Method and apparatus for pumping a cryogenic fluid from a storage tank

A method of pumping a cryogenic fluid from a storage tank with a reciprocating piston pump, said method comprising:

• in an induction stroke,
• retracting a piston within said reciprocating pump and drawing cryogenic fluid from said storage tank into a piston chamber associated with said piston;
• supplying vapor from said storage tank to said pump through a vapor supply pipe when a valve associated with said vapor supply pipe is open;
• supplying cryogenic liquid from said storage tank to said pump through a liquid supply pipe when said valve is closed;
• reducing vapor pressure within said storage tank and controlling pump flow rate by controlling the timing for opening said valve during said induction stroke;
• and
• (b) in a compression stroke,
• reversing the direction of said piston to compress and condense vapor and compress the cryogenic liquid within said piston chamber;
• and
• discharging compressed cryogenic fluid from said pump.

An apparatus for pumping a cryogenic fluid from a storage tank and reducing vapor pressure within said storage tank, said apparatus comprising:

• (a) a reciprocating pump for pumping said cryogenic fluid supplied from said storage tank;
• (b) a liquid supply pipe that fluidly connects said storage tank to an inlet of said pump;
• (c) a vapor supply pipe that fluidly connects an ullage space within said storage tank to said inlet;
• (d) an automatically actuated valve associated with said vapor supply pipe, said valve being operable between a closed and an open position for allowing vapor to flow through said vapor supply pipe when said valve is in said open position;
• (e) a controller for determining when to open said valve during an induction stroke of said pump, said controller making such determination to achieve a desired flow rate;
• and
• (f) a position sensor for determining the position of a piston of said pump, said position sensor in communication with said controller so that said controller opens said valve when said piston is in a position to corresponds to the desired proportion of liquid for said induction stroke.

An apparatus for pumping a cryogenic fluid from a storage tank and reducing vapor pressure within said storage tank, said apparatus comprising:

• (a) a reciprocating pump for pumping said cryogenic fluid supplied from said storage tank;
• (b) a liquid supply pipe that fluidly connects said storage tank to an inlet of said pump;
• (c) a vapor supply pipe that fluidly connects an ullage space within said storage tank to said inlet;
• (d) an automatically actuated valve associated with said vapor supply pipe, said valve being operable between a closed and an open position for allowing vapor to flow through said vapor supply pipe when said valve is in said open position;
• (e) a controller for determining when to open said valve during an induction stroke of said pump, said controller making such determination to achieve a desired flow rate;
• and
• (f) an inducer, which is fluidly disposed between said storage tank and said reciprocating pump, said inducer comprising an inlet for receiving cryogenic fluid from said storage tank, an inducer piston that is reciprocable within an inducer piston chamber for compressing and condensing cryogenic vapor and compressing cryogenic liquid;
• and
• said pump comprising an inlet for receiving compressed cryogenic fluid from said inducer, and a pump piston that is reciprocable within a pump piston chamber for further compressing said cryogenic fluid.