GB625226A - Improvements in or relating to closed feed systems for steam power plants - Google Patents

Abstract

625,226. Feedwater supply systems for steam boilers. WEIR, Ltd., G. & J., and HILLIER, H. June 20, 1947, No. 16308. [Class 123(ii)] A closed feedwater supply system for a steam power plant including a boiler 9 and a turbine (not shown), comprises, in series, a steam condenser 1, a condensate extraction pump 3 discharging through a conduit fitted with valves 4, 15 to a de-aerator 18 with associated de-aerated feed tank 22, and a de-aerator extraction pump 27 in a conduit 28, 29 leading to a boiler feed pump 30 having a disdischarge pipe 31 with valve 32. The condenser 1 and de-aerator 18 are provided with air ejectors 11, 19 and the valves 4, 15 and 32 are controlled by floats 5, 16, 33 respectively. The system additionally includes an external feed tank 8 in communication respectively with the discharge of the pump 3 through a pipe 7 with valve 6, also controlled by the float 5, and the condenser well 2 by a pipe 26 with valve 24 controlled by a second float 23 in the tank 22. The arrangement is such that, when the boiler load is reduced to zero, the water required to maintain the level in the boiler will be drawn from the tank 22, with the result that the valve 24 will open to permit make-up water to flow from the tank 8 to the condenser and thence to the de-aerator 22 to restore the level in the latter. When, however, the load is increased, the surplus water accumulating in the condenser well 2 will effect the opening of the valve 6 and permit surplus water to discharge to the tank 8. A pipe connection 34 with control valve 35 may be provided between the tank 22 and condenser 1 for the circulation of water under light loads to ensure an adequate flow of water through the condensers 10, 16a of the ejectors 11, 19, also a connection 36 with manually-controlled valve 37 between the tank 8 and condenser 1. The valves 15, 24 may be actuated by a single float. In a modification (not shown) the system includes an evaporator which is supplied with sea or fresh water and the vapour from which is condensed and led to the condenser, de-aerator or external feed tank. Two or more of the above systems may be arranged to function in parallel, in which case the external feed tanks 8 are interconnected to maintain a common level; the discharge sides of the pumps 3 may also be interconnected to permit operation with one de-aerator only and, similarly, the pipes between the. pumps 27, 30 are preferably interconnected so that the pumps 27 may deliver to a single feed pump 30. Specification 295,855, [Class 123(ii)], is referred to.