GB2141180A - Pumping apparatus - Google Patents

Abstract

A liquid or flowable medium is pumped using a tank for temporarily containing the medium. Gas is exhausted from the interior space 24 above the level of the medium in the tank, which is connected to a source 14 of the medium (by a valve V5) in order to suck the medium into the tank. When the medium reaches a maximum level in the tank 1, sensed by a sensor 16, the tank is disconnected from the source 14 (by the valve V5), gas is supplied to the space 14 (preferably under pressure), and the medium is let out of the lower part of the tank (by a valve V6), whereupon the sucking step is repeated. This cycle continues until the medium is no longer detected at the source. The invention is particularly applicable to groundwater lowering. <IMAGE>

Description

SPECIFICATION Pumping apparatus The present invention relates to the pumping of liquid or flowable media, such as water, slurries, sludge, and powders, and is particularly applicable to groundwater lowering by well points during civil engineering works. Normally when pumping media containing solids the medium comes into contact with moving parts of the pumping apparatus, resulting in heavy wear of the apparatus. It is an object of the present invention to avoid or mitigate this drawback.

The present invention provides a method of pumping a liquid or flowable medium, using a tank for temporarily containing the medium, the method comprising the sequential steps of (a) exhausting air or another gas from the interior space aoove the level of the medium in the tank and connecting the tank to a source of the medium, in order to suck the medium into the tank, and (b) supplying air or another gas to the said space, disconnecting the tank from the source, and letting the medium out of the lower part of the tank.

The steps (a) and (b) are preferably repeated in alternation, so that the medium is continually extracted from the source. In general step (b) will be shorter than step (a), particularly if the medium is forced out of the tank by the pressure of the incoming air or other gas. In most cases the gas will be air, but there may well be cases in which another gas has to be used, depending on the properties of the medium; for instance, if the medium is inflammable or explosive, an inert gas such as nitrogen may be preferable.

The invention also provides apparatus for pumping a liquid or flowable medium, comprising a tank for temporarily containing the medium, inlet means for admitting the medium to the tank, outlet means for letting the medium out of the lower part of the tank, exhaust means for exhausting air or another gas from the interior space above the level of the medium in the tank, supply means for supplying air or another gas to the said space, and control means for controlling the said inlet, outlet, exhaust, and supply means so that the medium is sucked into the tank via the inlet means by operation of the exhaust means and is then released from the tank via the outlet means by operation of the supply means.

The control means may be electrical, pneumatic, hydraulic, or manual.

The apparatus preferably includes means for sensing the level of the medium in the tank, an output of the sensing means being connected to an input of the control means. The sensing means may simply comprise a sensor of a maximum level of the medium, so as to avoid any risk of the medium entering the exhaust meahs. Preferably the sensing means also comprises a minimum level sensor (e.g.

at or near the bottom of the tank); alternatively, the control means could be arranged to operate the supply means for a given time (from sensing of the maximum level) equal to the estimated time required to release substantially all of the medium from the tank.

The inlet and outlet means may share a common port in the tank wall, but the inlet means preferably opens into the upper part of the tank so that the medium is (at least initially) discharged into the said interior space in order to avoid any flow resistance due to the medium already in the tank. To prevent the medium from being sprayed from the inlet means towards the exhaust means, a baffle is preferably arranged between them.

The exhaust and supply means may share a common port in the tank wall or may have separate ports. The exhaust means preferably comprises a pump. Similarly, the supply means preferably comprises a pump, which may conveniently be the same as that of the exhaust means, in which case the fuhctions of exhaust and supply (compression) can be achieved by making the pump reversible or (preferably) by an arrangement of valve means. Alternatively, the supply means may comprise a source of gas under pressure or simply a valve which can be opened so that air enters the tank, allowing the medium to leave under its own weight via the outlet means.

When using pumping apparatus for lowering groundwater it is conventional to run the apparatus continuously regardless of the presence or absehce of groundwater at the wellpoints. However, once the water table has been lowered to the required level, a considerable time may elapse before it starts to rise again.

Accordingly, the present invention provides groundwater lowering equipment comprising a wellpoint, pumping apparatus, means for connecting the pumping apparatus at the wellpoint, and means for controlling the pumping apparatus including means for detecting the presence or absence of groundwater at a given location or locations, the control means operating the pumping apparatus only when groundwater is present.

Thus the pumping apparatus is operated only when the presence of groundwater is detected at a given location (or at least one of the given locations). The detecting means may comprise a remote detector (e.g. a sonic detector) above ground or a detector in the weilpoint.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of pumping apparatus for use in groundwater lowering; Figure 2 is an end elevation of the apparatus; Figure 3 is a plan view of the pump and associated valves; and Figure 4 is a diagrammatic representation of the apparatus.

The apparatus illustrated comprises a tank 1 (e.g. 90 x 35 x 35 cm) having a semicylindrical base and a flat top on which are mouhted an air pump P and a motor M (e.g. a diesel engine) connected to it by a clutch 2. An air exhaust pipe 3 and ah air supply pipe 4 open into the tank 1 through respective ports in the top of the tank, adjacent the left-hand end (as viewed in Figure 1). The output 6 of the pump P communicates with the supply pipe 4 via a solenoid valve V, and with the atmosphere via a solenoid valve V2. The intake 7 of the pump communicates with the exhaust pipe 3 via a solenoid valve V3 and with the atmosphere via a solenoid valve V4.

The right-hand end of the tank 1 has a water inlet 8 adjacent the top and a water outlet 9 adjacent the bottom. A baffle 11 sloping at about 45 is positioned opposite the inlet B to deflect the incoming water downwards, in order to prevent water droplets from reachihg the exhaust pipe 3. The inlet 8 has a non-return (or solenoid) valve V6 and the outlet 9 has a non-return (or solenoid) valve V6. The valve V6 communicates via a hose 1 2 with a header 1 3 to which are connected a number of wellpoints 14 sunk into the ground to a given depth.

In order to control the operation of the valves, electrical sensors 1 6,1 7 of the water level are arranged mid-way along the tank 1.

The maximum level sensor 1 6 is about 7 cm from the top and the minimum level sensor 1 7 is about 2 cm from the bottom. The outputs of the sensors 1 6,1 7 are connected to the input interface 1 8 of a control unit C. The valves V,-V4 are connected to the output interface 1 9 of the control unit; if the valves V5,V6 are solenoid valves, they are also connected to the output interface 1 9 (as indicated in broken line in Figure 4).In order to control the operation of the pump, water detectors 21 are fitted ih the lower end parts of the wellpoints 14 and are electrically connected to the input interface 1 8 of the control unit; optionally (in addition or alternatively) a sonic detector 22 of the local water table 23 is placed aboveground and electrically connected to the input interface 1 9 is additionally connected to the motor M.

The control unit C is arranged to operate the pumping apparatus in the following manner.

So long as no water is detected by the detectors 21 (and/or the water table 23 detected by the detector 22, if present, is below the required level) the motor M is not operated.

When water is detected by at least one detector 21 (or the water table rises above the required level) the motor M driving the pump P is started and the valves V2,V3 are opened (and V6 if it is a solenoid valve), the valves V1,V4 (and V6) beihg closed. As a result, air is exhausted from the interior space 24 above the water 26 (if any) in the tank 1, and therefore water from the wellpoints 14 is sucked into the tank through the valve V5.

(The arrows in Figure 4 indicate the direction of flow of the water and air).

As soon as the water in the tank 1 reaches the maximum level detector 16, the valves V2,V3 (and V5) are closed and the valves V1,V4 (and V6) are opened. As a result, air compressed by the pump P is supplied to the interior space 24 in the tank so that the water is rapidly expelled through the valve V6 to a drainage area.

When the water level reaches the minimum level detector 1 7 the valves V1,V4 (and V6) are closed and the valves V2,V3 (and V5) are opened, and the above cycle is repeated until water is no longer detected by the detectors 21 (and/or the water table 23 is below the required level), whereupon the motor M is stopped.

The pump P used in the above-described embodiment is a rotary sliding vane exhauster/compressor. Any other design of compressor, such as a reciprocating or screw compressor, could of course be used instead.

Claims (11)

1. A method of pumping a liquid or flowable medium using a tank for temporarily containing the medium, the method comprising the sequential steps of (a) exhausting air or another gas from the interior space above the level of the medium in the tank and connecting the tank to a source of the medium, in order to suck the medium into the tank, and (b) supplying air or another gas to the said space, disconnecting the tank from the source, and letting the medium out of the lower part of the tank.

2. A method as claimed in claim 1, in which steps (a) and (b) are repeated in alternation.

3. A method as claimed in claim 1 or 2, including detecting the presence or absence of the medium at the source and performing step (a) only when the medium is present.

4. Apparatus for pumping a liquid or flowable medium, comprising a tank for temporarily containing the medium, inlet means for admitting the medium to the tank, outlet means for letting the medium out of the lower part of the tank, exhaust means for exhausting air or another gas from the interior space above the level of the medium in the tank, supply means for supplying air or another gas to the said space, and control means for controlling the said inlet, outlet, exhaust, and supply means so that the medium is sucked into the tank via the inlet means by operation of the exhaust means and is then released from the tank via the outlet means by operation of the supply means.

5. Apparatus as claimed in claim 4, including means for sensing the level of the medium in the tank, an output of the sensing means being connected to an input of the control means.

6. Apparatus as claimed in claim 5, in which the sensing means comprises a sensor of a maximum level of the medium.

7. Apparatus as claimed in claim 6, in which the sensing means further comprises a sensor or a minimum level of the medium.

8. Apparatus as claimed in any of claims 4 to 7, in which the inlet means includes means for detecting the presence or absence of the medium, an output of the detecting means being connected to an input of the control means.

9. Apparatus as claimed in any of claims 4 to 8, in which the inlet means opens into the upper part of the tank.

1 0. Apparatus as claimed in any of claims 4 to 9, in which the exhaust and supply means comprise a common pump.

11. Apparatus as claimed in claim 10, in which the exhaust and supply means further comprise valve means for selectively connecting the intake and the output of the pump to the said interior space in the tank.

1 2. Groundwater lowering equipment comprising a wellpoing, pumping apparatus, means for connecting the pumping apparatus at the wellpoint, and means for controlling the pumping apparatus including means for detecting the presence or absence of groundwater at a given location or locations, the control means operating the pumping apparatus only when groundwater is present.

1 3. A method of operating groundwater lowering equipment comprising pumping apparatus connected to a wellpoint, in which the presence or absence of groundwater is detected at a given location or locations and the pumping apparatus is operated only when groundwater is present.

1 4. A method of pumping substantially as described with reference to the accompanying drawings.

1 5. Pumping apparatus substantially as described with reference to, and as shown in, the accompanying drawings.