High Pressure, High Temperature Shaft Seal For A Multiphase Subsea Pump

Abstract

The paper describes a totally re-engineered mechanical seal for multiphase subsea pumps with a focus on extended metal and seal face material selection as well as more stable seal behavior, achieved with a new face concept, which provides enhanced reliability and robustness. It reports the design process, starting from the project description with definition of targets followed by a theoretical evaluation of the seal performance and a description of the final design features. Increasing demand for high pressure and high temperature (HP/HT) pumps in Subsea multiphase applications requires the development of mechanical seals designed for pressure levels up to 15 kpsi and product temperatures up to 350°F with the capability to handle reverse pressure conditions. With the high pressure requirements the application of spring-energized polymer gaskets as static and dynamic secondary seals using a specific design for enhanced reverse pressurization capability were selected. To achieve enhanced robustness of the seal faces in transient dry running condition which may occur during upset conditions (such as reverse pressure) the design was optimized to include microcrystalline diamond coated seal faces. A detailed analysis of face deformation and seal performance under load with a combined structure and fluid analysis software together with an extensive test campaign and specific cooling jacket features lead to a robust mechanical seal design with optimized pressure distribution and mechanical contact zones.