Study on Additively Manufactured Mechanical Seal (Part 1)

In oil refineries and petrochemical industries, a containment seal (CS) can be applied to a flashing hydrocarbon pump as a sealing device to prevent environmental pollution. It is extremely difficult to design a CS to ensure the contradictory functions of fluid-tight sealing and sealing-surface wear resistance, which are required under both conditions of dry running in gas and wet running in liquid. In this study, a new CS design concept, “CSAM” (Containment Seal by Additive Manufacturing), for the sealing surface and internal structure of a sealing ring was developed by additive manufacturing. A lubrication film formed on the sealing surfaces of mechanical seals is maintained by the opening force (OF) with fluid pressure and the closing force (CF) with fluid pressure and spring load. To obtain the desired OF, the CSAM controls the pressure distribution across the sealing surfaces by introducing outside pressure through slots on the sealing surfaces, and an annular cavity is formed within the sealing ring. Based on a series of numerical analyses and static tests, it has been found that the difference between OF and CF can be properly controlled using slot design parameters. The results suggest the possibility of achieving the contradictory functions of sealing and wear resistance under both the gas and liquid conditions required for CSs.