Unit Cell Approach: Verifying Flowline Insulation Coating Capacity Under High Tension Conditions

Abstract High pressure, high temperature deepwater field developments are becoming common in our industry. This combination can result in thick insulation coatings on heavy wall pipelines that require high-top tensions and subsequent shear forces for installation. This type of pipeline behaves as a steel and polymer composite that must maintain structural integrity under such loads. Wet Thermal Insulation standard exists for the coating applicator to validate the thermal performance and shear resistance of a wet thermal insulation system. However, the industry does not have guidelines in understanding the causes and sequence of events that would lead to a product defect or failure, due to the shear forces applied by a vessel’s tensioner or hang of module (HOM). A testing philosophy was developed to understand the coating’s sensitivities to welding thermal cycles, and installation loads. The understanding provides guidance on mitigating defect/failure risks and assigning a recommended safety factor for high shear loads during reel lay operations. The test philosophy included a ‘unit cell’ approach, which was a set of laboratory shear tests that replicated the installation conditions. The test procedure was then used to develop a finite element model which gave comparable results to the test. This paper presents the case for the industry to have guidelines to understand the potential causes and sequence of events that would lead to a coating defect or failure during installation.