WO1991018209A2

WO1991018209A2 - Liquid pump

Info

Publication number: WO1991018209A2
Application number: PCT/GB1991/000790
Authority: WO
Inventors: William Thomson Sweeney
Original assignee: William Thomson Sweeney
Priority date: 1990-05-19
Filing date: 1991-05-20
Publication date: 1991-11-28
Also published as: AU7875291A; WO1991018209A3; GB9011258D0

Abstract

A centrifugal pump has a shaft (10) mounted on bearings (11, 12) in a housing and carries a rotor (22, 23) which in use directs liquid to an oulet (25). A metal to metal seal (17) protects the bearings from the liquid being pumped. Coolant for the seal is directed at the seal through passages (33) and the water collects in a collection groove and is returned to the exterior of the pump. Any of the liquid which is being pumped which may approach the seal is also collected in the groove and is led away before it can reach the seal.

Description

LIQUID PUMP

This invention relates to a liquid pump of the kind comprising a pump housing, an annular liquid inlet which opens into an annular flow passage extending axially and outwardly in the housing, to a volute outlet at one end of the housing, a shaft mounted on bearings in the housing, the shaft extending from said one end of the housing and n use being connected to a drive motor and a rotor carried by the shaft, the rotor having a backing disc and blades located in the flow passage, the blades inducing a flow of liquid between the inlet and outlet, the backing disc being located in close proximity to the portion of the pump housing which defines the inner surface of the flow passage, the housing and shaft mounting the co-operating parts respectively of a seal which acts to prevent liquid in the flow passage reaching the bearings.

In order that the maintenance intervals of the pump should be as long as possible it is necessary to ensure that the seal is kept cool during the operation of the pump and also that solid matter, which may be carried in the liquid being pumped should be kept away from the seal. Solid matter contained in the liquid which is being pumped can be driven along the working clearance between the back of the back plate of the rotor and the adjacent surface of the housing by the pressure of liquid which is developed by the rotor blades in the volute outlet.

The object of the present invention is to provide a pump of the kind specified in a simple and convenient form.

According to the invention a pump of the kind specified comprises passage means through which clean coolant can be supplied to adjacent the seal, and a collection chamber in which the coolant collects said coolant being collected in said collection chamber and flowing to the exterior of the pump through said drain passage.

An example of a liquid pump in accordance with the invention will now be described with reference to the accompanying drawing Figure 1 of which shows the upper section of one half of the pump in sectional side elevation, Figure 2 showing the lower section of the pump.

The pump comprises a shaft 10 which is mounted to rotate about a substantially vertical axis, by a pair of spaced bearings 11, 12 located in a bearing housing generally indicated at 13. The bearing housing is of annular form and includes a base member 14 which supports the bearing 11 and a hollow truncated part 15 which carries the bearing 12. The shaft extends through the housing the part 15 carrying a lip seal 16 to prevent the ingress of dirt into the bearing 12. A further seal 17 is provided for the bearing 11 and this is of a more complex nature in view of the more arduous working conditions. The seal 17 includes a first part 18 fixed in an extension 19 which is secured to the base member 14 and a second part 20 which is secured to the shaft by means of a grub screw 19A. Intermediate the bearing 11 and the first part 18 of the seal is a lip seal 21 which provides limited protection for the bearing 11 in the event of failure of the seal 17. The first and second parts 18, 20 of the seal 17 mount contacting metallic members which form the seal.

Mounted about the shaft and rotatable therewith is a rotor which comprises a backing disc 22 upon which are mounted a plurality of outwardly extending blades 23, the blades and the backing disc being located in an annular flow passage 24 which extends upwardly and outwardly towards a volute outlet chamber 25. The inner surface of the flow passage is defined by the outer surfaces of the base member 14 and the extension 19 and the outer surface of the flow passage is defined by the inner surface of an annular casing 26 which extends between a casing part 27 which defines the volute outlet 25 and an outwardly extending flange 28. The casing 26 is strengthened at intervals about the axis of rotation of the shaft by apertured webs 29. A working clearance is established between the backing disc 22 and the outer surfaces of the base member and the extension 19 and this clearance includes a portion radially disposed relative to the shaft 10 and the outlet end of the rotor.

The rotor comprising the backing disc 22 and the blades 23 is secured to the shaft 10 in a manner to be described but the backing disc is formed integrally with a hub 30 located about the shaft.

In operation upon rotation of the shaft the rotor will act as a pump to direct liquid from the lower end of the flow passage 24 into the volute outlet 25. During this process even though the working clearance is small and extends upwardly and outwardly and includes the annular radial portion, there is a chance that some of the liquid being pumped will leak therealong. If the liquid which is being pumped is clean this will not matter however, if the liquid contains suspended solid material and the pump described is intended for pumping liquid having a substantial solids content, solid material will be driven towards the seal 17. As a result the contacting surfaces of the parts 18, 20 of the seal will be subject to accelerated wear.

In order to overcome this problem there is provided an collection chamber in which the liquid leaking along the aforesaid clearance can collect and extending from the collection chamber are a plurality of drain passages.

In the example the collection chamber is defined by a "Vee" shaped groove having a flat base and extending downwardly from the base of each recess is a series of drainage passages 32 and these continue downwardly through parts yet to be described, to the exterior of the pump. The groove 31 is formed in the upper surface of the boss 30 and projecting downwardly into the groove is the lower position of the extension 19. The contaminant therefore flows down one limb of the groove to the base therefore. The entrances to the passage 32 are flared to minimise the risk of the contaminant remaining in the groove.

In order to further prolong the life of the seal 17 it is proposed to direct liquid coolant eg clean water at the contacting surfaces thereof. As shown in the drawing there is formed in the extension 19 a plurality of angularly spaced passages 33 only one of which is shown. The passages 33 interconnect at their upstream ends with passages 34 in the base member 14 and these are connected with external supply pipes 35 by flexible hoses 36 which extend through the oil reservoir 37 in the bearing housing. The supply pipes 35 are connected to a source of clear water at a pressure of between 15 and 20 PSIG with a total flow rate capacity of 18-20 litres/min. The downstream ends of the passages 33 terminate in orifices positioned adjacent the contacting surfaces of the seal 17 with the result that in the use of the pump the surfaces are kept cool. The coolant flows downwardly along the other limb of the groove 31 and then through the drainage passages 32 and in so doing it helps to prevent accumulation of solid material in the groove and in the drainage passages 32. In order to enhance the efficiency of the pump as described further pump components are provided including a further rotor 37 which in conjunction with an annular part 38 secured to the underside of the flange 28 defines an inwardly and upwardly extending flow passage 39 which connects with the flow passage 24. The boss 40 of the rotor 37 is spaced from the boss 30 by a distance piece 41 and the boss 40 is secured to the shaft 10 by coupling members 42. The bosses 30 and 40 and the distance piece 41 are secured together by bolts. The distance piece 41 carries impeller blades 43 and interposed between the impeller blades 43 and the blades 23 are fixed guide blades 44. A further set of fixed guide blades 45 is provided and these are located downstream of a plurality of inlet blades 46 which are mounted on the rotor 37. Moreover, upstream of the inlet blades 46 is a further set of fixed guide blades 47.

As the rotor assembly is rotated liquid is entrained by the blades 46 to induce flow in the inwardly extending flow passage 39. The liquid is then directed by the impeller blades 43 into the flow passages 24 and is then directed into the volute outlet 25 by the blades 23. The guide blades 45 function to direct the liquid onto the impeller blades 43 and the fixed blades 44 ensure lamina flow of the liquid prior to entrainment by the blades 23.

A further improvement in the efficiency of the pump is obtained by ensuring that the liquid as it is discharged from the flow passage 24 enters into the volute outlet 25 in a tangential manner. The volute outlet 25 receives the liquid discharged from the flow passage by way of a circumferential inlet 25A. The outer boundary wall of the inlet 25A is continuous with the inner surface of the casing 26 and the outer boundary wall of the inlet merges smoothly with the wall of the volute outlet which in the example is of square section with rounded covers. The inner boundary wall of the inlet 25A diverges away from the surface of the backing disc 22 of the rotor to which the blades 23 are secured and the base member 14 has a lip 14A which besides defining with the backing disc, the aforesaid radially disposed clearance, also forms a surface continuous with the inner boundary wall of the inlet 25A.

The liquid discharged from the passage 25 enters the volute outlet 25 to one side of the axis 25B thereof and as a result the liquid as it flows towards the outlet end of the volute also rotates about the axis 25B in the manner of a spiral. The individual flows of liquid discharged by the blades 23 merge into the spiralling flow and turbulence and therefore losses are kept to a minimum. The action of the spiralling flow is to break down the functional adhesive effect of the liquid film at the wall of the volute outlet.

As will be seen from the drawing the downstream end of the drainage passage 32 communicate with further passages 48 extending to the underside of the rotor 37. The pump as described is capable of dealing with water having a substantial solids contact and therefore it can be used for pumping dirty liquid from tanks.

One application for such a pump is for removing mud from ponds or canals. In the past this operation has been carried out by dredging. This however can cause damage to the base of the pond or canal which in most cases is formed by a clay lining. Moreover, the dredged material is dragged through the water in the pond and this quickly results in discoloration of the water. The pump as described can be used to remove the mud but in so doing as the mud level is reduced a considerable quantity of water will be removed from the pond.

It is proposed therefore to provide an attachment for the pump as described to make it more suitable for removing mud from ponds and canals. As shown in dotted outline there is provided an annular casing 49 which is formed in three sections 50, 51, 52. The section 50 is mounted on an inner support rim 53 which is secured to the flange 28, and extends downwardly and outwardly. The section 51 extends downwardly and inwardly and the section 52 extends downwardly and inwardly at a shallower angle to define a lower inlet opening 54 which is approximately the same diameter as the rotor 37 but is positioned below the outer rim of the rotor. The casing carries adjustable support legs 55 and also the support rim 53 carries a plurality of fixed guide vanes 56.

Secured to the underside of the rotor 37 is a bowl 57 having an outer portion 58 which inclines downwardly and inwardly at a steep angle, an intermediate portion 59 which extends downwardly and inwardly at a much shallower angle and an inner portion 60 which is normal to the axis of rotation of the shaft. The portion 60 lies below the rim of the opening 54 but in use, is supported clear of the ground level by the support legs 55. The outer portion 58 of the bowl carries a plurality of low lift impeller blades 61 which extend outwardly to adjacent the inner surface of the section 51 of the casing. The drainage passages 48 in the rotor 37 are connected to outlets 62 in the portion 59 of the bowl by flexible couplings. In operation as the lower portion of the casing is lowered into the mud, the mud being in a liquid state will be drawn through the opening 54 and discharged through the outlet. The soft mud will form a seal about the casing and as a result very little if any, of the water in the pond or canal will be drawn through the pump. As mud is removed by the pump there will be a tendency for fresh mud to flow towards the pump from an appreciable distance around the pump. This flow of mud will take place smoothly and there will be little discoloration of the water.

It is to be expected that the lowermost section of the mud will be relatively hard and in order to remove this mud without damaging the clay base, water jets are employed. A plurality of nozzles 64 are mounted on the section 52 of the casing and these are supplied with water through suitable pipes 65. The jets of water produced by the nozzles are directed tangentially to the inner portion 60 of the bowl. The jets of water liquidify the hard mud without causing damage to the clay lining.

The nozzles 64 are so disposed that the water tends to swirl in the opposite direction to the direction of rotation of the shaft.

In order to minimise the possibility of "vena contracta" forming within the casing adjacent the opening 54 there is welded to the casing section 52 around the inner rim thereof a round steel rod, the resulting weld being ground so that the casing and rod form a "pear" section.

Claims

1. A liquid pump comprising a pump housing, an annular liquid inlet which opens into an annular flow passage (24) which extends axially and outwardly within the housing to a volute outlet (25) at one end of the housing, a shaft (10) mounted on bearings (11, 12) in the housing, the shaft extending from said one end of the housing and in use, being connected to a drive motor, a rotor mounted on the shaft, the rotor having a backing disc (22) and blades (23) mounted on one side of the backing disc, the rotor being located in the flow passage and in use, inducing a liquid flow along the flow passage from the inlet to the outlet, the backing disc being mounted in close proximity to the portion (14 ,19) of the pump housing which defines the inner surface of the flow passage (24), the housing and shaft mounting the cooperation parts respectively of a seal (17) which acts to prevent liquid in the flow passage (24) reaching said bearings, characterised by passage means (33, 35, 36) through which clean coolant can be supplied to adjacent the seal, a collection chamber (31) in which the coolant collects, and a drain passage (32, 48) from said collection chamber to the exterior of the pump.

2. A pump according to Claim 1, characterised in that said collection chamber is in the form of a groove (31) defined in a boss (30) to which the backing disc (22) is connected, the collection chamber also receiving any liquid which is being pumped by the pump which flows along a working clearance defined between the backing disc (22) and the pump housing.

3. A pump according to Claim 2, characterised in that the groove (31) is a Vee groove, whereby the coolant flows down one limb the base of the groove and the liquid being pumped can flow down the other limb.

4. A pump according to Claim 1, in which the liquid which is discharged from said flow passage (24) enters tangentially into said volute outlet (25) to minimise the turbulence therein.