Disc package for a centrifugal separator

#The invention relates to a disc package for a centrifugal separator comprising a plurality of separation discs, each provided with a separation surface with is inclined with respect to the radial direction and wherein the separation discs are arranged coaxially around an axis of rotation at a distance from each other such that to form passages between each two adjacent separation discs. The invention also relates to a centrifugal separator comprising such a disc package.

#From the early days of development of centrifugal separators it is known to provide each separation disc in a disc package with a brim extending radially outside the frustoconical portion of the disc, in order to improve the mechanical stability of the discs, see e.g. SE 22981.

#A disc stack having a single separation disc provided with a brim extending radially outside the rest of the separation discs of a disc stack is also previously known, see SE 227107. This is used to divide the disc stack into a first section where the cleaning of the light phase is optimised (purifier mode of operation) and a second section where the cleaning of the heavy phase is optimised (concentrator mode of operation).

#FIG. 1 shows an embodiment of a separation disc of the kind comprised by the first set in the disc package.

#FIG. 2 shows an embodiment of a separation disc of the kind comprised by the second set in the disc package.

#FIG. 3 shows a cross-section of a portion of a centrifugal separator having a disc package comprising a first and a second set of separation discs.

#In FIG. 1 a separation disc 1 of the kind comprised by the first set in the disc package is shown, having a frustoconical separation portion 2 with an inner and an outer separation surface. The separation portion is provided with a plurality of distance members in the form of elongated caulks 3 providing distances to form passages between each two adjacent separation discs in a package formed by a stack of separation discs. The caulks are fastened to the outer surface of the frustoconical separation portion of the disc and distributed around the circumference of the disc. The outer diameter A of the separation disc is 165 mm, and the inclined separation surface extend all the way out to this outer diameter. Thus the radially outer portion 4 of the separation disc is part of the inclined separation surface. The disc is provided with a plurality of cut-outs in the form of notches 5 at this radially outer portion 4 of the separation disc having a diameter A, which notches are open towards the outer radius of the separation disc. The number of notches 5 correspond to the number of caulks and the notches are distributed around the circumference of the disc in-between the caulks.

#In FIG. 2 a separation disc 6 of the kind comprised by the second set in the disc package is shown, having a frustoconical separation portion 2′ with an inner and an outer separation surface. The separation portion is provided with a plurality of distance members in the form of elongated caulks 3′ providing distances to form passages between each two adjacent separation discs in a package formed by a stack of separation discs. The caulks are fastened to the outer surface of the frustoconical separation portion of the disc and distributed around the circumference of the disc. The separation surface extends to the diameter A and radially outside the separation surface the disc is provided with a flat brim 7 (i.e. having an angle of zero degrees to the radial direction) extending to the outer diameter of the separation disc B. The diameter B is 185 mm and thus the radial extension of the brim is L=(B−A)/2, i.e. 10 mm. The diameter B is thus 12% larger than the diameter A. Each disc 6 has a generally circular outer edge at B as seen in, FIG. 2. The disc is provided with a plurality of cut-outs in the form of apertures 8 at the radially outer part of the separation portion, which cut-outs are closed towards the outer radius of the separation disc by means of the brim. The number of apertures 8 correspond to the number of caulks and the apertures are distributed around the circumference of the disc at positions corresponding to the notches of the separation disc 1 in the first set.

#FIG. 3 shows a portion of a centrifugal separator 9 for separation of a liquid mixture of components, the separator having a rotor 10 supported by a spindle 11 (partly shown) which is rotatably arranged in a frame around an axis of rotation (x). The rotor forms within itself a separation chamber 12 wherein a disc package 13 is arranged. The rotor further comprises an inlet chamber 14 formed within a distributor 15 into which a stationary inlet pipe 16 extends for supply of a liquid mixture of components to be separated. The inlet chamber communicates with the separation chamber via passages 17 formed in the rotor. The radially inner portion of the disc package communicates with an outlet 18 for a lighter liquid component of the mixture. The outlet 18 is delimited by a top disc 19 provided at the upper axial end of the disc package 13. The top disc 19 and the upper wall part of the rotor 10 delimits a passage for a denser liquid component of the mixture, the passage extending from the radially outer part of the separation space 12 to an outlet 20 for the a heavier component of the liquid mixture. The rotor is further provided with outlets 21 from the radially outer periphery of the separation space 12 for intermittent discharge of a sludge component of the liquid mixture comprising denser particles forming a sludge phase. The opening of the outlets 21 is controlled by means of an operating slide 22 actuated by operating water, as known in the art.