GB591942A - Improvements in automatic control systems for generators of superheated steam - Google Patents

Abstract

591,942. Automatic control systems for steam generators. KENT, Ltd.; G., and GROUT, J. A. M. Sept. 29, 1943, No. 16005. [Class 38 (iv)] Temperature: fluid pressure.-To maintain constant the temperature of .superheated steam and .reduce the delay in readjustment upon changes in load or firing conditions, a control is applied in respect of the ratio of the flow rates of furnace gas and superheated steam and is modified in response to actual temperature conditions. Fig. 1 shows a system in which the rates of flow of combustion products through an economiser 6 and of superheated steam through the steam main 4 are compared by resistances 8, 11, respectively, subject to these quantities, and forming part of a Wheatstone bridge operating an automatic controller of known type, which adjusts the length of a flexible cord operating a contact 13 which cooperates with contacts 14, 15 to control a motor 17 actuating means 18 regulating the final temperature of the steam. As shown, the device 18 exchanges heat between steam passing to the secondary superheater 3 and steam from the steam and water space of the boiler; the control valve thereof is coupled by a selsyn connection 21, 22 to the cord 16 for resetting purposes. The contacts 14, 15 are moved by a known type of automatic controller responsive through a thermocouple 20 to the temperature of the output steam. In a modification (Fig. 2, not shown) in which a. spray de-superheater is the temperature correcting means and in which the water supply thereto is controlled by the system, a further automatic controller of known type, responsive to the flow-rate of the spray water operates on the flexible cord 'for resetting purposes. The invention may be carried out by a control system operated by fluid pressure.