Patent GB-928055-A (GB)
IPC: F22D11/00
Abstract: 928,055. Feedwater supply systems. W. W. PALM. Sept. 13, 1960 [Sept. 18, 1959; May 19, 1960], No. 31526/60. Class 123 (2). A high temperature continuous feedwater system for a boiler and which eliminates the use of conventional pumps while at the same time de-aerating the feedwater comprises a pumping tank 12 which feeds water, by gravity, to a reservoir tank 6 from which water can flow, by gravity, to the boiler 2 through a conduit 8 and check valve 10. When the water level in the boiler 2 drops below the end 42 of a conduit 4 steam flows through the latter to equalize the pressure in the tank 6 so that water flows past the check valve 10 to the boiler 2 until the water level again reaches the conduit end 42. Steam is also introduced into the pumping tank 12 through a conduit 18 and a solenoid valve 20 so that water flows from the pumping tank 12, a conduit 14 and a check valve 16 to the reservoir tank 6. A solenoid valve 32 in a pipe 30 controls the supply of cold water to the tank 12 to periodically condense the steam therein, the vacuum thus produced drawing up water from a condensate tank 22 through a conduit 34 and a check valve 36, air and non- condensible gases being vented from the tank 12 to the tank 22 by a conduit 38 incorporating a solenoid valve 40. The condensate tank 22 has a water level responsive valve 24, a condensate return conduit 28, and an air vent 26. In the control circuit, Fig. 2, while either of holding probes 44, 48 are immersed an electromagnet 52 remains energized and its switches 54, 56, 58 close feed water and venting valves 32, 40 and open the steam valve 20. When neither of the holding probes are immersed the steam valve 20 is closed and the feedwater and venting valves 32, 40 are opened until the pumping action of the tank 12 raises the level of water therein to the probe 46 so that the electromagnet 52 is again energized. Since it is only desirable to continue the flow of cooling water in the conduit 30 for a short time sufficient to condensate the steam in the pumping tank 12 a bellows 65, responsive to the pressure in the tank 12, opens a switch 69 to close the valve 32 when the pressure within the tank drops sufficiently to pump water. In a modification, Fig. 3, not shown, some of the water flowing from the tank 12 to the tank 6 can be directed by a valve to a cascade heat exchanger which is located in the tank 6 and is supplied from the steam pipe 4. Water from the tank 6 is also fed through a primary heating circuit before being returned to the tank 22 through a back pressure control valve. Cooling water for condensing the steam in the tank 12 is supplied by a pressurizing unit under the influence of the steam pressure within the tank 6. A connection is also available with water under pressure to fill the tank 12 prior to starting the system from cold; alternatively water may be pumped from the tank 22 to the tank 12. Make-up water is supplied to the condensate tank by a pump controlled by probes the tank also being provided with a condensate trap. In a further modification, Fig. 4, not shown, in which the condensate<SP>2</SP>tank 22 is located above the level of the pumping tank steam from the boiler is supplied to the tank 6 through a valve which is controlled by a temperature bulb in the water in the tank 6 and which distributes steam either through a pipe discharging onto a baffle in the tank 6 or through a perforated pipe located in the water in the tank. A motorized steam valve controlled by probes in the tank 12 and an additional valve responsive to the pressure in the reservoir tank 6 regulate the supply of steam to the pumping tank 12. When the water in the tank 12 falls below a lower limit valve controlled conduits equalize the pressures in the two tanks so that water flows by gravity from the tank 22 to the tank 12. Instead of water, e.g. mercury or ammonia, may be employed as the working medium.