Patent ID: 8505572

Claim:
A pressure relief valve for cryogenic service, comprising: a base having a fluid inlet and a fluid outlet; a bonnet attached to the base, the base and the bonnet defining an internal cavity in fluid communication with the fluid inlet and the fluid outlet; a nozzle disposed within the fluid inlet and attached to the base, the nozzle having a substantially annular seat; a disc holder disposed in the internal cavity; and a closure disc disposed within a proximal end of the disc holder, the closure disc comprising a substantially cylindrical body having an upper portion adapted to be received in the distal end of the disc holder and a lower portion, the lower portion including a groove formed on an exterior radial surface of the cylindrical body and an outwardly disposed lip having an upper surface comprising a portion of an interior surface of the groove and a lower closure surface proximate the annular seat of the nozzle, wherein the lip of the closure disc is adapted to cause the lower closure surface to deflect downwardly and radially inwardly relative to the annular seat in response to a cryogenic thermal gradient applied across the lip, wherein said cryogenic thermal gradient created by a cryogenic temperature fluid flowing between the lower closure surface of the lip and the annular seat of the nozzle, and wherein, when subjected to the cryogenic thermal gradient the downwardly and radially inwardly deflection of the lower closure surface places the lower closure surface in contact with the annular seat of nozzle and substantially closes the valve.