| 摘要 |
A seal system for a motor pump unit includes a primary and a plurality of backup seals mounted in series within a seal housing. The primary seal is of a hydrostatic type and each of the backup seals is of a normally closed hydrodynamic type. Each of the primary and backup seals has a secondary seal between an axially movable seal ring thereof and the fixed seal housing, and at least one of these secondary seals is a spring-loaded, split piston ring seal. Two of the backup seals are of the Rayleigh type, where the Rayleigh pockets are formed in the seal runner, and the sealing dam is formed on the axially movable seal ring. An insert is provided in the runner of one of the backup seals, which insert is formed from a relatively harder material than the material forming the sealing dam. The other Rayleigh-type backup seal has pumping grooves extending downwardly and inwardly through the runner and toward the shaft to pump liquid into the Rayleigh pockets to ensure proper seal operation. A segmented backup shutdown seal is also provided, upstream of the two previously mentioned backup seals, which has pockets therein that pump any leakage back into the seal housing, yet in the unlikely event full system pressure appears across the segmented shutdown seal, that pressure will turn the shutdown seal into a rubbing seal with higher wear and prevent leakage from the seal housing. The seal system is designed so that the two Rayleigh-type backup seals may be mounted on a removable shaft sleeve and are removable as a unit by a single lift of the shaft sleeve. The shutdown seal is formed from two half-ring subassemblies, which are secured together and to the seal housing. The shutdown seal may be removed by disengaging the two subassemblies from the seal housing and from each other, so that the shaft need not be decoupled from its driver in the event of inspection or replacement of the shutdown seal.
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