Patent GB-1236718-A (GB)
Title: Improvements in or relating to centrifuges having means for indicating the sludge level in the sludge space of the rotor
Inventor: NILSSON VILGOT RAYMOND
IPC: B04B11/04
Filed: 1970-04-15
Abstract: 1,236,718. Centrifugal separators. ALFA LAVAL A.B. 15 April, 1970 [8 May, 1969], No. 18016/70. Heading B2P. In a centrifuge having an indicating channel 19, Fig. 1, rotatable with the rotor 1 and extending from the sludge space inwardly towards the centre of the rotor, clogging of the open end of the channel 19 by sludge 10 is sensed by means of a pressure difference gauge 29 one side of which is in pressure transmitting connection with the liquid in the indicating channel and the other side of which is in pressure transmitting connection with the liquid being separated in the centrifuge, one of said pressure transmitting connections including a pressure signal amplifier 27 for amplifying that signal. The indicating channel 19 may consist of one or more radially extending tubes or a disc interspace divided by radially extending ridges. The inner end of the channel 19 opens into a chamber 20 in which is disposed a stationary paring disc 21 connected to a pipeline 22 which in turn is connected to one side of the gauge 29 which is provided with an electric switch 31. Air is blown at 30 into the pipeline 22. Separated liquid flows from the inner edge of conical discs 9 into a chamber 16 in which is disposed a paring disc 17 connected to an outlet 18. On the outlet 18 is mounted a diaphragm housing 25, the diaphragm of which on one side is actuated by the liquid pressure in the outlet 18 and on the other side by the pressure of air blown at 28 into a pipeline 26. The latter connects the diaphragm housing 25 to the pressure signal amplifier 27 which has a pneumatic, hydraulic or electric connection 32 to the other side of the gauge 29. Adjusting screws 33, 34 are provided on the amplifier 27 and gauge 29 respectively. Instead of the connection for transmitting a pressure of the liquid being separated being connected, as shown, to the outlet for the separated liquid, it may be connected to the centrifuge inlet. In operation, air blown at 30 through the pipeline 22 flows through the disc 21 in the chamber 20 where it passes through the indicating liquid before it reaches the atmosphere. The level 24 of the indicating liquid indicates the counter-pressure which the air meets in its outflow and which actuates the pressure difference gauge 29 via the pipeline 22. The pressure of the separated liquid actuates the signal amplifier 27 in a pneumatic way through the air blown in the pipline 26 at 28. The pressure signal received by the amplifier 27 is transmitted via the pipeline 23 to the pressure difference gauge 29. When sludge clogs the opening of the channel 19 the indicating liquid level 24 moves radially outwards due to leakage through a hole 35 in the channel so that the air flowing out through the paring disc 21 meets a reduced counter-pressure so that the gauge 29 senses an increased difference between the pressure of the indicating liquid and that of the separated liquid. When this difference corresponds to the difference adjusted by the screw 34 the electric switch 31 initiates a sludge discharge. In a modification, Fig. 2 (not shown), the pipelines (18) and (22) are hermetically connected through seals to the centrifuge rotor and to the inner end of the indicating channel respectively, the paring discs 17, 21 being dispensed with. A diaphragm housing (25a) is interposed in the pipeline (22) upstream of the air injection point (30). In another modification, Fig. 3, the paring chamber 48 for separated liquid is connected to the inner edge of the discs 42 by a channel 47. The paring chamber 45 into which the indicating channel 45 opens is provided with two paring discs 50, 51. The lower paring disc 50 leads liquid pared by this disc back to the separating space of the rotor through a distributor 44 for the liquid to be separated. The function of the disc 50 is the same as that of the hole 35 in Fig. 1.