Patent ID: 7913496

Claim:
An apparatus for delivering a process fluid that is stored at a cryogenic temperature comprises: (a) a storage vessel defining a thermally insulated cryogen space for storing said process fluid; (b) a cryogenic pump with a suction inlet in communication with said cryogen space and a discharge outlet in communication with a delivery conduit; (c) a heat exchanger disposed along said delivery conduit such that process fluid flowing through said delivery conduit flows through said heat exchanger; (d) a pressure sensor for measuring process fluid pressure in said delivery conduit downstream from said heat exchanger; and (e) an electronic controller programmed to: (i) monitor a signal representative of process fluid pressure that is measured by said pressure sensor; (ii) process said signal to determine from measured process fluid pressure when cryogenic pump performance is degraded; and (iii) send a signal to an operator of the apparatus indicating when said electronic controller determines that cryogenic pump performance has degraded below a predetermined threshold volumetric efficiency; (f) an accumulator vessel disposed downstream from said cryogenic pump; wherein said pressure sensor measures process fluid pressure within said delivery conduit indirectly by measuring process fluid pressure within said accumulator vessel.