GB722203A - Improvements relating to centrifugal pumps - Google Patents

Abstract

722,203. Centrifugal PUMPS. HOPKINSONS, Ltd., BROWN, R. L., and SEWELL, G. April 20, 1953 [April 29, 1952], No. 10725/62. Class 110 (1). A centrifugal pump comprises a leak-off valve at the delivery, actuated by an electromagnet which is energized by a thermostatic switch subjected to the temperature of the water at the delivery or at the delivery and suction. Fig. 2 shows an arrangement in which water from the balance chamber c of the centrifugal pump a, or from the delivery pipe i, is circulated over a thermostat d and returned to the suction pipe e, while water from the suction pipe e is circulated by way of pipes k and m over a thermostat j. If the temperature at delivery rises unduly in relation to that at suction, the differential action of the two thermostats actuates a contactor f to cut off the current through the solenoid g of an electromagnetically operated leak-off valve h, thereby permitting the delivery pressure to open the valve. The consequent increase in the flow through the pump prevents the generation of excessive temperatures. A non-return valve n is provided in the delivery pipe i. Thermostat j may be omitted, the control of the valve h then being in accordance with delivery temperature only. Fig. 6 shows the electrical circuit. When the pump is put into operation, the switch 11 of the thermostat d is on contact 25, and current from the A.C. supply 12, 13 flows in the path indicated by heavy lines, thereby energizing the solenoid 15 of the contactor f and causing the contactor switches 16, 17 to close. Switch 16 energizes the solenoid g through metal rectifiers 14 to cause closure of the valve h, while switch 17 closes a circuit which maintainsthe current through the solenoid g in the event of the switch 11 moving off the contact 25. Switches 18 and 20, carried by the respective solenoid plungers, open to insert resistances 19 and 21 into the respective solenoid circuits to reduce the solenoid currents to the holding values. If the pump delivery temperature rises sufficiently, switch 11 closes on contact 26, thereby shorting out the solenoid 15 and causing the contactor f to return to the inoperative position. Valve h is then free to open.