Pump housing assembly with liner

A pump housing assembly which includes a pump casing and a liner, the pump casing including at least two parts which are adapted to be connected together in an assembled position wherein the pump casing includes opposed front and rear sides, the at least two parts of the pump casing when in the assembled position have a common junction region which is disposed within one or more planes which pass through the front and rear sides of the pump casing.

This invention relates generally to pumps such as for example end suction centrifugal pumps that have an outer casing and an internal liner. The invention is particularly suitable for slurry pumps that have an outer casing for withstanding the pressure and pipe loadings and an internal liner that is wear resistant and which in turn is supported by the outer casing.

Centrifugal slurry pumps typically utilise a cast outer casing made in Cast Iron or Ductile Iron with an internal liner moulded from a wear resisting elastomer compound. The casing and the liners are traditionally manufactured in two parts or halves held together with bolts at the periphery of the casing. When assembled the two parts form a pump housing having a front side with an inlet therein and a rear side with a pumping chamber therein in which is disposed an impeller mounted for rotation on an impeller shaft. The impeller shaft enters the pumping chamber from the rear side and an outlet is provided at the peripheral side edge. The casing and liner halves are convex on the outside and concave shape on the inside. The liners normally have a metal skeleton moulded inside the elastomer which helps maintain its shape but also provides attachment points for bolts or studs to fix the liner into the casing halves. The two parts join along a plane which is generally perpendicular to the axis of rotation of the pump impeller.

During assembly, the two liner halves must be squeezed together at their periphery by the casing and casing bolts to effect a pressure tight seal. The resulting joint line is a vulnerable wear area in the pump, especially as the joint line is adjacent to the impeller discharge. Any misalignment of the liner halves along this joint line will produce steps or gaps in the joint line that will lead to preferential wear. Once wear starts at a local spot, the continued disturbed flow pattern at the step or gap will lead to an accelerated wear point and in the worst case localised wear will cause the liner to be worn through thereby exposing the pressure containing casing to wear.

It is an object of the present invention to provide a pump housing assembly which alleviates one or more of the aforementioned disadvantages.

According to one aspect of the present invention there is provided a pump housing assembly which includes a pump casing and a liner, the pump casing including at least two parts which are adapted to be connected together in an assembled position wherein the pump casing includes opposed front and rear sides, the two parts of the pump casing when in the assembled position have a common junction region which is disposed within one or more planes which pass through the front and rear sides of the pump casing when in the assembled position.

When in the assembled position, the liner is disposed within the pump casing and forms a pumping chamber for an impeller rotatable about a rotation axis which extends between the front and rear sides of the pump casing.

In one form of the invention the two parts of the pump casing have the common junction region disposed in a plane which is aligned with the axis of rotation of the impeller.

Desirably, the liner is formed of one piece from an elastomer such as for example, rubber, synthetic rubber or the like. The liner may include annular flanges on each side thereof which are adapted to be clamped between the two casing parts in the assembled position. The flanges may include sealing portions thereon. The sealing portions may be adapted to be received within a cavity formed between the pump casing and a pump end plate assembly. The sealing portion may be generally wedge shaped formed integral with the liner and responsive to pressures produced before and during operation of the pump. This may form a separate aspect of the invention.

Referring toFIG. 1of the drawings there is shown an exploded view of a pump generally indicated at10which includes a pump casing12having two parts13and14which can be assembled together, an elastomeric liner20, a drive shaft assembly22, an impeller24, back and front side liners25and26(the front side liner is often referred to as the “throat bush”) and an end plate28.

In an assembled position the impeller24is disposed within a pump chamber29and operatively connected to drive shaft assembly22for rotation and about rotation axis X-X. Slurry is drawn into the pump chamber29via inlet27and discharged through outlet23as is conventional.

The pump casing12is best seen inFIGS. 3 and 4and includes two parts13and14which can be fitted together. Flanges15have apertures16therein for receiving mounting bolts to hold the two parts together. In the assembled position the casing includes a front side17having an inlet21therein and a rear side18to which the shaft assembly is operatively connected. The two parts13and14are fitted together in a plane which contains the axis of rotation X-X. Thus, the plane extends through the front and rear sides17and18of the casing.

The liner20is a one piece structure formed from a suitable elastomeric material. As best seen inFIGS. 5 to 7, the liner20includes annular flanges31and32which are adapted to be clamped between the flanges15on the pump casing parts13and14. The flanges31and32have seal portions33and34thereon which include flexible lips35and36. The flanges31and32and associated seal portions33and34have strengthening ribs38on the surface thereof. The section shown inFIG. 7shows the configuration of the flange and seal portions31and33whereas the section on the other side is taken through one of the ribs38.

Referring toFIG. 8the seal assembly is shown in an installed position. The seal portion34is disposed within a cavity42formed between the casing14and the end plate assembly19. The seal portion34fits within the cavity42. The diameter of the lip36is less than the outer diameter of side liner26so that the lip is compressed during assembly of the side liner26into the main liner20; that is a seal is effected and lip36ensures that the pump holds the static pressure when first filled. The cavity assists controlling the shape and pressure applied to the seal portion. During operation the internal area is pressurised the pressure acting on the seal to increase its sealing capacity.

Because the elastomer liner is produced in one-piece, it avoids the vertical joint line of conventional pumps and the weakness that it introduces due to wear at the joint line. Further the elastomer liner may not require an internal metal skeleton and consequently, the liner can be manufactured to a more uniform thickness or known high wear regions can be made thicker without affecting the liners manufacturability or compromising its wear life. Further, without internal reinforcement, the elastomer liner will more easily conform to the internal shape of the pump casing due to the internal pump pressure generated while the pump is running. Any looseness or gaps between the metal casing and the liner are thereby minimised leading to a more robust liner as looseness and gaps will potentially lead to vibration and hysteresis heating of the elastomer and therefore reduced life.

As described earlier, to enable the liner to be held by the outer metal casing, a thickened region is provided around the liner horizontal centreline and an extension is provided on either side of the liner to allow clamping by the outer metal casing. The extension on either side of the rubber liner further includes an integral seal which is activated initially by the clamping provided by the outer casing and then by the internal pressure of the pumped fluid. With this arrangement, no internal metal skeleton or reinforcing may be required which also more easily facilitates the liner sealing when the liner is moulded in different elastomer compounds.

The liner being one piece without a vertical split line simplifies the casing design as well as obviating the need for casing bolts. The liner projection and seal on either side of the liner is made of a large enough diameter to allow the impeller to be installed through the side of the liner and as well to suit the sideliner.

The outer casing is thereby required to be in two pieces to enable the fitment of the one-piece liner. It will be appreciated that the split line for the casing could be selected from a number of different positions. The requirements for casing bolts therefore reduce to a small number of bolts on the pump centreline. The casing bolts have the dual function of holding the casing halves together as well as squeezing the raised elastomer land to hold the liner in the casing. The sides of the outer metal casing also assist in compressing and holding the elastomer projections and seals on both sides of the elastomer liner and prevent it from both being pushed out under pressure or being sucked in under vacuum. The metal casing can be produced either as two separate pieces or cast as one and then later split in the manufacturing cycle.

The use of a one-piece liner and two piece casing assists to lower maintenance costs. In most cases, the pump discharge pipework can be left attached to the pump. By removing the pump's suction pipework, front liner and impeller, it is possible to gain access to the pump internals for inspection.

The casing design may or may not have ribs for high-pressure applications. The casing bolts are designed to take the full design pressure without passing their elastic limit.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Finally, it is to be understood that the inventive concept in any of its aspects can be incorporated in many different constructions so that the generality of the preceding description is not to be superseded by the particularity of the attached drawings. Various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.