Self generating lift cryogenic pump for mobile LNG fuel supply system

A device for removing vapor from a sump containing a cryogenic pump and a cryogenic liquid with a head space there above comprising:

• a. a vapor removal housing positioned above the sump;
• b. a vapor removal piston slidably disposed in said vapor removal housing so that upper and lower chambers are defined therein;
• c. a rod connected to the piston;
• d. a drive mechanism connected to said rod so that said vapor removal piston is moved by said rod in a reciprocating fashion;
• e. upper and lower suction valves in communication with the upper and lower chambers, respectively, and adapted to communicate with the head space of said sump;
• f. upper and lower discharge valves in communication with the upper and lower chambers, respectively, and a discharge line so that vapor from the head space flows through the discharge line when said vapor removal piston is reciprocated by said rod;
• and
• g. level control means sensing the level of cryogenic liquid within the sump and valve disabling means for disabling the suction valves before the level of cryogenic liquid reaches them.

A method of separately withdrawing a gaseous phase and a liquid phase of a liquid cryogen fuel from a storage tank for supply to an engine comprising the steps of:

• a. providing a vapor removal compressing device;
• b. providing a liquid pumping device having an inlet conduit and a low Net Positive Suction Head reciprocating piston pump with an inlet;
• c. withdrawing the liquid phase from the storage tank with the liquid pumping device;
• and
• d. withdrawing the gaseous phase from the storage tank with the vapor removal compressing device so that the liquid phase in said tank flows through the inlet conduit to at least the inlet of the pump.