SE336561B - - Google Patents

Abstract

1,253,799. Discharging sludge from centrifuges. ALFA LAVAL A.B. 22 Oct., 1970 [23 Oct., 1969], No. 50315/70. Heading B2P. A sludge centrifuge comprises a rotor 1 (11) having peripheral sludge outlets 3 arranged to be opened or closed during operation of the centrifuge by means of a piston 4, a control unit 17 arranged to actuate the sludge outlets 3 when the rotor is to be emptied of its contents such that at least part of the sludge settled in the rotor is discharged while liquid is maintained therein, and sensing means 15 arranged to sense the balance of the rotor and control the further discharging of the rotor contents. Liquid to be separated is led into the centrifuge through a conduit 12 and a hollow drive shaft 5. Purified liquid leaves via an overflow outlet 9 and a conduit 13. Sludge discharged through the outlets 3 leaves through a conduit 14. The means 15 senses vibrations arising from unbalance of the rotor and is connected to the control unit 17. The latter controls the operation of a valve 19 in the conduit 12 and of a valve 21 in a conduit 22 which supplies operating liquid at 4a for controlling the piston 4. By stopping the flow of operating liquid to the centrifuge for a given length of time, the control unit 17 may provide for either partial or total emptying of the rotor according to a predetermined programme. When the rotor is to be emptied totally, the supply of liquid to be separated through the conduit 12 is stopped by means of the valve 19. Then for a very short period the supply of operating liquid through the conduit 22 is stopped by means of the valve 21. Simultaneously the connection between the vibration sensing means 15 and the control unit 17 is broken. The piston 4 moves downwards to open the outlets 3 for discharge of sludge and a quantity of liquid. Supply of operating liquid is resumed and immediately after closure of the sludge outlets 3 the connection between the sensing means 15 and the control unit 17 is re-established. If now a portion of the sludge has adhered to the rotor wall and thus has not been discharged through the outlets 3, it will cause unbalance of the rotor which is sensed as heavy vibrations by the means 15 which sends a signal to the control unit 17 which in turn stops the planned total emptying operation; This may lead to an alarm signal leaving the control unit 17 or to the performance of suitable corrective operations. For instance, the speed of the rotor may be reduced to that at which continued total emptying of the rotor is possible without any risk of machine damage, after which the rotor is stopped in order to be freed manually of the adhering sludge portion. Alternatively, the rotor may be stopped without having been emptied. The rotor may also be emptied of sludge and liquid step by step.