GB1235968A - Centrifuge construction - Google Patents

Abstract

1,235,968. Centrifugal separators. PENNWALT CORP. 4 July, 1969 [8 July, 1968], No. 33877/69. Heading B2P. A heavy phase material, separated from a light phase material and accumulated on the peripheral wall 30 of a centrifuge bowl 22, is removed from the bowl by a skimmer 50 in response to the sensing action of a detector. The latter includes at least one overflow conduit 60 extending inwardly from an opening in the bowl wall to the maximum desired level A of the heavy phase material. The conduit 60 conducts a sample of material at the level A to a sensing device 72 which senses an increase in specific gravity above that of the light material, as would be occasioned by its contamination with heavy phase material, and responds by actuating the skimmer 50 for removing the heavy phase material from the bowl. The centrifuge may be used to separate liquids of different specific gravities, or solids or sludge from a mixture thereof with a light phase liquid. The bowl 22 which may contain axially extending radial vanes, is belt-driven by an electric motor 26 and is mounted in a housing 18 resiliently suspended by springs 16 from standards 14. The annular space between the housing and the bowl is divided into upper and lower portions 41, 43 by a sealing partition 44. When separating sludge from a liquid, the clarified liquid is discharged via the overflow lip 32 at the upper end of the bowl into the portion 41 and thence via a conduit 45 to a tank 46. The portion 43 communicates with a tank 64 via a conduit 66 in which the gravimetric sensing device 72 is inserted. The latter includes a chamber 74 in which a float 85 transmits small changes in specific gravity by mechanical means to a control box 86. The latter responds to a predetermined displacement of the float by transmitting an electric signal through a line 87 to a solenoid-operated valve 39 in the feed inlet tube 38 and to a traversing mechanism 56, e.g. of the pneumatic piston-cylinder assembly type, for the skimmer 50. Nozzles 62 may be screwed on to the end of the conduits 60, the length of each nozzle being chosen to correspond to the desired level A of the sludge. In operation, when sludge reaches the level A, it is discharged with some of the liquid into the space 43 and thence via the conduit 66 and sensing device 72 to the tank 64 where the liquid overflows through a pipe 70 and the sludge settles in the bottom of the tank which is provided with a normally closed valve 68. The control box 86 responds to the increase in specific gravity by closing the valve 39 to interrupt the feed and by actuating the mechanism 56 to effect outward traversing movement of the skimmer to empty the bowl 22 of both clarified liquid and accumulated sludge. The liquid and sludge removed by the skimmer are segregated by means of a solenoid-operated two-way valve 94 which is operated by a limit switch 92 actuated by a lug 90 on the skimmer 50. The clarified liquid may be conducted to the tank 46. A limit 95 which is actuated by the traversing mechanism 56 as it returns with the skimmer to the innermost position resets the valve 39 and the control box 86 for the next cycle.. The valve 68 may be solenoid-actuated by the control box 86 to the open position and de-energized to the closed position by the limit switch 95. The liquid discharged through the overflow pipe 70 may be directed to the tank 46, to a feed supply tank or to a sludge receiving tank. Alternatively, the tank 64 may be eliminated and the sample material discharged directly from the end of conduit 66. Instead of using the sensing device 72, a float-type gravimetric switch may be disposed in the tank 64.