AU2009206170A1

AU2009206170A1 - Sampling apparatus and method

Info

Publication number: AU2009206170A1
Application number: AU2009206170A
Authority: AU
Inventors: Colin Howard
Original assignee: Oscillation Pty Ltd
Current assignee: Oscillation Pty Ltd
Priority date: 2008-09-04
Filing date: 2009-08-05
Publication date: 2010-03-18
Anticipated expiration: 2029-08-05
Also published as: AU2009206170B2

Description

P/00/01i1 Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Sampling apparatus and method The following statement is a full description of this invention, including the best method of performing it known to us: 2 Oscillation Pty Ltd Field of the invention The present invention relates to an apparatus and method for obtaining a sample volume of a liquid. The apparatus and method are particularly useful for use in the 5 sampling of high temperature and/or potentially harmful or corrosive liquids, however the invention is not limited to such applications. Background of the invention Many processes require a sample volume of liquid to be obtained from a larger body of that liquid for analysis. From the analysis of the sample volume calculations can be 10 undertaken to determine/estimate the properties of the liquid in the larger body. For example, a sedimentation test of liquid may be undertaken in which the rate of settlement of particulate matter in the liquid is analysed. In the fields of mining, agriculture and waste water treatment, for example, it is necessary to separate particulate matter from liquid such as water. Removal of the particulate matter is 15 typically achieved via gravitational settlement of the particles, the rate of which is partly dependent on the mass of those particles. In many cases a flocculant is added to the body of water to induce the particles to aggregate or floc together which serves to increase the mass of the particles and accelerate the rate of sedimentation (and therefore the efficiency of the separation process). 20 As flocculant chemicals are expensive and may have undesirous environmental effects, it is desirable to add only sufficient flocculant to the body of water to achieve the most cost and/or environmentally efficient rate of sedimentation. By taking a sample of the liquid the rate of sedimentation of that sample can be determined (and extrapolated to the rate of sedimentation of the body of liquid) and the amount of flocculant required 25 calculated. In order to obtain an accurate measure of the rate of sedimentation the sample must be taken carefully, that is without undue turbulence, to avoid damaging the sample (i.e. by 3 breaking up the aggregated particles), which could lead to skewed calculations. Further, regular samples are taken to enable real-time information relating to the rate of sedimentation, to enable the amount of flocculant to be added to be adjusted as the characteristics of the inflow stream vary. 5 One known problem with sampling liquids in high temperature environments is that a suction force applied to the sample in order to draw the sample from the depth of the sampling tank tends to cause the sample to boil, thereby leading to undesirable turbulence and consequent break up of the flocculated particles. Reference to any prior art in the specification is not, and should not be taken as, an 10 acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art. Summary of the invention 15 In one aspect the present invention provides a sampling apparatus for obtaining a sample volume of a liquid from a body of liquid and delivering the sample volume to an external vessel, the apparatus including: a sample chamber adapted to be located below a liquid surface level of the body of liquid; a sample inlet from which liquid from the body of liquid can enter the sample chamber; a sample outlet providing for fluid 20 communication between the sample chamber and external vessel; a sample chamber pressure adjustment means operable to adjust pressure in the sample chamber; wherein operation of the sample chamber pressure adjustment means is used to apply a positive pressure to the sample chamber to thereby cause the sample volume to be evacuated from the sample chamber to the external vessel via the sample outlet. 25 The sample inlet may include an inlet valve selectively operable to open the sample chamber to allow fluid flow between the body of liquid and sample chamber and to close the sample chamber to prevent fluid flow between the body of liquid and sample chamber.

4 The sample chamber pressure adjustment means may include a sample chamber atmosphere valve by means of which the sample chamber can be opened to atmospheric pressure and a sample chamber pressure valve through which compressed gas can be directed into the sample chamber. 5 The external vessel may include an external vessel pressure adjustment means. The external vessel pressure adjustment means may include an external vessel atmosphere valve by which the external vessel can be opened to atmospheric pressure and an external vessel pressure valve through which compressed air can be directed into the external vessel. 10 The sampling apparatus may further include a sample controller, the sample controller configured to charge the sample chamber with at least the sample volume by opening the sampling apparatus to atmospheric pressure and opening the sample inlet. Opening the sampling apparatus to atmospheric pressure may include opening the sample chamber atmosphere valve and opening the external vessel atmosphere valve. 15 The sample controller may be configured to evacuate the sample volume from the sample chamber to the external vessel via the sample outlet by closing the sample chamber atmosphere valve, closing the sample inlet, opening the external vessel atmosphere valve, and applying compressed gas into the sample chamber via the sample chamber pressure valve. 20 The sample chamber may include a first sub-chamber and a second sub-chamber, the first and second sub-chambers being in fluid communication with each other. The sample chamber pressure adjustment means may be directly connected to the first sub-chamber and the sample outlet may be formed in the second sub-chamber. The sample chamber may be immersed in the body of liquid.

5 The external vessel may include an external vessel outlet through which any liquid in the external vessel may be drained away. The external vessel may include a cleaning solution supply operable to flush a cleaning solution though the external vessel. 5 In a second aspect the present invention provides a method for obtaining a sample volume of a liquid from a body of liquid using a sampling apparatus, the sampling apparatus including a sample chamber located below a liquid surface level of the body of liquid and in fluid communication with an external vessel, the method including: charging the sample chamber with at least the sample volume of the liquid by: opening 10 the sampling apparatus to atmospheric pressure; and opening a sample inlet valve through which liquid from the body of liquid can enter the sample chamber; evacuating the sample volume of the liquid from the sample chamber to the external vessel by: closing the sample inlet valve; applying positive pressure to the sample chamber to force the sample volume out of the sample chamber and into the external vessel. 15 The step of opening the sampling apparatus to atmospheric pressure may include opening the sample chamber to atmospheric pressure and opening the external vessel to atmospheric pressure. The step of evacuating the sample volume of the liquid from the sample chamber to the external vessel may include opening the external vessel to atmospheric pressure. 20 The step of applying positive pressure to the sample chamber may include introducing compressed air into the sample chamber. The method may further include: evacuating the sample volume of the liquid from the external vessel; and clearing the sampling apparatus. The step of evacuating the sample volume of the liquid from the external vessel may 25 include: opening the external vessel to atmosphere; and opening an external vessel outlet through which the sample volume drains from the external vessel.

6 The step of clearing the sampling apparatus may include: closing the external vessel to atmosphere; opening the sample inlet valve; introducing compressed gas into the external vessel, the compressed gas flushing any residual liquid in the sampling apparatus out through the sample inlet valve. 5 As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. Brief description of the drawings The present invention will now be described with reference to the following figures in 10 which: Figure 1 provides a schematic diagram of a sampling apparatus in accordance with an embodiment of the invention; Figure 2 provides a logical depiction of the control circuitry of the sampling apparatus depicted in figure 1; 15 Figure 3A provides a flowchart outlining the steps involved in obtaining a sample of a liquid using the apparatus of figure 1; Figure 3B provides a flowchart detailing the steps involved in charging a sample chamber of the sampling apparatus of figure 1; Figure 3C provides a flowchart detailing the steps involved in delivering a sample 20 volume from the sample chamber of the sampling apparatus of figure 1 to an external vessel; and Figure 3D provides a flowchart detailing the steps involved resetting the sampling apparatus of figure 1.

7 Detailed description of the embodiments The sampling apparatus and method of the present invention will be described in relation to sampling in the alumina industry. In the alumina industry samples are taken from a high-temperature (around 105*C) caustic liquid and then analysed to determine 5 the rate of sedimentation particulate matter in the liquid. It will be appreciated that despite this specific application of the invention, the sampling apparatus and method described herein may be suitably used in any industry or process requiring a sample volume of a liquid to be captured from a body of that liquid. The sampling apparatus 10 Figure 1 provides a schematic view of a sampling apparatus 100 in accordance with an embodiment of the invention. The sampling apparatus includes a sample chamber 102 which is immersed in a body of liquid 104. The body of liquid 104 is, in this instance, held in a tank 106, and has a liquid surface level 108. The sampling apparatus 100 further includes a sample inlet 110 which is controlled by a 15 sample inlet valve 112 which is operable to allow or prevent fluid flow from the body of liquid 104 into the sample chamber 102 and vice versa. As can be seen, the sample inlet valve 112 is located relatively close to the surface level 108. By so locating the sample inlet valve 112 access to the valve 112 (and consequently maintenance of the valve 112) is simplified. Further, by being located relatively close to the surface level 20 108 the valve 112 is subjected to less pressure than would be the case if it were located deeper in the body of liquid 104, reducing the likelihood of pressure leakage and/or damage to the valve 112. The sampling apparatus is also provided with a sample chamber pressure adjustment means, generally indicated by arrow 114, which is selectively operable to adjust the 25 pressure in the sample chamber 102. The pressure adjustment means 114 includes a sample chamber atmosphere valve 116 which is operable to open the sample chamber 102 to atmospheric air pressure and a sample chamber pressure valve 118 through which pressure can be applied to the sample chamber 102. In this embodiment the 8 pressure is applied via compressed air, and as such the sample chamber pressure valve 118 is connected to a compressed air supply 120 for supplying the compressed air and an air regulator 122 by which the pressure of the compressed air supplied through the compressed air pressure valve 118 can be regulated. 5 While the pressure adjustment means 114 has been described and depicted as including two separate valves 114 and 116 it would, of course, be possible to combine these into a single three-way valve if so desired. The sampling apparatus also includes a sample chamber outlet 124 providing fluid communication between the sample camber 102 and an external vessel 126 (and vice 10 versa) via a transfer conduit 128. As can be seen, in the illustrated embodiment the sample chamber 102 includes first and second vertical sub-chambers 130 and 132 in fluid communication with each other via a horizontal sub-chamber 134. The sample chamber inlet 110 and sample chamber pressure adjustment means 114 are connected at the first sub-chamber 130 and the 15 sample chamber outlet 124 is connected at the second sub-chamber 132. Alternative arrangements of the sample chamber 102 would, of course, be possible. For example, the sample chamber 102 could be provided as a single (or multiple) straight or coiled tube/pipe arrangement, and may be oriented vertically, horizontally or at any angle therebetween. 20 The location of the sample chamber 102 below the liquid surface level 108 allows the sample chamber 102 to be charged with a sample volume of the liquid simply by opening the sample chamber 102 to atmospheric pressure and opening the sample inlet valve 112 (i.e. without requiring additional positive or negative pressure to be applied to the sample chamber 102). While the sample chamber 102 has been depicted and 25 described as being immersed within the liquid in the tank 106, it would of course be possible to achieve this by locating the sample chamber 102 outside the tank 106 (though still below the liquid surface level 108). For example, the sample chamber 102 9 could be located outside the tank 106 with the sample inlet 110 passing through the wall (or floor) of the tank 106. Once the sample chamber 102 has been charged positive pressure is applied to the sample chamber 102 by the sample chamber pressure valve 118 in order to evacuate 5 the sample volume into the external vessel 126. During the evacuation under positive pressure not all of the liquid captured in the sample chamber 102 will be delivered to the external vessel 126. As such the volume of liquid captured in the sample chamber 102 (and hence the volume of the sample chamber 102 itself) may need to be greater than the desired sample volume (i.e. the final volume to be delivered to the external vessel 10 126 and analysed). The external vessel 126 (into which the liquid sample captured in the sample chamber 102 is delivered) includes an external vessel inlet 136 providing fluid communication between the external vessel 126 and the sample camber 102 (and vice versa) via the transfer conduit 128. While the external vessel inlet 136 is depicted as being at the top 15 of the external vessel 126 it could, of course, be located at the bottom (or a side) of the external vessel 126. The external vessel 126 also includes an external vessel pressure adjustment means, indicated generally by arrow 138. The external vessel pressure adjustment means 138 is similar to the sample chamber pressure adjustment means 114 and includes an 20 external vessel atmosphere valve 140 which is operable to open the external vessel 126 to atmospheric air pressure and an external vessel pressure valve 142 through which compressed air can be introduced into the external vessel 126. The external vessel pressure valve 142 is connected to a compressed air supply (not shown) and, if desired, may be connected to an air regulator (not shown). Depending on the physical 25 arrangement of the sampling apparatus 100 the external vessel pressure valve 142 may be connected to the same compressed air supply 120 and/or air regulator 122 which provide and regulate compressed air to the sample chamber pressure valve 118. The external vessel 126 also includes a drainage valve 144 operable to drain liquid from the external vessel 126, and a cleaning solution supply valve 146 connected to a 10 cleaning solution source (not shown) by which a cleaning solution (such as water or any other fluid) can be introduced into the external vessel 126. The external vessel 126 is also provided with a liquid level detection means 148 for detecting the liquid level in the external vessel 126 and preventing over-filling of the 5 external vessel 126. As will be appreciated, the external vessel 126 is the vessel from which the sample volume of the liquid is to be analysed. As such, the external vessel 126 may include further or alternative specific features appropriate to the analysis to be undertaken. By way of non-limiting example, and continuing with the alumina industry example where 10 the rate of sedimentation of the liquid is to be measured, the external vessel 126 may be provided with a light source opposite a photo-electric cell by which the rate of sedimentation can be measured. Any other appropriate monitoring and/or analysis device(s) or instrumentation may, of course, also or alternatively be used. The various components of the sampling apparatus 100 are automatically controlled. 15 Figure 2 provides a logical diagram of control circuitry 200 suitable for use with the sampling apparatus 100. The sampling apparatus may be controlled by a sampling controller 202. The sampling controller may be a processor which executes control instructions stored on a memory 204. The memory 204 may be of any type such as one or more RAM modules, one or 20 more EPROM's and/or one or more magnetic or optical discs. The sampling controller 202 will also be provided with additional hardware and/or software as is desired. For example, the sample controller 202 may be provided with input and output devices (e.g. mouse, keyboard, screens and/or speakers) to allow direct interaction with the controller 202 on-site. Alternatively (or additionally) the controller 202 may be provided with 25 communication means such as a network interface controller (allowing access to one or more networks) which allows remote control of the sampling apparatus 100, as well as the delivery of operational information on the apparatus 100 (e.g. readings from the sampling of the fluid and/or any maintenance information on the apparatus itself) to a remote networked device.

ll The sampling controller 202 is connected to each relevant component of the sampling apparatus 100, including: . the sample chamber inlet valve (SC inlet) 112 0 the sample chamber atmosphere valve (SC Atm) 116 5 . the sample chamber pressure valve (SC Pressure)1 18 . the external vessel atmosphere valve (EV Atm) 140 . the external vessel pressure valve (EV Pressure) 142 (and external vessel air compressor and air regulator if required) - the external vessel drainage valve (EV Drainage) 144 10 . the external vessel water supply valve (EV Water) 146 a the liquid level detection means (Level detect) 148 . any other analysis/measurement componentry as required (e.g. light source and photoelectric cell) If required the controller 202 may also be connected to the air compressor (Air Comp) 15 120 and/or the air regulator (Air Reg) 122 in order to monitor the status of f:hese components and/or control their operation. Connection between the controller 202 and components will typically be wired, however if desired may be wireless (e.g. blue-tooth or an alternative wireless communication protocol). 20 As discussed in greater detail below, the sampling controller 202 sends signals to and receives signals from each of the relevant components in order to operate the sampling apparatus. Method of obtaining a sample 12 Referring to figure 3A, an overview of a method 300 involved in obtaining a sample in accordance with an embodiment of the invention is illustrated. Further steps of the method are then described in greater detail with reference to figures 3B to 3D. While the method 300 is described with specific reference to the sampling apparatus 5 100 above, it will be appreciated that the method may also be used with alternative apparatus. Further, the process is described below as a fully automated method controlled by the sampling controller 202, however it would be equally possible to undertake at least some of the steps manually. Overview 10 In step 302 the sample chamber 102 is charged with a sample volume of liquid from the tank 106. In step 304 the sample volume of liquid is evacuated from the sample chamber 102 to the external vessel 126 under positive pressure. As will be appreciated, at the conclusion of step 304 a sample volume of the liquid in the 15 tank 106 has been delivered to the external vessel 126 and the sample volume can be analysed as required (step 306). Sampling apparatus and methods are, however, often used (either manually or automatically) to obtain periodic samples of the liquid in order to maintain up to date information regarding the liquid. To allow for this continual periodic sampling the 20 sampling apparatus 100 is reset in step 308 to allow a new sample volume of the liquid in the tank 106 to be collected (i.e. by returning to step 302). Charging the sample chamber Turning to figure 3B, step 302 (charging the sample chamber 102) will be described in further detail.

13 In step 310 the controller 202 opens the sample chamber atmosphere valve 116 to open the sample chamber 102 to atmospheric pressure. In step 312 the controller 202 opens the external vessel atmosphere valve 140 to open the external vessel 126 to atmospheric pressure. 5 In step 314 the controller opens the sample chamber inlet valve 112. As noted, the sample chamber 102 is located below the liquid surface level 108 either by being immersed in the liquid in the tank 106 or by being located outside the tank 106 but below the liquid surface level 108. By opening the sample chamber 102 and external vessel 126 to atmospheric air pressure, liquid from the tank 106 enters the sample 10 chamber 102, completely filling the horizontal sub-chamber 134 and filling the first and second vertical sub-chambers 130 and 132 (up to the liquid surface level 108). As the sample chamber outlet 124 lies above the liquid surface level 108 no liquid is transferred to the external vessel 126 at this stage. It will, of course, be appreciated that in order to charge the apparatus steps 310, 312 15 and 314 (i.e. opening the sample chamber and external vessel atmosphere valves 116 and 140 and the sample chamber inlet valve 112) may be undertaken in any order or simultaneously. Once the sample chamber 102 has been charged (i.e. has filled to the desired level) the controller 202 closes the sample chamber inlet valve 112 in step 316. To do this the 20 controller 202 is programmed to close the sample chamber inlet valve 112 after a suitable delay from opening the sample chamber inlet valve 112 (i.e. a delay sufficient to allow the sample chamber 102 to fill). Evacuating sample volume from sample chamber to external vessel Referring to figure 3C, step 304 (evacuating the sample volume from the sample 25 chamber 102 to the external vessel 126) will be further described.

14 In step 320 the controller 202 closes the sample chamber atmosphere valve 140. Recalling that the sample chamber inlet valve 112 is also closed, this leaves the only open passage in the sample chamber the sample chamber outlet 124. In step 322 the controller opens the sample chamber pressure valve 114 to apply a 5 positive pressure to the sample chamber 102. The positive pressure forces the volume of liquid captured in the sample chamber 102 to evacuate through the sample chamber outlet 124 and transfer conduit 128 to the external vessel 126. As air pressure in the external vessel 126 rises (due to the introduction of the liquid from the sample chamber 102) air from the external vessel 126 escapes to atmosphere via the external vessel 10 atmosphere valve 140 which is still open. As noted above, it may be critical that the sampled liquid is not damaged prior or during delivery to the external vessel 126. In traditional sampling systems a vacuum (i.e. negative pressure) is used to deliver the sample volume to the external vessel 126 which, in high temperature environments (such as the alumina industry) can be 15 detrimental as the reduced pressure causes the liquid to boil. By using positive pressure to evacuate the sample chamber 102 this problem is avoided. In the described embodiment the positive pressure has been provided by means of compressed air, however it would be possible to apply the positive pressure via alternative means (e.g. a plunger arrangement or similar). 20 To further calibrate the sampling apparatus 100 (and minimise danger of the sampled volume of liquid being compromised) the air regulator 122 may be configured (either manually or though controller 202) to ensure the pressure applied to the sample chamber 102 is suitable. For example, for sampling in the alumina industry a suitable pressure may be 300kPa. 25 Once the desired volume of liquid (i.e. the sample volume) has been evacuated to the external vessel 126 the controller 202 closes the sample chamber pressure valve 118 (step 324) and opens the sample chamber atmosphere valve 116 (step 326). By opening the sample chamber atmosphere valve 326 any residual liquid in the transfer conduit 128 will flow back into the sample chamber 102.

15 With regard to the timing for closing the sample chamber pressure valve 118 and opening the sample chamber atmosphere valve 116, the controller 202 may receive a signal from the liquid level detection means 148 in the external vessel 126. Alternatively, and depending on the intended use of the apparatus 100, the apparatus 100 may be 5 calibrated with sufficient accuracy that the controller 202 can close the sample chamber pressure valve 118 after a pre-determined time has elapsed (in which case no liquid level detection means 148 is required). Sample analysis In step 306 the sample volume of liquid transferred from the tank 106 to the external 10 vessel 126 may be analysed as is appropriate. In the example application (the alumina industry) the sample will typically be analysed to determine the rate of sedimentation of the particles in the liquid. This may be done, for example, by providing the external vessel 126 with a light source and complementarily placed photoelectric cell. When the sample volume of the liquid is delivered the particles 15 suspended in the liquid will prevent the light from the light source from activating the photoelectric cell. As sedimentation occurs the sample volume will gradually become clearer until the light can reach and activate the photoelectric cell. By measuring the time between delivery of the sample volume and activation of the photoelectric cell the rate of sedimentation of the sample volume (and, therefore, the liquid in the tank 106) 20 can be calculated/extrapolated. In alternative applications the sample volume may, for example, be analysed to determine chemical composition, chemical concentration, temperature, PH levels, density, turbidity, and/or any other relevant characteristic of the liquid/particles in the liquid. 25 Resetting the sampling apparatus Referring to figure 3D, the steps involved in resetting the sampling apparatus 100 after the sample volume has been analysed will be described.

16 In step 330 the controller opens the external vessel drainage valve 144. As the external vessel atmosphere valve 140 is still open to atmosphere, opening the drainage valve 144 allows any liquid in the external vessel 144 to drain away. If desired the drainage valve 144 may be linked back to the tank 106 such that any liquid drains back into the 5 tank 106. On completion of a suitable pre-determined time delay, the controller 202 closes the external vessel atmosphere valve 140 (step 332), opens the external vessel pressure valve 142 (step 334) and opens the external vessel water supply valve 146 (step 336). The compressed air from the external vessel pressure valve 142 and the water from the 10 external vessel water supply valve 146 act to flush out any residual liquid/material and clean the external vessel 126. The controller then closes the external vessel water supply valve 146 to stop the water flow (step 338), closes the external vessel drainage valve 144 (step 340), and closes the sample chamber atmosphere valve 116 (step 342). 15 Next, the controller opens the sample chamber inlet valve 112 to provide an exhaust port (step 344). Noting that the external vessel pressure valve 142 is open, the air pressure provided through that valve operates to purge any residual liquid/material from the sampling apparatus 100 back into the tank 106. After a short time delay the controller 202 opens the sample chamber pressure valve 118 (step 346) to purge any 20 residual liquid/material from the first vertical sub-chamber 130 into the tank 106. Once the sampling apparatus 100 has been purged the controller closes the sample chamber pressure valve 118 (step 348) and the external vessel pressure valve 142 (step 350) to stop air flow. The apparatus 100 is then ready to begin the sampling procedure 300 again (by 25 opening the sample chamber atmosphere valve 116 and the external vessel atmosphere valve 140.

17 If a delay is required prior to taking a further sample, the controller 202 may, of course, close the sample chamber inlet valve 112. Sampling controller instructions To operate the sampling apparatus 100 in accordance with the above method, the 5 sampling controller 202 may be programmed with the following sequence of instructions: . open sample chamber atmosphere valve 116, external vessel atmosphere valve 140, and sample chamber inlet valve 112 . wait predetermined time (sufficient for sample chamber 102 to fill) 10 - close sample chamber atmosphere valve 116 and sample chamber inlet valve 112 . open sample chamber pressure valve 118 a detect filling of external vessel 126 (e.g. via time delay or signal from level detection means 148) 15 . close sample chamber pressure valve 118 and open sample chamber atmosphere valve 116 . await signal indicating completion of analysis of sample volume in external vessel 126 (this may, for example, be a predetermined time or a signal from analysis equipment) 20 . open external vessel drainage valve 144 and external vessel atmosphere valve 140 . wait predetermined time (sufficient for liquid in external vessel 126 to drain) . close external vessel atmosphere valve 140, open external vessel 25 pressure valve 142, and open external vessel water supply valve 145 . wait predetermined time (sufficient for external vessel to be cleaned) . close external vessel water supply valve 146 18 . wait predetermined time (for water from water supply valve 146 to be evacuated from external vessel 126) . close external vessel drainage valve 144 . close sample chamber atmosphere valve 116 and open sample chamber 5 inlet valve 112 . wait predetermined time (for transfer conduit 128, second vertical sub chamber 132 and horizontal sub-chamber 134 to clear) . open sample chamber pressure valve 118 . wait predetermined time (for first vertical sub-chamber 130 to clear) 10 0 close sample chamber pressure valve 118 and external vessel pressure valve 142. . [if required] wait predetermined time (until next sample needs to be collected) . return to start. 15 Materials and components of apparatus The particular materials and components used in the sampling apparatus 100 will, of course, depend on the environment in which the apparatus 100 is to be used. As noted above, one possible use of the apparatus is for sampling in the alumina industry which provides particularly harsh conditions. In the alumina industry, the liquid 20 is sodium hydroxide (NaOH, typically known as caustic) having a ph approaching 14, and is high-temperature (up to 1050C). This liquid is both itself highly corrosive and produces a highly corrosive atmosphere. Further, the rapid corrosion in such an environment produce an effect called scaling - a build up on the surface of materials submersed in the liquid. The scaling is extremely difficult to remove and as such the 25 apparatus is designed in anticipation of scaling occurring. In this environment (and as described in further detail below) the sampling apparatus may be submerged to a depth of 2 to 3 meters.

19 The below provides a summary of suitable materials and components of the sampling apparatus 100 in such an environment by way of non-limiting example only. It will be appreciated that different materials and components may be used (and may, in fact, be more appropriate) in different environments. 5 Noting that the sample chamber 102 is submerged in the body of liquid 104, the sample chamber may be constructed of 316 stainless steel. As discussed above, the volume of the sample chamber will depend on the sample volume intended to be captured. If, for example, the sample volume is 3.5L the sample chamber 102 may be provided with two vertical sub-chambers 130and 132 of about 10 1150mm long, each having a diameter of about 50mm. The horizontal sub-chamber 134 may be approximately 200 mm (also with a diameter of about 50mm). The sample inlet valve 112 is also submerged in the body of liquid 104. A particularly suitable valve for this environment is a diaphragm valve which is advantageous in high temperature and caustic environments as they can be manufactured from 316 stainless 15 steel with appropriate high temperature seals. Additionally, the PTFE (Teflon) diaphragm hermetically seals the hazardous fluid from the operating mechanism of the valve. It will be appreciated, however, that any other type of valve (e.g. a ball valve, butterfly valve, solenoid valve, knife gate valve, pinch valve etc) may alternatively be used. 20 As noted above, the positioning of the sample inlet valve 112 near to the surface 108 of the liquid is also advantageous as it reduces the chances of pressure damage/leakage to the valve 112. The transfer conduit 128 may be a Teflon hose of approximately 20mm diameter and from 7m to 10m long (though, as noted above, may well vary beyond these bounds 25 depending on the intended use of the apparatus). As will be appreciated, the liquid passing through the transfer conduit 128 may well be a hazardous material at pressure, and as such the transfer conduit 128 may be further reinforced with a stainless steel braid.

20 As will be appreciated, due to the use of positive pressure to evacuate the sample volume of liquid from the sample chamber 102 to the external vessel 126, the dimensions of the sample chamber 102 and transfer conduit 128 are of relevance due to the surface area (and consequent surface tension) they provide to the sample 5 volume. The smaller the diameter of the sample chamber 102 and transfer conduit 128 the more efficient will be the evacuation thereof. However, efficiency of evacuation needs to be balanced against the overall design requirements of the apparatus. The componentry of the sample chamber pressure adjustment means 114 and the external vessel pressure adjustment means 138 is quite similar. As these components 10 are not submerged in the tank 106 and do not come into contact with the liquid in the tank, standard valves and components may be used. For example, the atmosphere valves 116 and 140 and the pressure valves 118 and 142 may be pneumatic solenoid valves as are readily commercially available. Further, and as noted above, it would be possible to combine the sample chamber 15 pressure valve 118 and sample chamber atmosphere valve 116 into a single three way valve, and (similarly) the external vessel pressure valve 142 and external vessel atmosphere valve 130 into a single three way valve. Any standard air compressor may be used as the compressed air supply 120 for delivering pressurised air to the pressure valves 118 and 142. Similarly, any standard 20 regulator 122 may be used to regulate the air pressure. If required, the liquid level determination means 148 may make use of optical, ultra sonic, vibration, magnetic, or any other level sensing technology. It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features 25 mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1. A sampling apparatus for obtaining a sample volume of a liquid from a body of liquid and delivering the sample volume to an external vessel, the apparatus including: a sample chamber adapted to be located below a liquid surface level of the body 5 of liquid; a sample inlet from which liquid from the body of liquid can enter the sample chamber; a sample outlet providing for fluid communication between the sample chamber and external vessel; 10 a sample chamber pressure adjustment means operable to adjust pressure in the sample chamber; wherein operation of the sample chamber pressure adjustment means is used to apply a positive pressure to the sample chamber to thereby cause the sample volume to be evacuated from the sample chamber to the external vessel via the sample outlet. 15

2. A sampling apparatus according to claim 1, wherein the sample inlet includes an inlet valve selectively operable to open the sample chamber to allow fluid flow between the body of liquid and sample chamber and to close the sample chamber to prevent fluid flow between the body of liquid and sample chamber.

3. A sampling apparatus according to either claim 1 or claim 2, wherein the sample 20 chamber pressure adjustment means includes a sample chamber atmosphere valve by means of which the sample chamber can be opened to atmospheric pressure and a sample chamber pressure valve through which compressed gas can be directed into the sample chamber.

4. A sampling apparatus according to any one of the preceding claims, wherein the 25 external vessel includes an external vessel pressure adjustment means. 22

5. A sampling apparatus according to any one of the preceding claims, wherein the external vessel pressure adjustment means includes an external vessel atmosphere valve by which the external vessel can be opened to atmospheric pressure and an external vessel pressure valve through which compressed air can be directed into the 5 external vessel.

6. A sampling apparatus according to claim 5 claims further including a sample controller, the sample controller configured to charge the sample chamber with at least the sample volume by opening the sampling apparatus to atmospheric pressure and opening the sample inlet. 10

7. A sampling apparatus according to claim 6, wherein opening the sampling apparatus to atmospheric pressure includes opening the sample chamber atmosphere valve and opening the external vessel atmosphere valve.

8. A sampling apparatus according to any one of claims 5 to 7, wherein the sample controller is configured to evacuate the sample volume from the sample chamber to the 15 external vessel via the sample outlet by closing the sample chamber atmosphere valve, closing the sample inlet, opening the external vessel atmosphere valve, and applying compressed gas into the sample chamber via the sample chamber pressure valve.

9. A sampling apparatus according to any one of the preceding claims, wherein the sample chamber includes a first sub-chamber and a second sub-chamber, the first and 20 second sub-chambers being in fluid communication with each other.

10. A sampling apparatus according to claim 9, wherein the sample chamber pressure adjustment means is directly connected to the first sub-chamber and the sample outlet is formed in the second sub-chamber.

11. A sampling apparatus according to any one of the preceding claims, wherein the 25 sample chamber is immersed in the body of liquid. 23

12. A sampling apparatus according to any one of the preceding claims, wherein the external vessel includes an external vessel outlet through which any liquid in the external vessel may be drained away.

13. A sampling apparatus according to any one of the preceding claims, wherein the 5 external vessel includes a cleaning solution supply operable to flush a cleaning solution though the external vessel.

14. A method for obtaining a sample volume of a liquid from a body of liquid using a sampling apparatus, the sampling apparatus including a sample chamber located below a liquid surface level of the body of liquid and in fluid communication with an external 10 vessel, the method including: charging the sample chamber with at least the sample volume of the liquid by: opening the sampling apparatus to atmospheric pressure; and opening a sample inlet valve through which liquid from the body of liquid can enter the sample chamber; 15 evacuating the sample volume of the liquid from the sample chamber to the external vessel by: closing the sample inlet valve; applying positive pressure to the sample chamber to force the sample volume out of the sample chamber and into the external vessel. 20

15. The method of claim 14, wherein the step of opening the sampling apparatus to atmospheric pressure includes opening the sample chamber to atmospheric pressure and opening the external vessel to atmospheric pressure. 24

16. The method of claim 14 or claim 15, wherein the step of evacuating the sample volume of the liquid from the sample chamber to the external vessel includes opening the external vessel to atmospheric pressure.

17. The method of any one of claims 14 to 16, wherein the step of applying positive 5 pressure to the sample chamber includes introducing compressed air into the sample chamber.

18. The method of any one of claims 14 to 17, further including: evacuating the sample volume of the liquid from the external vessel; and clearing the sampling apparatus. 10

19. The method of claim 18, wherein the step of evacuating the sample volume of the liquid from the external vessel includes: opening the external vessel to atmosphere; and opening an external vessel outlet through which the sample volume drains from the external vessel. 15

20. The method of claim 18 or 19, wherein the step of clearing the sampling apparatus includes: closing the external vessel to atmosphere; opening the sample inlet valve; introducing compressed gas into the external vessel, the compressed gas 20 flushing any residual liquid in the sampling apparatus out through the sample inlet valve.

21. The method of any one of claims 14 to 20, wherein the sample chamber is immersed in the body of liquid.