Unloading system for cryogenic pumps

An unloading system for deactivating a pump, comprising:

• a chamber;
• an inlet for admitting a liquid into said chamber;
• an inlet valve for closing said inlet;
• means in said chamber for pumping said liquid;
• an outlet valve for discharging said liquid from said chamber, said liquid having a discharge pressure;
• and
• means responsive to a pressure independent of said discharge pressure for engaging said inlet valve and preventing said inlet valve from completely closing said inlet.

An unloading system for a cryogenic pump, comprising:

• a pumping chamber;
• means located in said chamber for pumping a cryogenic liquid;
• an inlet for admitting said cryogenic liquid into said chamber, said cryogenic liquid having an inlet pressure;
• an outlet for discharging said cryogenic liquid from said chamber;
• inlet valve means for covering said inlet;
• and
• unloading means for selectively (i) holding said inlet valve means open to prevent said cryogenic liquid from exiting through said outlet, and (ii) permitting said inlet valve means to close said inlet so that said cryogenic liquid is pumped out of said outlet, said unloading means being responsive to a pressure differential formed between said inlet pressure and an external pressure source.

An unloading system for a cryogenic pump for preventing the discharge of a cryogenic liquid from said pump during the continuous operation of said pump, comprising:

• a pumping chamber;
• an inlet for admitting said cryogenic liquid into said pumping chamber;
• an outlet for discharging said cryogenic liquid from said chamber;
• means in said chamber for pumping said cryogenic liquid through said outlet;
• an annular valve for covering said inlet;
• a selectively extendable plunger for opening said annular valve to prevent said cryogenic liquid from being discharged from said chamber through said outlet, said plunger being activated by a higher pressure independent of the pressure of said cryogenic liquid.

An unloading system for a pump, comprising:

• a chamber;
• an inlet valve for admitting a liquid into said chamber, said liquid having an inlet pressure;
• means in said chamber for pumping said liquid;
• an outlet valve for discharging said liquid from said chamber;
• piston means for opening said inlet valve to prevent said liquid from being discharged through said outlet valve;
• and
• a pressure differential acting on said piston means for selectively operating said piston means, said pressure differential comprising said inlet pressure and a lower pressure independent of the pressure of said liquid.

An unloading system for a pump, comprising:

• a chamber;
• an inlet valve for admitting a liquid into said chamber;
• means in said chamber for discharging said liquid;
• an outlet valve for discharging said liquid;
• armature means for opening said inlet valve to prevent said liquid from being discharged from said chamber through said outlet valve;
• and
• solenoid means activating said armature means, said solenoid means being manually activated regardless of the pressure of said liquid.

An unloading system for a pump having an inlet valve for admitting a liquid at an inlet pressure into said pump, said unloading system comprising:

• a bore;
• an unloading rod for moving in said bore and engageable with said inlet valve;
• means for biasing said rod against said inlet valve to prevent said inlet valve from closing;
• a piston bore communicating with said inlet pressure, said inlet pressure providing pressure differential means for preventing said rod from engaging said inlet valve to permit said inlet valve to close;
• an unloading piston coupled to said unloading rod and located within said piston bore to react to said inlet pressure;
• and
• means for selectively decreasing said pressure differential to permit said biasing means to cause said rod to engage said inlet valve and prevent said inlet valve from closing, thereby unloading said pump.