Patent GB-993926-A (GB)
Title: Pressurized centrifuge
IPC: B04B9/12
Filed: 1963-06-17
Abstract: 993,926. Seels. BIRD MACHINE CO. June 17, 1963 [June 28, 1962], No. 24068/63. Heading F2B. [Also in Division B2] In a centrifugal separator comprising a pressurized casing 12 out of which extends a rotary shaft 30 driving a separator bowl 14 located in the casing, means to introduce into the bowl a slurry to be separated and gas to maintain super-atmospheric pressure within the bowl and casing, and a sealing chamber 46 surrounding the shaft 30 where it extends out of the casing and filled with sealing fluid at a pressure higher than that within the casing, a lowpressure-differential seal 84 is provided between the shaft 30 and the casing 12 against leakage from the chamber 46 into the casing, a highpressure-differential seal 96 is provided between a wall 94 of the chamber 46 and the shaft 30 against leakage from the chamber to the atmosphere, and a pressure regulator 62, having its outlet connected to the chamber 46 and leaving its inlet connected to a conduit 65 fed from a supply 58 with sealing fluid, e.g. a gas or liquid, at a pressure in excess of that within the casing, is caused by means of a pressure relay device 54 activated by the pressure within the casing to decrease the sealing fluid pressure from its supply value to a value providing a constant positive pressure differential above the pressure within the casing so as to subject the seal 84 to a constant load. The shaft 30 is mounted in ball-bearings 38, 39 and is driven by belting at 42. The end thrust caused by the high-pressure process gas introduced in the bowl 14 and casing 12 is counter-balanced by fluid supplied from a source 80 into chamber 67 and maintained by means of a pressure regulator 64 also controlled by the device 54 at a pressure equal to that in the casing. Mounted on ball-bearings 40 and a bush 15 within the shaft 30 and driven therefrom at a slower speed through a planetary gear unit 24 is the shaft 32 of a hollow-hubscrew-conveyer 16. The slurry is introduced into the bowl 14 through a stationary pipe 18, the hollow hub of the screw conveyer and holes 20. The separated liquid flows at one end over a weir 22 and the solids are moved by the conveyer blades 17 to the other end and are discharged by centrifugal force through an outlet 28. The seal 84 constituted by sequential carbon rings comprises a sealing ring 104, a back-up ring 108 and a cover ring 110 urged radially inwardly by garter springs 112, 114 and axially by a coil spring 92. The ring 104 is provided with sealing dam portions 86<SP>1</SP>, 88<SP>1</SP>, positioning pads 116 allowing slight leakage of sealing fluid radially, between the rings 104, 110 and the casing wall 90, into the casing interior, and grooves 106 which, together with similar grooves on the inner periphery of ring 108, allow slight axial leakage of the sealing fluid between the rings 104, 108 and a sleeve 33 secured to the shaft 30. The seal 96 is a stationary carbon ring 96 grooved at 120, 122 and urged into rubbing sealing contact with the wall 94 which rotates with the shaft 30. A second sealing chamber 48 provided between the shafts 30 and 32 is connected to the chamber 46 through passages 50 and is sealed by seals 124, 126.