GB1433324A - Sludge discharge control apparatus - Google Patents

Abstract

1433324 Fluid-pressure servomotor systems HAM BAKER & CO Ltd 17 April 1973 [17 Jan 1972] 2051/72 Heading G3P [Also in Division B1] An apparatus for controlling the discharge of sludge from a settlement tank 10 comprises a chamber 15 having a valve 21 controlling the flow of sludge into the chamber through inlet 17 and control means for automatically closing valve 21 when sludge in the chamber reaches a predetermined level. Settlement tank 10 is continuously supplied with water containing suspended solids, e.g. sewage, the solids settling on the tank bottom 12 and the solid-free water flowing over the tank rim which acts as a weir. The sludge is discharged through tank outlet 13 via pipe 18 to chamber 15 at regular intervals determined by a timing mechanism. When the latter operates, solenoid valve 31 is actuated to cause hydraulic piston and cylinder actuator 26 to partially open chamber outlet valve 22, the degree of opening being determined by an adjustable limit switch 32 controlling solenoid valve 51. Simultaneously solenoid valve 30 operates to cause actuator 25 to open valve 21 and permit sludge to enter chamber 15 under the effect of the differential head between level L 1 of water in tank 10 and level of sludge in the chamber. The latter level reaches a certain value, at which it remains until all the sludge has been discharged from tank 10, some sludge flowing past outlet valve 22 to a disposal point. When solid-free water starts to enter chamber 15 the sludge density therein is reduced causing the level to rise until the sludge contacts an electrode 29. The latter thereupon causes solenoid valve 30 to operate actuator 25 to close valve 21 and shut-off the flow of water from tank 10. In a modification opening and closing of outlet valve 22 is controlled in response to sludge level as sensed by electrode 54. In the event of blockage of chamber outlet 19 solenoid valve 31 may be manually operated to fully open and close valve 22 to clear the obstruction. Valve 22 may be arranged to close if inlet valve 21 fails to close correctly. In other modifications valves 21, 22 may be operated mechanically rather than hydraulically or outlet valve 22 may be replaced by a fixed restriction. The hydraulic circuit for actuators 25, 26 includes an electric motor 35 driving pump 36, reservoir 38 and an accumulator 47.