GB2173256A

GB2173256A - Centrifugal pump

Info

Publication number: GB2173256A
Application number: GB08508678A
Authority: GB
Inventors: Ernest William Potter
Original assignee: EWPUMP Ltd
Current assignee: EWPUMP Ltd
Priority date: 1985-04-03
Filing date: 1985-04-03
Publication date: 1986-10-08
Also published as: GB8508678D0

Abstract

A centrifugal pump has a part- spherical, pressed steel casing 1 and an impeller 11 whose axis is eccentric to the casing; each blade 17 of the impeller 11 is curved in diametrical section, the convex side facing forwards with respect to the direction of rotation and the chord of the curve being inclined rearwards with respect to the direction of rotation. The inlet ends of the blades 17 have a 45 DEG chamfer connecting their roots and the axially facing surfaces so that the clearance between adjacent blades 17 at the inlet end is not substantially less than the internal diameter of the inlet. A tangential outlet 7 starts in the part of the casing 1 which is furthest from the impeller axis. In this way, a non-choking pump can be provided which can pump for instance pig slurry from cess pits. <IMAGE>

Description

SPECIFICATION Centrifugal pump The Invention The present invention provides centrifugal pumps as set forth in Claim 1, 7 or 14. The remaining Claims set forth preferred features of the invention.

The centrifugal pump of the present invention can be arranged to be non-jamming, being capable of pumping slurries containing rags and paper-for instance, it can pump pig slurry from a cess pit without choking. In particular, this can be achieved by having the clearance between the blades at the inlet end, i.e. at the entry eye, greater than the diameter of the suction inlet.

The pump can be fabricated without great expense from light section material due to the contouring of the casing and of the blades.

For instance, the blade thickness can be less than 10% of the blade radial length; specifically a blade thickness of 3 mm can be used for a 50 mm unit and a blade thickness of 5.5 mm can be used for a 150 mm or 200 mm unit (the size of the unit being the maximum internal diameter of the casing). Specifically in relation to the blades, a 5.5 mm blade could be used for a length (root to tip) of about 100 mm.

By using a casing whose inner periphery is of a simple circular section and an eccentrically-mounted impeller, non-cast components can be used, making up the pump by simple fabrication from e.g. pressed mild steel; nonetheless the gap between the impeller and the casing widens like an involute.

The Drawings The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a centrifugal pump of the invention, with the front suction cover removed; Figure 2 is a view showing the impeller in elevation but the casing in section along the line ll-ll in Fig. 3; and Figure 3 is an end view looking in the direction of the arrow Ill in Fig. 1.

The pump has a casing 1 which is a steel pressing and is of substantially part-spherical shape, being curved in axial and in diametrical direction at the same radius. The casing 1 carries a bearing housng 2 at one end, and at the other end carries a front suction cover 3 which is held by e.g. dowels 4 and quickrelease nuts 5; the cover 3 in turn carries a suction inlet 6 which is coaxial with the bearing housing 2. The axis of the bearing housing 2 and inlet 6 is eccentric to that of the casing 1, as described further below. There is a tangential outlet 7 adjacent the part of the casing which is furthest from the inlet axis; specifically the outlet 7 begins at 8, i.e. at the part of the casing 1 which is furthest from the axis of the inlet 6. The outlet 7 is a tube whose lower end has been suitably curved.A fillet 10 is welded into the casing 1 at the end of the outlet opening, to act as a cut water point. It projects into the interior of the casing 1 and terminates just short of an impeller 11.

A shaft 12 is mounted by bearings 13 (shown in part) in the bearing housing 2, protected by seals 14. The shaft 12 is coaxial with the inlet 6. To form the impeller 11, a boss 15 is welded to a back carrying plate 16. The boss 15 is then welded to the end part of the shaft 12. Light gauge blades 17 are welded to the boss 14 and back plate 15, forming an overhung impeller. Though four blades 17 are shown, there may for instance be just three blades 17. Each blade 17 is curved in diametrical section (see Fig. 3), the convex side facing forwards with respect to the direction of rotation (see the arrow in Fig.

3), the chord 18 being inclined rearwards with respect to the direction of rotation and being at roughly 90" to the radius at the root of the blade 17. The curve of the blade 17 is circular, with the radius of the circle roughly equal to three quarters of the length of the chord 18.

The radially outer edges of the blades 17 are substantially rectilinear and parallel to the impeller axis. The inner ends of the blades 17 have a substantially 45" chamfer connecting their roots and their axially facing surfaces, as can be seen in Figs. 1 and 2. In this way, the clearance between adjacent blades 17 at the inlet end of the impeller is not substantially less than the internal diameter of the inlet 6.

The blade tips are chamfered on all their radially outer edges, as shown in Fig. 3. The front edges of the blades 17 (that edge nearest the inlet 6) are at right angles to the impeller axis, and pass close to the front suction cover 3.

As is apparent in Fig. 3, the eccentricity of the impeller 11 forms an involute between the casing 1 and the tips of the blades 17, terminated by the cut water fillet 10. Though not shown, the outlet 7 could be of greater diameter, equal to the internal length of the casing 1 or coincident with and equal to the axial length of the blades 17.

The pump illustrated can be fabricated from mild steel which has been formed by pressing.

Any suitable arrangement can be provided for connecting pipes to the inlet 6 or outlet 7.

Fig. 1 shows a standard connector on the outlet 7 and a one-way ball valve 19.

1. A centrifugal pump comprising: a casing whose inner periphery is substantially circular in diametrical section; an impeller mounted for rotation about an axis which is eccentric to the casing; and

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Centrifugal pump The Invention The present invention provides centrifugal pumps as set forth in Claim 1, 7 or 14. The remaining Claims set forth preferred features of the invention. The centrifugal pump of the present invention can be arranged to be non-jamming, being capable of pumping slurries containing rags and paper-for instance, it can pump pig slurry from a cess pit without choking. In particular, this can be achieved by having the clearance between the blades at the inlet end, i.e. at the entry eye, greater than the diameter of the suction inlet. The pump can be fabricated without great expense from light section material due to the contouring of the casing and of the blades. For instance, the blade thickness can be less than 10% of the blade radial length; specifically a blade thickness of 3 mm can be used for a 50 mm unit and a blade thickness of 5.5 mm can be used for a 150 mm or 200 mm unit (the size of the unit being the maximum internal diameter of the casing). Specifically in relation to the blades, a 5.5 mm blade could be used for a length (root to tip) of about 100 mm. By using a casing whose inner periphery is of a simple circular section and an eccentrically-mounted impeller, non-cast components can be used, making up the pump by simple fabrication from e.g. pressed mild steel; nonetheless the gap between the impeller and the casing widens like an involute. The Drawings The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a centrifugal pump of the invention, with the front suction cover removed; Figure 2 is a view showing the impeller in elevation but the casing in section along the line ll-ll in Fig. 3; and Figure 3 is an end view looking in the direction of the arrow Ill in Fig. 1. The pump has a casing 1 which is a steel pressing and is of substantially part-spherical shape, being curved in axial and in diametrical direction at the same radius. The casing 1 carries a bearing housng 2 at one end, and at the other end carries a front suction cover 3 which is held by e.g. dowels 4 and quickrelease nuts 5; the cover 3 in turn carries a suction inlet 6 which is coaxial with the bearing housing 2. The axis of the bearing housing 2 and inlet 6 is eccentric to that of the casing 1, as described further below. There is a tangential outlet 7 adjacent the part of the casing which is furthest from the inlet axis; specifically the outlet 7 begins at 8, i.e. at the part of the casing 1 which is furthest from the axis of the inlet 6. The outlet 7 is a tube whose lower end has been suitably curved.A fillet 10 is welded into the casing 1 at the end of the outlet opening, to act as a cut water point. It projects into the interior of the casing 1 and terminates just short of an impeller 11. A shaft 12 is mounted by bearings 13 (shown in part) in the bearing housing 2, protected by seals 14. The shaft 12 is coaxial with the inlet 6. To form the impeller 11, a boss 15 is welded to a back carrying plate 16. The boss 15 is then welded to the end part of the shaft 12. Light gauge blades 17 are welded to the boss 14 and back plate 15, forming an overhung impeller. Though four blades 17 are shown, there may for instance be just three blades 17. Each blade 17 is curved in diametrical section (see Fig. 3), the convex side facing forwards with respect to the direction of rotation (see the arrow in Fig. 3), the chord 18 being inclined rearwards with respect to the direction of rotation and being at roughly 90" to the radius at the root of the blade 17. The curve of the blade 17 is circular, with the radius of the circle roughly equal to three quarters of the length of the chord 18. The radially outer edges of the blades 17 are substantially rectilinear and parallel to the impeller axis. The inner ends of the blades 17 have a substantially 45" chamfer connecting their roots and their axially facing surfaces, as can be seen in Figs. 1 and 2. In this way, the clearance between adjacent blades 17 at the inlet end of the impeller is not substantially less than the internal diameter of the inlet 6. The blade tips are chamfered on all their radially outer edges, as shown in Fig. 3. The front edges of the blades 17 (that edge nearest the inlet 6) are at right angles to the impeller axis, and pass close to the front suction cover 3. As is apparent in Fig. 3, the eccentricity of the impeller 11 forms an involute between the casing 1 and the tips of the blades 17, terminated by the cut water fillet 10. Though not shown, the outlet 7 could be of greater diameter, equal to the internal length of the casing 1 or coincident with and equal to the axial length of the blades 17. The pump illustrated can be fabricated from mild steel which has been formed by pressing. Any suitable arrangement can be provided for connecting pipes to the inlet 6 or outlet 7. Fig. 1 shows a standard connector on the outlet 7 and a one-way ball valve 19. CLAIMS

1. A centrifugal pump comprising: a casing whose inner periphery is substantially circular in diametrical section; an impeller mounted for rotation about an axis which is eccentric to the casing; and a substantially tangential outlet adjacent the part of the casing which is furthest from the impeller axis.

2. The pump of Claim 1, wherein, as considered in the direction of rotation of the impeller, the initial part of the outlet is substantially in the part of the casing which is furthest from the impeller axis.

3. The centrifugal pump of Claim 1 or 2, wherein, at the end of the outlet opening from the casing, there is a projecting member which extends to adjacent the radially outer edge of the impeller.

4. The centrifugal pump of any of the preceding Claims, wherein the inner periphery of the casing is concave curved in axial section.

5. The centrifugal pump of Claim 4, wherein the concave curve is substantially part-circular and approximately of the same radius as the radius of the diametrical section.

6. The centrifugal pump of any of the preceding Claims, wherein the casing is formed of pressed steel.

7. A centrifugal pump having an impeller comprising a plurality of blades, each of which is curved in diametrical section, the convex side facing forwards with respect to the direction of rotation, the chord of the curve being inclined rearwards with respect to the direction of rotation.

8. The centrifugal pump of Claim 7, wherein the chord is at roughly 90" to the radius at the root of the blade.

9. The centrifugal pump of Claim 7 or 8, wherein the curve of the blade is substantially circular with the radius roughly equal to three quarters of the length of the chord.

10. The centrigual pump of any of the preceding Claims, wherein the impeller comprises a plurality of blades whose radially outer edges are substantially rectilinear and parallel to the impeller axis.

11. The centrifugal pump of any of the preceding Claims, wherein the impeller is overhung and the inlet is substantially circular and substantially coaxial with the impeller and at the free end of the impeller, the clearance between adjacent blades at the inlet end of the impeller being not substantially less than the internal diameter of the inlet.

12. The centrifugal pump of any of the preceding Claims, wherein the impeller is overhung and the inlet is substantially circular and substantially coaxial with the impeller and at the free end of the impeller, the inlet ends of the impeller blades having a substantially 45" chamfer connecting their roots and their axially facing surfaces.

13. The centrifugal pump of any of the preceding Claims, wherein the blades are of a thickness which is less than 10% of their radial length.

14. A centrifugal pump, substantially as herein described with reference to, and as shown in, the accompanying drawing.