Multi-stage vacuum pump

Claim 2

A multi-stage vacuum pumping system, including in combination a first stage positive displacement pump, a second stage liquid ring pump, means providing direct fluid communication between the outlet of the first stage pump and the inlet of the second stage pump, first and second constant speed driving means for said first and second stage pumps respectively, constant torque coupling means coupling said first driving means to said first stage pump, direct non-slipping coupling means coupling said second driving means to said second stage liquid ring pump, said constant torque coupling means having means to provide slip whereby the speed of said first stage pump is reduced when the established torque loading of said first coupling is attained thereby maintaining a pressure differential across said first stage pump below a predetermined value.

Claim 3

A vacuum pumping system in accordance with claim 1 including auxiliary cooling means at the output of said first stAge pump to reduce temperature of vapor-gas mixture being pumped through the system.

Claim 4

A vacuum pumping system in accordance with claim 1 including interstage cooling means disposed between the first stage positive displacement pump and the second stage liquid ring pump to provide additional cooling liquid at the inlet to the second stage liquid ring pump.

Claim 5

A vacuum pumping system in accordance with claim 1 including a separator tank for receiving the discharged consensate-gas-liquid seal mixture from the outlet of the second stage liquid ring pump with a gas vent disposed in the upper portion of said separator tank for discharging gases from the system.

Claim 6

A vacuum pumping system in accordance with claim 1 including a liquid recirculation loop interconnecting the outlet of the second stage liquid ring pump with the inlet thereof to provide sufficient liquid to the second stage liquid ring pump for uninterrupted operation of the vacuum pumping system.

Claim 7

A vacuum pumping system in accordance with claim 5 including heat exchanger means disposed in said liquid recirculation loop for regulating the temperature of the liquid recirculated to the second stage liquid ring pump.

Claim 8

A vacuum pumping system in accordance with claim 4 including vapor-gas by-pass conduit means with non-return flow valve connecting the first stage pump discharge to atmosphere whereby pressure is relieved at the interstage between first and second stage pumps during start-up of the system and periods of operation when capacity of second stage pump is temporarily exceeded.

Claim 9

A vacuum pumping system in accordance with claim 2 in which the auxiliary cooling means includes a liquid spray injected into the fluid stream downstream from the positive displacement pump and upstream from the liquid ring pump.

Claim 10

A multi-stage vacuum pumping system for pumping a saturated vapor-gas-liquid mixture including in combination a first stage positive displacement pump, a second stage liquid ring pump, means providing direct fluid communication from the outlet of the first stage positive displacement pump to the inlet of the second stage liquid ring pump, a second stage liquid recirculation loop interconnecting the outlet of said second stage liquid ring pump with the inlet thereof to provide sufficient liquid to said second stage liquid ring pump for uninterrupted operation of the vacuum pumping system, first stage constant torque driving means for controlling rotative speed of the first stage pump so as to limit pressure differential across the first stage pump, direct non-slipping driving means for said second stage pump, a first stage liquid recirculation loop connected to said second stage liquid recirculation loop and to the inlet to said first stage pump, each of said first and second stage liquid recirculation loops including valve means for controlling flow therethrough whereby the quantity of recirculated cooling liquid is regulated to maintain the optimum thermodynamic conditions in the vacuum pumping system.

Claim 11

A multi-stage vacuum pumping system for pumping a saturated vapor-gas-liquid mixture including in combination a first stage positive displacement pump, a second stage liquid ring pump, means providing direct fluid communication from the outlet of the first stage positive displacement pump to the inlet of the second stage liquid ring pump, a second stage liquid recirculation loop interconnecting the outlet of said second stage liquid ring pump with the inlet thereof to provide sufficient liquid to said second stage liquid ring pump for uninterrupted operation of the vacuum pumping system, first stage constant torque driving means for controlling rotative speed of the first stage pump so as to limit pressure differential across the first stage pump, direct non-slipping driving means for said second stage pump, a first stage liquid recirculation loop connected to said second stage liquid recirculation loop and to the inlet to said first stage pump, each of said first and second stage liquid recirculation loops including valve means for controlling flow therethrough whereby the quantity of recirculated cooling liquid is regulated to maintain the optimum thermodynamic conditions in the vacuum pumping system.

Claim 12

A vacuum pumping system in accordance with claim 9 including a vapor-gas by-pass means with non-return flow valve connecting first stage pump discharge to atmosphere whereby pressure is relieved at the interstage between said first and second stage pumps during start-up of the system and periods of operation when capacity of said second stage pump is temporarily exceeded.

Claim 13

A vacuum pumping system in accordance with claim 9 including a separator tank disposed in communication with the outlet of said liquid ring pump said separator tank separating gases from liquids discharged from said liquid ring pump.

Claim 14

A vacuum pumping system in accordance with claim 11 including an auxiliary by-pass conduit means connected to the outlet of the positive displacement pump and pressure responsive valve means in said conduit providing an auxiliary flow path by-passing liquid ring pump when the quantity of fluid pumped through the positive displacement pump exceeds the capacity of the liquid ring pump.