AU2007219209A1

AU2007219209A1 - Pump seal apparatus

Info

Publication number: AU2007219209A1
Application number: AU2007219209A
Authority: AU
Inventors: Denis Michael William Winslow
Original assignee: Winsome Eng Pty Ltd
Current assignee: WINSOME ENGINEERING Pty Ltd
Priority date: 2006-02-20
Filing date: 2007-02-20
Publication date: 2007-08-30
Also published as: WO2007096736A1

Description

WO 2007/096736 PCT/IB2007/000394 -1 "PUMP SEAL APPARATUS" BACKGROUND TO THE INVENTION THIS invention relates to a pump seal apparatus. The invention is particularly but not solely concerned with slurry pumps used in various applications to pump slurries, i.e. fluent suspensions of solid particles in liquid, typically water. In a typical slurry pump, the pump impeller is mounted fast on a shaft which rotates it in a pump casing. The shaft is driven by an external motor and is supported by bearings outside the casing. Given the highly abrasive nature of the slurry and the importance of proper bearing operation, it is important that the bearing assembly be isolated from the slurry. In order to achieve the desired isolation, conventional slurry pumps have sealing arrangements between the pump casing and the bearing housing. A typical sealing arrangement includes a series of packing rings, and possibly also a labyrinth seal, in a stuffing box located between the pump casing and the bearing housing. Conventional seal arrangements of the kind described above have limited effectiveness and may allow leakage of slurry material from the pump casing into the bearing housing. There, the abrasive nature of the slurry can cause rapid bearing wear and a necessity for frequent bearing replacement. Apart from the cost of the actual bearings themselves and the labour involved in replacing them, the pump must be taken off-line. It is an objective of this invention to provide a seal apparatus for slurry pumps which can improve the longevity of the bearings. CONFIRMATION COPY WO 2007/096736 PCT/IB2007/000394 -2 SUMMARY OF THE INVENTION The present invention provides a pump seal apparatus for a pump having a rotatable shaft supported by a bearing assembly in a bearing housing, a pump casing and a pump impeller mounted fast on the shaft for rotation in the casing in order to pump liquid material from the casing, the pump seal apparatus comprising: - a seal housing mountable non-rotatably to the bearing housing at a position between the pump casing and the bearing housing, the seal housing having a radially outer wall with an opening therein at an operatively low level, - a sleeve mountable fast on the shaft partially within the seal housing and between the pump casing and the bearing housing, the sleeve carrying fast thereon a vaned expulsion impeller operative to impel, outwardly against the radially outer wall of the seal housing, liquid material which enters the seal housing from the pump casing, whereby the liquid material is expelled from seal housing through the opening; and - means forming a labyrinth seal between the sleeve and the housing. Preferably, the labyrinth seal is located downstream of the expulsion impeller, i.e. on the bearing assembly side thereof. The labyrinth seal may be defined between a radially inner wall of the seal housing and an annular member fast on the sleeve. The seal apparatus may furthermore comprise a lip seal carried by the annular member and arranged to seal against a surface of the seal housing which is transverse to the shaft. The lip seal may be arranged between the expulsion impeller and the labyrinth seal.

WO 2007/096736 PCT/IB2007/000394 -3 BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 diagrammatically illustrates a centrifugal slurry pump fitted with a seal apparatus according to the invention; Figure 2 shows a diagrammatic enlargement of the area 2 in Figure 1; and Figure 3 shows a cross-section at the line 3-3 in Figure 2. DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The slurry pump 10 seen in Figure 1 has a pump casing 12 with an inlet 14 and an outlet 16. The casing 12 accommodates a pump impeller 18 which is fast on a shaft 20 driven by a motor (not shown) and supported by bearings (not shown) in a bearing housing 22. In use liquid material, in this case slurry, is drawn into the pump casing 12 through the inlet 14 and is expelled therefrom under pressure through the outlet 16 by the action of the rotating pump impeller 18. Between the pump casing 12 and the bearing housing 22 is a stuffing box 24 accommodating a series of packing rings which are provided to prevent slurry from leaking from the pump casing along the shaft and into the bearing housing. A seal apparatus according to the invention is designated by the numeral 26. It includes a seal housing 28 which is bolted to the bearing housing 22 through bolt holes 30, a sleeve 34 on the shaft 20 and an annular member 36 on the sleeve.

WO 2007/096736 PCT/IB2007/000394 -4 The sleeve is sealed with respect to the shaft by an O-ring 38 which allows it to slide on the shaft, and the member 36 is sealed with respect to the sleeve by O-rings 40. At its upstream end, i.e. the end nearest to the pump casing 12, the sleeve carries a radial extension 42 having an inner face 44 formed with circumferentially spaced recesses 46 shaped to form intermediate vanes 48. In use, with the shaft 20 and sleeve 34 rotating, the radial extension 42 acts as an expulsion impeller, rotating in a chamber 49 defined by the seal housing 28, to expel slurry radially from the housing as described below. The radially outer wall 50 of the chamber 49 is formed at a low level with a waste opening 52 in the form of an elongate slot. The slot 52 extends for some distance in the circumferential direction. The annular member 36 is located downstream of the expulsion impeller 42. Its radially outer surface is formed with an annular groove in which the inner end of a lip seal 54 is anchored. The radially outer end of the lip seal, which is made of rubber or other suitable, resiliently flexible material, acts against a transverse, annular wall 56 of the seal housing. Adjacent the lip seal 54 the radially outer surface of the member 36 and a radially inner surface of the seal housing 28 are formed with cooperating grooves defining a labyrinth seal designated generally by the numeral 60. The numeral 56 designates the interior of the bearing housing 22 which accommodates the conventional bearing assembly (not shown) that supports the shaft 20. The interior 56 is charged in the normal way with grease through a grease nipple (not shown). In use, with the shaft 20, sleeve 34 and expulsion impeller 42 rotating, slurry which bypasses the stuffing box and enters the chamber 49 is thrown outwardly against the outer wall of the chamber by the expulsion impeller 42.

WO 2007/096736 PCT/IB2007/000394 -5 The slurry migrates about the inner surface of the wall and is expelled to waste through the slot 52. The lip seal 54, which acts against the wall 56 of the seal housing as a result of the prevailing pressure, acts to prevent slurry which bypasses the expulsion impeller 42 from reaching the interior 56 of the bearing housing. Slurry arrested by the lip seal flows to waste through a waste opening in the form of an elongate, circumferentially extending slot 57 similar to the slot 52. Slurry which manages to bypass the lip seal is arrested by the labyrinth seal 60. In initial experimentation it has been found that the illustrated apparatus, in which the expulsion impeller, labyrinth seal and lip seal act in series with one another in what is effectively a compact cartridge that can be retro fitted to an existing slurry pump, is effective in reducing the amount of slurry that can reach the bearings of the bearing assembly in the bearing housing, and that this in turn can prolong the life the bearings. In the embodiment described above, the housing 28 is bolted to the bearing housing 22. In an alternative configuration, the housing 28 could be pressed into position with the provision of an O-ring seal 80, as also illustrated in Figure 2.

Claims

1. A pump seal apparatus for a pump which has a rotatable shaft supported by a bearing assembly located in a bearing housing, a pump casing and a pump impeller mounted fast on the shaft for rotation in the pump casing in order to pump liquid material from the casing, the pump seal apparatus comprising: - a seal housing mountable non-rotatably to the bearing housing at a position between the pump casing and the bearing housing, the seal housing defining a chamber arranged to receive liquid material which enters the seal housing from the pump casing, - a waste outlet from the chamber at an operatively low level, - a sleeve mountable fast on the shaft at least partially within the seal housing and between the pump casing and the bearing housing, the sleeve carrying fast thereon a vaned expulsion impeller rotatable in the chamber to expel liquid material received by the chamber through the waste outlet, and - a labyrinth seal between the sleeve and the seal housing.

2. A pump seal apparatus according to claim 1 wherein the expulsion impeller is provided by a radial extension of the sleeve, the extension having an inner face, facing into the chamber, which is formed with circumferentially spaced recesses defining intermediate vanes between the recesses.

3. A pump seal apparatus according to either one of the preceding claims wherein the waste outlet from the chamber is in the form of an elongate, circumferentially extending slot. WO 2007/096736 PCT/IB2007/000394 -7

4. A pump seal apparatus according to any one of the preceding claims wherein the labyrinth seal is located downstream of the expulsion impeller, i.e. between the expulsion impeller and the bearing assembly in use.

5. A pump seal apparatus according to claim 4 wherein the labyrinth seal is defined between a radially inner surface of the seal housing and a radially outer surface of an annular member fast on the sleeve.

6. A pump seal apparatus according to claim 5 and comprising a lip seal carried by the annular member and arranged to seal against a surface of the seal housing which is transverse to the shaft.

7. A pump seal apparatus according to claim 6 wherein the lip seal is arranged between the expulsion impeller and the labyrinth seal.

8. A pump seal apparatus according to claim 7 and comprising a waste opening in a wall of the seal housing to exhaust liquid material arrested by the lip seal.

9. A pump seal apparatus according to claim 8 wherein the waste opening is in the form of an elongate, circumferentially extending slot at an operatively low level in the wall of the seal housing. WO 2007/096736 PCT/IB2007/000394 -8

10. A pump seal apparatus according to any one of the preceding claims wherein the seal housing is formed with bolt holes through which bolts can be passed to mount the seal housing to the bearing housing.