GB864136A - Improvements in or relating to steam generators - Google Patents

Abstract

864,136. Forced-flow steam boilers. INTERNATIONAL COMBUSTION (HOLDINGS) Ltd. July 31, 1959 [Aug. 21. 1958], No. 26971/58. Class 123(2) In a forced circulation boiler which may be associated with a nuclear reactor and wherein an evaporator 2 is supplied with water from a steam and water drum 1 by pumps 4 having respective isolating valves 5, 6 and delivering through respective non- return valves 6a, a pipe 8, 9 having an automatically operating valve 7 is provided to by-pass the pumps in the event of their failure, thereby to establish a natural circulation through the evaporator to avoid a complete shutdown whilst the pump defects are being corrected. The by-pass valve 7 may be held closed by the pressure head across the pumps whilst they are operating whereby pump failure would permit the valve to open. Alternatively, the valve may be solenoid operated, the solenoid being interlinked with the circuit of an electric motor driving the pumps. In the latter case the valves 6a may also be solenoid operated and interlinked in the same circuit whereby they are normally held open whilst the valve 7 is held closed but, on pump failure, are closed and the valve 7 is opened. In a modification, Fig. 4, a downcomer 11 from the steam and water drum is connected-to the upper chamber 16 of a header 12, the upper chamber being separated from a lower chamber 21 by a partition B in which is mounted a nap valve 14. A pump 17 draws water from the upper chamber and delivers it into the lower chamber whence it passes to the boiler heating surfaces through pipes 24. Normally the flap valve 14 is held closed by the pressure differential between the chambers. If the pump 17 fails, however, the flap 14 falls and the water from the downcomer passes directly through the header 12 to the boiler.