Patent GB-637502-A (GB)
Title: Automatic feed regulator for boilers
IPC: F22D5/06
Filed: 1945-04-10
Abstract: 637,502. Fluid-pressure servomotor-control systems. EHLINGER, M. April 10, 1945, No. 8889. Convention date, Feb. 8. [Class 135] A boiler feed-water regulator having an expansion coil the outflow from which of a mixture of water and steam tapped from the boiler varies with the water level in the boiler is provided with an intake device which delivers the mixture to the coil and a deformable chamber having a movable wall operatively connected to the feed-water supply cock to regulate the water supply to the boiler. As shown in Fig. 1, the intake device comprises an inlet pipe 5, open to boiler steam below the lowest permissible water level and immersed in a vessel 6 open at its upper end above the highest permissible water level, and so dimensioned that water may fall freely into its bottom through an orifice 8 before being carried away by the steam to an expansion coil 9. To shield the device from turbulence within the boiler 2, a tube 12 is fitted and to prevent the entry of foreign matter a filter 11. The mixture, after passing through the coil 9 and an expansion tank 37, issues as a jet from a pipe 14 into a deformable chamber 20 and acts on an obturator 16 controlling an opening from the chamber and ports 18 leading to an exhaust tank. The chamber 20 is loaded by a spring 21 and connected by a lever 22 to the water supply cock 23, whilst the obturator 16 is urged towards its fully open position by a spring 28. The loading on the spring 28 may be adjusted by a spring-loaded diaphragm 25 subjected to the difference in pressure between the inlet and the throat of a Venturi 27 passing steam from the boiler and by a diaphragm 32, Fig. 2, subjected on its upper side to the upstream pressure and on its lower side to the downstream pressure of the water passing through the cock 23. A pressure gauge graduated in water levels may be fitted to a chamber subjected to the pressure within the chamber 20. In operation, on the level of the water in the boiler rising an increased quantity of water flows through the orifice 8 and as a result the specific volume of 'the mixture issuing from the coil 9 increases with consequential increase in the speed of the jet. The obturator 16 is hence urged downwards to reduce the opening of the ports 18 and increase the pressure in the chamber 20 to lift the lever 22 and so reduce the supply of feed water to the boiler through the cock 23. On an increase in steam consumption there will be an increased steam flow through the Venturi 27 and an increase in the partial vacuum on the throat side of the diaphragm 25 which is moved downwards to increase the loading on the spring 28, raise the obturator 16 and increase the opening of the supply cock 23. The diaphragm 32 compensates for fluctuations in pump supply pressure and in boiler pressure and should, e.g. the steam demand from the boiler be reduced the pump will supply water at a greater rate than necessary with a consequent increase in pressure difference acting on the two sides of the diaphragm 32. The diaphragm 32 will hence move downwards to lower the obturator 16, increase the pressure in the chamber 20 and reduce the opening of the cock 23. In a modification, the jet acting on the obturator enters a non-deformable chamber and the pressure therein is transmitted to a chamber housing a spring-loaded diaphragm operatively connected to the cock 23. The expansion tank 37, the Venturi 27 and its associated diaphragm 25, and the diaphragm 32, if desired, may be dispensed with. In another modification, the Venturi 27 may be replaced by a superheater whose upstream and downstream sides are connected to opposite sides of the diaphragm 25. When the boiler comprises two upper drums an intake device is installed in each drum and the cock 23 is then controlled by the average level of the water in the two drums. In marine practice to compensate for roll and pitch two intake devices may be installed in each drum.