US3101671A

US3101671A - Adjustable seal for pumps

Info

Publication number: US3101671A
Application number: US170877A
Authority: US
Inventors: Earle E Schroeder
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1962-02-05
Filing date: 1962-02-05
Publication date: 1963-08-27
Anticipated expiration: 1980-08-27

Description

Aug. 27, 1963 E. E. scHRoEDER ADJUSTABLE SEAL FOR PUMPS Filed Feb. 5, 1962 lllH N llllll z5 ff f4' 57 @ikke/hwg United 'heaters This invention relates generally to pumps. More speciiically this invention relates to seals to reduce the amount of leakage along the shaft behind the impeller of a centrifugal pump.

It is common practice in the pump art to use a stutling box that surrounds the shaft behind the impeller to prevent leakage of fluid that flows behind the impeller and along the driving shaft of the pump. Although this type of `seal is generally adequate, it is not good enough in situations where a highly abrasive fluid is being pumped or in conditions where no leakage can be permitted. The life of the stuiling box type of seal is significantly shortcned when a highly abrasive liquid is being pumped. The excessive wear on the stuiing box necessitates frequent shutdowns of the pump lfor replacement of the seal packing or the casing of the seal itself.

This invention overcomes the problems mentioned above by providing an axially adjustable member behind the impeller for varying the amount of clearance between the impeller and the adjustable member to thereby hold the amount of leakage behind the impeller to a minimum. Furthermore, the pump of this invention is provided with a bypass conduit that directs any fluid that flows past the adjustable clearance back to the low pressure or suction side of the pump. This has the eiiect of reducing the pres` sure on the stufling box and thereby helps to prolong the life of the packing in the stuffing box and the stuffing box casing itself.

Therefore, it is lthe object of this invention to provide a new and improved pump. y

Another object of this invention is to provide -a newand improved seal for pumps.

Another object of this invention is to provide a new and improved centrifugal pump having less leakage.

Another object of this invention is to provide a new and improved seal for centrifugal pumps having a longer life.

Other objects and advantages of this invention will be apparent from the following description when read in connection with the accompanying drawing, in which:

FIG. 1 is a cross sectional .view of a centrifugal pump of this invention; and

FIG. 2 is a cross sectional view of a portion of a modified pump of this invention.

Referring more specifically tothe drawing, the centrifugal pump has a casing 11 having an axial inlet 12 and a radially spaced discharge volute 13. The casing 11 is provided with a rear cover 14 which combines 'with the rest of the casing to deiine an impeller chamber 15. A suitable impeller 1S is mounted on one er1-d of a drive shaft 19 and positioned within the'impeller chamber 15 with the other end of the shaft extending through an opening 20 in the rear cover 14. The shaft is adapted to be driven by a suitable source of power such as an electric motor.

A stutlingbox 23 having an annular cavity 24 surrounding the shaft 19 is connected to the rear cover 14. The cavity 24 inthe stuing box is lled with suitable packing material 25 and the outboard end of the stuffing box is closed `olf Iby an annular gland 26. Suitable means such arent 37 that also forms' the rear surface of the impeller. In the alternate arrangement of FIG. 2, this surface 37 eX- tends vradially outward lbeyond the inboard end of the stuliing box.

The pump casing 11 is provided with an annular iiange for connecting it to the frame 31 of a driving mechanism which is normally an electric motor. The rear cover 14 of the pump is clamped between the ilange 30 and the frame 31 so as to hx its position relative to the casing 11. The rear cover 14 maybe provided with an annular wear plate 33 that is connected to the cover and positioned within the impeller chamber 15 `adjacent the impeller 18 to absorb the wear of the fluid being pumped.

The inboard end 35 of the stuffing box 23 is positioned adjacent the rear surface 37 ofthe hub 38 of the impeller and they combine `to define a clearance 39 therebetween.

If this clearance is very small, there is -a minimum amount of leakagebehind the impeller and through the clearance. However, in operation there is a certain amount of wear on the parts that form the clearance and the space therebetween tends to increase as the pump is yused and the leakage increases accordingly. When the leakage becomes too great, :the stuing box is moved forward axially i to reduce the clearance.

An` adjusting mechanism `lll Iis providedr to vary the axial position of the stuiling box relative to the impeller 18. This adjusting mechanism 40 could be in any suitlable for-m but as illustrated in the drawing, it comprises a series of arcuately spaced bolts 41 that extend through countersunk holes 42 in a ange 43 on the stufling box 23 and ythreadedly engage aligned holes 44 in the rear cover 14 of the pump. With this mechanism, the clearance 39 between the inboard end 3S of the stuliing box and the rear surface 37 of the hub of the impeller can be reduced by merely tightening up the bolts 41. Y

In the alternate arrangement shown in FIG. 2, the ,wear plate 33 is adjustable axially relative to the impeller. The wear plate 33 forms a clearance 47 with theextended portion of the rear surface 37 of the hub 38 which forms a portion of the rear surface of the impeller. The means for varying the axial position of the Wear plate 33 include a set of bolts 48 that extend through :the arcuately spaced holes 49 in the rear cover 14 and threadedly engage aligned holes 50 in the wear plate 33 and a plurality of set screws 51 that operatively engage spaced apart threaded holes 52 in the rear cover and abut the wear plate 33. When it is desired to move the wear plate closer to the impeller the bolts 48 are loosened and the set screws 51 tightened to move the plate 33 closer to the rear surface 37 of the hub of the impeller and thereby reduce the size of -clearance 47. Then the bolts 48 are tightened to lock as grease conduit 27 are provided for supplying lubricant to the packing material 25.

The impeller 18 has an intake 28- aligned with the inlet 12 and a set of blades 29 that throw liquid radially outward into the discharge volute 13.v In the preferred embodirnent the impeller has a hub 3S that is connected to the shaft 19.

The rear end of the hub has la ilat surface l the wear plate in position.

The rear cover 14 has a projection 53` that extends within an annular ange 54 on the wear plate 33. A suitable sealing material such as an O ring 55 is Positioned between adjacent annular surfaces of the flange and the projection to provide a seal and still permit relative movement between the wear plate and the rear cover.

To further improve the seal of this invention and prolong the life of the stuing box, a bypass conduit is provided that extends yfrom an annular space 56 between the clearance 39 or 47 and the packing 25 in the stuiiing box 23 to a low pressure'area such as the inlet 12 or suction side ofthe pump. In the illustrated arrangement in FIG. 1 any liquid that flows past the clearance 391 into theA space 56 is diverted through the bypass conduit 5S to the lower pressure area at the inlet 12 of the pump. In the embodiment shown in FIG. 2 any liquid that flows past the clearance 47 ilows through the conduit 59 in the impeller to the lower pressure area near the intake of the impeller. Hence the liquid is not forced to ilow past the packing in the stutling box. Furthermore, since the pressure in the conduit is substantially the same #as `that at the inlet of the pump, it thereby reduces the lamount of pressure to which the packing in the stuing box would normally be sub jected.

1n operation, Ias the pump shown in FIG. 1 is started up the liquid is brought into the impeller chamber through the inlet 12 and thrown radially outward by the impeller through the discharge volute 131. However, a small amount of liquid flows behind the impeller 1S and through the clearance 39 between the hub of the impeller andthe in* board end 35 of the stuing box 23'. If the volume of liquid owing through this clearance becomes excessive, the bolts 41 may be tightened down to move the stuing box 23 axially toward the rear surface 37 of the hub 38 of Ithe impeller and thereby reduce the size of the clearance therebetween. This in turn reduces the amount of liquid flowing through the clearance. Any liquid that passes through the clearance liows through the conduit 58 back to the inlet 12 of the pump and hence is again brought into the impeller and thrown radially outward.

The embodiment of FIG. 2 operates in substantially the same Way as the embodiment of FIG. 1 as described above except that the liquid passing the clearance 47 is returned to the low pressure area through conduit 59 in the impeller.

Although but two embodiments of this invention have been illustrated and described, it will be apparent to those skilled in the art that various rnodications and changes can be made therein without departing from the spirit of the invention or the scope of the appended claims.

Having now particularly described and ascertained the nature of my said invention `and the manner in which it is to Ibe performed, I declare that what I claim is:

1. A pump comprising a `casing defining a pumping chamber having an inlet andan outlet, a shaft adapted to be connected to a source of power and extending through said casing into the said chamber, an impeller positioned in said chamber; said impeller having a hub connected to said shaft; a stuing box surrounding said shaft and engag -ing said casing, the inboard end of said stuffing box being positionable adjacent the hub of said impeller to form a clearance therebetween; adjusting means for moving said stung box axially relative said hub tovary the size of said clearance; packing means positioned within said stufng box and spaced from said hub, a recess area formed in said stuing ybox between said inboard end and said packing means and a bypass conduit connecting said recess area to an area of lower pressure.

2. A centrifugal pump comprising -a casing defining a pumping chamber having an `axial inlet in a radially spaced discharge, a shaft adapted to be connected to a source of power and extending through said casing into the said chamber, an impeller positioned in said chamber; said impeller having an intake facing said inlet and a hub connected to said shaft; a stuffing box surrounding said shaft and engaging said casing, the inboard end of said stuing box being positionable adjacent the hub of said impeller to form a clearance therebetween; adjusting means connected to said casing for moving said stuiiing ybox axially toward said hub to vary the size of said clearance, packing means positioned within said stuing box and spaced axially from said hub, a recess Iarea formed in said stufng box between said inboard end and said packing means for collecting fluid passing said clearance and a bypass conduit connecting said recess area to the inlet of said pump.

References Cited in the file of this patent UNITED STATES PATENTS 1,555,023 Prokofieir sept. 29, 1925 1,563,129 Weil Nov. 24, 1925 2,365,058 Crawford Dec. 12, 1944 2,583,777 Jacobsen Ian. 29, 1952 2,707,920 Creasy May 10, 1955 2,858,768 Gaylor et al Nov. 4, 1958 2,900,919 Anderson et a1 Aug. 25, 1959 FOREIGN PATENTS 432,743 Great Britain Aug. 1, 1935

Claims

1. A PUMP COMPRISING A CASING DEFINING A PUMPING CHAMBER HAVING AN INLET AND AN OUTLET, A SHAFT ADAPTED TO BE CONNECTED TO A SOURCE OF POWER AND EXTENDING THROUGH SAID CASING INTO THE SAID CHAMBER, AN IMPELLER POSITIONED IN SAID CHAMBER; SAID IMPELLER HAVING A HUB CONNECTED TO SAID SHAFT; A STUFFING BOX SURROUNDING SAID SHAFT AND ENGAGING SAID CASING, THE INBOARD END OF SAID STUFFING BOX BEING POSITIONABLE ADJACENT THE HUB OF SAID IMPELLER TO FORM A CLEARANCE THEREBETWEEN; ADJUSTABLE MEANS FOR MOVING SAID STUFFING BOX AXIALLY RELATIVE SAID HUB TO VARY THE SIZE OF SAID CLEARANCE; PACKING MEANS POSITIONED WITHIN SAID STUFFING BOX AND SPACED FROM SAID HUB, A RECESS AREA FORMED IN SAID STUFFING BOX BETWEEN SAID INBOARD END AND SAID PACKING MEANS AND A BYPASS CONDUIT CONNECTING SAID RECESS AREA TO AN AREA OF LOWER PRESSURE.