U.S. patent application number 14/782084 was filed with the patent office on 2016-02-18 for puming system.
The applicant listed for this patent is ERLS MINING (PTY) LTD. Invention is credited to Murray BREDIN, Richard Roy WOOD.
Application Number | 20160047369 14/782084 |
Document ID | / |
Family ID | 51989556 |
Filed Date | 2016-02-18 |
United States Patent
Application |
20160047369 |
Kind Code |
A1 |
WOOD; Richard Roy ; et
al. |
February 18, 2016 |
PUMING SYSTEM
Abstract
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.
Inventors: |
WOOD; Richard Roy;
(Johannesburg, ZA) ; BREDIN; Murray;
(Johannesburg, ZA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ERLS MINING (PTY) LTD |
Johannesburg |
|
ZA |
|
|
Family ID: |
51989556 |
Appl. No.: |
14/782084 |
Filed: |
April 4, 2014 |
PCT Filed: |
April 4, 2014 |
PCT NO: |
PCT/ZA2014/000016 |
371 Date: |
October 2, 2015 |
Current U.S.
Class: |
417/53 ;
417/472 |
Current CPC
Class: |
F04B 15/02 20130101;
F04B 43/1136 20130101; F04B 43/113 20130101 |
International
Class: |
F04B 43/113 20060101
F04B043/113; F04B 15/02 20060101 F04B015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2013 |
ZA |
2013/02446 |
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.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to pumping apparatus.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] Apart from the aforementioned flow constraint, the pumping
system described in the international specification has some
further drawbacks.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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 INVENTION
[0018] The invention provides in the first instance a pump unit
which includes: [0019] (a) an elongate tubular housing with an
inner bore, a first end and an opposing second end, [0020] (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, [0021] (c) a port for an actuating fluid which is provided
on the housing in communication with said operating volume, [0022]
(d) an inlet non-return valve connected to the first end of the
tubular housing, [0023] (e) an outlet non-return valve connected to
the second end of the tubular housing, [0024] (f) a first control
valve for controlling the flow of the actuating fluid through the
port into the operating volume, and [0025] (g) a second control
valve for controlling the flow of the actuating fluid from the
operating volume through the port.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] The port may be formed through a wall of the pipe.
[0030] The bladder, which is of tubular form, may be made from an
appropriate material e.g. rubber.
[0031] 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.
[0032] 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.
[0033] The outlet non-return valve may be adapted to allow the
medium which is pumped to pass, under pressure, into a discharge
line.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] The invention is further described by way of examples with
reference to the accompanying drawings in which:
[0054] FIG. 1 is a view in perspective of three pump units,
included in pumping apparatus according to the invention, mounted
to support structure which is in the form of a conventional large
container which has a standard length, height and width,
[0055] FIG. 2 is a view in elevation of the arrangement shown in
FIG. 1,
[0056] FIG. 3 is a plan view of the arrangement in FIG. 1,
[0057] FIG. 4 is an end view of the arrangement, in the direction
of an arrow marked 4 in FIG. 3.
[0058] FIG. 5 illustrates in perspective a bladder used in a pump
unit,
[0059] FIG. 6 is a schematic view from one side and in
cross-section depicting the mounting of the bladder of FIG. 5 to a
pipe,
[0060] FIG. 7 is a view from one side of the pump units (i.e.
similar to what is shown in FIG. 2) with first and second manifolds
and non-return valves connected to the pump units,
[0061] FIG. 8 is a side view on an enlarged scale and in section of
part of a first manifold and an inlet non-return valve shown in
FIG. 7,
[0062] FIG. 9 is similar to FIG. 8, but showing a portion of a
second manifold and an outlet non-return valve;
[0063] FIG. 10 has four images namely FIG. 10A which shows a
slurry-in manifold, FIG. 10B which shows a water-in manifold; FIG.
10C which shows a water-out manifold; and FIG. 10D which shows a
slurry-out manifold;
[0064] FIG. 11 illustrates in plan, and from one side,
respectively, an assembled pump unit;
[0065] FIG. 12 illustrates support structure in the form of two
conventional small containers, each of a standard length, height
and width, which can be interconnected to form an arrangement
similar to that shown in FIG. 1; and
[0066] FIG. 13 is a schematic representation of an alternative
embodiment of the invention in which sensors and not water meters
are used to control the individual pump units to ensure an
effective sequencing operation.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0067] FIGS. 1 to 4 are different views of three pump units 10, 12
and 14 respectively which are mounted to supporting structure
18.
[0068] 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 (FIG. 1) which conform to the
dimensions of a conventional container. Sides of the supporting
structure are not closed--this facilitates access to equipment
mounted to the structure.
[0069] The construction of the unit 14 only is described
hereinafter. The units 10 and 12 are similar to the unit 14.
[0070] 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.
[0071] Near the first end 34 (FIG. 2) the pipe 24 is formed with
connecting structure 46 which includes an inlet port 48. A water
supply pipe 50 is connected to the port 48. A bi-directional water
meter 52 is connected in line to the pipe 50. At an end remote from
the port 48 the pipe 50 is connected to a control valve 54 which is
coupled to a water-in manifold 54A and to a control valve 56 which
is coupled to a water-out manifold 56A.
[0072] The pipe 24 slopes downwardly, from the left to the right in
FIG. 2, when the supporting structure (container) 18 is on level
ground.
[0073] 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.
[0074] 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 (FIG. 8), and three second
non-return valves 64 (FIG. 9) (one of each for each pump unit), a
slurry-in manifold 66 (FIG. 10A), a slurry-out manifold 68 (FIG.
10D), the water-in manifold 54A (FIG. 10B) and the water-out
manifold 56A (FIG. 10C). The second container is also shipped, with
its contents secure inside, to the installation site. At this site
use can be made of jibs or cranes 74 which are fixed to the first
container (FIG. 7), i.e. to the supporting structure 18, to assist
in mounting the manifolds and valves to the respective ends of the
pipes of the three pump units.
[0075] FIG. 6 illustrates in cross-section, and from one side, the
pipe 24. Positioned inside the pipe is a bladder 76 which is made
from a flexible material such as rubber and which is shown in FIG.
5. The bladder is of elongate tubular form and has flange
formations 78 and 80 at opposed ends. These flange formations
respectively overlie faces of the flanges 40 and 42 and, in use,
are clamped between a mating flange 84 of the non-return valve 62
and a mating flange 86 of the non-return valve 64, respectively.
The bladder has a nominal diameter 30A which is the same as the
diameter 30. A first, open end 76A of the bladder 76 is in direct
communication with the first end of the pipe 24, and an opposing,
second, open end 76B of the bladder is in direct communication with
the second end of the housing. An operating volume 88, of variable
size, is formed between an inner surface 90 of the pipe 24 and an
opposing outer surface 92 of the bladder 76. The inlet port 48 is
in direct communication with the operating volume 88. The bladder
is reinforced e.g. by means of additional layers 94 of rubber or
other material, over a portion of its length adjacent the flange
78. The reinforcing is adjacent the port 48 when the bladder is
placed inside the pipe.
[0076] FIG. 8 shows from one side and in cross-section a portion of
the inlet non-return valve 62 and the pipe 24. The port 48, which
is an opening in a side wall of the pipe 24, is crossed by a grid
structure 96 which, in use, prevents the bladder 76 from being
forced into the water pipe 50, when the bladder is filled with
slurry. The reinforcing layers 94 also assist in this respect.
[0077] 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 FIG. 9.
[0078] 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 FIG. 10A. The three outlet
non-return valves 64, associated with the respective pump units,
are connected at their outlets to the slurry-out manifold 68 shown
in FIG. 10D. This manifold is connected to a discharge line.
[0079] The slurry-in manifold 66 is connected to a slurry supply
line 100 from a slurry supply source 102--see FIG. 7. An upper
level of the slurry in the source is above the highest points of
the bladder.
[0080] The inlets to the valves 54 of the three pump units are
connected to the water-in manifold 54A shown in FIG. 10B. The
outlets from the valves 56 of the three pump units are connected to
the water-out manifold 56A shown in FIG. 10C.
[0081] 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.
[0082] 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.
[0083] The slurry is gravity-fed from the source 102, see FIG. 7,
through the non-return valve 62 into the bladder of the pump unit
14. Water flows from the operating volume of that pump unit via the
port 48 into the line 50 and, from there, through the control valve
56 to the water tank 106. This water is expelled by the pressure
exerted by the slurry inside the interior of the bladder. Once the
bladder is filled with slurry the size of the respective operating
volume 88, for practical purposes, is zero. The quantity of water
flowing out is monitored by the corresponding meter 52 and is
recorded in the controller 60.
[0084] 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.
[0085] 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.
[0086] 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 FIG. 100. The diversion is done without producing any
pressure spikes and without interrupting the slurry flow. The
quantity of water which goes into the second pump unit 12 is
monitored, as before, by the appropriate bi-directional water meter
52. This is an important aspect because, each time water is
expelled from a pump unit, the volume of water is metered and
controlled to be equal to the volume of water which previously
flowed into the pump unit.
[0087] 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.
[0088] 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 FIG. 5. These inserts are embedded into the rubber or
otherwise attached to the rubber from which the bladder is made.
The pipe in which the bladder is located has a sensor 126 or a
number of sensors which are responsive to the presence or absence
of the inserts.
[0089] FIG. 6 illustrates somewhat schematically how the bladder is
deformed when water is introduced into the operating volume 88. As
water flows into the volume 88 the bladder, at an upper end, is
compressed and an upper half of the bladder is forced onto a lower
half of the bladder. With an increasing view of water into the
volume 88 the bladder is collapsed over its length into a trough
shape, lying on a lower half of the pipe 24--see the
cross-sectional view in FIG. 6A. The collapse/compression should
stop while the metal inserts 120 are still within range of the
corresponding sensors 126. If the bladder is collapsed beyond this
point then bladder can be damaged and the metal inserts to be moved
away from the sensors. The provision of the metal plates thus acts
as a backup in that, if a metal plate is separated from its
corresponding sensor, this is immediately detected and a signal is
sent to the controller 60 which automatically terminates the
pumping operation.
[0090] FIG. 1 shows an arrangement wherein the pumping apparatus,
which includes the three pump units, is mounted to supporting
structure 18 which is in the form of a conventional large shipping
container, typically with a length L equal to 40 ft. A container of
this size can be awkward to handle and transport particularly if
installation of the pumping apparatus is required at a remote site.
To address this aspect, at least to some extent, use can be made of
the structure shown in FIG. 11. The support structure 18 is divided
into two sub-containers 18A and 188 respectively. Each
sub-container is of the size of a conventional small shipping
container which has a standard length of 20 ft. The pump units are
divided into respective half sections i.e. each of the pipes 24
which comprise the housings for the pump units are divided into two
sections and the sections are fitted with flanges 130 which enable
the sections to be coupled together on site, when appropriate. Once
this coupling has been effected each assembled pipe can have a
corresponding bladder inserted into it.
[0091] 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.
[0092] In a second preferred embodiment of the invention the flow
meters are dispensed with. Instead, referring for example to FIG.
6, use is made of a plurality of sensors 132, 134 and 136 which are
axially spaced apart to monitor the position of the bladder
relative to the pipe 24 at each location at which a respective
sensor is installed. The sensor 132 is close to the water inlet
port 48. The sensor 136 is close to an opposing end of the pipe
which is adjacent the slurry-out manifold 56A. The sensor 134 is
positioned at a location which is between the sensors 132 and 136.
Ideally a fourth sensor is employed. Effectively this is the same
as the sensor 126 and it is used to ensure that if adequate
switching of the pumping operation is not achieved through the
sensors 132 to 136 and an undesirable condition arises due to the
bladder being forced away from the inner surface of the pipe 24 at
the end which is close to the slurry-out manifold, that the pumping
operation can be stopped. This occurs as the sensor 126 detects
movement of the bladder away from the opposing surface of the
pipe.
[0093] 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.
[0094] 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.
[0095] In this respect, reference is made to FIG. 13 which
illustrates three pump units in each of which sensors are used in
place of the water meters referred to. For the sake of convenience
reference numerals which have been employed hereinbefore are again
used in FIG. 13 to indicate like components. The water meters are
of course absent from FIG. 13 which shows the sensors 132 to 136
for the three pump units as 132A, 134A and 136A, 132B. 134B and
1368, and 132C, 134C and 136C respectively. Water to the pump units
is pumped from a source 140 by a pump 142 through a network 144 and
is returned via a network 146. Slurry 150 from a source 152 is
gravity fed to the pump units through a network 154 and as a result
of the pumping operation is expelled into a slurry discharge line
156. In FIG. 13, the water inlets to the pump units are
respectively marked WIA; WIB and WIC; the water outlets are marked
WOA; WOB and WOC; the slurry inlets are marked SIA; SIB and SIC;
and the slurry outlets are marked SOA; SOB and SOC. The operation
of the pumping apparatus shown in FIG. 13 can be described,
briefly, as follows: [0096] 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;
[0097] 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 FIG. 6 and moves away from the sensor
132C. the bladder progressively deforms until the sensor 134C is
reached at which point the water-in valve on the pump unit 12 is
caused to open slightly to pressurize the operating volume 88 of
the pump unit 12; [0098] 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; [0099] 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;
[0100] 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.
[0101] 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.
[0102] 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.
[0103] Further benefits include the following, some of which have
already been referred to: [0104] The slurry supply source 102 (152
in FIG. 13), only needs to be slightly higher than the pump units.
[0105] 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. [0106] 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. [0107] Maintenance of the components in the pumping
apparatus can be effected at ground level. [0108] 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.
[0109] 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.
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