A Case Study on Engineering Techniques to Enhance the Reliability and Process Safety of Critical High Pressure Bolted Joints in the Oil & Gas Sector

Abstract The bolted flanged joints assembly has a complex interaction between the bolts, gaskets and body of the flange. Joint integrity and sealing performance are dependent on the various characteristics such as gasket properties, geometry, material, bolt pretension loads, assembly process and service conditions. In accurate bolt pre-tensioning can be the prevailing cause for joint leakage. On the other hand, excessive pre-tensioning can lead to damage to the bolts and gaskets. Any upset or abnormal loads which may occur during the service period can also adversely affect the bolted flanges joint integrity and thereby increase their tendency to leak and elevate the risk of damage. Therefore, critical bolted flanged joints subjected to complex working conditions in the Oil & Gas Industry require a safe and reliable design approach. This paper demonstrates a case study as how elastic-plastic stress analysis with the aid of cutting-edge Finite Element Analysis was applied to handle the modification of change of the 46″ New Main Gas Pipe Line (NMGL) which was impacting the large bolted flanged assemblies installed in the ADNOC Offshore upstream processing facility subject to the complex working conditions. The key objective here is to determine the appropriate bolt pre-tension loads to maintain the joint's leak tightness without damaging the components, establish the maximum plastic collapse load for the assembly, assess the joint leakage performance for the complex service conditions thereby achieve optimal design, ensure joint integrity, process safety and prevent any major modifications to the associated facilities.