| 摘要 |
<p>775,751. Steam boilers. THOMPSON WATER TUBE BOILERS, Ltd., J. April 4, 1952 [Jan. 17, 1951], No. 1327/51. Class 123(2) In a forced-circulation boiler comprising for example, steam-generating tubes 1, a 'steam-and-water separator 7 and a superheater 9, the flow of water to the tubes 1 is controlled by a valve 4 on the output side of the feed pump 2 so as to maintain a substantially constant steam to water ratio at the outlet 6 thereof under all conditions of load. Preferably the valve 4 is acuated by a diaphragm or bellows 17 mounted in a pressure chamber 18 which is connected to the outlet 6 through a bleed passage 11, a resistance 12, e.g. a coiled choke tube, and an adjustable preset leak-off valve 14 with expansion chamber 22, the under side of the diaphragm being open to atmosphere and the valve proper 20 being biased by a spring 21 towards its open position. The off-take 10 of the separator 7 may lead to waste or be connected through a pilot-operated non- return valve to the water inlet side of the valve 4. The invention may be applied to a natural-circulation boiler in which case the usual downcomer is connected to the inlet side of the valve 4.</p> |
