SPIRAL GROOVE SEAL ARRANGEMENT FOR HIGH VAPOR-PRESSURE LIQUIDS

摘要

A seal system is disclosed for sealing a housing and rotatable shaft against leakage of high vapor-pressure liquids such as natural gas. The method of sealing contemplates phase change of the liquefied hydrocarbon fluid across a first module. The gas so formed is contained by a second seal module which operates as a dry running gas seal. The seal system has plural, axially spaced spiral-groove seal modules mounted between the shaft and housing. Each seal module has a primary ring affixed to the housing and a mating ring affixed for rotation with the shaft and the modules define an intermediate cavity. The rings have opposed, radially extending faces, one of which has a plurality of downstream pumping spiral grooves extending from one circumference. The grooves of the grooved ring of the upstream module have a pattern which upon shaft rotation creates shear heating of the liquefied hydrocarbon fluid. The pattern has a land/groove surface area ratio greater than one and preferably a ratio of approximately three. The dam portion relative to groove portion surface area is also preferably greater than one and the preferred dam/groove ratio is approximately three.