Flow restricting devices in pumps

Abstract

Restriction of flow along a shaft by interposing a split ring in the annulus between the shaft and housing. When the ends of the split ring are separated, the effective diameter of the ring is increased and a clearance between the ID of the split ring and the shaft is maintained permitting flow. When the ends are released and allowed to come together the split ring closes the annular gap and restricts the flow. Also contemplated is the restriction of flow along a shaft by interposing an axially movable sleeve in the annulus between the shaft and housing. Flow through the annulus between the movable sleeve and the shaft is resisted by the clearance or features such as labyrinths, to thereby create a differential pressure from one end of the sleeve to the other.

Description

FIELD OF THE INVENTION [0001] The present invention generally relates to rotary pumps, such as chemical processing pumps or nuclear reactor coolant pumps, and constituent components therefor, such as flow restricting devices. BACKGROUND OF THE INVENTION [0002] In pressurized water nuclear power plants, a reactor coolant system is used to transport heat from the reactor core to steam generators for the production of steam. The steam is then used to drive a turbine generator. The reactor coolant system includes a plurality of separate cooling loops, each connected to the reactor core and containing a steam generator and a rotary coolant pump. Other venues also present situations where containment of a process fluid is critical, such as in the case of rotary chemical processing pumps. [0003] A rotary pump such as a reactor coolant pump or chemical processing pump typically is a centrifugal pump designed to move large volumes of process fluid (e.g., reactor coolant) at high temperatures...

AI Technical Summary

Benefits of technology

[0011] Further, there is broadly contemplated herein, in accordance with at least one presently preferred embodiment of the present invention, a rotary pump comprising: a motor; a shaft member extending from the motor; an impeller attached to a free end of the shaft member; a housing which encloses a major portion of the shaft member; the housing comprising a seal housing which circumscribes at least a portion of the shaft member, the seal housing including at least one sealing element for restricting fluid flow along the shaft member; the motor being configured for rotating the shaft in a manner to drive the impeller; and an arrangement for restricting fluid flow along the shaft relative to the seal housing in at least one annular space defined between the shaft member and the seal housing; the fluid flow restricting arrangement comprising a discontinuous ring member disposed about the shaft member; the discontinuous ring member having two ends; the discontinuous ring member being actuable between: a first condition, wherein the ends are spaced apart over a first distance; and a second condition, wherein the ends are spaced apart over a second distance, the second distance being less than the first distance; wherein, in the first condition, a greater flow path for fluid is afforded, in the at least one annular space defined between the shaft member and the seal housing, than in the second condition.

Problems solved by technology

In the case of nuclear reactor coolant pumps, since pump sealing assemblies can be prone to failure, e.g. in response to unmitigated high temperatures of reactor coolant, any resultant excessive leakage rates could lead to reactor coolant uncovering of a reactor core, and subsequent core damage.

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