EP0076083A2

EP0076083A2 - Airlift pump and method of operation

Info

Publication number: EP0076083A2
Application number: EP82304966A
Authority: EP
Inventors: Jacob Johan Mostert
Original assignee: AIR WATER PUMPS Pty Ltd
Current assignee: AIR WATER PUMPS Pty Ltd
Priority date: 1981-09-21
Filing date: 1982-09-21
Publication date: 1983-04-06
Also published as: IL66829A0; EP0076083A3

Abstract

An airlift borehole pump 10 has a pressure vessel 14 to balance a column of water in the rising main 12 in the borehole 18. The rising main 12 and pressure vessel 14 maybe of flexible tubing capable of being transported in roll form. The pump is used primarily for providing drinking water for domestic purposes and for livestock or game, and can be quickly installed in an emergency.

Description

THIS INVENTION relates to a method of pumping water from a borehole by means of an airlift pump. It also relates to an airlift pump for carrying out the method.
Accordingly, a method of pumping water from a borehole is characterized in that it includes an airlift pump having a rising main extending up the borehole, an air inlet leading into the rising main at a level below the level of water in the borehole, the method including the provision of at least one additional water flow passage leading into the rising main at or near the air inlet into the rising main; and the connection of an air pressure vessel operatively to the rising main.
The additional water flow passage may slope upwardly into the rising main. The air inlet may discharge into the additional water flow passage in a direction towards the rising main.
The connection of the air pressure vessel to the rising main may be via the additional water flow passage, the air inlet into the additional flow passage taking place between the air pressure vessel and the rising main.
The invention extends also to a borehole airlift pumping installation characterized in that it comprises

a rising main;
an air inlet for admitting air under pressure into the rising main at a level below the level of water.in the borehole; and
an air pressure vessel connected to the rising main and adapted in use to provide a balance pressure to balance at least partially a column of water in the rising main.

The air pressure vessel may be provided within the borehole, and may be in the form of a tube of finite length, alongside the rising main. It may have a length extending to about the level of the water in the borehole. It may be of the same diameter as the rising main. The rising main and the pressure vessel may be of flexible synthetic plastics tubing capable of being rolled up into roll form.
A cover may be provided over the mouth of the borehole, the rising main leading sidewardly out of the borehole under the cover, and a flexible compressed air supply tube leading to the air inlet of the rising main. The cover may itself be covered with soil, and even grass or other plants growing in the soil.
The borehole installation may have a plurality of rising mains each served by its own air supply tube provided with an air pressure regulator for regulating the pressure of the air flowing into the rising main.
The invention may usefully be applied to a borehole brine airlift pumping installation for pumping brine from an array of boreholes in a salt pan, the pumping installation comprising

an airlift pump in each of the boreholes, each airlift pump having its rising main of flexible synthetic plastics tubing down its borehole; and
for each pump, a flexible air supply conduit having connecting means for connecting it to a supply of air under pressure.

The boreholes may be of varying depths, and the connecting means of the various air supply conduits may be connected in parallel to the same air supply. Each connecting means may include an air pressure regulator for regulating the air pressure to match the pumping requirements of the borehole.
The invention also provides airlift pumping equipment for pumping water from a borehole, which comprises

a roll of flexible tubing;
a branch connection defining an additional flow passage leading into the tubing a short distance from one end;
an air inlet connection leading into the tubing a short distance from the same end; and
an air pressure vessel of flexible tubing alongside the flexible tubing and connected to the additional flow passage.

The air inlet connection may lead into the additional flow passage in a direction towards the tubing. There may be provided a portable air compressor.
The invention will now be described by way of example, as applied to a borehole pump, with reference to the accompanying diagrammatic drawings.
In the drawings,

Figure 1 shows a side elevation of an airlift pumping installation in accordance with the invention;
Figure 2 shows a side elevation of an alternative arrangement for the lower end of the rising main and a pressure vessel interconnected by an additional water flow passage;
Figure 3 shows a sectional side elevation of a fitting suitable for connection to the lower ends of a rising main and a pressure vessel, the fitting incorporating the additional water flow passage;
Figure 4 shows an oblique three-dimensional view of a cylinder at the bottom of the airlift pump;
Figure 5 shows a detailed part axial section of the lower part of the tubes in the cylinder of Figure 4;
Figure 6 shows a cross-sectional view of an alternative cylinder construction having a nest of tubes;
Figure 7 shows a sectional side elevation through another embodiment of pumping installation according to the invention;
Figure 8 shows a graphical representation of the relationship between certain pumping variables; and
Figure 9 shows another graphical representation showing the relationship between other pumping variables.

Referring to the drawings, reference numural 10 refers to an airlift pump installation according to the invention. It comprises a rising main column 12, a pressure vessel 14 and a branch connection in the form of a T-piece 16, providing an additional water flow passage and interconnecting the rising main and the pressure vessel 14 at or near their lower ends in a borehole 18. The branch connection provides an additional water flow passage into the rising main. The branch connection preferably has a flow area of the same order as the rising main.
The rising main 12 and the pressure vessel 14 have openings 12.1 and 14.1 respectively to admit water. The water stands at a level 20 in the borehole 18. The branch connection 16 further has a connection for connection to an air supply pipe 22 fed from a compressor 24 driven. by an internal combustion engine 26.
The rising main 12, has a delivery end 12.2 adapted to deliver water into the dam 28.
In use, air is compressed by the compressor 24 driven by the engine 26. Compressed air is then fed down the borehole via the compressed air tube 22, into the branch connection 16 where air passes up the rising main 12 thereby lessening the specific gravity of the water column in the rising main and causing the column in the rising main to rise above the level of water in the borehole, and to discharge water from the delivery end 12.2. Air under pressure also passes into the pressure vessel 14.
While the Applicant does not wish to be bound by theory, he believes that the air in the pressure vessel 14 balances and assists the flow of water into the rising main_'12.
Referring to Figure 2 of the drawings, there is shown an alternative arrangement in which the branch passage 16 is arranged at a slope so as to ensure the rapid discharge of air into the rising main 12. The fitting for attachment to the lower ends of the tubes 12 and 14, comprises a pair of tubes 12.3 and 14.3 interconnected by the branch connection 16 and coupled to the lower ends of the rising mains 12 and 14, by means of clamps 30.
Referring now to Figure 3 of the drawings, there is shown a specially made fitting for coupling to the lower end of the rising main 12 and balance column 14. The fitting is generally indicated by reference numeral 40. It has a rising main connection 42, a pressure vessel connection 44 and an air conduit connection 46. The branch connection 16 interconnects the rising main counterpart 50 and pressure vessel counterpart 52. The air conduit connection 46 has a passage which opens into the rising main counterpart at 55.
The rising main counterpart and pressure vessel counterparts 50 and 52 are seated within one cylindrical casing 54. At the lower end of the casing 54, there is provided a plug 56 carrying a sieve 58 in the form of a sleeve, and which seats sealingly against the inner periphery of the casing 54 of the fitting 40. The casing 54, has openings 62 through which water can enter the fitting 40. The plug 56 is screwed into the lower end of the casing 54. The lower end of the casing is bevelled as at 60, to ensure easy entry into the borehole so that it does not get caught on ridges or surface imperfections in the borehole.
Referring now to Figure 4 of the drawings, there is shown an alternative construction comprising a cylinder 130 of synthetic plastics material having a manifold generally indicated by reference numeral 132. The manifold has three nipple connections 134, 136 and 138 for connection respectively to the rising main 12, the pressure vessel 14, and the air supply tube 22 respectively. The rising main 12, the pressure vessel 14, and the compressed air supply tube 22 all extend downwardly below the manifold 132 into the cylinder 130. In addition to the openings 12.1 and 14.1 being provided near the lower ends of the rising main and the pressure vessel 14, the lower ends of the tubes are also open and are slightly above the grid 140, all provided at the lower end of the cylinder 30. This is to ensure that there will be an adequate cross-sectional flow area for water to enter the rising main and the pressure vessel.
The cylinder 30 is provided with an air bleed hole 142, near its upper end, so as to allow air to bleed out of the cylinder 130 as it passes down a borehole into the water in the borehole.
Referring now to Figure 5 of the drawings, there is shown a detail of the T-piece passing into the rising main and into the pressure vessel. The T-piece 16 has its air delivery ends cut in such a way that in the rising main the opening 16.1 is directed partly upwardly, whereas in the pressure vessel, the opening 16.2 is directed partly downwardly.
Referring now to Figure 6 of the drawings, there is shown a cross-sectional view of a cylinder 150, similar to the cylinder 130 but having instead, three rising mains 152, 154 and 156, each with its pressure vessel 152.1, -.. 154.1 and 156.1. The rising mains are interconnected with their respective pressure vessels by means of T- pieces 162, 164 and 166, at different elevations, all being fed from separate air tubes 22. Each of the air tubes 22 will be provided.at its upper end with a pressure regulator.
The overall diameter of the cylinder 150 will be more or less the same as that of cylinder 130, i.e. it must pass down a borehole.
The Applicant believes that by making use of a nest of small diameter tubes, as shown in Figure 6 of the drawings, the piping will be more easily handled and can be rolled up into smaller rolls than when large diameter piping of equivalent cross-sectional area is used.
Referring now to Figure 8 of the drawings, the graphical representation of total height H in metres, relative to lift in metres, is shown. This graphical representation is used to determine a flow factor and the required air pressure for a borehole having a total delivery height H and a lift L in metres.
Thus, in the design of a pumping installation for a particular borehole, assume that the water is to be delivered at a total H of 40 metres above the branch connection 16. Assume further that the lift L above the level of the water in the borehole, is 20 metres. This yields a flow factor of 0,53 at a pressure of about 200 kPa. Using this flow factor of 0,53, it is then possible, from Figure 9, to determine the pipe diameter which is to be used, depending upon the quantity of-water which is to be pumped. Thus, if no more than 10 litres per minute are to be pumped, then tubing having a diameter of 20 mm, will suffice. However, if it is desired to pump 40 litres per minute (assuming that the borehole is capable of yielding such a deliveryl, then a tube diameter of about 40 mm will be needed. Pumping characteristics of the pumps for other boreholes having other parameters, can be derived in similar fashion.
The flow factor lines of Figure 8 are shown solid and are indicated by reference numeral 160. The air pressure lines are shown broken and are indicated by reference numeral 162. The rate of flow lines in Figure _-9, in litres per minute, are indicated by reference numeral 164.
It is an advantage of this invention that boreholes which are out of line or not vertical, will not cause difficulties in operation of the pump. The tube 12 may conveniently be of synthetic plastic material and may therefore be in a continuous length extending down the borehole. Such a tube may easily be lifted by hand, without the need for using block and tackle. If the-borehole is very deep, and if the tube 12 is too heavy for being lifted by hand, then it may be pulled out by means of a tractor. A large drum at the mouth of the borehole can serve as deflecting sheave. Accordingly, for raising the tube from a borehole, it will not be necessary to make provision for an elevated suspension point for supporting block and tackle.
The Applicant has found that an adequate volume of water can be pumped for most domestic purposes from a variety of borehole depths, by making use of a tube of 32 mm inside diameter, a pressure vessel formed by plugging a length of tube of the same size, and an engine of 1,4 Kw driving a small compressor delivering air at a rate of about 200 litres per minute at a pressure of between 200 and 300 kPa.
The Applicant has found that the engine and compressor is far less costly than conventional pumps and motors. In addition, the tubing to go down the borehole, is much less costly than that used with conventional pumps.
The Applicant has found the pump according to the invention very useful in pumping brine from boreholes in salt pans. The use of synthetic plastics material for the cylinders 130, 150 and the rising mains 12, 152, 154, 156 renders the pump less vulnerable to breakdown as a result of corrosion than windmills presently used for this purpose. In addition, pumping can take place from deep down the borehole where the brine has a high concentration. With windmills used conventionally, pumping takes place from a shallow depth in order to minimise corrosion. At such shallow depths, the salt concentration in the brine is lower than deeper down in the borehole.
About 10% to 15% extra air pressure will have to be provided over and above the value as determined by the curves of Figure 8. This is needed because brine has a higher density than ordinary water. Hence, the pressure to discharge the air from the submerged branch connection 16 will need to be higher than that given in Figure 8.
The invention also lends itself to utilization of boreholes from which it would be awkward or inconvenient to pump with conventional pumps. Thus, where a conventional pump would be an eyesore in a front garden of a house or would be damaged by stock or game unless robust pump houses are built, the boreholes may be fitted in a special way with pumps according to the invention, as described below.
Referring to Figure 7 of the drawings, the upper end of the borehole 18 is fitted with a casing 70 having a collar 72 and a removable cover 74 which may have a handle 76. The casing defines a cavity within which a tube support plate 78 is housed, supporting the air supply tube 22 and the rising main 12. The rising main 12 has a delivery 12.3 which is led under the soil surface 80 to a reservoir, drinking trough, or pond 82.
The air supply tube 22 has a connector 22.1 whereby a compressed air supply may be connected to the tube 22 while pumping is required. After pumping has been completed, the compressed air supply is removed and the cover 74 is replaced.
Where a borehole is located in such a position that it would be inconvenient to have a pumping installation at that point, then a pump according to the invention may still be installed and the cover 74 may then be completely covered with soil or grass 80.1. The pump will then be completely hidden from view. The compressed air supply tube 22 will then be fed via an air feed tube 22.2 which is buried underground for protection and which is itself fed with compressed air from a convenient or safe place remote from the borehole. Thus, it may be more convenient and less expensive to have the compressor 24 and the motor or engine 26 in a safe place such as a garage or store or shed remote from the borehole 18. Such an arrangement would be useful where a borehole is, say, in the front garden of a house.
For pumping water for game in a game reserve, the boreholes may be equipped as shown'in Figure 7 of the drawings. The game ranger, when doing his rounds, may take his compressor and engine along with him in his truck and can then connect the compressor delivery to the connection 22.1. After pumping is completed, he disconnects the compressor from the pump and moves on to the next borehole and connects the compressor to the pump in that borehole.
Alternatively, the game ranger may have a number of vessels containing compressed air which he takes with him on his rounds of inspection. If he finds that a water hole needs water, he connects a vessel to the pump via the connection 22.1 and leaves it to activate the pump. Pumping will continue until the air in the vessel is exhausted. On his next inspection, the empty vessel can be replaced .by a full one, if necessary, so that pumping can continue.
In this way, a single game ranger can go on his rounds serving a number of boreholes by replacing full compressed air vessels for empty ones. The empty air vessels may be charged at a central compressor station. The compressed air vessels may be in the form of cylinders such as are used for oxygen and acetylene under high pressure. The air vessels may contain compressed air at a pressure much higher than that required to secure pumping from a particular borehole. Each borehole, adapted for pumping by means of an air vessel, may accordingly have a setting for a pressure-reducing valve to deliver air at a pressure and rate suitable for that borehole.
If desired, the air vessels themselves, and their fittings or connections, may be protected against damage by stock or game by being housed in a casing similar to casing 70, and being also protected by a removable cover similar to cover 74. Such covers may be lockable if desired, by locks, hasps and staples. The casing 70 and cover 74 may be mouldings of concrete or of synthetic plastics material. Thus, the feed end of the air supply tube 22.2 with connection may be housed in a housing or casing similar to casing 70, and may be covered by a cover similar to cover 74.
It is an advantage of this invention that if the borehole should run dry, no damage can result. At worst, the air from the vessel will be lost. Using pumping installations according to the invention in the manner described, can bring about substantial savings in repair bills when compared with conventional pumping installations in game reserves.
Pumps according to the invention are adapted not only for use in game reserves but also for providing water for domestic consumption and for livestock, and can be quickly installed in an emergency. A pump installation as shown in Figure 7 is less likely to be damaged by stock or game than are pumps known to the Applicant, used in such situations heretofore.

Claims

1. A method of pumping water from a borehole characterised in that it includes an airlift pump having a rising main extending up the borehole, an air inlet leading into the rising main at a level below the level (20) of water in the borehole, the method including the provision of at least one additional water flow passage (16) leading into the rising main (12) at or near the air inlet into the rising main; and the connection of an air pressure vessel (14) operatively to the rising main.

2. A method as claimed in Claim 1, characterized in that the additional water flow passage (16) slopes upwardly into the rising main (12).

3. A method as claimed in Claim 1 or Claim 2, characterised in that the air inlet discharges (16.1) into the additional water flow passage (16) in a direction towards the rising main (12).

4. A method as claimed in any one of the preceding claims, characterized in that the connection of the air pressure vessel (14) to the rising main (12) is via the additional water flow passage (16), the air inlet into the additional flow passage taking place between the air pressure vessel (14) and the rising main (12).

5. A borehole airlift pumping installation (10) characterized in that it comprises

a rising main (12);

an air inlet (55) for admitting air under pressure into the rising main (12) at a level below the level (20) of water in the borehole (18); and

an air pressure vessel (14) connected to the rising main (12) and adapted in use to provide a balance pressure to balance at least partially a column of water in the rising main (12).

6. An installation as claimed in Claim 5, characterized in that the air pressure vessel (14) is within the borehole.

7. An installation as claimed in Claim 6, characterized in that the air pressure vessel (14) is in the form of a tube of finite length, alongside the rising main (12).

8. An installation as claimed in any one of Claims 5 to 7 inclusive, characterized in that the rising main (12) is of flexible tubing capable of being rolled up into roll form.

9. An installation as claimed in any one of Claims 5 to 8 inclusive, characterized in that there is provided

a cover (74) over the mouth of the borehole (18), the rising main (12) leading sidewardly out of the borehole under the cover (741; and

a flexible air supply tube (221 leading to the air inlet of the rising main and having connecting means (22.1) for connection to an air supply under pressure.

10. A method of pumping, characterized in that it includes charging a high pressure vessel with compressed air at a central charging station, and then connecting the said vessel to the air supply tube of an installation as claimed in any one of Claims 5 to 9 inclusive.

11. Air lift pumping equipment for pumping water from a borehole, characterized in that-it comprises

a roll of flexible tubing;

a branch connection defining an additional flow passage leading into the tubing a short distance from one end;

an air inlet connection leading into the tubing a short distance from the same end; and

an air pressure vessel of flexible tubing alongside the flexible tubing and connected to the additional flow passage.

12. Air lift pumping equipment as claimed in Claim 11, characterized in that the air inlet connection leads into the additional flow passage in a direction towards the tubing.