WO1994029599A1

WO1994029599A1 - Apparatus for handling slurry

Info

Publication number: WO1994029599A1
Application number: PCT/NZ1994/000055
Authority: WO
Inventors: Nicolaas Laurisse Sieling
Original assignee: Rotacon Engineering Limited
Priority date: 1993-06-03
Filing date: 1994-06-02
Publication date: 1994-12-22
Also published as: AU6900294A

Abstract

Apparatus for pumping slurry out of a reservoir (10) comprises outlet pipework (34, 32, 52) for carrying the slurry out of the reservoir (10) and a pumping arrangement (18, 30) for pumping the slurry from the reservoir (10) into the outlet pipework (34, 32, 52). The pumping arrangement (18, 30) has an outlet end (30b) through which the slurry passes into the inlet end (34) of the outlet pipework (34, 32, 52). The respective outlet end (30b) and the inlet end (34) can be moved between first and second relative positions in which they are respectively in and out of mutual alignment. In the first relative position, the slurry is pumped out of the reservoir (10) via the outlet pipework (34, 32, 52) by the pumping arrangement (18, 30), and in the second relative position the slurry is returned to the reservoir (10) by-passing the outlet pipework (34, 32, 52) to stir and agitate the slurry in the reservoir (10).

Description

TITLE: APPARATUS FOR HANDLING SLURRY

FIELD OF THE INVENTION

This invention relates to apparatus for handling slurry.

BACKGROUND OF THE INVENTION

Farmers of livestock such as cattle and pigs have to dispose of slurry comprising animal droppings entrained in water collected in the course of washing down milk sheds, pens and other enclosures where stock is concentrated for one purpose or another. Usually the slurry flows initially to a first reservoir called an anaerobic tank or pond and from there to s second reservoir called an aerobic tank or pond. For convenience these reservoirs will be referred to herein as "ponds". Chemical reactions take place in each of the ponds in the course of which the droppings are broken down to a form which renders the slurry suitable for disposal. In pastoral farming practice the slurry can beneficially be used as a fertiliser. This is achieved by spreading the slurry over the land and mechanised slurry spreading apparatus has been used for this purpose for many years.

DISCUSSION OF THE PRIOR ART

In one kind of commercially available such apparatus known to the applicant, the slurry is pumped from the pond into mobile holding reservoir in the form of a tank mounted on a tractor-drawn trailer. A vacuum pump is mounted on the tank. The pump is driven by the power take off (PTO) of the tractor. The vacuum pump serves two purposes. In the first place it can be operated through a suitable valve arrangement to withdraw air from the tank. Slurry is thereby drawn into the tank from the pond through a feed pipe leading from the pond to the tank. The feed pipe can be quick coupled to a valve mounted on the tank. Second, by adjusting the valve arrangement the vacuum pump can be operated to pump air into the tank. By this means, after the slurry has been transported in the tank to the land over which it is to be spread, the slurry is expelled from the tank under pressure.

The conventional apparatus, the tank is provided with a slurry discharge pipe which leads out of the bottom of the tank. The discharge pipe is controlled by a valve which must be closed to prevent slurry gravitating out of the tank. The discharge pipe has at its outer end a spreading nozzle which causes the slurry to emerge from the discharge pipe in a fan shaped spray. This spray is directed upwardly so that it spreads over a path which is typically about 10 to 14 metres wide

Such conventional apparatus has certain disadvantages. Because of the use of a vacuum pump, the pressure or vacuum head which can be applied to the tank is somewhat. Notwithstanding this, the tank must be constructed sufficiently strongly to sustain the vacuum and pressure head which is applied to it. The deadweight of the tank is thereby increased and the maximum payload correspondingly diminished. Third, it is necessary for the operator to dismount from the tractor to couple and uncouple the feed pipe and also to open and close the valves at the beginning and end of both the tank loading and the spreading operations. This slows the operations down. Moreover, the pipe is large and heavy which makes the coupling and uncoupling operations tiring for the operator.

In conventional operations it is necessary to stir or agitate the slurry in the pond before it is pumped into the tank since the solids in the slurry gravitate to the bottom of the pond. Conventionally the stirring has been carried out by a simple device comprising a propeller or similar impelling device mounted on the end of a shaft which is coupled to the PTO of a tractor through a flexible joint. This is not an ideal arrangement since the shaft will often be disposed at a considerable angle to the PTO as the level of the slurry in the pond changes. For the same reason it is often necessary to move the position of the tractor to ensure that the impelling device is able to stir the slurry adequately. In addition there is a tendency for objects such as wire or string in the slurry to become wrapped around the propeller. SUMMARY OF THE INVENTION

The provision of a pump, and more especially a vortex pump, able to operate at higher pressure than a vacuum pump, at least in the handling of livestock slurry in farming operations, should materially increase the speed of slurry spreading operations. It should also simplify the apparatus since there is a reduced need for providing a filtering arrangement to prevent solids entrained in the slurry from passing into the pump. Use of a positive displacement pump should also help to reduce the deadweight of the slurry tank since no pressure or vacuum is applied to the tank. Pipe blockage should also be reduced by reducing the length of pipe work through which the slurry is fed into the pump.

According to the invention apparatus for pumping slurry out of a reservoir comprises conveyor means (usually but not necessarily comprisng one or more pipes) for conveying the slurry out of the reservoir and pump means for pumping the slurry from the reservoir to the conveyor means. The pump means has an outlet through which the slurry passes out of the pump means. The conveyor means comprises a first duct having an inlet through which the slurry enters the first duct. The apparatus comprises means for moving the pump means or the first duct between a first relative position in which the inlet and the outlet are in mutual alignment and a second relative position in which the inlet and the outlet are out of mutual alignment.

According to one aspect of the invention, the pump means and the conveyor means are mounted on a vehicle.

Advantageously, the vehicle is a trailer on which the pump means and the conveyor means are mounted and the pump means comprises a pump and means for coupling the pump to drive means on a second vehicle by which the trailer can be towed.

The second vehicle may be a tractor. The pump is conveniently mounted in front of the container so that it can be directly coupled to the PTO of the tractor.

In another aspect of the invention the reservoir is a container which is mounted on the vehicle and the apparatus comprises a second duct arranged to feed slurry from the container to the pump means. Advantageously the pump is located outside the container.

It is advantageous to position the pump so that the slurry gravitates from the container to the pump through the second duct.

In yet another aspect of the invention the conveyor means is provided with an outlet through which the slurry is discharged, the outlet being located substantially above the highest level which the slurry reaches in the container. No valve is thus needed to close the first duct.

Advantageously the inlet and the outlet are located in the reservoir so that in the second relative position the slurry which emerges from the outlet is returned to the reservoir.

In one aspect of the invention the outlet is movable relative to the inlet.

In one form of the invention the pump means includes a pump and means for holding the pump immersed in the slurry in the reservoir.

The second duct may comprise a channel and there may be a baffle plate or the like mounted inside the tank and arranged to channel the slurry emerging from the pump means into the channel. If the slurry emerging from the pump means is directed away from the pump, the baffle may be shaped and positioned to redirect the slurry into the channel.

Because the tank has no vacuum pump it is necessary to provide an apparatus for feeding the tank which includes a slurry pump. This pump is conveniently also a vortex pump driven by the PTO of a tractor. Advantageously the tractor carries a structure for holding the pump immersed in the slurry in a pond or other reservoir. Advantageously the pump can be arranged to discharge the slurry into a discharge pipe via a bimodal channelling means operable in a first mode to channel the slurry to the discharge pipe and in a second mode to return the slurry to the pond. Advantageously the channelling means can comprise a pipe assembly which can be adjusted between a first operational position in which the slurry is delivered to the tank and a second operational position in which the slurry is returned to the pond in a manner such as to stir or agitate the slurry in the pond. BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is described by way of example with reference to the accompanying drawings in which

Figure 1 is a sectional side view of a reservoir for slurry in the form of a tank provided with an apparatus for spreading the slurry;

Figure 2 is a view, partly in section, from the front end of the tank shown in

Figure 1;

Figure 3 is a perspective detail of one part of the apparatus shown in Figure 1;

Figure 4 is a side view detail of a second part of the apparatus shown in Figure

1;

Figure 5 is a sectional side view detail of a third part of the apparatus shown in Figure 1;

Figure 6 is a side view of a tractor mounted apparatus for pumping slurry from a reservoir into the tank shown in Figure 1;

Figure 7 is a detailed plan view, partly in section, of pipe work connected to output side of a pump incorporated in the apparatus shown in Figure 6;

Figure 8 is a side view on arrow A in Figure 7;

Figure 9 is a perspective view of another part of the apparatus shown in Figure 6;

Figure 10 is a schematic side view illustrating the manner of positioning the apparatus shown in Figure 6 for transport;

Figure 11 is a sectional side view detail of a modified pump arrangement which could be incorporated in the apparatus shown in Figure 6; and Figure 12 is a sectional view on arrow B in Figure 11.

DETAILED DESCRIPTION OF THE EXAMPLES SHOWN IN THE DRAWINGS

Referring first to Figures 1 and 2, there is shown a reservoir in the form of a steel tank 10 mounted on a trailer 12 coupled to the drawbar of a tractor 14. The tank 10 is generally cylindrical but has a trough 16 running along its bottom and becoming deeper towards its front. The design is such that, when the tank is level, the forward end of the trough constitutes the deepest part of the tank and any slurry in the tank will thus gravitate to that part.

A pump 18 is mounted on the trailer frame at the forward end of and outside the tank. The pump is preferably a vortex pump. This type of pump is designed to deal with large lumps of solid matter entrained in the material being pumped. A "Robot" brand (6" size) pump is suitable in the present application. An aperture 20 in the front wall of the tank connects the trough with the inlet of the pump 18. A baffle plate 21 is mounted above the aperture 20. The baffle plate helps to avoid a vortex forming in the slurry as it passes through the aperture.

A flat rimmed pulley 22 is mounted on the drive shaft 24 of the pump. The pulley 22 is driven by a rubber tyred wheel 26 which is rotatably mounted above the pulley 22 and bears frictionally thereon. The wheel 26 is coupled to the PTO of the tractor by a conventional, flexible drive shaft arrangement indicated schematically at 28. In the present case the diameter of the tyre on the wheel 26 is about twice that of the pulley 22.

The outlet of the pump is connected to an elbow 27. The outlet end of the elbow is in alignment with one end 30a of a straight steel pipe 30 (hereinafter referred to as the "delivery" pipe) which is located in the tank. The end 30a of the delivery pipe is located in position by a collar 31 welded to the front wall of the tank. The delivery pipe is fits tightly enough in the collar to form a seal against the leakage of slurry but is nevertheless such that the opposite end 30b of the pipe can move up and down to a limited extent. The opposite end 30b is located near the rear end of the tank and hangs suspended on a chain 46. The end 30b is held between vertical guide posts 33 fixed to the bottom of the tank. The end 30b can move in a vertical direction between the guide posts. The pipe 30 is disposed a little way above the bottom of the tank. A second chain 35 fixed between the front wall of the tank and the pipe 30 prevents the pipe 30 from moving further into the tank from the position shown in the drawing.

A second pipe 32 (hereinafter referred to as the "discharge" pipe) is mounted in vertical disposition in the tank adjacent the rear end thereof. A 90 degree elbow 34 is mounted on the lower end of the discharge pipe. The free end of the elbow faces forward and is located a little way above and to the rear of the delivery pipe when the latter is in its natural position.

A shaft 36 is slung from the roof of the tank by means of brackets 38 in which it can pivot. The shaft projects through the front wall of the tank and a first crank 40 is mounted thereon outside the tank. The crank 40 is linked to an hydraulic ram 42 which itself is operably connected to the hydraulic system of the tractor. A second crank 44 is mounted on the opposite end of the shaft above the rear end of the delivery pipe. The chain 46 connects the second crank 44 to the end 30b of the delivery pipe. By this means, when the ram 42 is actuated the shaft pivots and the end 30b is lifted or lowered by the chain 46.

When the end 30b is lifted it is axially aligned with the free end of the elbow 34. As shown in Figure 4, to ensure proper alignment a first hemi-cylindrical plate 48 is welded to the top of the elbow, overlapping the end thereof. Similarly, a second hemi-cylindrical plate 50 is welded to, and overlaps the end of, the delivery pipe. These plates form seats which guide and hold the free end of the delivery pipe in the correct position for directing slurry from the delivery pipe into the discharge pipe.

To reduce leakage of slurry at the joint, the gap between the end 30b of the delivery pipe free end of the elbow 34 is desirably as small as possible, say 5 mm. For the same reason the gaps between the adjacent straight edges of the plates 48 and 50 should also be small, also of the order of 5 mm.

The ram 42 can be retracted to cause the crank 44 to lower the end 30b of the delivery pipe to a position (shown in dotted outline at 37 in Figure 1) in which it is below the elbow and aligned with a baffle 39 welded to the bottom of the tank. Slurry which is discharged from the delivery pipe is thus returned to the tank. The baffle is shaped so that slurry which issues in a rearward direction from the delivery pipe is redirected, upon striking the baffle, into the trough. The resulting strong flow of slurry in a forward direction through the trough is useful to clear and large lumps of solid matter which become lodged in the trough.

The above described arrangement for mounting the pipe 30 avoids the use of valves. This is desirable because there is a relatively large pressure drop through valves, owing to the tight bends therein.

In the above described arrangement the only component which need be moved to return the slurry to the reservoir is the delivery pipe. It will be clear that this arrangement could be modified. For example, the delivery pipe could be rigidly joined to the pump. In this case the pump would have to be moved with the delivery pipe.

A second 90 degree elbow 52 is mounted on the upper end of the discharge pipe outside the tank. The opposite end of the elbow 52 faces to the rear and has a stub pipe 54 welded thereon. As detailed in Figure 4, a notch is cut into the wall of the stub pipe as shown at 56. A disc-shaped plate 58 is mounted in alignment with the outlet end of the stub pipe by means of a strong compression spring mounted on the downwardly depending leg 60 of a bracket welded to the stub pipe. Adjustment of the shape of the notch 56 and the position and size of the plate 58 enables the slurry to be discharged in a spray of controlled characteristics. For example, deepening the upper portion of the notch (as indicated in dotted outline at 56a) will increase the proportion of slurry which is directed towards the outer limits of the angle through which the spray fans out transversely to the direction in which the tractor is moving. A spray which is of uniform density in the transverse direction is thus achieved.

The location of the nozzle at a high level enables the spray to be directed entirely downwardly. This feature, together with the provision of a nozzle which is constructed and functions as described, has two results. First, the angle through which the spray fans out in the direction of motion of the tractor is very narrow; in fact it can be kept substantially flat. This is useful because uniform application of slurry can be achieved even close up to boundary fences and other obstacles in the land. Second, the high level location of the nozzle reduces the amount of spray which is caught up in high winds. A spray which is λ ϊde, 15 metres across "here it hits the ground and of uniform density throughout t sngth is easily achit /ith the apparatus described herein.

The tank 10 is filled from a fet ipe 62 forr.. :g part of an apparatus for loading slurry into the tank as will be described with reference to Figures 6 to 9. The end of the feed pipe is inserted in a chute 64 mounted in the roof of the tank. The chute is wide at its upper end and tapers inwardly. As the end of the feed pipe is inserted in the chute it is thus guided towards the lower end of the chute which is marginally larger than the feed pipe. The small clearance between the feed pipe and the lower end of the chute ensures that a minimal amount of slurry will splash out of the chute during the filling operation.

Vent holes 65 are advantageously provided in the chute ; ,ide the -rank just I ow the junction of the chute with the tank wall. The vent holes i militate the passage . -_ air out of the tank when it is being filled. However, the applicant has found that when the tank is nearly full, foam from the slurry in the tank begins to emerge from the vent holes. This provides a reliable signal to the operator that the tank is nearly full. Moreover if the tank is filled to the point where a small amount of slurry begins to pass through the vent holes, this slurry will be returned to the tank through the chute.

A sight glass 66 may be provided on the front wall of the tank to check the level of slurry therein. Furthermore a float device 67 may be mounted at the top of the tank to provide a visual indication that the tank is full.

The tank is typically about 4 metres long and about 1.8 metres in diameter so that it holds about 10,000 litres of slurry. The delivery pipe and the discharge pipe are typically 150 mm in diameter. It may be necessary to provide cutouts in the tank to accommodate the wheels. In any event to maximise traction it is advantageous to position the wheels so that as much of the weight of the loaded tank is transferred to the tractor as possible without overloading it.

Referring to Figures 6 to 12, the apparatus for pumping slurry from a reservoir in the form of a pond 140 into the tank 10 comprises a gantry 70 mounted on the three point hitch of a tractor 142. Two legs of the gantry are mounted directly on the plough arms of the three point hitch. A hydraulic ram 72 is mounted between the upper link of the three point hitch and a third leg of the gantry. The ram 72 is connected to the hydraulic system of the tractor. Actuation of the ram 72 and adjustment of the plough arms causes the gantry to be lifted or lowered to any position between the lowered position shown in solid outline in Figure 6 and the upper position shown in dotted outline.

The gantry supports a vortex pump 74 mounted on one end of a tube 76 the other end of which is connected to the housing of a gearbox 80. The gearbox 80 is mounted to pivot at 81 on the end of the gantry so that the tube 76 can swing to remain vertical when the gantry is moved between the two positions as mentioned. The tube houses a shaft 78 which is coupled at one end through a flexible coupling to the output of the gearbox and at the other end to the pump 74. The input of the gearbox 80 is coupled to a drive shaft assembly shown schematically at 82 to the PTO of the tractor.

The pump 74 may be substantially identical to the pump 18.

A tube assembly 84 is provided which, as will be described in greater detail, connects the output of the pump 74 to the feed pipe 62. The assembly 84 is supported partly by the gantry 70 and partly by hydraulically actuated front arms 86 with which the tractor is usually provided for carrying various implements. Certain of the tubes making up the assembly 84 are flexible to allow for movement of the gantry and the arms 86.

The assembly 84 includes at one end a rigid down pipe 88 mounted on the tube 76. A 90 degree elbow 92 is mounted on the lower end of the down pipe 88. As indicated in Figures 7 and 8, what may be described as an assembly 94 of 90 degree elbows is mounted on the output side of the pump. The assembly 94 comprises a first elbow 94a directly connected to the pump. The output end of this elbow faces upwardly. This elbow 94a is connected to a second elbow 94b so as to be capable of pivoting (relative to the elbow 94a) about a vertical axis 96 passing through the centre of the joint. The output end of the elbow 94b faces in a horizontal direction and is joined to a third elbow 94c the output end of which also faces in a horizontal direction but is turned through 90 degrees to the output end of the elbow 94b. The elbows 92 and the three elbows in the assembly 94 are positioned so that, when the assembly 94 is in a first operational position shown in solid outline at 98a in Figure 7, the output end of the elbow 94c is aligned with the input end of the elbow 92. Slurry which is discharged from the pump thus passes into the elbow 92 and hence the tube assembly 84. A chain 100 is connected to a lug on the elbow 94c (see Figure 8) and passes through guide pipes 102 to a hydraulic ram (not shown) connected to the hydraulic system of the tractor. Actuation of the ram draws the assembly 94 to the first operational position. However, when the pressure in the ram is released with the vortex pump in operation, the reaction of the slurry passing through the assembly 94 causes it to pivot about the axis 96 and the slurry is discharged back into the pond at a level which can be close to the bottom of the pond. This recirculation very effectively causes the slurry to be stirred or agitated. The direction in which the slurry is discharged into the pond can be controlled by repositioning the elbow assembly 94.

By raising the gantry so that the elbow 94c is above the level of the slurry in the pond, the jet of slurry pumped through the elbow 94c can be directed at the sides of the pond, thereby helping to wash solids lodged on the sides back into the pond.

Referring particularly to Figure 9, a support assembly 108 is provided for carrying the feed pipe 62. The support assembly is mountable on the tractor arms 86 but can be readily detached therefrom. A 90 degree elbow 110 is welded to the upper end of the feed pipe 62. The elbow 110 is connected to and forms part of the assembly 84. The support assembly comprises a lug 112 welded to a short length of pipe 114. The pipe 114 is slidably mounted on a cross member 116 joining a pair of arms 118 carrying tubes 120 in which the arms 86 are received. A lug 122 is welded to the elbow 110 and is pivotably joined to the lug 112. By this arrangement the feed pipe can swing fore-and-aft and sideways and can move along the cross member 116 so that it can align itself with the chute 64 when being inserted therein.

For transporting the apparatus over long distances the gantry is first raised to the position shown in Figure 6 and moved by the tractor away from the pond. The gantry is then brought down so that the pump comes into contact with the ground in the position of the gantry and tube shown at 130 in Figure 10. For clarity the back wheel of the tractor is indicated at 136. The tractor may then be backed and the gantry lowered further so that the tube 76 folds against the gantry with a jack-knife action to a position 132. The tube 76 can be clamped in this position 132 to the gantry, optionally by means of an automatically operating locking arrangement (not shown). The gantry is now raised again and the apparatus is ready for transport.

A substantial advantage of the apparatus is that the drivers of both tractors do not need to leave their seats in using the apparatus.

In one modification of the apparatus the pipe assembly 84 passes over the back end of the tractor as shown in dotted outline at 150 in Figure 6. For this purpose it could be supported by a suitable supporting structure mounted on the back of the tractor.

In another modification, a specially designed vortex pump 160 may be used instead of the commercially available pump 74. The pump 160 comprises a housing 162 having a substantially conventional inlet aperture 164 and outlet nozzle 166. Slurry which passes through the pump is discharged through the nozzle directly into the elbow 92. However, the pump 160 comprises an impeller 168 which is mounted directly on the end of the drive shaft 78 housed in the tube 76. For this purpose, a bearing 170 for the shaft 78 is mounted near the lower end of the tube 76. An annular flange 172 is mounted on the lower end of the tube 176. This flange 172 is sandwiched between the upper wall 173 of the pump housing 162 and a retaining ring 174. The retaining ring is retained on the pump housing by nuts 178 mounted on bolts or studs 180 which are welded or otherwise fixed to the housing and pass through the retaining ring. The tightness of the nuts can be adjusted so that the pump can rotate about the tube 76.

The pump is able to rotate between a first position shown in solid outline Figure 12 and a second position shown in dotted outline. In the first position the nozzle 166 is aligned with the elbow 92 mounted at the lower end of the down pipe 88 as described with reference to Figures 6 to 8. The pump is held in this position by the chain 100, as before and the slurry which issues from the nozzle passes into the pipe assembly 84. In the second position the nozzle is no longer in alignment with the elbow 92 and the slurry is returned to the pond. When the chain 100 is slack, the reaction of the slurry issuing from the nozzle 166 is sufficient to turn the pump.

This modification has the advantage that the nozzle 166, and hence the jet of slurry issuing therefrom, can be located very close to the bottom of the pond where most of the solids in the slurry are settled and which most needs stirring or agitating. Also, fewer elbows are required.

The pump 160 incorporates another important modification. The applicant has learned by experience that the seal which is mounted over the shaft of the conventional pump 74 which carries the impeller is prone to failure as a result of abrasion by the solids in the slurry. In the present pump arrangement, a conventional seal 190 is located over the shaft 78 just below the bearing 170. Some distance (say, 60 mm) below the seal 190, a baffle ring 192 is mounted in the tube 76 over the shaft 78. The baffle ring may be a conventional seal but this is not essential since there can be a clearance of about 1 mm between the baffle ring and the shaft. Just below the baffle ring a small diameter vent pipe 194 opens into the tube. The upper end of the vent pipe is open to atmosphere above the slurry in the pond.

When the impeller is rotating at its operating speed, there is a substantial negative pressure in what may be described as a barrier zone 196 of the tube located between the seal and the impeller. The presence of the vent pipe causes a flow of air downwardly through the barrier zone and prevents any slurry from getting into the barrier zone 196 while the impeller is rotating. When the impeller is at rest, slurry will migrate into the barrier zone and the vent pipe but some air will remain in the barrier zone above the opening to the vent pipe, forming an air lock which prevents slurry in the barrier zone from getting to the seal. This residual slurry will be removed as soon as the impeller again begins to rotate. The baffle ring helps to prevent the residual slurry from impinging on the seal before the impeller has attained its working speed and the residual slurry has been removed.

The use of a vent pipe, barrier zone and baffle ring is not confined to a pump in which the shaft 78 on which the impeller 168 is mounted is externally supported (i.e. on the bearing 170 in the present example). Clearly, it would be possible to provide a pump unit incorporating a stub shaft on which the impeller is mounted and which is carried on one or more bearings mounted in the casing 162. Such a pump could moreover be suitable for mounting on the trailer 12 (in place of the pump 18) for pumping the slurry out of the tank 10.

Although the apparatus described herein has particular application to farmyard slurry, the invention is not necessarily restricted to the handling of such slurry.

Claims

1. Apparatus for pumping slurry out of a reservoir [10, 140], the apparatus comprising conveyor means [32-34-52, 84-92] for conveying the slurry out of the reservoir and pump means 18-30, 74-94, 160] for pumping the slurry from the reservoir to the conveyor means, the pμmp means having an outlet through which the slurry passes out of the pump means and the conveyor means comprising a first duct [34, 92] having an inlet through which the slurry enters the first duct, CHARACTERISED IN THAT the apparatus comprises means for moving the pump means or the first duct between a first relative position in which the inlet and the outlet are in mutual alignment and a second relative position in which the inlet and the outlet are out of mutual alignment.

2.

Apparatus according to claim 1, CHARACTERISED IN THAT the pump means and the conveyor means are mounted on a vehicle [12, 142].

3. Apparatus according to claim 2, CHARACTERISED IN THAT the reservoir is a container [10] which is mounted on the vehicle and the apparatus comprises a second duct [16] arranged to feed slurry from the container to the pump means.

4. Apparatus according to claim 1 , CHARACTERISED IN THAT the vehicle is a trailer [12] on which the pump means and the conveyor means are mounted and the pump means comprises a pump [18] and means [26-28] for coupling the pump to drive means on a second vehicle [14] by which the trailer can be towed.

5.

Apparatus according to claim 4, CHARACTERISED IN THAT the pump is located outside the container.

6. Apparatus according to claim 3, CHARACTERISED IN THAT the pump is positioned so that the slurry gravitates from the container to the pump through the second duct

7.

Apparatus according to claim 3, CHARACTERISED IN THAT the conveyor means is provided with an outlet [56,56a] through which the slurry is discharged, the outlet being located substantially above the highest level which the slurry reaches in the container.

8.

Apparatus according tp claim 1, CHARACTERISED IN THAT the inlet and the outlet are located in the reservoir so that in the second relative position the slurry which emerges from the outlet is returned to the reservoir.

9.

Apparatus according to claim 8, CHARACTERISED IN THAT the outlet is movable relative to the inlet.

10.

Apparatus according to claim 2, CHARACTERISED IN THAT the pump means includes a pump [74] and means [70-76] for holding the pump immersed in the slurry in the reservoir [140].