WO2018053560A1

WO2018053560A1 - Dry gland stuffing box

Info

Publication number: WO2018053560A1
Application number: PCT/ZA2017/050068
Authority: WO
Inventors: Siegfried Geldenhuys
Original assignee: Mechanical Engineering Transcendent Technology Pty Ltd
Current assignee: Mechanical Engineering Transcendent Technology Pty Ltd
Priority date: 2016-09-15
Filing date: 2017-09-15
Publication date: 2018-03-22
Anticipated expiration: 2019-03-15

Abstract

A slurry pump with a drive shaft, an expeller mounted to the drive shaft, a stuffing box on a shaft sleeve and spaced apart seals on the shaft sleeve with an annular cylindrical gap around the shaft sleeve between the seals.

Description

DRY GLAND STUFFING BOX BACKGROUND OF THE INVENTION

[0001] This invention relates to a sealing arrangement for the drive shaft of an end suction slurry pump. SUMMARY OF THE I NVENTION

[0002] The invention provides an end suction slurry pump which includes a drive shaft for driving an impeller and an impeller which is mounted to the drive shaft, wherein the expeller includes a body with a central bore, a machined annular face on one side of the body surrounding the bore, and a plurality of vanes which extend radially on a radial outer side of the machined annular face, a stuffing box arrangement on a shaft sleeve, wherein the expeller is positioned inside a chamber between the stuffing box arrangement and the impeller, and wherein, in operation of the pump, the expeller creates a fluid ring of annular shape around the shaft which prevents the ingress of slurry into the stuffing box arrangement.

[0003] The function of the machined annular face is such as to promote the development of vortices which arise upon rotation of the shaft, thereby to establish a region around the shaft which encloses the machined annular face which is at atmospheric pressure.

[0004] The invention further provides that a lantern ring is engaged with the shaft and is positioned between the stuffing box arrangement and the impeller. The lantern ring is preferably made from an ultra-hard material such as a chrome iron alloy and preferably has a hardness in excess of 500 Brinel. [0005] Preferably the lantern ring includes at least one stationary seal on a radial outer surface. On a radial inner surface of the lantern ring which opposes a rotating surface, e.g. a rotating surface of the shaft but, preferably, a rotating surface of the shaft sleeve which supports the shaft, the lantern ring may have one seal, but preferably has two seals which are directly brought into engagement with the rotating surface. The design is such that, upon rotation of the surface, the seals wear slightly and in this way a small annular cylindrical gap is established around the shaft sleeve bounded by the spaced apart seals. When the pump is stopped and is inoperative, slurry under static conditions enters the gap and becomes compacted, and thus provides a solid seal which is bounded by these seals. BRIEF DESCRI PTION OF THE DRAWINGS

[0006] The invention is further described by way of example with reference to the accompanying drawings in which :

Figure 1 is a side view in section of a slurry pump which includes a seal arrangement according to the invention,

Figure 2 is a perspective illustration of an expeller included in the slurry pump of Figure 1 , and Figure 3 illustrates on an enlarged scale and in cross section details of a lantern ring which is engaged with a shaft sleeve and which is used to promote a sealing action for the shaft.

DESCRIPTION OF PREFERRED EMBODIMENT [0007] Figure 1 of the accompanying drawings illustrates from one side and in cross section an end suction slurry pump 10. The pump 10 includes an impeller 12 which is mounted for rotatable drive to a shaft 14. The impeller 12 is enclosed in a housing 16 which includes an axially directed slurry inlet 18.

[0008] A stuffing box arrangement 20 (see as well Figure 3) abuts a lantern ring 22. The stuffing box arrangement 20 and the lantern ring 22 are mounted to a radial outer surface 30A of a shaft sleeve 30 which provides rotatable support for the shaft 14.

[0009] An expeller 34 is mounted to the shaft sleeve 30 and is rotatable together with the shaft sleeve 30. The expeller 34 (see Figure 2) includes a circular, disc-like body 40 with a central bore 42 which is engaged with the sleeve 30. The bore 42 is surrounded by a circular wall 44 which forms a circular enclosure 46 which is centred on the bore 42. A rim 48 of the wall is machined and forms a smooth annular surface 48A around the bore 42. A plurality of vanes 50 extend radially from a radial outer surface 48B of the wall 44.

[0010] In use of the pump 10 the expeller 34 is rotated by the shaft 14. The function of the expeller 34 is to prevent the ingress of slurry into the shaft seal region i.e. the region of the stuffing box 20 and the lantern ring 22. When the expeller 34 is rotated the vanes 50 move through the slurry which accumulates under static conditions in a chamber 52 in which the vanes are located. The rotating vanes 50 lead to the development of vortices in the slurry in the chamber 52, and the slurry in the chamber 52 is expelled in a manner which leads to the establishment of an annular pocket of air at atmospheric pressure adjacent the surface 48A around the shaft 14 which, in turn, is surrounded by a fluid ring of the slurry. The position of the interface between the air and the fluid ring is dependent on a number of factors but, in particular, on the density of the slurry and on the height of a slurry head connected to the inlet 18. [001 1] It has been found that the machined surface 48A of the rim 48, which is closely spaced from a surface 56 of adjacent cover structure 58, prevents a so-called "bridging action" in which slurry from the chamber 52 could enter into the region of the enclosure 46 of the expeller 34. An effective isolating action is thereby established by the expeller 34. An additional sealing action is provided by the lantern ring 22.

[0012] The lantern ring 22 is made from an ultra-hard material such as a chrome-iron alloy and preferably has a hardness in excess of 500 Brinel. On an external surface 60 the lantern ring 22 has a groove 62 in which is located an O-ring seal 64 - see Figure 3. The seal 64 provides a stationary seal between the lantern ring 22 and an opposing surface 58A of the cover structure 58. On a radial inner surface 70, which abuts the outer surface 30A of the shaft sleeve 30, the lantern ring 22 is formed with at least one groove, but preferably two grooves 72, 74 which respectively accommodate slightly spaced apart O-ring seals 72A and 74A.

[0013] An additional O-ring seal 76 is provided on the radial inner surface 70 close to the stuffing box arrangement 20. A fluid passage 80 extends through the structure 58 and terminates in a radial outer groove 82 in the outer surface 60 of the lantern ring 22. An inner annular groove 86 which faces onto the outer surface 30A of the sleeve 30 is positioned between the O-rings 72A and 74A on the one hand, and the O-ring 76 on the other hand. A number of fluid passages 88, (only one is shown), place the grooves 82 and 86 in communication with one another. [0014] The lantern ring 22, due to its ultra-high hardness, is capable of resisting abrasive conditions. The O-rings 72A and 74A are designed to abut, initially, closely against the outer surface 30A of the shaft sleeve 30 so that upon operation of the pump 10, when the sleeve 30 rotates, the O-rings 72A, 74A are worn to a slight extent. This is a design feature. The action is such that when the pump 10 is stationary (inoperative) slurry 90 under pressure, coming from a suction side of a slurry tank can flow as indicated by an arrow 92 to a small extent and enter a cylindrical annular gap 96 between the outer surface 30A of the sleeve 30 and an opposing portion of the inner surface 70 of the lantern ring 22 between the O-rings 72A and 74A. The slurry compacts and sets in the gap 96 and thereby provides a solid seal which prevents further slurry from passing towards the stuffing box arrangement 20.

Claims

1 . An end suction slurry pump (10) which includes a drive shaft (14) for driving an impeller (12) and an expeller which is mounted to the drive shaft (14), wherein the expeller (34) includes a body (40) with a central bore (42), and a machined annular face (48A) on one side of the body (40) surrounding the bore (42) and a plurality of vanes (50) which extend radially on a radial outer side of the machined annular face (48A), a stuffing box arrangement (20) on a shaft sleeve (30), wherein the expeller (34) is positioned inside a chamber (52) which is between the stuffing box arrangement (20) and the impeller (12), and wherein, in operation of the pump (10), the expeller (34) creates a fluid ring of annular shape around the shaft (14) which prevents the ingress of slurry into the stuffing box arrangement (20).

2. An end suction slurry pump (10) according to claim 1 wherein the machined annular face (48A) promotes the development of vortices in the chamber (52) which arise upon rotation of the shaft (14), thereby to establish a region around the shaft (14), adjacent the machined annular face (48A), which is at atmospheric pressure.

3. An end suction slurry pump (10) according to claim 2 which includes a lantern ring (22) which is engaged with the shaft (14) and which is positioned between the stuffing box arrangement (20) and the impeller (12).

4. An end suction slurry pump (10) according to claim 3 wherein the lantern ring (22) has a hardness in excess of 500 Brinel.

5. An end suction slurry pump (10) according to claim 3 or 4 which includes at least one stationary seal (64) on a radial outer surface (60) of the lantern ring (22) and, on a radial inner surface (70) of the lantern ring (22) which opposes a rotating outer surface (30A) of the shaft sleeve (30) which supports the shaft (14), the lantern ring (22) includes at least one seal (72A, 74A) which is directly brought into engagement with the rotating outer surface (30A).

6. An end suction slurry pump (10) according to claim 3 or 4 which includes two seals (72A, 74A) on a rotating outer surface (30A) of the shaft sleeve (30), configured so that upon rotation of the shaft sleeve (30), the seals (72A, 74A) wear slightly and a small annular cylindrical gap (96) is established around said outer surface (30A) bounded by the spaced apart seals and, when the pump (10) is inoperative, slurry under static conditions enters the gap (96) and becomes compacted, and thus provides a solid seal which is bounded by the seals (72A, 74A).

7. An end suction slurry pump (10) which includes a drive shaft (14) for driving an impeller (12) and an expeller which is mounted to the drive shaft (14), wherein the expeller (34) includes a body (40) with a central bore (42), and a machined annular face (48A) on one side of the body (40) surrounding the bore (42) and a plurality of vanes (50) which extend radially on a radial outer side of the machined annular face (48A), a stuffing box arrangement (20) on a shaft sleeve (30), wherein the expeller (34) is positioned inside a chamber (52) which is between the stuffing box arrangement (20) and the impeller (12) and two seals (72A, 74A) on an outer surface (30A) of the shaft sleeve (30) and wherein an annular cylindrical gap (96) extends around said outer surface (30A) bounded by the spaced apart seals (72A, 74A).