PUMING SYSTEM
A pump unit which includes a pipe, a flexible bladder inside the pipe, an operating volume between an outer surface of the bladder and an opposing inner surface of the pipe, a valve arrangement to introduce pressurised water into the operating volume and to allow pressurised water to flow from the operating volume and another valve arrangement to allow slurry to flow into the interior of the bladder as water is expelled from the operating volume and to—allow slurry to flow from the bladder when water is introduced into the operating volume.
This invention relates to pumping apparatus.
The apparatus of the invention is suitable for pumping media such as slurries. The invention is described hereinafter with reference to this application, i.e. to the pumping of a slurry, but this is exemplary only and is non-limiting.
The specification of international application No. PCT/ZA2009/000071 describes a pumping system which makes use of two pressure vessels. Each vessel is cylindrical with hemispherical ends and is orientated so that its longitudinal axis is vertical. Nozzles are provided at upper and lower ends of the vessel.
Each vessel contains an elongate flexible bladder which is aligned with the longitudinal axis. The bladder, at an upper end, has an open neck which is sealingly engaged with the upper nozzle to define a first volume within the bladder and a second volume between the bladder and an opposing inner surface of the wall of the vessel.
Slurry is fed gravitationally via a first one-way check valve through the bottom nozzle to fill the second volume. This action displaces the bladder inwardly around the longitudinal axis and, in so doing, water inside the bladder is displaced from the bladder through the upper nozzle. A measured volume of water under pressure from a pump is then introduced into the bladder through the open neck. The bladder expands and, in so doing, the slurry in the second volume is expelled through the bottom nozzle via a second one-way check valve into a discharge line.
While one vessel is being filled with water, to pump out its slurry contents, the other vessel is being refilled with slurry and displaces its water to an inlet of the pump.
The process continues indefinitely in this way with the pumping operation being changed from one pressure vessel to the other to produce a smooth discharge flow of slurry.
During the period that water is being pumped into the bladder of one vessel the other vessel must be depressurised and the slurry flow rate must be increased, from a zero value, in order to fill the second volume. Thereafter the slurry flow rate must be progressively decreased to zero. The pressure in the vessel is then raised to an operating value in readiness for the changeover of the pumping operation. A few seconds of waiting time, known as “overlap time”, are then allowed before the switchover is implemented.
The various functions in the second vessel, which are essential for effective pumping operation, are time consuming and place a limit on the rate at which the bladder in each vessel is filled with water i.e. the slurry pumping rate is restricted.
Apart from the aforementioned flow constraint, the pumping system described in the international specification has some further drawbacks.
The vessels are expensive to manufacture. The hemispherical ends are complex and costly to form and the nozzles, at the upper and lower ends, are forgings which are machined. This is expensive and requires substantial production time. As the diameter of each vessel increases cyclic hoop stresses which are generated in use by the pumping operation increase and the thickness of the wall of the vessel must be increased to be able to handle the hoop stress. An internal surface of the vessel which is in contact with the slurry requires a protective lining to resist abrasion.
Each vessel is vertically aligned so that slurry can flow into and out of the second volume through the lower nozzle. This results in a tall structure with a high centre of gravity which, in turn, calls for an extensive structural support framework as well as substantial civil foundations for stability, particularly in regions which are subject to seismic or similar events.
If the pumping system is assembled in a building then sufficient clearance must be allowed above the structure for a crane which is used to assemble the vessels. The pump assemblies are large and, when transported, are regarded as abnormal loads and the relevant regulations then come into play.
High level service platforms and stairways must be provided, in conformance with safety requirements, so that the vessels and associated valves can be accessed for maintenance purposes. In addition, the system must have a lifting device which can extract and insert the bladders, and valve tubes through the upper nozzle, as service is required.
As slurry is gravity-fed into the system, the level of a slurry supply tank must be higher than the top of the pressure vessels.
In general a substantial amount of on-site work is required to install and commission the pumping system. A water pump and motor unit must be installed separately on appropriate foundations; a VSD (variable speed drive) must be installed in an air-conditioned room on site; and stairways and service decks must be assembled on site as they are too bulky to be transported in an assembled condition.
An object of the present invention is to provide pumping apparatus which aims to address, at least partly, a number of the aforementioned aspects.
SUMMARY OF THE INVENTIONThe invention provides in the first instance a pump unit which includes:
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- (a) an elongate tubular housing with an inner bore, a first end and an opposing second end,
- (b) an elongate flexible bladder of tubular form with an interior, an inlet, at one end of the bladder, to the interior, and an outlet, at an opposing end of the bladder, from the interior, wherein the bladder is positioned Inside the bore with the bladder in sealing engagement with the housing at opposed ends of the bladder whereby the inlet is in communication with the first end of the housing, the outlet is in communication with the second end of the housing and an operating volume of variable size is formed between an outer surface of the bladder and an opposing inner surface of the housing,
- (c) a port for an actuating fluid which is provided on the housing in communication with said operating volume,
- (d) an inlet non-return valve connected to the first end of the tubular housing,
- (e) an outlet non-return valve connected to the second end of the tubular housing,
- (f) a first control valve for controlling the flow of the actuating fluid through the port into the operating volume, and
- (g) a second control valve for controlling the flow of the actuating fluid from the operating volume through the port.
In one form of the invention the pump unit includes metering means for metering the flow of the actuating fluid through the port. This may be done on a volume basis. The metering means may comprise a bi-directional flow meter.
The metering means may be connected to a controller and the controller may monitor the volume of actuating fluid which flows into the operating volume, and out of the operating volume.
The elongate tubular housing may be formed in any appropriate way and preferably, in this respect, use is made of a pipe of a suitable specification. Opposing first and second ends of the pipe may be flanged.
The port may be formed through a wall of the pipe.
The bladder, which is of tubular form, may be made from an appropriate material e.g. rubber.
Opposing ends of the bladder, i.e. at the inlet and the outlet, may be sealingly engaged with respective flanges at the first and second ends of the pipe.
The inlet non-return valve may be adapted to allow the medium which is to be pumped to move, preferably under gravity action, into the interior of the bladder.
The outlet non-return valve may be adapted to allow the medium which is pumped to pass, under pressure, into a discharge line.
The actuating fluid may be of any suitable kind but, preferably, is water. Water flow into, and out of, the operating volume is monitored by the bi-directional water meter i.e. the meter can measure the quantity of water which flows through it in one direction and then in an opposing direction. This is important as the pumping operation, in one embodiment of the invention, is based on volume measurements, and not on time or other measurements, to obtain a precisely controlled pumping sequence.
In a variation of the invention the metering means (in the preceding specific example the bi-directional flow meter) is not employed, and one or more sensors are used instead to control the flow of the actuating fluid. Each sensor is positioned at a chosen location to obtain an indication of the position of the bladder relative to the tubular housing at or near the chosen location. Each sensor may be of any suitable kind. For example, a sensing function may be provided by locating a magnet on or in the bladder and using a Hall-effect device or a similar appliance to detect the proximity of the magnet, or to detect when the magnet is moved away from a sensing region of the Hall-effect device or appliance. A capacitive sensing system may also be employed. The capacitance sensed by an appropriate detector varies as the bladder approaches a location at which the sensor is positioned and this is used as an indication of the position of the bladder relative to the tubular housing in an area which is at, or adjacent, the sensor. In another approach a metallic insert is positioned on or otherwise attached to the bladder and as the bladder moves the insert moves by a corresponding amount and this movement can be detected by an appropriate sensor e.g. a magnetic device which responds to the presence or absence of the metallic insert. These examples are exemplary only and are non-limiting.
In a preferred form of the invention multiple sensors are used with a first sensor being employed to detect when the bladder is full and a second sensor being employed to detect when the bladder is effectively emptied i.e. its contents are depleted. At least one intermediate sensor (a third sensor) may be positioned at a location which is between the first and second sensors to detect when a predetermined bladder configuration has arisen e.g. when the bladder (say) is half full. This can be used, as is further described hereinafter, to ensure a smooth and controllable sequencing operation when a plurality of the pump units are employed.
One or more sensors (apart from the sensors mentioned) may be used as failsafe devices. For example, a sensor can be used to ensure that when a bladder is emptied, i.e. its contents are expelled from the bladder, that further operation does not take place which could cause damage to the bladder.
A particular benefit of this approach, i.e. the use of the sensors, is that it enables the bi-directional flow meter to be eliminated. The flow meter is expensive and requires careful operation to ensure its integrity of functioning. Sensors of the kind referred to on the other hand are robust and relatively low-cost devices. As the bladder is constrained within the tubular housing and is secured to the housing at its inlet and outlet, any possible movement of the bladder relative to the housing during operation is limited essentially to movement between a fully collapsed configuration and a fully expanded configuration. Because the movement of the bladder between these configurations is predictable it is possible to make use of the sensors, as indicated, to detect, in a reliable manner, movement of the bladder. Effectively this means that when the pump unit is employed it can be controlled by signals which are generated in response to the bladder movement as opposed to the other embodiment in which control signals are generated in response to signals determined by metering the volume flow of the actuating fluid.
The invention extends, in the second instance, to pumping apparatus which includes three pump units, each pump unit being of the aforementioned kind, wherein the three pump units are mounted substantially parallel to each other on supporting structure which preferably has outer dimensions which are substantially the same as the outer dimensions of a conventional shipping container.
With the supporting structure on a level surface the first ends of the tubular housings are preferably elevated so that each housing then slopes downwardly over the length of the supporting structure towards its second end.
The first non-return valves and a first manifold may, in use, be positioned so that they lie outside the supporting structure. Similarly the second non-return valves and a second manifold may, in use, lie outside the supporting structure.
The use of three pump units, under the control of a suitable controller, enables the medium to be pumped continuously without meaningful pressure variations. Of substantial importance is the fact that the pumping rate is approximately twice the pumping rate of the pumping system described in the aforementioned international patent application. In other words, by using three pump units instead of two pump units, a hundred percent increase in pumping rate is achieved. The pumping rate can match the rate at which the medium to be pumped flows into the pumping apparatus. Typically the medium is a slurry which flows under gravity action to the pumping apparatus.
In general terms the increased pumping rate results from the sequenced operation of the pump units which can each work at a maximum rate for there is no need to interrupt the pumping rate to allow for sufficient time within which a second pump unit can be readied for operation, as is the case with the pumping system in the international application. Thus, in the three pump unit arrangement the medium is pumped from a first pump unit and, at the same time, a second pump unit is prepared for pumping. Thereafter the pumping operation is transferred from the first pump unit to a third pump unit and pumping from the third pump unit takes place, the preparation of the second pump unit is completed and the preparation of the first pump unit for pumping operation is commenced. The pumping operation is then transferred to the second pump unit, the preparation of the first pump unit is completed and the preparation of the third pump unit for pumping operation is commenced.
The aforementioned process continues in this way, under the control of the control unit, indefinitely. The pumping sequence is controlled by monitoring the volume of the actuating fluid (typically water) which flows into, and subsequently out of, each operating volume. In the first embodiment use is made of bi-directional flow meters to monitor these water volumes. This approach practically eliminates the prospect of incremental creep or overlap, due to inaccurate water measurements, causing a malfunction in the pumping operation. On each count cycle each flow meter is reset to a zero value. Subsequently the flow meter counts the volume of water which flows into the pump unit and thereafter out of the pump unit.
However, in the second embodiment the bi-directional flow meters are not employed. Instead, the sensors referred to are used. These sensors also monitor the passage of the actuating fluid which flows into, and subsequently out of, each operative volume. Arguably the monitoring accuracy of the sensors is not of the same order of what is achieved through the use of the flow meters. However, when the sensors are used precise accuracy is not called for. Instead what is required is an indication (and this can be done within an acceptable degree of tolerance) when each bladder has been filled with a medium which is to be pumped and when each bladder has been emptied. Additionally, for assistance in controlling the sequencing operation of the various pump units at least one intermediate sensor is used to determine the condition of a bladder between full and empty.
Control of the pumping process is readily effected. In the first embodiment, as slurry flows into a bladder water is expelled from the operating volume between an outer surface of the bladder, and an inner surface of the pipe in which the bladder is located.
The water which flows out is monitored by the respective water meter. When the water flow stops this is indicative that the bladder has been filled with slurry. A count of the water meter is then reset to zero in the controller, typically a PLC. In practice pulses from the water meter are generated at regular volume intervals, typically one pulse for 10 litres of water. When the slurry is to be discharged from the bladder water is introduced into the operating volume.
Water flow is diverted from a first pump unit to a second pump unit. Before such diversion takes place the pressure in the operating volume of the second pump unit is increased to the prevailing operating pressure. Consequently, when the water flow is diverted to the second pump unit, there is substantially zero pressure difference between the pressure of the incoming water and the water in the operating volume and the diversion takes place without generating pressure spikes or the like.
As indicated, an equivalent and equally effective process can be implemented by replacing the water meters with the sensors. The sensors provide equivalent information to that generated by the water meters, namely an indication of when each bladder has been filled with slurry, an indication when each bladder has been emptied, and an indication of an intermediate position (e.g. that the bladder is half-full) at which suitable sequencing actions can be implemented to ensure a smooth operation.
Preferably, the supporting structure used for the pump units is in the nature of a conventional container. This substantially facilitates assembly of the pumping apparatus, its transport to a usage site and, at the usage site, installation and commissioning thereof. Site preparation requirements are minimised. Typically, at an installation site, the first and the second manifolds and the attendant one way and control valves, which are separately transported, e.g. in a second container, are connected to the pump units. The supporting structure (container) used for the pump units can have mounted to it gantries or jibs to facilitate assembly processes on site.
Depending on the size of the pump units a conventional 40 ft container could be employed to accommodate the pump units. However, a container of this size can be awkward to handle and transport, particularly if the arrangement is to be used in a remote region. It is therefore possible to use two smaller containers, say, each the size of a conventional 20 ft container, and to form the pump units in respective half sections. When the smaller containers are assembled on site in an abutting relationship, the pump unit sections can be coupled together, as required, to form an integral arrangement.
In the aforementioned arrangement the pump units are placed in structure which, as noted, is in the nature of a conventional shipping container. The pump units are thus fairly close to the ground. Gravity flow of slurry into each pump unit, as required, during the pumping process can take place from a slurry supply tank which thus need only be higher than the pump units. In other words it is not necessary to have a slurry supply source a substantial height as is the case in the pumping system in the aforementioned PCT application.
The invention is further described by way of examples with reference to the accompanying drawings in which:
The supporting structure is shown in skeletal form. Typically the supporting structure is embodied in, or constituted by, a conventional transport container i.e. the structure 18 has a length L, a height H and a width W (
The construction of the unit 14 only is described hereinafter. The units 10 and 12 are similar to the unit 14.
The unit 14 includes an elongate tubular housing 24 in the form of a pipe which is made to a suitable specification and which has a length 26 and a diameter 30. The pipe 24 has a first end 34 and an opposing second end 36. Each end is provided with a respective flange 40, 42.
Near the first end 34 (
The pipe 24 slopes downwardly, from the left to the right in
The pump units are assembled, as indicated, under factory conditions. The supporting structure and the pump units can then be shipped using conventional container transport techniques to an installation site.
A second container, not shown, houses a control unit 60 such as a PLC, a VSD, an air-conditioner, a pump set, a store and a site office, three first non-return valves 62 (
The first end 34 of the pipe is connected via tubular structure 98 to the non-return valve 62 and the second end 36 is connected by means of tubular structure 102 to the non-return valve 64, see
The three inlet non-return valves 62 associated with the respective pump units are connected at their inlets to the slurry-in manifold 66 shown in
The slurry-in manifold 66 is connected to a slurry supply line 100 from a slurry supply source 102—see
The inlets to the valves 54 of the three pump units are connected to the water-in manifold 54A shown in
The water meters provide data on water flow to the controller 60. The control valves 54 and 56 are responsive to signals from the controller 60 which functions in accordance with a proprietary algorithm to regulate the operation of each pumping unit.
Assume that the pumping apparatus is used to pump slurry at high pressure using an actuating fluid such as water which is drawn from a water tank 106 using a high pressure water pump 108.
The slurry is gravity-fed from the source 102, see
The quantity of water pumped into the volume 88 of the pump unit 14 is measured by the water meter and is controlled to be equal to the quantity previously expelled from the bladder and measured by the meter. The size of the operating volume 88 of the pump unit 14 is increased as this volume is pressurised. The volume of the bladder undergoes a corresponding decrease in size. Slurry is thus expelled from the bladder into the slurry-out manifold 68 through the respective one-way valve 64, and into the discharge line.
While the pump unit 14 is being used to pump slurry the second pump unit 12 is readied to ensure that there is no water in the operating volume of the second pump unit and that the bladder of the second pump unit is filled with slurry. The pressure prevailing in the operating volume 88 of the second pump unit is controlled via the controller 60 and is set to be equal to the pressure available from the water pump which is used to pump water into the pump unit. Effectively, the water in this operating volume is brought to an operating pressure by slightly opening the corresponding control valve 54. This is done at a time which is shortly before pumping from the pump unit 12 is to start. As the water is incompressible the amount of water which must be introduced into the operating volume 88, to raise the pressure therein to the desired level, is minimal.
Once the pump unit 14 has completed its pumping cycle, as determined by the measurements from the water meter, the water meter count held in the controller is set to zero. At this point water flow is diverted into the operating volume 88 of the second pump unit 12. The pumping operation is moved smoothly from the third pump unit 14 to the second pump unit 12 so that slurry is discharged from the bladder of the second pump unit via the corresponding non-return valve 64 into the slurry-out manifold 68 shown in
While the pump unit 14 is being operated and when switching takes place from the pump unit 14 to the pump unit 12, the pump unit 10 is readied for operation i.e. the operating volume 88 of the pump unit 12 is pressurised with water. Consequently, when the pump unit 12 has fully expelled its slurry, switching of the pumping cycle to the pump unit 10 can be accomplished with ease and without pressure spikes or flow interruptions. Before this happens and after it happens the pump unit 14 is readied for operation so that the pumping process can be continued by the pump unit 14.
In each pump unit, the corresponding bladder 76, at what in use is a lower end, has one or more metallic inserts 120, see for example
In the embodiment referred to, use is made of bi-directional flow meters to provide an accurate measure of the volume of water flowing into each pipe 24 and out of each pipe 24. At the end of each measurement cycle, each flow meter is set to zero. These bi-directional flow meters are expensive and adequate safeguards should be implemented to ensure that they are not inadvertently damaged particularly in the robust and arduous conditions which may exist at an operational pumping site.
In a second preferred embodiment of the invention the flow meters are dispensed with. Instead, referring for example to
The sensor 132 is, for example, in the nature of a Hall-sensor and is responsive to a magnetic field generated by one or more magnets 132A which are attached to a corresponding and opposing surface of the bladder. When the magnets are close to the sensor 132 a first output signal results but if the magnets move away from the sensor 132 a different signal is produced by the sensor 132. Similar arrangements are provided for the sensors 134 and 136 in that magnets 134A and 136A respectively are fixed at suitable locations to the bladder.
The sensors can be used effectively, in place of the water meters, as it has been realized that it is not necessary to obtain a precise measure of the volume of water which flows into and out of each pump unit provided that reliable and safe switching occurs at a determined position in a pumping sequence. Thus, if the sensors simultaneously detect respective magnetic fields this is a positive indication that the bladder has been filled with slurry. If the sensors 134 and 136 only are positive this is an indication that the bladder at the water inlet end of the pump unit has commenced its collapsing sequence. In the further collapsing of the bladder a stage is reached at which the magnets 134A move away from the sensor 134 and, again, this is clearly reflected in a change in the output signal from the sensor 134. A similar situation occurs when the magnets 136A move away from the sensor 136. Provided these indications are given reliably and consistently, in a repeatable manner, the signals can be used to effect control of the pumping apparatus which includes three pump units, much in the manner which has already been described wherein reliance is placed on the use of the water meters.
In this respect, reference is made to
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- 1) each bladder is filled with slurry by opening the water-out valves and water is fully expelled from each pipe into the water tank. The water-out valves are then closed;
2) the water-in valve for the pump unit 14 is opened and the water pump 142 is then used to pump water into the operating volume 88 of the pump unit 14. The bladder starts collapsing as has been described in connection with
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- 3) when the sensor 136C detects movement of the bladder away from the pipe, it is taken that all of the slurry has been expelled from the bladder inside the pump unit 14. At this point the water flow is diverted to the bladder in the pump unit 12;
- 4) when the sensor 136B is reached water is diverted to the pump unit 10, which has previously been fully pressurized and a similar sequence to what has been described in connection with the pump unit 14 takes place with the pump unit 10;
- 5) when the water-in valve of the pump unit 14 is fully closed, the controller causes the water-out valve of the pump unit 14 to be opened. Slurry flows into the bladder of the pump unit 14 and displaces the water from the operating volume 88 of the pump unit 14. When the centrally positioned sensor 134C is closed the controller causes the water-out valve to start closing slowly until the valve is almost fully closed. When the sensor 132C is closed the controller closes the water-out valve fully. This process of controlling the flow of the water prevents water hammer.
The sequence continues in this way with the operating volume of each pump unit being internally pressurized to a desired operating value before actual pumping takes place from that unit. This process effectively eliminates pressure spikes from the system and ensures that the slurry flow from the pumping apparatus remains constant and is matched to the water flow rate of the pump 142.
The invention holds a number of benefits. The construction of the pumping apparatus is simplified compared, for example, to the pumping system described in the aforementioned international application. On-site requirements are reduced primarily because construction and assembly take place essentially under factory conditions. Through the use of three pump units the pumping rate, compared to the pumping system in the aforementioned international application, is effectively doubled.
Further benefits include the following, some of which have already been referred to:
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- The slurry supply source 102 (152 in
FIG. 13 ), only needs to be slightly higher than the pump units. - As the containers to which the components of the pumping apparatus are mounted, and which are used for transport purposes, are, for practical purposes, conventional containers, the shipping and transport thereof can be accomplished on a worldwide basis using standard techniques.
- Within each pump unit the respective bladder is protected against on-stream slurry or water pressure losses. By way of contrast in the pumping system described in the international application referred to, if there is a downstream slurry pressure loss at least one of the bladders, which is filled with water, would, inevitably, be destroyed in that it would not be surrounded and supported by slurry inside the pressure vessel.
- Maintenance of the components in the pumping apparatus can be effected at ground level.
- The water in the apparatus is returned to the water tank 106 (or 140). This tank thus acts only as a buffer. The arrangements shown in
FIGS. 7 and 13 establish a net positive suction head for the pump which means that possible cavitation conditions for the pump are for practical purposes eliminated.
- The slurry supply source 102 (152 in
In the preceding description reference has been made to the non-return valve 62 and 64. In a preferred embodiment of the present invention each non-return valve 62, 64 is of the kind described in the specification of international patent application No. PCT/ZA2012/000005.
Claims
1. A pump unit comprising:
- an elongate tubular housing with an inner surface, an inner bore, a first end and an opposing second end,
- an elongate flexible bladder of tubular form with an outer surface, an interior, an inlet, at one end of the bladder, to the interior, and an outlet, at an opposing end of the bladder, from the interior, wherein the bladder is positioned inside the bore with the bladder in sealing engagement with the housing at opposed ends of the bladder whereby the inlet is in communication with the first end of the housing, the outlet Is in communication with the second end of the housing and an operating volume of variable size is formed between the outer surface of the bladder and the opposing inner surface of the housing,
- a port for an actuating fluid which is provided on the housing in communication with said operating volume,
- an inlet non-return valve connected to the first end of the tubular housing,
- an outlet non-return valve connected to the second end of the tubular housing,
- a first control valve for controlling the flow of the actuating fluid through the port into the operating volume, and
- a second control valve for controlling the flow of the actuating fluid from the operating volume through the port.
2. The pump unit according to claim 1, wherein the elongate tubular housing is a pipe with opposing first and second ends which are flanged and opposing ends of the bladder are sealingly engaged with respective flanges at the first and second ends of the pipe.
3. The pump unit according to claim 1, wherein the inlet non-return valve allows the medium which is to be pumped to move, under gravity action, into the interior of the bladder.
4. The pump unit according to claim 1, wherein the outlet non-return valve is adapted to allow the medium which is pumped to pass, under pressure, into a discharge line.
5. The pump unit according to claim 1, further comprising a bi-directional flow meter for metering the flow of the actuating fluid through the port.
6. The pump unit according to claim 5, further comprising a controller which is connected to the flow meter and which monitors the volume of actuating fluid which flows into the operating volume, and out of the operating volume.
7. The pump unit according to claim 1, further comprising a plurality of sensors at respective axially spaced locations on the tubular housing, each sensor providing a respective signal which indicates the proximity of the bladder to the respective location of the tubular housing.
8. A Pumping apparatus comprising three pump units, each pump unit being according to claim 1, wherein the three pump units are mounted substantially parallel to each other on supporting structure, and wherein with the supporting structure on a level surface, the first ends of the tubular housings are elevated so that each housing then slopes downwardly over the length of the supporting structure towards the second end.
9. The Pumping apparatus according to claim 8, wherein the first non-return valves and a first manifold are, in use, positioned so that they lie outside the supporting structure and the second non-return valves and a second manifold, in use, lie outside the supporting structure.
10. A method of operating the pumping apparatus of claim 8 wherein, in sequence:
- pumping a medium from a first pump unit and, at the same time, preparing a second pump unit for pumping,
- pumping the medium from a third pump unit and the preparation of the second pump unit is completed.
- preparing the first pump unit for pumping is
- preparing the first pump unit is completed and the preparation of the third pump unit for pumping is commenced.
Type: Application
Filed: Apr 4, 2014
Publication Date: Feb 18, 2016
Inventors: Richard Roy WOOD (Johannesburg), Murray BREDIN (Johannesburg)
Application Number: 14/782,084