Improvements in or relating to high and low water level safety control apparatus for steam generators

摘要

661,134. Fluid-pressure servomotor control systems; valves. MICHAEL, N. F., WILSON, S., and STEPHEN & SONS, Ltd. A. Aug. 13,1949. 21133/49. Class 135. A combined high and low water level safety control for the steam drum of a steam generator comprises a single float actuating a pair of valves so that it opens one valve when it moves beyond a predetermined position in one direction, and opens the other valve when it moves beyond a predetermined position in the other direction, one of said valves controlling the supply of feed water to the steam drum, and the other controlling the fuel supply to the furnace of the generator. In an embodiment, the float 14, Fig. 2, operates in a chamber provided with water and steam inlets 20, 21, respectively, and the float lever which is pivoted in a block 16 carries counterweights 13 and a cam 15. When the water level rises unduly, the cam 15 acts on and rotates a lever 11, and the other end of the lever, which is connected to a needle valve 18, opens the latter to allow steam from the upper portion of the float chamber to act on a piston-actuated feed water inlet valve B, Fig. 1, to shut off the supply of feed water. When the water level falls unduly, the float causes a second needle valve 18a to open to allow water to flow to a device which closes down a valve F through which fuel-oil is supplied to the furnaces C of the steam generator. The feed-water pump valve 33 and the fuel valve F can be shut down under steam pressure supplied through a line 30 by means of the manually-actuated control valve D. The valve B comprises a lift valve 89, Fig. 4, or an apertured gate valve and it is actuated by a differential or single-landed piston 85. The return movement takes place after the flow of steam through pipe 27 is cut off, and it may be due to a spring 90 or to steam acting on the lower and smaller piston. Steam in the upper part of the cylinder leaks away through a vent 96, this also giving an indication that the valve has operated. The valve may be shut by rotating a handwheel 97 which rotates a sleeve 98 having a screw-threaded connection with the valve spindle. Remote control is provided by a shaft 104 carrying a pinion 103 engaging with a further pinion 102 on the sleeve 98. The valve spindle carries an indicating pointer 101.