WO2003098191A2

WO2003098191A2 - Liquid sampling device

Info

Publication number: WO2003098191A2
Application number: PCT/GB2003/002168
Authority: WO
Inventors: Alastair Bewsher
Original assignee: The Victoria Universtiy Of Manchester
Priority date: 2002-05-21
Filing date: 2003-05-21
Publication date: 2003-11-27
Also published as: WO2003098191A3; AU2003244739A1; GB0211602D0

Abstract

A liquid sampling device comprising a sampling vessel connected to one end of a tube, the vessel defining a chamber (2) having a sample liquid inlet passage (5) and an outlet (6) connected to the tube, pump means being provided at the end of the tube remote from the vessel for removing gas from the chamber through the tube, in order to draw sample liquid into the vessel through an end of the inlet passage which opens outside the vessel, wherein an opposite end of the inlet passage opens into a portion of the chamber which is uppermost when the vessel is in a predetermined orientation, and the outlet opens into the portion of the chamber which is uppermost when the vessel is in the predetermined orientation.

Description

LIQUID SAMPLING DEVICE

The present invention relates to a liquid sampling device, and particularly but not exclusively to a remote water sampling device.

It is often necessary to sample water for the purposes of, inter alia, monitoring pollution, contaminants and water quality. Water may be sampled for example in open water or in a well.

A simple form of water sampler is a long-handled ladle. A user leans over a well or riverbank and scoops up the water using the ladle.

A water sampler may comprise a bailer formed from metal or dense plastic, which is suspended on a rope. The bailer is lowered into water, and when it sinks water fills the bailer by flowing over sides of the bailer. The bailer is raised from the water, and the water sample is transferred from the bailer to a storage vessel.

An alternative water sampler comprises a plastics cylinder provided with an opening at a lowermost end, the opening being covered by a plastics ball. The bailer is lowered into water to be sampled, such that the plastics ball lifts upwards to allow water into the cylinder. The bailer is then lifted from the water, the ball covering the opening to seal the lowermost end of the bailer, thereby retaining the water sample. The water sample is transferred from the bailer to a storage vessel.

A more complicated form of sampler comprises a cylinder having spring- loaded caps at both ends. The sampler is connected to two ropes. The first rope holds the sampler and the second rope guides a 'sender' down to the sampler. The sender is arranged to close the spring-loaded caps when it arrives at the sampler. In use, the sampler is lowered into the water using the first rope. The caps of the sampler are open so that water is free to flow through it, allowing the sampler to sink. When the sampler has reached a desired depth, the sender is released. The sender slides down the second rope and closes the spring-loaded caps, thereby sealing the sampler. The sampler is brought to the surface with the water sample inside. The water sample is transferred from the sampler to a storage vessel.

A sampler may comprise a metal cylinder containing a valve or series of valves activated by air lines which are connected to a pump. Pressure is used to keep the valves closed when lowering the sampler into water, until the sampler is at the desired depth. The pressure inside the sampler is then reduced, to allow water to enter the sampler. The pressure is then increased to close the valve and seal the sampler. The sampler is brought to the surface, and the water sample is transferred to a storage vessel.

When using the more complicated water samplers described above, once a sample has been transferred to a storage vessel the sampler is rinsed and used to obtain a new sample. This gives rise to the disadvantage that cross contamination between samples may occur, since rinsing of the sampler is difficult to perform properly when in the field. The simpler water samplers may be disposable. However, they suffer from the disadvantage that they provide a very limited degree of control when obtaining a water sample.

It is an object of the present invention to provide a liquid sampling device which obviates or mitigates at least one of the above disadvantages.

According to the present invention there is provided a liquid sampling device comprising a sampling vessel connected to one end of a tube, the vessel defining a chamber having a sample liquid inlet passage and an outlet connected to the tube, pump means being provided at the end of the tube remote from the vessel for removing gas from the chamber through the tube, in order to draw sample liquid into the vessel through an end of the inlet passage which opens outside the vessel, wherein an opposite end of the inlet passage opens into a portion of the chamber which is uppermost when the vessel is in a predetermined orientation, and the outlet opens into the portion of the chamber which is uppermost when the vessel is in the predetermined orientation.

The invention is advantageous because sample liquid which is drawn into the vessel via the inlet passage in unable to subsequently leave the vessel via the inlet passage, since it is located below the end of the inlet passage. This allows the liquid sampling device to be used as a liquid storage vessel, which stores the liquid sample for subsequent analysis.

Preferably, the vessel comprises a tubular body, and the inlet passage comprises an open-ended tube extending within and along the length of the tubular body.

The invention also provides a method of sampling a liquid using a liquid sampling device comprising a sampling vessel connected to one end of a tube, the vessel defining a chamber having a sample liquid inlet passage and an outlet connected to the tube, the method comprising locating the vessel in a liquid to be sampled, the vessel being held in a predetermined orientation in which the outlet and one end of the inlet passage open into a portion of the chamber which is uppermost, then removing gas from the chamber via the tube to draw the liquid into the vessel via an opposite end of the inlet passage which opens outside the vessel.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a cross-sectional view of a first water sampler which embodies the invention;

Figure 2 is a cross-sectional view of a lowermost end of the water sampler shown in figure 1 ;

Figure 3 is a cross-sectional view of a second water sampler which embodies the invention; and Figure 4 is a cross-sectional view of a lowermost end of the water sampler shown in figure 3.

Referring to figures 1 and 2, a first water sampler 1 comprises a tubular cylindrical chamber body 2 with end caps 3, 4 provided on each end thereof. End cap 3 is provided on the lower end of the body 2 and has a central aperture through which a tube 5 passes. End cap 4 is provided on the upper end of the body 2 and defines a spigot 6 onto which a flexible hose 7 is fitted. A weight 8 is also provided around the outside of the body 2.

The flexible hose 7 is of sufficient length to allow the sampler 1 to be dropped to a suitable depth to allow sampling of water, so that one end of the hose remains on the surface with the operator. A manually operable pump 9 is attached to the hose. The illustrated pump 9 includes a pressure gauge, but a simple syringe could be used as a pump.

In use, the sampler 1 is either lowered into a borehole or well for sampling the water therein, or is 'cast' in a similar manner to an angling float onto open water, the weight 8 causing at least the weighted end of the sampler to sink. The flexible hose 7 is played out so that the sampler 1 assumes a position from which a sample is to be taken.

Once the desired position has been reached the pump 9 is operated to suck air from the sampler 1 , causing a volume of water to be drawn through tube 5 into body 2. If a simple syringe is used, the increase in volume of the syringe corresponds to the volume of air drawn from the sampler. The overall system thus operates as a remote syringe with the sample held at the point of collection, enabling the volume of water drawn into the sampler to be easily controlled, thereby avoiding the risk of the sample entering the hose 7. The sampler 1 is then withdrawn from the water. The end cap 3 prevents water in the sampler 1 escaping from the space around the tube 5. The water in tube 5 is lost but the water retained in the body 2 is sufficient for sampling purposes.

Once the sampler 1 has been withdrawn from the water, the hose 7 is removed. The sampler 1 is then put in a storage rack which holds the sampler in a substantially vertical orientation. The sampler 1 is used as a storage vessel to retain the water sample for subsequent analysis, avoiding the need to transfer the water sample to a separate storage vessel.

A replacement sampler is fitted to the hose 7, and used to obtain a new sample. Since a new sampler is used to obtain each water sample, the possibility of contamination between water samples is avoided. This is a significant advantage over prior art water samplers, where the same sampler is used to obtain each sample.

Since the sampler 1 is formed from plastics, and has no moving parts, the sampler 1 is cheap and easy to manufacture. The cost of using a new water sampler 1 to obtain each water sample is therefore low.

It is usually the case that water samples obtained in the field are subsequently analysed in a laboratory. A water sample may be transferred from the sampler 1 to analysis equipment by pouring the water from the spigot 6 in the end cap 4. The water sampler 1 may then be disposed of. Alternatively, the water sampler 1 may be washed by placing the water sampler 1 in suitable washing equipment (the end cap 4 may be removed). Washing of the water sampler 1 using laboratory washing equipment will clean the sampler 1 thoroughly, thereby avoiding cross contamination between samples. This is advantageous compared to conventional rinsing of a conventional sampler in the field, which does not provide thorough cleaning of the conventional sampler.

Referring to figure 1 it can be seen that the tube 5 prevents water from leaking from the sampler 1 during storage. Provided that the sampler 1 remains in a substantially vertical orientation, it is extremely difficult for any water in the sampler 1 to leave the sampler 1 via the tube 5, even if the sampler is shaken vigorously.

Although not required to prevent water from leaking from the sampler 1 , plugs (not shown) may be used to close the lowermost end of the tube 5, and the spigot 6. This prevents airflow through the sampler 1, thereby preventing possible evaporation of a water sample from the sampler 1.

The weight 8 is removable, and may be removed from the sampler 1 , once a sample has been obtained, and located on a new sampler as required.

Referring to figures 3 and 4, a second sampler 10 which embodies the invention comprises a tubular cylindrical chamber body 11, provided with a nozzle 12 at a lowermost end, and a spigot 13 at an uppermost end. An uppermost end of the nozzle 12 tapers outwards, and is connected to a tube 14. A polystyrene ball 15 is located within the nozzle 12, the ball 15 having a diameter which is less than the largest diameter of the taper 12 but greater than the smallest diameter of the taper 12. In order to prevent the ball 15 from leaving the tube 14, a constriction (not shown) having a diameter less than that of the ball may be provided within the tube 14. Alternatively, a mesh, reverse taper, or other suitable retaining means may be provided, for example at the top of the taper of the nozzle 12.

A flexible hose 16 is fitted to the spigot 13, and is of sufficient length to allow the sampler 10 to be dropped to a required sampling depth, with an opposite end of the hose 16 remaining on the surface with an operator. A syringe (not shown) is attached to the hose 16.

In use, prior to sampling, the plunger of the syringe is pushed part way into the body of the syringe to provide positive pressure within the hose 16 and the chamber body 11. The positive pressure forces the ball 15 downwards into the tapered nozzle 12 thereby closing the nozzle 12 and preventing the ingress of water into the sampler 10. The sampler 10 is then lowered into water to be sampled. A weighted collar 17 may be used to overcome the buoyancy of the sampler 10. A float collar 18 may be provided at an upper end of the chamber body 11 to ensure that the sampler 10 maintains a substantially vertical orientation when in water.

When the sampler 10 has reached a required depth, the plunger of the syringe is drawn outwards by a limited amount (i.e. the plunger is not fully removed from the body of the syringe), thereby reducing the positive pressure within the chamber body 11 and allowing water to enter the sampler 10. The amount of water that enters the sampler 10 is determined by the movement of the plunger. Once a sample has been obtained the plunger is pushed into the syringe to again apply positive pressure and thereby close the nozzle 12 using the ball 15. The sampler 10 is removed from the water by pulling the hose 16.

The sampler shown in figures 3 and 4 is advantageous compared with that shown in figures 1 and 2 because it can obtain samples at a depth which is determined by the operator.

It will be appreciated that the nozzle 12 is closed by the ball 15 most easily if the sampler 10 is in a substantially vertical orientation (as shown in figure 1). Deviations away from the vertical will not prevent the sampler 10 from working provided that the positive pressure applied to the interior of the sampler 10 is sufficient to locate the ball 15 over the nozzle 12. The sampler 10 will usually be in a substantially vertical orientation by virtue of the fact that it is suspended from its uppermost end.

A second sample (or more) may be obtained prior to removing the sampler 10 from the water, by again reducing the positive pressure within the chamber body 11. Where this is done the samples will mix together within the sampler 10. When the sampler 10 has been recovered, the hose 16 is removed. The sampler 10 is then put in a storage rack which holds the sampler in a substantially vertical orientation. A new sampler is connected to the hose 16, to allow a new sample to be taken.

The water sample is held in the sampler 10 until it is desired to analyse the water sample. This is usually done using analysis equipment in a laboratory. The water sample is poured from the sampler 10 via the spigot 13 into the analysis equipment.

The sampler is sufficiently cheap and easy to manufacture that a large number may be used to obtain and store a series of samples for later analysis. This is convenient because it eliminates the possibility of contamination between samples being caused by a sampler not being properly rinsed. Following transfer of a water sample to analysis equipment, the sampler 10 may be disposed of, or may be washed by placing the sampler 10 in suitable washing equipment.

Referring to figure 3 it can be seen that the tube 14 prevents water from leaking from the sampler 10 during storage. The ball 15 cannot be relied upon to seal the nozzle 12 since positive pressure is not applied to the sampler 10 when the sampler 10 is being used to store the sample.

Although not required to prevent water from leaking from the sampler 10, plugs (not shown) may be used to close the nozzle 12, and the spigot 13. This prevents airflow through the sampler 10, thereby preventing possible evaporation of a water sample from the sampler 10.

The hose 16 should not be contaminated by a sample, since the amount of water drawn into the sampler 10 can be carefully controlled to prevent the water reaching the top of the chamber body 11. However, if the hose is contaminated by a sample, then the hose 16 may be rinsed by passing rinsing water through it. If the contamination is present at a lower end of the hose 16 only, then the hose 16 may be rinsed by placing the end of the hose in rinsing water, and drawing the rinsing water into the hose 16 using the syringe.

The ball 15 is made from a chemically inert substance, and may be for example polystyrene, glass, or any other suitable inert material. The use of a material which provides a small amount of resilience is preferred because it will provide a good seal against the tapered nozzle 12 of the sampler 10.

Since the sampler 10 is sealed when it is in water prior to taking a sample, a fluid may be located within the sampler 10 prior to taking the sample. For example, where it is known that a sample may react with air, thereby changing the composition of the sample, air within the sampler 10 may be replaced with an inert gas prior to obtaining the sample. Alternatively, oil could be provided in the sampler 10, the oil forming a layer over water which enters the sampler 10 thereby preventing the air from reacting with air within the sampler 10.

The fluid may be an acid, for example nitric acid, to minimise the risk of metals precipitating out of the fluid when the sample enters the sampler 10.

Depth markers may be provided on the hose 7, 16 of the sampler 1, 10 to allow an operator to determine easily the depth of the water sampler 1, 10.

The sampler may be used to sample from a bore hole, from open water or from any other suitable environment. For open water, the sampler 1, 10 may be 'cast' into open water in a similar manner to an angling float, the weighted collar 8, 17 causing at least the weighted end of the sampler to sink. The hose 6, 16 is played out so that the sampler 1, 10 assumes a position from which a sample is to be taken.

A filter may be located in the nozzle 12 or tube 5, 14 to prevent particulate from entering the sampler 1, 10. The sampler 1, 10 may be operated using any suitable manually operable pump, or a powered vacuum pump.

The chamber body 2, 11 of the sampler 1, 10 can vary in diameter and length depending on the size of sample to be taken and the size of borehole available. The sampler 1, 10 may be used to take samples from very narrow tubes, for example tubes which are 2cm or less in diameter.

The sampler 1, 10 may be used to sample shallow water, for example a depth of a millimetre or so. To sample shallow water the water sampler 1 , 10 should be orientated in a substantially vertical orientation such that the tube 5 or nozzle 12 penetrates the water.

The tube 5 or nozzle 12 may be curved in a hook shape so that an end of the tube is oriented in a substantially upwards direction. A curve of this shape would be advantageous in circumstances where it is desired not to disturb bottom sediments, the water sampler 1, 10 drawing water from just above the sediment. The end of the nozzle (or tube) may be at any point, for example below the lowermost end of the water sampler 1, 10, between ends of the water sampler 1, 10, or above an uppermost end of the water sampler 1, 10.

The weights 8, 17 are used to ensure that the sampler 1, 10 remains in a substantially vertical configuration when the sampler 1, 10 is suspended in a body of water to be sampled (the float 18 may also be used for this purpose). The weights 8, 17 may not be required for example if the sampler 1, 10 is to take water from a narrow borehole which constrains the sampler 1, 10 to remain in a substantially vertical configuration.

The hose 7, 16 is formed from flexible plastics, and is held onto the spigot 6, 13 by friction between the hose and the spigot. The friction is sufficient to ensure that the hose 7, 16 remains connected to the spigot 6, 13 under normal operating conditions. The hose 7, 16 is removed from the spigot 6, 13 by pulling the hose with sufficient force to overcome the friction.

Claims

1. A liquid sampling device comprising a sampling vessel connected to one end of a tube, the vessel defining a chamber having a sample liquid inlet passage and an outlet connected to the tube, pump means being provided at the end of the tube remote from the vessel for removing gas from the chamber through the tube, in order to draw sample liquid into the vessel through an end of the inlet passage which opens outside the vessel, wherein an opposite end of the inlet passage opens into a portion of the chamber which is uppermost when the vessel is in a predetermined orientation, and the outlet opens into the portion of the chamber which is uppermost when the vessel is in the predetermined orientation.

2. A device according to claim 1, wherein the vessel comprises a tubular body, and the inlet passage comprises an open-ended tube extending within the tubular body.

3. A device according to claim 2, wherein the inlet passage opens outside the chamber beneath the vessel when the vessel is in the predetermined orientation

4. A device according to any preceding claim, wherein the vessel is weighted to assume the predetermined orientation when suspended in a body of liquid to be sampled.

5. A device according to any preceding claim, wherein the vessel is provided with a float which assist the device to assume the predetermined orientation when suspended in a body of liquid to be sampled.

6. A device according to any preceding claim, wherein the predetermined orientation is substantially vertical.

7. A device according to any preceding claim, wherein the gas removal means comprises a pump connected to the tube.

8. A device according to claim 7, wherein the pump is a syringe connected to the tube.

9. A device according to claim 8, wherein the syringe is arranged such that movement of a plunger within a body of the syringe may be used to determine the amount of fluid that is allowed to enter the chamber.

10. A device according to any preceding claim, wherein the tube attached to the outlet of the vessel is provided with spaced apart distance markings indicative of the distance to the vessel.

11. A device according to any preceding claim, wherein the sample liquid inlet passage is provided with sealing, the sealing means being operative to close the inlet passage when gas is added to the chamber such that the pressure within the chamber exceeds the pressure of liquid at the inlet passage, and being operative to open the inlet passage when gas is removed from the chamber such that the pressure within the chamber is less than the pressure of the liquid at the inlet passage.

12. A device according to claim 11, wherein at least part of the inlet is tapered, and the sealing means comprises a ball located at the tapered part of the inlet, the ball being dimensioned so as to seal the inlet when pushed into the tapered part of the inlet by the pressure within the chamber.

13. A device according to claim 12, wherein movement of the ball within the device is restricted by retaining means.

14. A device according to claim 13, wherein the retaining means comprises a constriction provided in the inlet passage.

15. A device according to any preceding claim, wherein the inlet passage further comprises a nozzle which extends outwards from the vessel.

16. A device according to claim 15, wherein the nozzle is curved.

17. A device according to any preceding claim, wherein a fluid is provided within the chamber to restrict interaction of a sample with air.

18. A device according to claim 17, wherein the fluid is an inert gas.

19. A device according to claim 18, wherein the fluid is oil.

20. A device according to any preceding claim, wherein the inlet passage is provided with a filter to restrict the ingress of particulate into the chamber.

21. A device according to any preceding claim, wherein the device is fabricated from plastics.

22. A device according to any preceding claim, wherein the outlet and the tube are releasably connected, to allow the tube to be removed from the outlet and subsequently connected to the outlet of another water sampler.

23. A device according to any preceding claim, wherein the device further comprises a plug which may be releasably engaged with the end of the inlet passage which is exterior of the vessel, to seal the inlet passage.

24. A device according to any preceding claim, wherein the device further comprises a plug which may be releasably engaged with the outlet to seal the outlet.

25. A method of sampling a liquid using a liquid sampling device comprising a sampling vessel connected to one end of a tube, the vessel defining a chamber having a sample liquid inlet passage and an outlet connected to the tube, the method comprising locating the vessel in a liquid to be sampled, the vessel being held in a predetermined orientation in which the outlet and one end of the inlet passage open into a portion of the chamber which is uppermost, then removing gas from the chamber via the tube to draw the liquid into the vessel via an opposite end of the inlet passage which opens outside the vessel.

26. A method according to claim 25, wherein the amount of liquid allowed into the chamber is determined by the amount of gas removed from the chamber.

27. A method according to claim 25 or claim 26, wherein the liquid inlet means is provided with sealing means, and the method further comprises closing the inlet by adding gas to the chamber such that the pressure within the chamber exceeds the pressure of liquid at the inlet, then when the chamber is at a depth at which liquid is to be sampled opening the inlet by removing gas from the chamber such that the pressure within the chamber is less than the pressure of liquid at the inlet, and subsequently closing the inlet by adding gas to the chamber such that the pressure within the chamber exceeds the pressure of liquid at the inlet.

28. A method according to claim 27, wherein the method is repeated without removing the sampling vessel from the liquid, to sample liquid at more than one location.

29. A liquid sampling device substantially as hereinbefore described with reference to figures 1 and 2, or figures 3 and 4.

30. A method for sampling a liquid substantially as hereinbefore with reference to figures 1 and 2, or figures 3 and 4.