US2663262A - Centrifugal pump with sealing device - Google Patents

Description

Dec.

MALMVIK E1- AL CENTRIFUGAL PUMP WITH SEALING DEVICE Filed Feb. 19, 194

Patented Dec. 22, 1953 CENTRIFUGAL PUMP WITH SEALING DEVICE Elof Malmvik and Edwin Dunr, Jonkoping, Sweden, assignors to Jonkopings Mekaniska Werkstads Aktiebolag, Jonkoping, Sweden, a

joint-stock company Application February 19, 1948, Serial N 0. 9,465

- In Sweden December 16, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires December 16, 1962 3 Claims.

. 1 t r This invention relates to a centrifugal pump with a sealing device and is especially intended for use in connection with pumping of corrosive liquids, such as waste liquid from the cellulose industry and liquids containing, for instance, sulphuric, hydrochloric or nitric acid, ammonia, chlorine or the like. Such liquids attack chemically and mechanically the stuffing boxes in the pumps, especially as the liquids often have a high temperature, and the pumps, therefore. have to be repaired frequently.

One object of the invention is to secure the sealing between the pump shaft and the casing by means or a hydraulic seal of a simple but efficient construction.

An other object is to provide a sealing device of such a construction which requires noor only very little attendance.

A further object is to reduce, the power consumption in the hydraulic seal.

A still further object is to provide a sealing device adapted to resist pressure as well as vacuum.

These and other features, characteristics and advantages of the present invention will become apparent from the following disclosures taken in conjunction with the accompanying drawing,in which: i I

Figure 1 is an axial section of acentrifugal pump with an appendant sealing device accord ing to one form of the invention.

Figure 2 is an axial section onlan enlarged scale of another form of the sealing device, and

'Figure 3 is a similar axial section of a'third form of the sealing device. 1

In the pump shown in Figure l the pump shaft I is mounted in a bearing 2, shown only in part, and the lower end of the pump shaft is provided with a runner 3. The pump casing 4 is designed in such a Way that the liquid tobe propelled flows through an inlet conduit 5 into an inlet chamber a situated at the .same side of the runneras the sealing device, the, liquid flowing from said chamber-through a coaxial opening 7 into the very runner chamber 8, where'- in it is being impelled in known manner towards the outlet 9. The pump shaft 1 which would be attacked by the corrosive liquid if brought into contact therewith, is covered by sleeves l6, ll of resistant material which have been slid, on e after another, onto the shaft over the free end thereof, said sleeves serving also as distance pieces for keeping the sealing impeller I2 in correct position axially, which impeller is positioned between the inlet chamber 6 and the iii bearing arrangement 2. This position of the sealing device and the inlet chamber implies that a seal must be provided only for the overpressure or vacuum arising at thesuction side of the pump, which pressure, as a rule, is much lower than at the pressure side of the pump, whereby the power consumption in the sealing device is correspondingly reduced.

' The sealing impeller which consists of a disc l4, projecting from the nave l3, and a cylindrical rim or flange l5 projecting axially from the edge of'said disc, is provided on both sides with blades or vanes. the lower blades I 6 facing the inlet chamber 6. extending inwardly from the rim l5 to a certain distance from the shaft, or the'sleeve l6 surrounding the same, whereas the upper blades 11 facing the bearing arrangement 2 extend from the rim [5 to the nave l3 of the sealing impeller. By means of a key I B the sealing impeller is keyed to the shaft l and it rotates in a chamber [9 separated from the inlet chamber by means of a transverse partition wall 20 carrying a central, naveshaped portion 2| surrounding the sleeve ID with a clearance just sufiieient to permit a frictionless rotation of said sleeve together with the pump shaft I, thereby allowing a communication between the sealing impeller and the pump chamber 8. The nave-shapedportion extends somewhatabove the lower edge of the blades l6 of the sealing impeller. :The chamber l9 will thus constitute a fluid'pocketcontaining a sealing fluid which may be constituted by the liquid conveyed by the pump. and in the pocket the sealing wheel is submerged with the lower portion of its rim l5 and the blades !6. Towards the bearing means 2 the chamber 19 is bounded by a partition 22 joining the-sleeve II with a slight clearance. On theopposite side of this partition ther isafurther chamber 23 with an outlet 7Z4 for liquid possibly leaking through in the moment as the pump is started. It is understood, however, that the pump should be provided with a valve in the suction pipe and another valve in the pressuresystem to be closed when the pump is at rest.

The operation of the, device is as follows. When the pump is to be started, the sealing chamber I9 is or should'be at least partly filled with the pump liquid or another liquid. By the use of the annular pocket it is always assured that the necessary quantity of sealing liquid is at hand. As the shaft begins to rotate all sealing liquid in the'cha mber ls is caused to rotate by the blades and thrown towards the periphery by the centrifugal force thereby forming between the sealing wheel and the casing a sealing ring which :keeps the connection between the pump chamber 8 and the chamber 23 leading to the open air entirely closed. The valves in the suction pipe and thereafter in the pressure system are now opened.

It is now assumed that a certain vacuum exists in the inlet chamber ii. The fluid in chamber 12 will then be forced. 111033-361 less to the portion of the chamber occupied by the ower blades until the suction act-ion is balanced pumping action of the blades. lion the hand, the pump is connected zanztlie suct with a container, in which the liquid lever beginning causes a certain overpressure in th inlet chamber a, then the sealing liquid in the chamber iii and flows over the upper blades, As these have a greater radial extension than the lower blades they can overcome the action of the lower blades andalso exert an additional pressure for balancing the overpressure in the inlet chamber. nsanexampleiit rnaybe mentioned t a such. a ealing Whe l having Ti /2'} diam ter of the upper blades and 51%; diameter of the lower blades rnay seal fora .suctionof 1 1 lbs/sq. in. up to, an ,cverpressurein the inlet chamber of 43 lbs/sq. in. Tfjhe liquid level in the container may thus yary between wide limits without causns any leaka in the hydra i s l- ,For umps op ratin under still h her Overpressure i th linl t chamber ,6 the m odim nts how ..f i eure. ..or 3 may b used,-

Fiaure 2 show a c nstruetie Of a s l n w el, herein the d sc and he blades ll provi e the eon have be n ex d d ra a ly, whereas the lower blades have maintained their o m a d te sio sliownj n F gu ,1 rather have been reduced in size. By maintaining only the 'lowerportion ofthe rim [5 bounding the blades 16 and extending the .disc 14 b yond said it is possible to obtain a considerably increased length of the upperblades l1" counteracting overpressure.

In the embodiment, shown in Figure 3 the sealing wheel comprises two radially disposed discs, a lower disc M which, as in the embodiment according to Figures 1 and 2 is provided with upper blades i1 andlower blades I6, and an upper disc 25 provided with blades 26 on its upper side only and'arranged to rotate in a chamber 2] separated by means of a radial partition 28' from the fluid pock' e't chamber l9 previously described. If, in a pump provided with such a sealing device, the pressurem the inlet chamber 6 increases to such an extent that-the single sealing wheel l4 is'not sufficient to prevent escape of the liquid, thebs'aidiliquid flows into the second chamber 2''! constituting," together with the disc 25, a'secondiluid seal, the lower branch of whichis not'act'ed upon by blades and, consequentlyfnot very effectively thrown outwardly in'the direction ofaction of the overpressure prevailing in the inlet chamber, the upper branch of which, however, is operatedupon by a number of blades of comparatively large adial extent a d whi h ar a epted to c ate a c ntri u al rce co sti utin n thi bra h a s b tantia1 counteraction again t pre sure ac n to drivetbe liguid throu h the sealin .de-

vice. i

We claim: a

1. In a vertical centrifugal pump, a pump shaft, run r ounted o ie-lcwe end ofisaid pump ha t a pump chamber su roundin said runner and being closed downwardly, an upper inlet to said pump chamber, a sealing chem er around the pump shaft abovesaid inlet, s sealing chamber having a bottom with a short upright ring-shaped inner wall so as to form a pocket for receiving and retaining sufficient pump liquid to form a sealing ring of pump liquid, said bottom of said sealing chamber having an opening for the pump shaft which opening is larger than said shaft .so as to provide a ring-shaped space around the pump shaft to allow admittance of p mp liquid from said inlet to the pocket in said sealing chamber, and a sealing impeller mounted on the pump shaft in said sealing chamber and comprising a horizontal disc, a series of lower blades on the lower surface of said. said lower blades having free inner edges so as to leave a space occupied by said upright wall ex tending into said pocket, and a series of upper blades on the upper surface of said disc, said upper blades having a greater radial extension than said lower blades.

' ,2. In a vertical centrifugal pump, a pump shaft, a runnerinounted on the lower end of said pump shaft, a pump chamber surrounding said runner and being closed dow an upper inlet to said pump chamber, soiling chamber around the pump above s let, said sealing chamber having a bottom with a short upright inner wall so as to form a pocket for receiving and retaining sufiicient pump liquid to form a sealing ring of pump liquid, said bottom of said sealing chamber having an opening for the pump shaft which opening is larger than said shaft so as to provide a ring-shaped space around the pump shaft to allow admittance of pump liquid from said inlet to the pocket in said sealing chamber, and ,a sealing impeller mounted on the pump shaft in said sealing chamber and comprising a horizontal disc having a downwardly extending circular flange, a series of lower blades on the lower surface of said disc, said lower blades having free inner edges so as to leave a space occupied by said upright wall extending into said pocket and being united at their outer ends with said flange, and a series of upper blades on the upper surface of said disc, said upper blades having a greater radial extension than said lower blades,

3. In a vertical centrifugal pump, a pump shaft, a runner mounted on the lower end of said pump shaft, a pump chamber surrounding said runner and being closed downwardly, an upper inlet to said pump chamber, a sealing chamber around the pump shaft above said inlet, said sealing chamber having abottom with a short upright inner wall so as to form a pocket for receiving and retaining sufficient pump liquid to form a sealing ring of pump liquid, said bottom of said sealing chamber having an opening for the pump shaft which opening is larger than said shaft so as to provide a ring-shaped space around the pump shaft to allow admittance of pump liquid from said inlet to the pocket in said sealing ber, and a sealing impeller mounted on the pump shaft in said sealing chamber and comprising a horizontal disc having a downwardly extending circular flange, an upwardly extending flange, a seriesof lower blades on the lower surface of said disc, said lower blades having free inner edges so as to leave a space occupied by said upright wall extending into said pocket and being united at their outer ends with said downwardly extending flange, and a series of upper blades on the upper surface of said disc, said upper blades having a, greater iidial extension than said lower blades and being united at their outer ends with said upwardly extending flange.

ELOF MALMVIK. EDWIN DUNE'R.

References Cited in the file of this patent Number UNITED STATES PATENTS Number 6 Name Date Haug June 4, 1929 Marsland Oct. 22, 1929 Bath May 26, 1931 Schleyer June 16, 1931 Allen Sept. 29, 1931 Goddard Aug. 23, 1938 Collins June 6, 1944 Wilsmann May 22, 1945 La Bour Aug. 7, 1945

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