GB577691A - Improvements relating to the control of boiler feed pumps - Google Patents

Abstract

577,691. Feed-water supply systems for boilers. WEIR, Ltd., G. & J., HILLIER, H., and McALPINE, T. May 19, 1944, No. 9649. [Class 123 (ii)] [Also in Group XXIX] Main and emergency feed-water pumps 6, 2 respectively are associated with a boiler 5, the emergency pump or pumps being brought into operation automatically when the water level in the boiler falls below a predetermined level due to oreakdown of the main pump or pumps or failure of the latter to maintain the required output or pressure. As shown the main pump 6 supplies the boiler through a pipe 7 and float-operated regulating valve 8 and the emergency pump 2 through a pipe 24 which is connected either to the valve 8 or to an independent regulating valve, the pump 2 being driven by a steam turbine 1 to which steam is supplied through pipes 4, 17 and valve 3 when the latter is opened by the action of a pilot valve 11 which is itself actuated by means, such as a float 13, responsive to a fall in the boiler water level to the predetermined minimum. Associated with the valve 3 is an hydraulic piston 10 the underside of which is in communication both with the main pump outlet 7 through a restriction orifice 16 and with one side of the valve 11 through a line 12, the opposite sides of the piston 10 and valve 11 communicating respectively with the outlet 20 of the pump 2, on the pump side of a non- return valve 23, through a line 22 and with the suction pipe 15 of said pump through a line 14. The arrangement is such that, if for any reason, e.g., a failure of the main pump 6, the boiler water level falls beyond the lower range of the float 9 of the valve 8, the float 13 will effect opening of the valve 11 to release the pressure on the underside of the piston 10 and so permit the valve 3 to open, the emergency pump 2 thus being brought into operation and continuing to function until a normally-open steam supply valve 26 in the pipe 17 is closed by hand. A throttle valve 18 is associated with the valve 26, said throttle valve being actuated by a pressure governor 19 which is controlled by the pressure in the discharge pipe of the pump 2 applied through a line 21. A modified arrangement includes a second pilot valve which is normally closed by the pressure in the main pump outlet 7 but is adapted to open to release the pressure on the underside of the piston 10, and thus permit opening of the valve 3, when the pressure in the outlet 7 falls.