| 摘要 |
A seal system is disclosed for sealing a housing (14) and rotatable shaft (34) 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 (22). The gas so formed is contained by a second seal module (24) which operates as a dry running gas seal. The seal system has plural, axially spaced spiral-groove seal modules (22,24) mounted between the shaft (34) and housing (14). Each seal module has a primary ring (26A,26B) affixed to the housing (14) and a mating ring (30A,30B) affixed for rotation with the shaft (34) and the modules (22,24) define an intermediate cavity (25). The rings have opposed, radially extending faces (28A,28B) (32A,32B), one of which has a plurality of downstream pumping spiral grooves (80) extending from one circumference. The grooves (80) of the grooved ring of the upstream module (22) 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 (82) relative to groove portion surface area is also preferably greater than one and the preferred dam/groove ratio is approximately three. <IMAGE> |
