Multi-stage vacuum pump
A multi-stage vacuum pumping system utilizing a first stage positive displacement pump and a second stage liquid ring pump, and wherein a pressure differential below a predetermined value is maintained across the first stage pump due to the provision of a slip producing constant torque coupling means. 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. 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.
Shanghai Kaida Pump Mfg. Co., Ltd.