US2263708A - Centrifugal separator - Google Patents

Description

O N. E. SVENSJO ETAL 2,253,708

CENTRIFUGAL SEPARATOR Filed Nov. 22, 1938 2 Sheets-Sheet 2 mmfss" I /Vz'/s f/uzk Jae/1s 0" zrzam maerxlif Patented Nov. 25, 1941 CENTRIFUGAL SEPARATOR Nils Edvin Svensjii, Alsten, and Erland Viktor Jung, Stockholm, Sweden, assignors to The De Laval Separator Company, New York, N. Y., a corporation of New Jersey Application November 22, 1938, Serial No. 241,740 In Sweden December 4, 1937 4- Claims.

Centrifugal bowls provided with discs are generally composed of a great number of parts. In order to ensure smooth running of the bowl, the parts in question must be well guided in relation to each other, which generally is effected by cylindrical guiding surfaces. In case a centrifugal bowl made of ordinary steel is used for the separation of etching or fretting liquids, the guiding surfaces are attached, which in turn permits a displacement of the parts relative to each other, so that the bowl becomes unbalanced and runs roughly.

The invention relates to a separator bowl, more particularly intended for the separation of corrosive liquids, which comprises a number of parts which are centralized in relation to each other, and is characterized by centralizing surfaces so located that corrosion of the material is rendered difficult. The invention also relates to arrangements by which any substantial radial displacement of the mutual position of the parts is avoided, even if some material of the said guiding surfaces is destroyed by corrosion.

Fig. 1 is a vertical sectional view of a centrifugal bowl embodying our invention, the section being taken on only one side of the bowls axis.

Fig. 2 is a vertical sectional view of a modification of one of the details of Fig. 1.

Fig. 3 is a plan View of one of the elements of Fig. 2.

Fig. 4 is a vertical sectional view of another modification of one of the details of Fig. 1.

Fig. 5 is a vertical sectional view of another modification of Fig. l. a

Fig. 6 is a vertical sectional view of a modified construction for discharging from the bowl the separated heaviest liquid when the bowl is used for separating three constituents of different specific gravities.

Referring first to Fig. 1: l is the upper part or the bowl hood, 2 the lower part or bowl body. These parts are held together by a nut 5. The bowl body 2 guides a central element 8 (comprising a tubular feed shaft and skirt) on which a number of discs 5| are positioned. It is very important that the hood I, the body 2, and the element 8 should be kept in a true central relation to each other. This may be insured by making the guiding surface- 3 between parts I and 2 conical and by providing a-packing ring 4. The

nut 5 is provided with a conical surface which is centered by a corresponding surface on the hood. As it is not certain that a tight joint will always be-effected by the packing ring 4, the nut 5 is provided with a collecting groove 6, which communicates with discharge openings 1. Any leakage liquid is collected in the groove 6 and is discharged without attacking the threads. In order to have still greater safety it may be advantageous to arrange two or more consecutive grooves 6.

The central part 8 is guided on the bowl body by a conical surface 9 which may suitably be provided by tapered exchangeable filling pieces ll, I2 which may be made of a material which is more resistant to corrosion than that of the principal parts of the bowl. If a conical guiding surface 9 is provided, by the described or other means, between the bowl body and the central part 8, the latter part must be pressed down on the bowl body. This may be effected by means of a nut Ill, which is threaded in the neck of the part I and presses the part 8 on the part 2. In order to prevent corrosion, the nut l0 may be located so far inside the liquid level in the upper part I that the thread and the guiding surface do not come into contact with the corrosive liquid. In order to obtain a reliable guiding relation between the upper part I and the part 8, it is advantageous to provide a conical guiding surface I4 between the nut l0 and the central part 8. Such an arrangement is particularly advisable where sufficient differences of level cannot be obtained between the tightening surface and the inner surface of the liquid.

Instead of threading a nut ID in the neck of the bowlhood, a ring l5 (see Fig. 2) maybe wedged between the hood neck and the part 8 by means of a spring l3 confined between the ring l5 and a nut l6 threaded on the upper end of part 8. The ring may be completely out through at one point I! and nearly cut through at others I8, I8, so that it can be expanded and contracted to fit the inside of the bowl neck while at the same time it fits the taper on the tabular shaft.

In Fig. 4 is shown a modification in which, for the nut I0, is substituted a nut l9 and a ring 28, the latter being confined by the nut between the parts I and 8 and being made, if found necessary or desirable, of corrosion resistant material.

22 provided with discharge openings 23. The disc 22 may be pressed down on a packing ring 25 by a nut 26 threaded on the neck of the hood I. Wings 28 may be positioned in the chamber 2| to break up the liquid. As the wings are strongly attachable both by erosion and corrosion they should be exchangeable. They are preferably carried by a central ring 21. The ring 21 is guided on the part I by a surface which is located inside the liquid level in the chamber 2|.

When ordinary bowls are used for the separation of corrosive liquids, it has been found that those parts of the disc 5| which are guided by the central part 8 are quickly eaten away, so that the whole pile of discs maybe displaced in the bowl, which may then get out of balance. Because the height of the whole pile of discs is reduced, owing to the etching effects of the liquids, the discs will therefore not be secured in position between the hood and the conical lower portion of the central part 8, and some parts of the pile of discs may be displaced relative to each other and the bowl then also becomes unbalanced after a short time.

This condition may be remedied by the insertion of an extra disc or by other expedients, such as making the discs sufiiciently elastic so that they will straighten themselves out under the infiuence of centrifugal force. Considerable deformation may be provided for by slitting the discs radially. Or one or more of the discs, preferably the lowermost one, may be plaited or corrugated.

It is, however, highly advisable to reduce corrosion of the discs, which is most serious ad- J'acent the tubular shaft of the central element 8, on which the discs 5| must be guided and centered. It is therefore advantageous to locate the guiding surface inside the liquid level in the separating chamber. It is also advantageous to make the inner edges of the discs, or the guiding surfaces on the central element, or both, of a material having higher resistance to corrosion than that used in the central member and the discs. In exceptional cases it may be advantageous to keep the discs together by a lock device in the form of a nut 50, located on the central member 8. The said member may be provided with holes 29 through which the liquid is conducted to the discharge openings. If, notwithstanding these precautionary measures, corrosion should take place on the guiding surfaces between the discs and the member 8, such corrosion may be prevented by arranging adjustable guiding surfaces on the member 8, which surfaces may be provided in many different ways, for instance, as axial wedges 40, Fig. 5, which are movably arranged on the central member 8.

Fig. 1 shows the bowl hood as provided with a number of channels 3| which open into the separating chamber closer to the bowl wall than the channel system 30. intended for the discharge of the heaviest component of the liquid when the liquid is separated into three products in the separating chamber. This is, for instance, the case when mineral oil refined with sulfuric acid is treated, three products, sulphuric acid, goudron, and refined mineral oil, thereby being obtained. It is thereby important to locate the openings for sulphuric acid and goudron at suitable distances from the bowl wall and at suitable distances from the inlet zone of the unseparated liquid.

The channels 3| should open at the bowl wall and the channel orifice should have a comparatively small radial extension, because they must be completely covered by the layer of the heaviest liquid in order to prevent the medium liquid from flowing into the channel system 3|. If this should take place the specific gravity of the liquid in the channel system 3| would be reduced, and It may then happen that the pressure of the The channel system 3| is liquid in the channel system 3| would not be sufficient to counteract the pressure exerted in the separating chamber by the two lighter liquids.

The outer edges of the inlets to channels 30 may extend to the inner surface of the bowl wall, but their inner edges must be at a certain distance from the inner surface of the bowl body which is sufficiently great to allow variations in thickness of the layer of heaviest liquid. This is necessary in order to ensure that the liquid of intermediate specific gravity cannot penetrate to the channel 3| for the heaviest liquid.

It is also advantageous to have a certain radial difference between the inner edges of the inlets to channels 30 and the inlet zone for unseparated liquid in order to allow a certain displacement of the inner surface of the layer of liquid of intermediate specific gravity without afiecting the process of separation. If the specific gravity of the treated liquid is increased but not that of the medium liquid and assuming unchanged regulating members in the channel systems 30 and 3|, a displacement outward of the inner boundary surface of the medium liquid would result. The displacement of such surface outside the inner edge of the channel system 30 must now be avoided, because oil would then fiow out of the channel system 30 and the separation would be interrupted. If, on the other hand, the specific gravity of the treated liquid is reduced without any change of the specific gravity of the medium liquid taking place, the boundary surface between the latter and the lightest liquid is displaced inwards. If the said surface should come inside the supply zone of the unseparated liquid, the latter would have to pass through already separated medium liquid, which would entail an enrichment of the latter in the lightest liquid and thus make the separation more diificult.

The regulating members for the channel systems 30 and 3| should be so dimensioned that by replacing or adjusting them, oils (for example) can be treated in the bowl the specific gravity of which varies between 0.80-0.95, leaving a goudron of a specific gravity between 1.10-1.40 and sulfuric acid of a specific gravity which can be varied between 1.40-4.90.

It is not only necessary, as above described, that the radial distances between the bowl wall and the inner edge of the channel system 30, and between the latter edge and the inner edge of the channel system 3 should be sufiiciently great to permit the changes which may occur in the specific gravities of the treated liquids without necessitating an exchange of the regulating.

members. In dimensioning these distances it must also be borne in mind that the amounts, as well as the specific gravities, of the medium and heavy liquids may change, and the distances above considered should therefore be so dimensioned that not only the specific gravity, but also the amount, of medium liquid can be allowed to vary between 0-20% of the amount of light liquid, and that the amount of heavy liquid can vary from 0-50% of the amount of light liquid, without necessitating an exchange of the regulating members. It is assumed that both liquids are conducted through channel systems in which no special throttles are provided.

It is not necessary that the outlets for both medium and heavy liquids should be located in the top of the bowl. When it is desired to separately collect these liquids one of the channel systems 30 and 3| may be arranged at the top part, and the other (preferably the channel system 3 I) at the bottom part, of the bowl, as shown, for example, in the Strezynski Patent No. 2,068,520.

Fig. 6 shows a modification in which the discharge for the heaviest liquid is located in the lower part of the bowl wall. The system consists of two concentrically arranged tubes 33 and 32. The annular chamber formed between the two tubes receives the heaviest liquid through opening 34, and is partly filled therewith when the bowl is being put into rotation. The said annular chamber communicates with the central outflow channel of tube 32 through an opening 35. The said opening 35 should be so placed that the layer of heaviest liquid between the bowl wall and the opening counterbalances the liquid layers outside the tube 33. As previously mentioned, the opening in tube 33 should be so dimensioned that it is kept completely covered by the heaviest liquid in order to prevent the medium liquid from flowing thereinto and destroying the desired equilibrium. In order to make the system adjustable to different conditions of operation, the tube 32 may be made exchangeable with other tubes having openings 35 located at difierent radial distances. The system illustrated in Fig. 6 can also be used for emptying the bowl by screwing in the inner tube 32, an opening thereby being formed through which the liquid contained in the bowl can discharge.

What we claim and desire to protect by Letters Patent is:

l. A centrifugal separator comprising a bowl body having an upper face tapering upward and outward and a separable bowl hood having a similarly tapered lower face, a nut threaded on the bowl body and bearing against the hood and holding said hood on the body and said tapered faces in contact, the contacting bearing faces of the nut and hood being tapered downward and outward. 1

2. A centrifugal separator comprising a bowl body having a central upstanding stem, a bowl hood clamped on the bowl body, a removable central feed supply element and exchangeable filling pieces between the lower parts of the bowl body and central element, said filling pieces having contacting conical faces, and means to press down the central element and thereby clamp said filling pieces between the central element and the bowl body.

3. A centrifugal separator comprising a separable bowl body, a separable bowl hood having an upstanding neck within which is a passage for outflow of separated liquid and a separable central feed supply element, there being a conical bearing surface between the bowl body and bowl hood, a conical bearing surface between the lower part of the central element and the lower part of the bowl body, and a member providing an adjustable conical annular bearing surface between the neck of the bowl hood and the upper part of the central element above the outlet from said passage, said conical bearing surfaces so positioned enabling all three parts to be held in tight centralizing relationship each to the other two notwithstanding corrosion or wear.

4. A centrifugal separator as defined in claim 3 comprising also a liner of discs in the bowl body and means separate from the specified conical bearing surface between the bowl hood and central element, to place the discs under such tension that they may be maintained in a fixed position in relation to the surrounding parts of the bowl notwithstanding corrosion of some of the material of the discs.

NILS EDVIN SVENSJO. ERLAND VIKTOR JUNG.

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