Best Practices Implementation for Monolithic Isolation Joints on Ultra Sour Gas Applications

Abstract Monolithic Isolation Joints (MIJ) are widely used on pipeline systems to electrically split the line into two (2) sections for Cathodic Protection (CP) coverage delimitation, as example. Failure of two MIJ are investigated for the gathering system handling ultra-sour gas multiphase fluid from ADNOC Sour Gas field, containing more than 23% H2S and 10% CO2 and operating at 90 °C and 93 barg conditions (design data: 118 °C and 96.5 barg). The testing aimed to assess the mechanical and chemical properties of the materials to identify any detrimental situation contributing to the failure. The results indicated that metallic sections of the MIJs did not contribute to the failure of the joint. Instead, the non-metallic components within the joint were identified as the source of the leak, with Glass Reinforced Epoxy (GRE) gasket material showing signs of degradation due to exposure to the ultra-sour service conditions. It was found that the GRE gasket material showed inadequate thermal resistance, likely due to manufacturing deficiencies such as insufficient curing, was a primary factor in the degradation observed. To prevent such issues, it is recommended to use materials with higher thermal ratings, such as ASTM D709 G11, which offers a nominal thermal resistance of 140 °C, and to implement meticulous quality control measures throughout the manufacturing process. The O-rings have been significantly compressed and exhibited cracking after one (1) cycle of decompression which is classified as premature considering resistance required as per ISO 23936-2. Selected FKM materials were found not suitable for long-term aging resistance to the service conditions. Literature [8,9] reflects a suitable compatibility by utilization of FFKM elastomer to the intended service. Material selection is a crucial aspect to ensure optimal performance, and it is equally critical to implement stringent quality control and assurance throughout the manufacturing process. This dual focus guarantees that the materials not only meet the nominal requirements but also exhibit minimal variance, thus preventing potential failures and ensuring reliability.