WO2018049439A1

WO2018049439A1 - Volute liner arrangement

Info

Publication number: WO2018049439A1
Application number: PCT/ZA2017/050062
Authority: WO
Inventors: Siegfried Geldenhuys
Original assignee: Mechanical Engineering Transcendent Technology Pty Ltd
Current assignee: Mechanical Engineering Transcendent Technology Pty Ltd
Priority date: 2016-09-12
Filing date: 2017-09-12
Publication date: 2018-03-15
Anticipated expiration: 2019-03-12

Abstract

A volute liner for a centrifugal pump which liner has a body of integral construction which extends around a central axis with a radial outer surface and a radial inner surface which is concave in cross section facing the central axis.

Description

VOLUTE LINER ARRANGEMENT BACKGROUND OF THE INVENTION

[0001] This invention relates to a centrifugal pump and to the construction of a volute liner for a centrifugal pump. PRIOR ART

[0002] Figure 1 of the accompanying drawings illustrates from one side a prior art centrifugal pump 10 while Figure 2 illustrates the pump 10 of Figure 1 in cross section taken on a line 2-2.

[0003] The pump 10 includes a casing 12 formed from two casing sections 14 and 16 respectively which have opposed peripherally located mating flanges 18 and 20 respectively. [0004] A volute liner 26 which is made from a natural or synthetic elastic polymer is located inside a chamber 30 formed by the casing sections 14 and 16. The liner 26 is made in two components 32 and 34 respectively. The component 32 fits snugly inside the casing section 14 and the component 34, similarly, is snugly engaged with an inner surface of the casing section 16. The liner components 32 and 34 have respective peripheral flanges 36 and 38 which, in an assembled condition, are located abutting one another between the flanges 18 and 20 of the casing sections. An impeller 40 is positioned inside the volute liner 26. Slurry to be pumped flows axially to the impeller 40 through an inlet 44. The impeller 40 is rotatable by means of a drive shaft, not shown, which is connected to a drive formation 46 accessible through an opening 50 defined at least partly by the liner component 34 and the surrounding casing section 16. [0005] The liner 26 thus has a split line 54 at a radial junction of the abutting surfaces of the flanges 36 and 38. The split line 54 is vulnerable to concentrated or localized wear during operation of the pump 10. This is particularly so due to the proximity of the radial split line 54 to a peripheral surface 56 of the impeller 40. In practice it is difficult to align the liner components 32 and 34 so that there is a continuous interface on an inner surface of the liner at the radial split line. Any misalignment between the liner components 32, 34 at the inner surface of the radial split line 54 produces a step or a gap which results in undue wear and premature failure of the liner.

[0006] The handling of the two liner components 32, 34 and the fitting of these components into the casing sections 14 and 16 are easy tasks and the difficulty thereof becomes pronounced with a large pump. The liner 26 is made from an elastomeric material which has elastic characteristics. Thus, generally, a liner cannot support its own weight and therefore cannot retain its fundamental shape when handled. These aspects lead to shortened service intervals of this type of centrifugal pump with an increase in operating costs. [0007] An object of the present invention is to address the aforementioned factors.

SUMMARY OF THE INVENTION

[0008] The invention provides a volute liner for a volute of a centrifugal pump, the liner comprising an integral body which is radially spaced from and which extends circumferentially around a central axis, first and second axially spaced apart side surfaces a radial outer surface and a radial inner surface, and wherein a portion of the radial inner surface which, in any plane which lies on the central axis, is concave in cross section facing the central axis. [0009] Preferably a plane which is at a right angle to the central axis intersects a central region of the concave inner surface along a path which, moving in one circumferential direction around the central axis, is radially spaced from the central axis by an increasing distance.

[0010] Preferably the arrangement is such that said path, at a first end, is spaced from the central axis by a minimum distance and, at a second end, is spaced from the central axis by a maximum distance, and the body includes an outlet from the concave inner surface between said first end and said second end.

[0011] In one embodiment, said first side surface of the body defines a first rim, which is perpendicular to said central axis and which encloses a first circular aperture which is centered on said central axis and said second side surface of the body defines a second rim which is perpendicular to said central axis and which defines a second circular aperture which is centered on said central axis.

[0012] The invention also extends to a centrifugal pump which includes a casing, a back plate which is engageabie with the casing, the casing and engaged back plate thereby forming an impeller chamber, and a volute liner of the aforementioned kind which is in the impeller chamber and an impeller operatively mounted inside the impeller chamber with its periphery bounded by the body of the liner.

[0013] The invention also relates to a centrifugal pump which includes a casing, a back plate which is engageabie with the casing thereby to form an impeller chamber for an impeller, a volute liner, in the impeller chamber, comprising an integral body with a concave inner surface which faces towards a central axis and which includes an outlet at a periphery of the body, a first side liner which includes a centrally located axiaily directed inlet formation which is located in the casing, and a second side liner, located between the impeller and the back plate, and wherein the volute liner forms a first circular formation with which the first side liner is sealingly engaged and a second circular formation with which the second side liner is sealingly engaged.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention is further described by way of example with reference to the accompanying drawings in which :

Figure 3 is an exploded perspective view of a centrifugal pump with a volute liner according to the invention,

Figure 4 is an end view of a volute liner according to the invention,

Figure 5 is a side view of the volute liner of Figure 4,

Figure 6 shows the volute liner of Figure 4 in cross section taken on a line 6-6 in Figure 4, Figure 7 shows the volute liner of Figure 4 in the direction of an arrow marked 7 in Figure 4, Figure 8 is a cross sectional view on an enlarged scale illustrating a portion of the volute liner enclosed in a circle marked 8 in Figure 6,

Figure 9 is a view in cross section of the volute liner on a line 9 - 9 in Figure 4, and

Figure 10 is a view in cross section of an upper portion of the centrifugal pump shown in Figure

3 in an assembled condition. DESCRIPTION OF PREFERRED EMBODIMENT

[0015] Figure 3 of the accompanying drawings illustrates in perspective components of a centrifugal pump 100 according to the invention. The pump 100 includes a casing 02, a first side liner 104, a volute liner 106, an impeller 108, a back plate 110 and a motorised drive arrangement 120.

[0016] The casing 102 is of complex form. It includes an axially directed inlet 122, a shaped body 124 which, on an inner surface, is generally concave (see Figure 10), a peripheral flange structure 26 and a U-shaped outlet formation 130.

[0017] The first side liner 104 is of circular form and includes a machined rim 134 and a centrally positioned tubular formation 36 which, in use, is aligned with the axial inlet 122.

[0018] The impeller 108 has a front shroud 140, a rear shroud 142 and a plurality of primary vanes 144 positioned between opposing surfaces of the front shroud 140 and the rear shroud 142. An inlet 150 through the front shroud 140 to the primary vanes 144 is axially aligned with the tubular formation 136. [0019] The back plate 1 10 has an outer portion 156 which, as is shown in Figure 10, is engageable with the flange structure 126 of the casing 102. The back plate 1 0 has an inner second side liner 158 with a machined rim 160 and a centrally positioned and axially directed drive formation 62.

[0020] The drive arrangement 120 includes a pedestal 170 to which is mounted an electric motor 172. A drive shaft 174 of the motor, centred on an axis of rotation 176, can extend through the drive formation 162 and can then be engaged with a coupling structure 80 on an outer side of the rear shroud 142 - see Figure 10. The drive arrangement 120 is mechanically fixed to the casing 02 and the back plate 1 10 using appropriate fasteners.

[0021] Figures 4 to 9 are different views of different parts of the volute liner 106. [0022] The volute liner 106 includes a body 190 which is moulded from a wear-resistant natural or synthetic elastomeric material. The body 90 is integrally formed. This constitutes a primary benefit of the invention. The body 190 has a first outer side surface 192, a second outer side surface 194, a radial outermost surface 96 and a radial concave inner surface 198, see Figures 6 and 8. [0023] The radial outermost surface 196 has a width L (see Figure 8) extending between the first and second outer side surfaces 92 and 194. The surfaces 192 and 194 are parallel to each other and are at a right angle to the central axis of rotation 76. A substantial portion 202 of the outer surface 196 has a width W, is flat, and is generally parallel to the central axis 176. L is more than half W i.e. L > W/2. The length W is flanked by radially inwardly extending sections 204 and 206 respectively which respectively terminate in a first mating surface 208 and a second mating surface 210.

[0024] The mating surface 208 intersects the first outer side surface 192 and these surfaces define an angle 214, between them, which is greater than 90°. The second mating surface 210 intersects the second outer side surface 194 and these surfaces define an included angle 216 which is greater than 90°, between them. [0025] The radial inner surface 198 has a first inner edge surface 220 adjacent the first outer side surface 192, a second inner edge surface 222, which is aligned with the surface 220, adjacent the second outer side surface 194, and a concave inner surface 228.

[0026] The first inner edge surface 220 forms a rim 220A for a first circular aperture 230 which is centred on the axis of rotation 176. The second inner edge surface 222 forms a rim 222A for a second circular aperture 232, with the same diameter as the first circular aperture 230, which is also centred on the axis of rotation 176. The first and second rims 220A and 222A are in line, and are parallel to the central axis of rotation 176. This is the case in one embodiment. However the rims 220A and 222A may taper outwardly (upwardly in Figure 8) by up to 2.5 degrees to assist in fitting (assembly) and removal (disassembly) particularly in large pumps.

[0027] The concave inner surface 228 has a central region 240 which is radially spaced from the axis of rotation 176 by a variable distance 244. Figure 4 illustrates that, proceeding in a counterclockwise direction around the central axis of rotation 176, the distance 244 increases from a minimum value 244A to a maximum value 244B. Thus the radially outer surface 196 follows a spiral path through an angle of rotation which is greater than 270°. At the location of the maximum radial spacing 244B the outer surface 196 has a flat surface extension 248 which is tangential relative to an adjacent portion of the outer surface 196.

[0028] The surface 248 is on one side of an outlet 250. The surface 248 is opposed by a surface 252. Transversely thereto are a curved wall portion 256 and an opposing flat wall portion 258 (Figure 9). A centre line 260 of the outlet extends at a right angle to the central axis of rotation 176 (Figure 4). [0029] The spiral shape of the outer surface 196 which is between the minimum radial distance 244A and the maximum radial distance 244B means that the depth of the concave inner surface 228 relative to the aligned first and second inner edge surfaces 220 and 222 increases - this is evident from Figure 6 which shows the volute liner 106 in cross section. An upper portion of the volute liner 106 has a depth of the concave inner surface marked 270A while a lower portion of the volute liner has a depth of the concave inner surface marked 270B, and 270B > 270A.

[0030] The radial outer surface 196 is formed with a number of keying formations 284 at spaced intervals - these are in the form of square projections integral with the remainder of the body 190.

[0031] The installation of the volute liner 106 and the assembly of the pump 100 are greatly facilitated due to the integral construction of the body 190 of the volute liner, by the design of the casing 102, and by the use of the first side liner 104 and of the back plate 1 10 which incorporates the second side liner 156. [0032] Figure 10 shows that the casing 102 forms an enclosure for the volute liner 106 with the arrangement being such that the volute liner 106 can be inserted directly into the casing 102 by moving the volute liner 06 axially i.e. parallel to the central axis of rotation 176. The machined rim 134 of the first side liner 104 fits directly into the second circular aperture 232. The inclination of the second mating surface 210 to the axis of rotation 176 means that a wedging action is achieved as the volute liner 106 enters a chamber formed by the interior of the casing 102. Appropriate fasteners 300 are used to draw the volute liner into sealing engagement with the first side liner 104. [0033] The flat outer surface portion 202 is such that it extends against an opposing surface 302 of the casing 102 up to an edge 126A of the flange structure 126. At this point the impeller 108 is inserted into an interior space of the volute liner 106 which is surrounded by the body 124 of the casing 102. Prior thereto the back plate 1 10, which carries the second side liner 158, is attached to the drive arrangement 120. The drive shaft 174 is engaged with the coupling structure on the rear shroud 142 of the impeller 108. With the drive arrangement 20 correctly positioned relative to the casing 102 the back plate 110 is then fixed to the flange structure 126 using fasteners 306. During the fastening process the second side liner 158 is drawn into the first circular aperture 230 and its machined rim 160 is engaged in sealing contact with the first outer side surface 192 of the volute liner 106.

[0034] The body 190 has an intervening section 310 between the flat section or portion 202 and the second mating surface 210 which has a convex shape which is of complementary form to the concave portion 228 of the concave inner surface. The thickness of this intervening section 310 does not alter materially proceeding in a circumferential direction around the axis of rotation.

[0035] The flat face of the portion 202 substantially facilitates location of the liner 106 into the casing 102. It is possible though to dome this portion outwards, in cross section. As the liner 106 is made from a flexible material it is possible to insert the liner 106 into the casing 102 despite the doming, provided the degree of doming (curvature) is not so pronounced as to interfere with the installation process.

[0036] The keying formations 284 help to ensure that the liner 106 is correctly positioned inside the casing 102 inside the installation process. [0037] In operation of the pump 100 material to be pumped is directed via the axial inlet 122 towards the impeller 108 which is driven by the drive arrangement 120 and slurry under pressure and at the appropriate rate is directed through the outlet 250.

[0038] As the volute liner 106 has a single piece, integral construction the radial split associated with two-part liners of the kind shown in Figure 2 is eliminated and wear problems linked to the split are obviated. The casing 102, the first side liner 104 and the back plate 110, with its attendant second side liner 158, are designed to work in a complementary fashion with the volute liner 106 and, as a consequence, assembly of the pump 100 is substantially facilitated. This means that when repair or maintenance is required the task associated with disassembly and the replacement of a worn liner with a fresh liner is reduced.

Claims

1. A volute liner (106) for a volute of a centrifugal pump, the volute liner (106) comprising an integral body (190) which is radially spaced from and which extends circumferentially around a central axis (176), first and second axially spaced apart side surfaces (192, 194), a radial outer surface (196) and a radial inner surface (198), and wherein a portion (228) of the radial inner surface (198), in any plane which lies on the central axis (176), is concave in cross section facing the central axis.

2. A liner according to claim 1 wherein a plane which is at a right angle to the central axis(176) intersects a central region of the concave inner surface (228) along a path which, moving in one circumferential direction around the central axis, is radially spaced from the central axis by an increasing distance (244).

3. A liner according to claim 2 wherein said path, at a first end, is spaced from the central axis (176) by a minimum distance (244A) and, at a second end, is spaced from the central axis ( 176) by a maximum distance (244B) and wherein the body (190) includes an outlet (250) from the concave inner surface (228) between said first end and said second end.

4. A liner according to claim 3 wherein the outlet (250) has an outer surface (248) which extends tangentially from an adjacent portion of said outer surface (196) of the body (190) at said second end.

5. A liner according to claim 1 wherein the body (190) on said outer surface (196) has a plurality of spaced apart keying formations (284). A liner according to claim 1 wherein said first side surface (192) of the body defines a first rim (220A), which encloses a first circular aperture (230) which is centered on said central axis (176) and said second side surface ( 194) of the body defines a second rim which encloses a second circular aperture (232) which is centered on said central axis (176).

A liner according to claim 6 wherein said concave inner surface (228) is flanked on opposed sides by first and second spaced apart inner edge surfaces (220, 222) which respectively bound said first aperture (230) and said second aperture (232).

A liner according to claim 1 wherein said radial outer surface (196) of the body, in cross section, between said first and second axially spaced apart side surfaces (192, 194) has a flat section (202) with a length (W) which is greater than half the axial spacing (L) between said first and second axially spaced apart side surfaces (192, 194).

A liner according to claim 8 wherein said radial outer surface (196) of the body has a first mating surface (208) adjacent said first side surface (192) which, in cross section, is inclined to said central axis (176) and wherein said first side surface (192) and said first mating surface (208) form an included angle (214) which is greater than 90° .

A liner according to claim 9 wherein said radial outer surface (196) of the body includes a second mating surface (210) adjacent said second side surface (194) which, in cross section, is inclined to said central axis (176) and wherein said second mating surface (210) and said second side surface (194) form a second included angle (216) which is greater than 90°. A liner according to claim 10 wherein the body ( 190) has an intervening section (310) between the flat section (202) and the second mating surface (210) which has a convex shape and which is of complementary shape to the concave inner surface (208) and wherein the intervening section (310) has a substantially constant thickness.

A centrifugal pump which includes a casing (102), a back plate (1 10) which is engageable with the casing (102), the casing and engaged back plate thereby forming an impeller chamber, and a volute liner (106) according to claim 6 which is in the impeller chamber and an impeller (108) operatively mounted inside the impeller chamber with its periphery bounded by the body (190) of the liner.

A centrifugal pump according to claim 12 which includes a first side liner (104), inside the casing (102), which is sealingly engaged with the first circular aperture (230) and a second side liner ( 158) between the impeller (108) and the back plate (1 10) which is sealingly engaged with the second circular aperture (232).

A centrifugal pump which includes a casing (102), a back plate (1 10) which is engageable with the casing (102) thereby to form an impeller chamber for an impeller (108), a volute liner (106) comprising an integral body (190) with a concave inner surface (228) which faces towards a central axis (176) and which includes an outlet (250) at a periphery of the body, a first side liner (104) which includes a centrally located axially directed inlet formation (136) which is located in the casing (102), a second side liner (158), located between the impeller (108) and the back plate (1 10), the volute liner (106) including forming a first circular formation (230) with which the first side liner (104) is sealingly engaged and, a second circular formation (232) with which the second side liner (158) is sealingly engaged.