Materials Performance

JUN 2019

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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31 MATERIALS PERFORMANCE: VOL. 58, NO. 6 JUNE 2019 of the steel at the MIJ. Based on geometrical considerations, the distribution of the cor- rosion at the 4 and 8 o'clock positions on the unprotected (anodic) side of the MIJ, next to the isolating material, suggest a level of water inside the pipe, corresponding to ~20% of the pipe section. The corrosion fea- tures observed at these positions can be jus- tified by the fact that part of the current car- ried through the pipe by the electrolyte discharges at this location, increasing the local anodic current density. If the current leakage would have been captured by early CP data gathering; for example, by testing the isolating joint with the four-point method, its effects on the unprotected side of the pipe immediately downstream of the internally coated sec- tion could have been detected in-service by manual ultrasonic thickness (UT) scanning of the lower half of the pipe. The corrosion observed at the MIJ itself is much harder to detect, requiring a skilled UT operator. Conclusions The failure resulted from corrosion due to current leakage across the protected and unprotected sides of the monolithic isolat- ing joint. This was caused by a deficient design of the MIJ and the electrical proper- ties of the produced fluids. Stresses applied on the MIJ and an inadequate material specification for the nonmetallic resin used in the isolating material were contributing factors. The design calculation of the isolating spool length should be clarified, as existing models present rather different results. Engineering best practices should consider issues such as: • L a ck of sp a c e to impl em ent th e required spool length. • Limiting the use of internally coated CS spools longer than a pipe length, as internal coatings of the weld areas represents a challenge for the current stage of technology. • Th e u s e of GRE i n st al l e d ab o v e ground is not allowed by some oper- ating companies, presenting a fur- ther challenge for pressure rating and/or temperature. References 1 NACE SP0286-2007, "Electrical Isolation of Cathodically Protected Pipelines" (Houston, TX: NACE International, 2007). 2 M. Monica, et al., "In Defense of the Mono- lithic Isolation Joint," CORROSION 2017, paper no. 8993 (Houston, TX: NACE, 2017). 3 K. Doering, et al ., "Monolithic Isolation Joints: A Possible Weak Link in Pipeline In- tegrity," CORROSION 2014, paper no. 3989 (Houston, TX: NACE, 2014). 4 ADNOC Onshore, unpublished results, 2018. 5 ASTM A106, "Standard Specification for S e a m l e ss C a rb o n S t e e l P i p e f o r Hi g h - Temperature Service" (West Conshohocken, PA: ASTM International, 2018). 6 NEMA LI 1-1998 (R2011), "Industrial Lami- nated Thermosetting Products" (Rosslyn, VA: National Electrical Manufacturers Asso- ciation, 2012). 7 ASTM D709, "Standard Specification for Laminated Thermosetting Materials" (West Conshohocken, PA: ASTM, 2017). 8 NACE MR0175/ISO 15156, "Petroleum and natural gas industries—Materials for use in H 2 S- containing environments in oil and gas production" (Houston, TX: NACE, 2015). 9 API RP 45, "Recommended Practice for Anal- ysis of Oilfield Waters" (Washington, DC: American Petroleum Institute, 1998). 10 Shell DEP 31.40.30.39. 11 J.L. Brazy, "Dimensionnement d´une Manch- ette Isolante—Étude Theorique," private communication, 1980. 12 W. von Baeckmann, W. Schwenk, W. Prinz, Handbook of Cathodic Corrosion Protection— Theory and Practice of Electrochemical Pro- tection Processes, 3rd ed. (Houston, TX: Gulf Professional Publishing—Elsevier, 1997). GERVÁSIO PIMENTA is a senior corrosion engineer at ADNOC Onshore, Abu Dhabi, UAE, email: gervasio.mafpimenta@gmail. com. He has experience working in materi- als selection for surface facilities and downhole—inhibitors, CP, and failure investigations. Pimenta holds a Ph.D. in materials engineering. He is certified to NACE CP3, is a Chemical Treatment Spe- cialist, and is a Senior Internal Corrosion Technologist. He has been a member of NACE for over 15 years. ABDULLA LUQMAN is a project engineer- ing managaer at ADNOC Onshore, Abu Dhabi, UAE. He has over 10 years of expe- rience working in the oil and gas industry and has worked in engineering design as a metallurgist and in project management for a multidisciplinary team. Luqman has been a NACE member for eight years. Isolating Joint Failure

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