HRC for low alloy steels. Further, NACE MR0175/ISO15156-2 allows downhole casing, tubing and tubular components made of AISI 41xx steels, quenched and tempered in tubular form, to have a hardness of 26HRC, but each heat should be qualified by Sulfide Stress Cracking (SSC) testing in accordance with NACE MR0175/ISO15156-2 Clause B.1 using the tensile test. During production of AISI 4130 Q&T drilling riser choke and kill lines weld cap hardness over 237HB/22HRC was experienced. This article describes Capcis HSE OTI 95-635 full pipe ring sour corrosion tests on high hardness AISI 4130 Q&T P-line pipe and weldments. In the full pipe ring tests, welded pipes were loaded by squeezing up to a Hoop stress of 552MPa (SMYS) in the outer surface. Test solution was the NACE TM0177 solution A, with H_2S partial pressure of 0.01, 0.1 and 1.0 bar (1, 10 and 100 kPa), respectively. Pipes and welds (weld cap and heat affected zone) with hardness that ranged from 230HV_(10) to 357HV_(10) did not show any signs of hydrogen induced sulfide stress cracking after the 30 days exposure. Test procedure and an overview of actual pipe and HAZ hardness variations are presented.