US2840302A - Centrifugal separators - Google Patents

Description

n 1958 P. STEINACKER ETAL 2,840,302

CENTRIFUGAL SEPARATORS Filed June 1, 1954 INVENTOR PE TER STEINACKER HEINRICH HEMFORT ATTORNEY United States Patent CENTRIFUGAL SEPARATORS Peter Steinacker and Heinrich Hemfort, Oelde, Westphalia, Germany, assignors to Westfalia Separator A. G., Oelde, Westphalia, Germany, a corporation of Germany 7 Application June 1, 1954, Serial No. 433,709

1 Claim. (Cl. 23320) This invention relates to improvements in centrifugal separators. The invention more particularly relates to improvements in centrifugal separators provided with means for periodically discharging accumulated solids or sludge from the centrifugal bowl.

Centrifugal separators are known in which accumulated solids or sludge is discharged through peripheral ports or openings in the centrifugal bowl. These centrifuges may be provided with an axially movable sleeve valve positioned in the lower portion of the bowl for movement between a position closing the sludge discharge introducing liquid below and/or above the flange tomove the sleeve valve in'either direction.

Thus, for example, the centrifugal bowl may comprise an outer casing with an inner member forming the bottom of the centrifugal bowl. The inner member may be spaced from the outer casing to form a place for the sleeve valve. The sleeve valve may have an inwardly projecting radial flange positioned in the space defined between the bottom of the outer casing and the bottom of the inner member. In order to move the sleeve valve upward to close the sludge discharge and openings,-liquid is introduced into the space between the casing bottom and the inner member below the radial flange. In order to move the piston in the opposite direction, liquid is introduced into the space above the flange.

The sleeve valve is conventionally constructed so that the same has an outer cylindrical surface which is guided and moved along a corresponding innercylindrical surface of the bowl casing. While the sleeve valve issubstantially rigid at its base portion in operation due to the radial flange, the upper cylindrical portion which effects the sealing and opening of the sludge discharge openings is subjected to deformation by the centrifugalpressure of the liquid and sludge in the bowl during operation and by the pressure of the control liquid used to open the sludge discharge openings. This deformation often causes the sleeve valve to be pressed so firmly against the inner wall surface of the bowl casing that the same cannot be readily and reliably moved by the control liquids for the opening and closing of the sludge discharge openings. This, of course, impairs normal and eflicient operation and leads to some considerable disturbances.

These disadvantages may be avoided by taking the deformation of the sleeve valve into consideration'and. leaving suflicient space between the outer surface of the valve and the inner surface of the bowl casing so that the valve can no longer jam. This measure, however, presents a positive and accurate guiding of the sleeve valve which is extremely desirable. In addition, certain other advantages are caused by such a construction. Sludge containing liquid may penetrate into the guide surface between the valve and the casing of the wall during the discharge of sludge. The inside of the centrifugal bowl is generally composed of upper and lower frusto-conically shaped portions which mate at their widest crosssections. The solids deposit on these inclined walls and slide outwardly during the centrifugal action. As the sludge space fills up, the moisture content, particularly.

of the solids present in the region of greater centrifugal force increases and these solids under the continuous action of the centrifugal force form a more or less firmly coherent layer depending upon the nature of the material being centrifuged. If the sleeve valve is then moved to the position opening the sludge discharge openings, the pressure of the liquid head within the bowl acting on the sludge layer can only break this layer or push the same away after the annular space formed between the upper edge of the sleeve valve and the adjacent portion of the bowl against which it seals has attained a certain width. Only after this occurs will the contents from the; sludge spacebe centrifuged to the sludge outlet open-- The centrifuging; of the solids out through these openings which are gen-j erally formed as discharge ports or holes can, however,,. not take place as rapidly as the passage of the solids through the annular channel formed above the upper:

ings at the periphery of the bowl.

edge of the sleeve valve. The duration of the sludge re-- moval depends upon a number of factors, as for example, the size of the sludge face, the size of the outlet opening, the size of the solid particles, etc. For this reason, i

a pressure head is produced in the space between the. an-

nular gap and the outlet ports and forces the sludge containing liquid down the side of the valve sleeve. During further centrifuging, the water separates from the solids which soon dry out andform a crust. These encrustedsolids, after a period of time, will block further.

movement of the sleeve valve.

The insert which is placed at the lower portion of the bowl casing and forms a bottom surface of the bowl is usually positioned and centered on a central hub in the bowl bottom; When the centrifuge is used in connection with the separation of preheated materials, the insert, due to the thermal expansion, will freeze on the hub and can be withdrawn from its seat only after the bowl has cooled. Even when operating at normal temperatures, it is frequently diflicult to remove this insert from the bowl.

One object of this invention is to overcome the above mentioned disadvantages. This and still further objects will become apparent from the following description read in conjunction with the drawing in which:

Fig. l is a vertical section 'of an embodiment of av centrifugal separator in accordance with the invention showing the sleeve valve in the closed position, and

Fig. 2 is a vertical section corresponding to Fig. l but showing the sleeve valve in the open position.

It has now been found that all the above mentioned, disadvantages are eliminated if the sleeve valve is guided at its inner surface by the insert which forms the bottom surface of the bowl rather than being guided at its .outer surface by the bowl casing. The portion of the insert which guides the sleeve valve should have a wall thickness and be so dimensioned that its deformation under the operating conditions closely approximates that of the sleeve valve itself. The upper extending portion of the sleeve valve should be spaced from the'adjacent inner portion of the bowl casing. This space should be sludge which has collected in the bowl may discharge. A

sleeve valve 5 is axially movable within the bowl between anupper position at which its upper edge abuts the gasket 6 sealing the discharge ports 8 and a lower position at which its upper edge is spaced from the gasket 6 leaving an annular discharge opening to the sludge dischargeports 8. The upper closedposition is shown in the left-hand side of the drawing and the lower open position is shown in the right-hand side of the drawing. A lower insert in the form of a false bottom 23 is positioned within the bowl in spaced relation to the bottornj of the casing 1'. The upper surface of the false bottom 3 forms the actual bottom surface of the in-.

terior of thebowl and, the sludge. supporting surface. The'false bottom 23 is connected as an integral part of the distributor '4 which extends centrally upwardly through the bowl and into which the material to be treated is introduced through the inlet pipe 24. This arrangement allows the distributor and bottom insert to be easily removed from the centrifuge as a unit after removal of the distributor discs for plates 25.

The sleeve valve 5 has connected at its baserportion the inwardly extending radial flange 5 which is positionedin the space between the false bottom 23 and the casing 1.

'Liquid may be introduced into the portion of this space 9 below the flange 5 through the conduits 10 and 14 to maintain the sleeve valve 5 in the closed position. A discharge, conduit 15 .is also provided in con nectiou withthis portion of the space.

Liquid may be. introduced into theportion f the space above the flange through the conduits and 11 to open thesleeve valve 5. A peripheral discharge conduit 13 is provided in communication with this portion of the space above the flange 5'. n

'fThe portion of the centrifugal bowl casing 1 adjacent the upper portion of the sleeve valve 5', at which the deformation can take place, is tapered conically outwardly toform the free space 17 between the inner surface to this adjacent portion of the casing l and the outer surface of thesleeve valve 5. The discharge conduit 13 is in communication with this space and a washing liquid conduit 20 is positionedfor passing washing liquid into this spacefrom the conduit 10 and conduit 18.

The sleeve valve 5 slides along and is guided on its inner surface by the outer annular surface 16 of the false bottom 23. This'portion of the false bottom23 is so dimensioned with respect to the sleeve valve 5 that centrifugal force exerted on these two elements will cause each of them to undergo substantially the same deformation and thus a positive and accurateguidingof the sleeve valve 5 is effected under all operating'conditions without any chance of jamming. a

The entire centrifugal bowl is mounted for rotation on the spindle 26. c

"In operation, the bowl is rotated by rotation of the spindle 26 in the conventional manner. A control liquid,

such as water, is introduced into the space 9 below the flange 5". This water builds up a centrifugal head up tothe discharge and the pressure thereof forces theflange 5f and its connected sleeve valve 5,so that the connectedupper edge of sleeve valve 5 abuts the gasket 6 and seals the chamber.

The material to be treated is. passed in through the inlet pipe 24 and is distributed in the interior of the centrifugal bowl by means of the, distributor 4 through conduit 22. Due to thejcentrifugal" force, the solids or sludge are thrown outwardly and accumulate in the V-shaped sector of the upper portion of the casing 2 and the upwardly sloped portioii of false bottom 23. The clarified heavier and lighter liquids are discharged over the overflow lips 28 and 29 in the conventional manner.

After a period of operation, in order to effect discharge of the accumulated sludge, an increased amount of liquid, such as water, is introduced through the conduit 10 as, for example, by means of control valve 27. Due to the centrifugal action, this water passes through the conduit 11 into the space 12 above the flange 5. The rate of inlet through the conduit 10 is controlled so that liquid will be passed into the space 12 faster than it passes out of discharge conduit 13. A centrifugal head of liquid will thus build up in the space 12. As the liquid in the space 12 is built up to a greater centrifugal head than in the space 9 since the head which may be built up in space 9 is limited by the discharge conduit 15, greater pressure is developed by the centrifugal action of the liquid in the space 12 than in the space 9 and the flange 5" and sleeve valve 5 are forced downwardly to the position indicated on the right-hand side of the draw- The sleeve valve 5 is accurately guided, at its inner surface by the surface .16 of the false bottom 23. Since these two portions undergo the same deformation under the centrifugal force in the bowl the guiding friction therebetween remains always substantially constant and no jamming, etc., can take place. The solid material is discharged by the centrifugal force through the annular space between the valve 5 and gasket 6 and through the sludge discharge ports 8. Liquid from conduit 10 is passed by centrifugal action through the conduits 18, 19 and 20 into the space 17 and out through the sludge discharge ports .8. This liquid effects a flushing and washingof the space 17 and prevents any accumulation of sludgetherein. This flushing action is additionally aided by liquid passing from the space 12 through the conduit '13.

After the discharge of the sludge has beencompleted, the liquid passing through the conduit 10 is throttled down as, for example, by means of the valve 27 so that the amount passing in the space 12 is less than the amount 7 passing out through'theconduit 13. The portion of the liquid from the conduit 10 passing through the conduit 14 into the lower space 9"always builds up to the point of the discharge "conduit 15. The centrifugal head of liquid up to this point now exceeds the centrifugal head in the space 12 and thus the pressure below the flange 5' is greater than, the pressure above flange 5 and the samewith the'sleeve valve 5 is forced to the upper closed position asshown inthe left-hand side of the drawing. The liquid from the conduit 10 may be continuously passed in at this rate and will merely overflow through conduit 15 to insure that adequate closing pressure is maintained at all times. Due to the design of the false bottom-23 and sleeve valve 5, the valve will not be retarted in itsrnotion even in the case of expansion, etc., due, to the centrifugal action. Inasmuch as the washing or flushing liquid is introduced into'the space 17 prior to the opening actuation of "the sleeve valve 5, the sludge despite the pressure head in front ofthe outlet openings 8, cannot penetrate into thisspace 17. against the flow of the washing liquid. The channel 19 may be closed by means of a plug 21 if the flushing of the .space 17 is not necessary. Instead of a plug, there may also be used a nozzle in order to limit or control the quantity of the washing liquid.

The bowl, inaccordance'with the invention, has a reduced number of parts and the construction is simplified' since the distributor and false bottom 23 are, constructed of one piece.

After the bowl cover has been removed for cleaning,

the bowl:

We. claim:

In a centrifugal separator having a centrifugal bowl with peripheral sludge outlet openings, a sleeve valve axially movable between a position opening and a position closing said openings, a bottom insert member defining the lower surface of the bowl interior and means for moving said sleeve valve for the periodic discharge of sludge from the bowl; and the improvement which comprises the sleeve valve positioned with a major portion of its outer surface in spaced relationship to the adjacent inner surface of the bowl, forming a free space therebetween in communication with said sludge outlet openings, said sleeve valve having an inwardly extending flange connected to the lower portion thereof, means for passing liquid into said space in the direction of said 15 sludge outlet openings, which means includes a liquid passage defined through said flange through the lower portion of said sleeve valve, means for passing liquid to said liquid passage and the bottom insert member 'defining an outer guide surface positioned in sliding contact with the inner surface of said sleeve valve.

References Cited in the file of this patent UNITED STATES PATENTS Ortenblad Nov. 8, 1949 FOREIGN PATENTS 122,937 Sweden Oct. 5, 1948 616,442 Great Britain Jan. 21, 1949 819,529 Germany Oct. 31, 1951

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