Multistage vacuum pumping system

Claim 2

A multistage evacuating pumping system, comprising in combination a first stage pump and a second stage pump each having an inlet and outlet, said first stage pump comprising a positive displacement pump and said second stage pump comprising a liquid ring pump, means providing direct fluid communication from the outlet of the first stage pump to the inlet of the second stage pump, recirculation conduit means connecting the outlet of the first stage pump to the inlet of the first stage pump and valve means operatively associated with said recirculation conduit and responsive to the pressure difference between said first stage pump outlet and said first stage pump inlet for maintaining the pressure across said first stage pump below a predetermined value.

Claim 3

The vacuum pumping system of claim 1, including auxiliary cooling means for further reducing the temperature of the vapor-gas-liquid mixture being pumped through the system.

Claim 4

The vacuum pumping system of 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 mixture upstream from the inlet to the second stage liquid ring pump.

Claim 5

The vacuum pumping system of claim 1, including a separator tank for receiving the discharged condensed vapor-gas-liquid mixture from the outlet of the second stage liquid ring pump, and a gas vent disposed in the upper portion of said separator tank for discharging gases from the system.

Claim 6

The apparatus of claim 1, including a second stage 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

The apparatus of 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

The apparatus of claim 1, 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 9

The apparatus of claim 1, including a separator tank disposed in communication with the outlet of the liquid ring pump said tank providing means for separating gases from liquids discharged from the liquid ring pump.

Claim 10

The apparatus of claim 1, including an auxiliary bypass conduit mean connected to the outlet of the positive displacement pump and pressure-responsive valve means in said conduit to provide an auxiliary flow path bypassing said liquid ring pump at times when the quantity of fluid pumped through the positive displacement pump exceeds the capacity of the liquid ring pump.

Claim 11

The apparatus set forth in claim 1 and including a first stage liquid recirculation loop connected to the second stage liquid recirculation loop and to the inlet of the first stage pump, said first and second stage liquid recirculation loops including valve means for controlling flow therethrough, whereby the quantity of recirculated cooling liquid mixture is regulated to maintain optimum thermodynamic conditIons in a vacuum pumping system.

Claim 12

A multistage evacuating pumping system for pumping a saturated vapor-gas-liquid mixture comprising a combination, a first stage, positive displacement pump having an inlet and outlet, a second stage liquid ring pump having an inlet and outlet, and 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 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, the first stage recirculation conduit for the first stage for recirculating the saturated vapor-gas mixture from the outlet of the first stage pump to the inlet of the first stage positive displacement pump, and a first stage liquid recirculation loop connected to the second stage liquid recirculation loop and to the inlet to the first stage pump, said first and second stage liquid recirculation loops including valve means for controlling flow therethrough, whereby the quantity of recirculated cooling liquid mixture is regulated to maintain the optimum thermodynamic conditions in the vacuum pumping system.

Claim 13

A multistage evacuating pumping system for pumping a saturated vapor-gas-liquid mixture comprising a combination, a first stage, positive displacement pump having an inlet and outlet, a second stage liquid ring pump having an inlet and outlet, and 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 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, the first stage recirculation conduit for the first stage for recirculating the saturated vapor-gas mixture from the outlet of the first stage pump to the inlet of the first stage positive displacement pump, and a first stage liquid recirculation loop connected to the second stage liquid recirculation loop and to the inlet to the first stage pump, said first and second stage liquid recirculation loops including valve means for controlling flow therethrough, whereby the quantity of recirculated cooling liquid mixture is regulated to maintain the optimum thermodynamic conditions in the vacuum pumping system.

Claim 14

The apparatus of claim 11, including a bypass discharge conduit means interconnecting the first stage recirculating conduit to a discharge outlet bypassing the second stage liquid ring pump to provide an auxiliary discharge outlet for said first stage positive displacement during startup of the system and periods of operation when the capacity of the second stage liquid ring pump is temporarily exceeded.

Claim 15

The apparatus of claim 12, including valve means in the bypass discharge conduit for regulating the discharge therethrough.