Abstract: A thermally actuated shutdown seal for a rotating shaft having a narrow annular fluid flow path surrounding the shaft. The seal surrounds the shaft with the annulus therebetween during normal operation and constricts against the shaft when the shaft slows or stops rotating. The annulus is maintained open during normal operation by a spacer interposed between opposing ends of a split ring. When the shaft stops rotating, the temperature of the annulus rises, which actuates removal of the spacer from the split ring constricting the split ring against the shaft blocking the annulus. The blocked annulus causes a pressure differential across the seal which urges a polymer seal ring, downstream of the split ring against the shaft which seals the annulus. In one embodiment, the spacer is formed of a meltable material. In a second embodiment, the spacer is removed from the split ring by a thermally responsive actuator.

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.