Patent GB-1359157-A (GB)
Title: Centrifugal separators
IPC: B04B1/18
Filed: 1971-12-06
Abstract: 1359157 Centrifugal separator A L F A LAVAL AB 6 Dec 1971 [7 Dec 1970] 56604/71 Heading B2P A centrifugal separator comprises a rotor 1, 2, Fig. 1, provided with an inlet 5 for a mixture to be separated, an outlet 16 for a separated light liquid constituent, e.g. of oil, the mixture, an outlet 11 at the periphery of the rotor arranged to open intermittently in use for the discharge of separated sediment, and a further outlet for a separated heavy liquid constituent, e.g. water, of the mixture arranged in a radial sense between the outlets 11 and 16, a passage 20, 22, 23 arranged to conduct liquid from said further outlet to a reception place (not shown) for heavy liquid constituent, means 32, e.g. a valve, Fig. 2, arranged to allow or prevent liquid flow to the reception place through said passage, and sensing means 30 for determining when the heavy liquid is at a predetermined level within the rotor, the sensing means being then operable to actuate the means 32 to allow flow through the passage to the reception place. The inlet 5 is constituted by a central duct through the drive shaft 4 of the rotor. The mixture is direced by a distributor 7 provided with vanes 6 into the rotor separating chamber 8 in which conical plates 9 are mounted. A valve disc 12 forming the bottom of the chamber 8 is operable to open or close sediment outlets 11 by liquid supplied to a space 14 underneath the disc 12 through a supply chamber 13, throttled openings 15 being provided for the escape of the operating liquid. The light liquid leaving the chamber through the outlet 16 flows into a chamber 17 from which it is pumped out through a conduit 19 by a paring disc 19. A duct 20 extends inwardly towards a chamber 21 from which liquid is pumped out through a conduit 23 by a paring disc 22. A conduit 27, Fig. 2, connects the conduit 23 to a supply conduit 25 which in turn is connected to the feed duct 5. The conduit 27 incorporates a throttle 28 and a check valve 29, the latter being arranged to open when a predetermined pressure is reached in the conduit. The sensing means 30 is arranged to sense the dielectric constant of the liquid flowing through conduit 23 and, in response to the sensed valve, to actuate the valve 32 through a connection 31. The sensing means 33 is further arranged to actuate through a connection 33 a control equipment 34 which at predetermined time intervals initiates an operation for opening the sediment outlets 11. A conduit 35 connected to the supply conduit 25 and to a pump 36 is provided to add an extra amount of heavy liquid to the rotor. In operation, an interface between the light and heavy liquids is first formed in a zone of the chamber 8 lying between the opening of the duct 20 and the rotor periphery. The separated light liquid will then leave the chamber 8 through the outlet 16 and also through the duct 20 and the conduit 23. Valve 32 in conduit 23 is closed a the start of the operation and the light liquid flowing through the conduit 23 is pumped back via the conduit 27 to the supply conduit 25. As more and more sediment and heavy liquid are collected in the rotor chamber, the interface between the light and heavy liquids moves radially inwards until it reaches a position 42 at the opening of the duct 20. Heavy liquid then begins to flow through the duct 20 and through the conduit 23 where it is sensed by the sensing means 30 which then opens valve 32 causing the liquid pressure in conduit 27 to fall whereby valve 29 is closed and the heavy liquid flows along conduit 23 to a receptacle or outlet. At the same time the sensing means 30 sends a signal to the control equipment 34 to open the outlets 11 for the discharge of accumulated sediment. To avoid too long periods of time between successive openings of the outlets 11 in case the sediment is packed too hard additional heavy liquid is supplied continuously or intermittently via pump 36 and conduit 35 to alter the position of the interface. The interface is prevented from moving back radially outward during separation by an overflow outlet 24 for the heavy liquid. This would also be achieved without the overflow outlet 24 if the valve 32 in the conduit 23 is a constant pressure valve. The sensing means 30 may alternatively be one for sensing the liquid pressure in the duct 20 and conduit 23 which pressure is used as an indication of the position in the chamber 8 of the interface between the heavy and light liquids. In this arrangement, the conduit 27 may be omitted. Again, a sensing means 30 may be used to directly sense the position of the interface and in this case can be fixed to and rotate with the rotor. In a further arrangement, the sensing means may comprise both means for sensing the dielectric constant of the liquid flowing through the conduit 23 and the pressure change in the duct 20 and conduit 23.