GB1029789A - Once through vapor generator - Google Patents

Abstract

1,029,789. Steam -generators. BABCOCK & WILCOX CO. Dec. 6, 1963, No. 48321/63. Heading F4A. A once-through steam generating unit comprises a feed pump 24 supplying water from a deaerator 20 through a feed water control valve 50 and a feed water flow meter 41 to a boiler having a number of parallel tubes 4 between inlet and outlet headers 26, 28 and heated by a heat source 8 which may be fossil fuel fired burners or heating fluid from a nuclear reactor system. Heated fluid passes via lines 32, 34 into the upper and lower portions of a steam drum 6 containing in its lower portion water 36 maintained by the flow through pipe 32 at saturation temperature. Steam contained in the upper portion 38 of the drum passes through a steam flow meter 40 to a turbine 10 and a condenser 14. Condensate is returned to pump 18 via the deaerator which also receives low-pressure steam through line 22 from a turbine interstage. An emergency line 42 from the lower portion of drum 6 leads through a valve controlled branch 42A to the deaerator and acts as a blow-down line. A second branch 42B having a non-return valve 44 permits flow only in the direction from the drum to the tube inlet header 26 when the pressure at the header falls below that in the drum, e.g. when pump 24 stops. The control 46 receiving signals from the steam and water flow meters operates valve 50 to maintain the two flows substantially equal and is biased by a signal from a water level indicating device 48 located on the drum 6 to maintain the water level in the drum at a predetermined level.