GB2094266A

GB2094266A - Sampler for fluids

Info

Publication number: GB2094266A
Application number: GB8107670A
Authority: GB
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1981-03-11
Filing date: 1981-03-11
Publication date: 1982-09-15
Also published as: GB2094266B

Abstract

A fluid sampler comprising a casing (1) having a stop on the internal surface thereof and having two ports in the walls thereof. There is a piston sleeve (14) having a base (9) and in slideable contact with the inner surface of said casing and having portholes (10,) therein adjacent to the base (9) thereof capable of aligning with the ports. There is a piston (18) in slideable contact with the inner surface of said sleeve (14) movable therein from a position just clear of the portholes (10) past the portholes (10) to a position in contact with the base (9). The piston (18) has a passageway (21) therein extending the length thereof and a compression spring (27) enabling pressure on the piston (18) to move the sleeve (14) and piston (18) past the ports until the base (9) contacts the stop (68) of the casing (1) when further pressure on the piston (18) forces the piston (18) into contact with the base (9). The sample is then forced up through the passageway (21) and can be collected through conduit (43) by way of aperture (42). <IMAGE>

Description

SPECIFICATION Sampler This invention relates to a sampler for the extraction of fluid samples in flowing or static state.

There is a great need to sample liquids, for example crude oil under substantially isoki- netic conditions. Many devices exist but they do not take representative samples because they do not operate in accordance with isokinetic principles. Some for example use complex bypass loops with motor driven circulating pumps. Some lack facilities for positive ejection of the sample and have a long and complex flow path to the sample receptacle.

Others are not bi-directional and others are extremely complex units with many compo- nent parts. Some have no facilities for changing the quantity of sample.

We have now conceived a device which largely overcomes the above-mentioned disadvantages and which is simple with few parts.

According to this invention a fluid sampler comprises a casing having two ports in the wall thereof, the casing being capable of being in communication with a pipeline so that fluid in the pipeline can flow into one port and out of the other port, the axis of the pipeline being substantially at right angles to the axis of the casing. The fluid in the pipeline should be able to flow at constant velocity into one port and out of the other port, i.e. at the same velocity and direction of the pipeline stream passing around the casing. There is a sleeve reciprocatable within the casing provided with two portholes capable of aligning with the ports in the casing, each porthole being substantially no greater in size than its adjacent port. The sleeve has a chamber formed therein at least when said ports and portholes are aligned.The boundary of the chamber comprises a pair of walls, the planes of which are substantially at right angles to the longitudinal axes of the casing and sleeve.

When the portholes are aligned with ports of the casing these walls meet the portholes of the sleeve at the perimeters thereof. In this manner fluid which flows through one aligned port and porthole, through the chamber and out through the other aligned porthole and port has a substantially smooth path without obstacles and there are substantially no unwanted cavities in the chamber. Finally there are means for removing from the chamber fluid which has been collected in the chamber.

In using the sampler the sleeve is raised or lowered so that both ports and portholes are aligned. At this stage fluid if flowing through the sampler, entering through one port of the casing and leaving by the other port. This flow is at constant velocity and at the same velocity as the flow of fluid passing around the casing. ThereaRer, the sleeve is shifted so that there is no longer any passage of fluid through the sampler i.e. the ports in the casing are blocked by the walls of the sleeve.

A sample of fluid is therefore trapped in the chamber and it can be removed from this chamber by the means provided and it can then be analysed, if desired.

In its simplest form the casing and sleeve are of circular cross-section and the ports and portholes are circular or oval. Usually the ports and portholes are diametrically opposite one another. There should be means to prevent relative rotation of the casing and the sleeve so as to prevent the possibility that the ports and portholes are misaligned radially.

One such means comprises a protrusion in the casing mating with a longitudinal channel in the sleeve. Alternatively the casing can have a longitudinal slot or channel and the casing can have a protrusion.

Also in its simplest form, the chamber is formed by two transverse circular plates fixed to the inside of the cylindrical sleeve and meeting the inner surface of the sleeve at the e=eremities of the portholes in the sleeve, i.e.

tangentially. In this manner there is no spread of the fluid in the longitudinal direction of the sleeve as the fluid flows straight through the charnlber in a direction which is at right angles to the longitudinal nazis of the casing and sleeve. Also the fluid has an uninterrupted flow through the casing and sleeve. Finally there are means for removing from the chamber fluid which has been collected in the chamber.The simplest form would be a tap in the bottom of the chamber which could be shut when the chamber is being used to collect fluid and opened when fluid no longer flows into the chamber and it is desired to collect the fluid.

Although the above briefly described sam pler can be used for various applications, in practice it has been found necessary to use a rather more sophisticated design of sampler.

Accordingly such a fluid sampler comprises a casing having a stop on the internal surface thereof and having two ports in the walls thereof, the easing being capable of being in communication with a pipeline so that fluid in the pipeline can flow into one port and out of the other port, the axis axis or the pipeline being substantially at right angles to the axis of the casing. There is a piston sleeve having a base in slideable contact with the inner surface of said casing and having portholes therein adjacent to the base thereof capable of aligning or registering with the ports of the casing. Each porthole should be substantially no greater in size than its aligned port.There is a piston in slideable contact wkh the inner surface of said sleeve, movable therein from a position just clear of the portholes, past the portholes to a position in contact with the base of the piston sleeve and having a passageway therein ex tending the length thereof. There are resilient means enabling pressure on the piston to move the sleeve and piston together past the ports in the casing until the base of the piston sleeve contacts the stop of the casing when further pressure on the piston forces the piston into contact with the base of the piston sleeve.

When depressing the piston and sleeve in using the preferred sampler of the invention, the ports of the casing are closed by the piston sleeve and a sample of fluid is isolated in the volume bounded by the base of the piston sleeve, the inner surface of the casing and the lower end of the piston. On further depressing the piston so that it contacts the base of the piston sleeve the fluid is forced up through the passageway in the piston when it can be collected in a receptacle. In this manner only a single downward short stroke is required.

It is preferred but not essential that the casing, sleeve and piston are circular in crosssection. This form is cheaper to make and less likely to result in jamming than if the crosssection were square or rectangular. However, when the cross-section is circular there are means to ensure that there is no relative rotation between the sleeve and the casing so that the ports and portholes can always be aligned by shifting the sleeve relative to the casing along their longitudinal axes. Generally a mating longitudinal channel and protrusion achieves this result.

Generally the casing should be elongate, i.e. be of a length considerably greater than its diameter if cylindrical or its greatest crosssectional dimension if not circular in cross section.

The two ports are usually near but not at the end of the casing so that there is space for the sleeve to be depressed so as to close the ports in the casing. The casing has a stop on the internal wall thereof so as to prevent the piston sleeve from sliding past the end of the casing and to enable further pressure on the piston to force the piston into contact with the base of the piston sleeve. This stop can be any lug or internal protrusion, preferably at least two, but the most preferred stop is a seat collar, the outer dimensions of which are substantially the same as the internal dimensions of the casing. A particularly preferred form when the casing is cylindrical is a collar with an external screw thread capable of screwing into the base of the casing.It is essential that the stop does not close the end of the casing completely because it is necessary to permit displacement of any fluid trapped below the base of the piston sleeve when the piston sleeve descends. Hence a seat collar is particularly suitable.

The two ports are preferably aligned i.e.

diametrically opposite one another if the casing is cylindrical. However this is not absolutely necessary and the ports could be located so that they co-operate with two ends of a pipeline which are at right angles to one another. It is essential however that the axis of the pipeline is substantially at right angles to the axis of the casing, the axis of the casing being the direction in which piston and piston sleeve reciprocate.

If desired each port can be provided with a flange so that they can be bolted to flanges on the ends of the pipeline. Preferably a seal is interposed between the flange on a port and on the pipeline.

It is preferred however for the sampler to be designed so that it can be inserted through an aperture in the pipeline and suspended in the pipeline so that fluid can flow through one port and out through the other port. This can be achieved by fixing a socket to the aperture, the inner surface of the socket having a screw thread. The upper portion of the casing of the sampler can be provided with a screw thread which co-operates with that of the socket.

Alternatively the upper end of the sampler can screw into a block, the upper end of the block having the yoke of a pneumatic actuator attached thereto.

The piston sleeve must be capable of sliding within the casing and there should be only the minimum gap between the outer surface of the sleeve and the inner surface of the casing. The sleeve serves as a valve to block the ports of the casing and at the same time trap a sample of fluid flowing through the pipeline.

There are portholes in the sleeve designed to be capable of aligning or registering with the ports in the casing. This alignment is achieved by shifting the sleeve longitudinally within the casing until the ports and portholes are level with each other. Each porthole should preferably be the same size as the port with which it registers. Preferably all portholes and ports should be oval, the longer axis being transverse to the longitudinal axes of the sleeve and casing. Less desirably the ports and portholes are circular, square or rectangular.

The lower end of the sleeve is provided with a base. Preferably this is achieved by threading internally the lower end of the sleeve and fitting it with a sealing plug.

Slideable within the piston sleeve is a piston. There is preferably also a piston rod also having a passageway extending the length thereof. Preferably the piston sleeve is provided with an end section opposite the base thereof so that this piston rod can pass through an aperture in the top end section of the piston sleeve. In order to equalise pressure piston sleeves with end members should be provided with one or more apertures, these preferably being located in the member itself.

The passageway within the piston (and piston rod) and extending the length thereof is preferably located centrally of the cross-section of the piston i.e. along the axis when casing, piston sleeve and piston have circular cross-section. The purpose of this passageway is to allow the sample of fluid to be forced out of the sampler when the piston is forced into contact with the base of the sleeve.

The passageway in the piston or piston rod is preferably provided with a non-return valve for example ball and spring so that there is no flow of the fluid being sampled passing to a receptacle or drain back of sample fluid from a receptacle when the sampler is not being used.

The resilient means are preferably a compression spring which may be located between the piston sleeve and a shoulder formed on the piston rod or a shoulder formed within the casing. The shoulder formed on the piston rod if of the same diameter as the inner diameter of the casing can also act as a guide disc for the piston rod. If the shoulder formed on the piston rod is in slideable contact with the interior of the casing then it should be provided with one or more apertures so as to equalise the pressure both sides of the should der.

The passageway should comnaunic2te with a receptacle for the sample. Since the piston moves, the connecting tube or pipe between the passageway and receptacle will usually be flexible. Alternatively it is possible to have an elongated aperture from the passageway in communication with the connecting tube or pipe such that with the further movement of the piston after the piston sleeve has con tacted the closed end there is still communication between the passageway and said tube or pipe.

To obtain a sample from fluid flowing in a pipeline after the sampler has been positioned in the pipeline with the portholes of the sleeve aligned with the ports of the casing, pressure is exerted on the piston via the piston rod.

This forces down the piston and piston sleeve, the latter closing the ports of the casing, the piston sleeve eventually contacting the stop of the casing. Further pressure on the piston forces the piston down further until it contacts the base of the piston sleeve. At the same time the sample of fluid originally trapped within the confines of the piston sleeve is forced out of the sampler through the passageway within the piston and piston rod.

Usually the fluid will be a liquid, for example oil, but it can be a gas. In the case where gases are sampled it is preferred that the wall of the piston be provided with an "O-ring" seal so that there is no leakage between the piston and piston sleeve and also for "O-ring" seals to be provided between the piston rod and sleeve to prevent leakage near the outlet from the passageway to the tube or pipe connected to the receptacle. In fact the presence of an O-ring seal could be desirable even when sampling liquids.

The sampler of this invention may be operated by a relatively simple control system involving the use of compressed air, a dia phragm and solenoid valves as will be described later.

The advantages of the sampler of this invention are manifold. It operates in accordance with isokinetic principles and there are very few moving parts or small complex components. There is unlimited compression power for positive injection. Also there is bidirectional operation, and the quantity of sample may be adjusted on-line. Furthermore the sampler may be easily coupled to a simple pneumatic pulse integrator to log the number of samples taken.

The preferred form of the fluid sampler of the invention is now described with reference to the drawings in which: Figure 1 shows a view in part section, of the top portion of a sampler; Figure 2 shows a section through the bottom portion of the sampler of Fig. 1; Figure 3 to 5 diagrammatically the various positions of the piston and sleeve within the casing as the piston and piston sleeve are depressed; Figure 6 to 8 show the sequence of operations wherein the sample of fluid is automatically collected from a pipeline and discharged from the sampler of Fig. 1 to 5.

Referring to Fig. 1 to 5 the cylindrical casing 1 is provided with two oval ports 2 and 3. The casing 1 is provided with a seat ring 7 screwed into the bottom thereof.

Slideable within casing 1 is the piston sleeve 14, the lower and of which is internally threaded and fitted with a sealing plug 9. The sleeve 14 has two apertures 1 5 and 1 6 to equalise pressure each side of the sleeve and a central aperture 1 7 to accommodate the piston rod 1 9. The sleeve 1 4 also has two diametrically opposed oval portholes 10 and 11 the same size as the ports 2 and 3 and capable of registering therewith. Relative rotation between casing 1 and sleeve 1 4 is prevented by a protrusion pin 68 communicating with a longitudinal channel in sleeve 14.

The piston 1 8 into which piston rod 1 9 is screwed is provided with an O-ring seal 20 and an axially located passageway 21 which extends the length of the piston 1 8 and piston rod 1 9. There are during seals 38 making a fluid-tight seal when the piston rod slides in the block 35 forming a shoulder 40.

Located within the passageway 21 is a nonreturn valve comprising a ball 25 and a compression spring 26. Between the top of the piston sleeve 1 4 and the shoulder 40 formed in the casing 1 is a compression spring 27.

Apertures 28 and 29 are for equalising pressure.

Further up the casing there is an inspection plug 41 and there are also some further 0 ring seals 39 at the top of the casing. Surmounting the casing 1 is a sampler transfer block 45 which is screwed onto casing 1 by means of screw thread 46. A standard pneumatic actuator (including yoke 33) is indicated in Fig. 1 generally as 44 and is screwed into sampler transfer block 46 by thread 47.

There is also an isolation valve 50 whereby when the sampler is removed from the pipeline 6 the aperture at the top of the pipeline can be sealed off.

The sample of fluid which is collected emerges from the top of the passageway 21 by means of an elongated aperture 42 which is always in communication with conduit 43 which is connected to pipe-line 57. Leakage of fluid in transferring from passageway 21 to conduit 43 is prevented by the O-ring seals 39.

The stroke adjustment whereby the volume of sample can be altered is by means of the nuts 48 and 49 indicated in Fig. 1.

Referring to Fig. 3 to 5 to obtain a sample it is necessary to move the piston 18 and piston sleeve 14 upwards so that the portholes 10 and 11 register with the ports 2 and 3, respectively, as shown in Fig. 3.

The presence of the compression spring 27 located between the shoulder 40 and the top of piston sleeve 14 means that when the piston rod 19 is moved upwards, both piston 1 8 and sleeve 14 ascend together. Likewise when the piston rod 1 9 is depressed both piston 1 8 and sleeve 14 descend together.

Thereafter it is necessary to exert further force, forcing down the piston 10 and piston sleeve 14 until the sealing plug 9 of the latter contacts the seat ring 7 of the casing 1 as shown in Fig. 4.

The sample is trapped between the bottom of the piston 1 8 and the plug 9 of the piston sleeve 14. Further pressure on the piston rod 1 9 results in the piston 1 8 being forced down into contact with the plug 9 of the sleeve 14 as shown in Fig. 5, thereby forcing the sample up the passageway 21, through aperture 42, conduit 43, pipe-line 57 and to the sample receptacle.

Referring now to Fig. 6 is a signal from controlling elements via a short time delay unit (not shown) connected to line 51 immediately energises solenoid 52. This energising of the solenoid 52 causes supply air from reservoir 53 to pass to the diaphragm 54, this diaphragm 54 and a compression spring 58 forming part of a standard pneumatic actuator. Since this diaphragm 54 is pressurised this causes the piston rod 19, piston 18 and piston sleeve 14 to move downwards together, compressing compression spring 58.

Referring to Fig. 7 when the pressure in the diaphragm 54 reaches the region of 0.85 kg/cm2 the sealing plug 9 of the sleeve 14 will be firmly seated on the seat ring 7 of the casing 1, the sleeve holding the captive sample.

Referring to Fig. 8 as the pressure of the diaphragm 54 rises the piston 14 is now driven downwards, compressing the fluid and transferring it through line 57 to the sample receptacle.

Just as full air pressure is appled to the diaphragm 54 the short time delay unit has come to the end of the time cycle and the electrical signal is removed from the solenoid valve 52. The de-energising of the solenoid 52 vents the air from diaphragm 54 via the vent (V) on the solenoid valve 52 and the compression spring 58 causes the piston rod 19, piston 18 and piston sleeve 14 to move upward.

Claims

1. A fluid sampler comprising a casing having two ports in the wall thereof, the casing being capable of being in communication with a pipeline so that fluid in the pipeline can flow into one port and out of the other port, the axis of the pipeline being substantially at right angles to the axis of the casing, a sleeve reciprocatable within the casing provided with two portholes capable of aligning with the ports in the casing, each porthole being substantially no greater in size than its adjacent port, said sleeve having a chamber formed therein, at least when said ports and portholes are aligned, the boundary of the chamber comprising a pair of walls, the planes of which are substantially at right angles to the longitudinal axis of the sleeve and which when the portholes are aligned with the ports of the casing, meet the portholes at the perimeters thereof so that fluid flowing through one aligned port and porthole and out through the other aligned porthole and port has a substantially uninterrupted path and without there being substantially any cavities in the chamber and means for removing from the chamber fluid which has been collected in the chamber.

2. A sampler according to claim 1 wherein the sleeve is cylindrical and the chamber is formed by two transverse circular plates fixed to the inside of the sleeve and meeting the inner surface of the sleeve at the extremities of the portholes.

3. A fluid sampler comprising a casing having a stop on-the internal surface thereof and having two ports in the walls thereof, the casing being capable of being in communication with a pipeline so that fluid in the pipeline can flow into one port and out of the other port, the axis of the pipeline being substantially at right angles to the axis of the casing, a piston sleeve having a base and in slideable contact with the inner surface of said casing and having portholes therein adjacent to the base thereof capable of aligning with the ports of the casing, each porthole being substantially no greater in size than its aligned port, a piston in slideable contact with the inner surface of said sleeve movable therein from a position just clear of the portholes, past the portholes to a position in contact with the base of the piston sleeve, the piston having a passageway therein extending the length thereof and resilient means enabling pressure on the piston to move the sleeve and piston past the ports in the casing until the base of the piston sleeve contacts the stop of the casing when further pressure on the piston forces the piston into contact with the base of the piston sleeve.

4. A sampler according to claim 3 which is designed so that it can be inserted through an aperture in the pipeline and suspended in the pipeline so that fluid can flow through one port and out through the other port.

5. A sampler according to either of claims 3 and 4 wherein the passageway is located centrally with respect to the cross-section of piston.

6. A sampler according to claim 5 wherein the piston has an end section opposite the base thereof and the piston is connected to a piston rod having a passageway therein extending the length thereof and in communication with the passageway in the piston, said piston rod passing through an aperture in the end section of the sleeve.

7. A sampler according to any one of claims 3 to 6 wherein the passageway in the piston or piston rod has a non-return valve therein.

8. A sampler according to any one of claims 3 to 7 wherein the resilient means comprises a compression spring located between the piston sleeve and a shoulder formed within the casing.

9. A sampler according to any one of claims 3 to 8 wherein the passageway communicates via a flexible tube or pipe with a receptacle for the sample.

1 0. A sampler according to any one of claims 3 to 8 wherein the passageway terminates in an elongated aperture which throughout the stroke of the piston is always in communication with a conduit capable of being connected to a receptacle for the sample.

11. A sampler according to any one of the preceding claims wherein the two ports are diametrically opposite one another.

1 2. A sampler according to any one of the preceding claims wherein each port is the same size as the porthole with which it registers.

1 3. A sampler according to claim 3 substantially as hereinbefore described with reference to Fig. 1 to 5 of the drawings.

1 4. A fluid sampler comprising a casing having two ports in the wall thereof so that the casing can be arranged in communication with a pipeline, one of the ports enabling fluid in the pipeline to flow into the sampler and the other port enabling fluid in the sampler to flow out of it, a sleeve reciprocably mounted within the casing, a piston reciprocably mounted within the sleeve, and actuator means operable for selectively changing the relative positions of the casing, sleeve and piston such that in a first relative position communication is provided through a chamber between the two ports, in a second relative position a sample of the fluid is isolated from the fluid flow within a space bounded by the piston, sleeve and casing, and in a third relative position the volume of said space is reduced for discharging fluid in said space through a passageway in communication with said space.

1 5. A fluid sampler according to claim 1 4 which is so designed that it can be inserted through an aperture in the pipeline and suspended in the pipeline so that fluid can flow into one port and can also flow out through the other port.

1 6. A fluid sampler according to claim 14 or 1 5, wherein resilient means is provided for biasing the sleeve towards a position in which the fluid sample is isolated within said space.

1 7. A fluid sampler according to claim 16, wherein the resilient means is a compres sion spring.

18. A fluid sampler according to claim 17, wherein the compression spring is located between said piston sleeve and a shoulder formed within said casing.

1 9. A fluid sampler according to claim 17, wherein the compression spring acts at its lower end on a top part of said sleeve.

20. A fluid sampler according to any one of claims 1 7 to 19, wherein the spring is in its state of greatest compression when the casing, sleeve and piston are in their first relative position.

21. A fluid sampler according to any one of claims 1 4 to 20, wherein said body, sleeve and piston are of circular cross-section.

22. A fluid sampler according to any one of claims 14 to 21, wherein the two ports are diametrically opposite one another.

23. A fluid sampler according to any one of claims 14 to 22, wherein the casing and piston provide flat surfaces which are substantially at right angles to the longitudinal axis of the sleeve and define opposite walls of said chamber when the casing, sleeve and piston are in their first relative position.

24. A fluid sampler according to any preceding claim, wherein the shape and design of said ports and said chamber is such that the flow through the fluid sampler, when the casing, sleeve and piston are in their first relative position, is substantially isokinetic.

25. A fluid sampler according to claim 23, wherein the planes of said flat surfaces meet the portholes at the perimeters thereof in the first relative position of said casing, sleeve and piston.

26. A fluid sampler according to claim 25, wherein the shape and design of said chamber is such that fluid flowing through one port and out through the other port, when the casing, sleeve and piston are in their first relative position, has a substantially uninterrupted path and without there being substantially any cavities in the chamber

27. A fluid sampler according to any one of claims 14 to 27, wherein the wall of the sleeve is formed with two portholes which align one with each of said two ports when the casing, sleeve and piston are in their first relative position.

28. A fluid sampler according to claim 27, wherein each port is the same size as the porthole with which it registers.

29. A fluid sampler according to claim 27 or 28, wherein the arrangement of the sleeve and piston is such that they are moved together by the actuator means relative to the casing during the changeover from the first to the second relative positions of the casing, sleeve and piston, but the piston alone is moved further, in the longitudinal direction of the sleeve, during the changeover from the second to the third relative positions.

30. A fluid sampler according to claim 27, 28, 29, wherein the sleeve is cylindrical and the chamber is bounded by two transverse circular plates fixed to the inside of the sleeve and meeting the inner surface of the sleeve at the extremities of the portholes.

31. A fluid sampler according to any one of claims 14 to 30, wherein the casing includes a plug mounted in the bottom region of the casing and having a flat surface constituting a boundary wall of said chamber.

32. A fluid sampler according to claim 31, wherein the plug is mounted in contact with the inner surface of the sleeve.

33. A fluid sampler according to claim 31, wherein the plug is secured in a screwthreaded bore in an end region of the sleeve.

34. A fluid sampler according to any one of claims 14 to 33, wherein the ports are oval in shape.

35. A fluid sampler according to any one of claims 14 to 34, wherein a stop is provided for arresting the sleeve from further movement in the same direction after arriving in the second relative position of the casing, sleeve and piston from the first relative position.

36. A fluid sampler according to any one of claims 14 to 35, wherein said passageway is formed in the piston.

37. A fluid sampler according to claim 36, wherein said passageway is centrally located with respect to the cross-section of the piston.

38. A fluid sampler according to claim 36 or 37, wherein the piston is provided with a piston rod which extends within the sleeve, said passageway being extended to pass within the piston rod in the longitudinal direction thereof.

39. A fluid sampler according to claim 38, wherein the passageway extends the length of the piston rod.

40. A fluid sampler according to claim 38 or 39, wherein the piston rod passes through, and can slide relative to, an aperture in an end section of the sleeve.

41. A fluid sampler according to any one of claims 14 to 40, wherein the passageway has a non-return valve therein for preventing return of fluid in said passageway to said enclosed space or chamber.

42. A fluid sampler according to claim 36 or any one of claims 37 to 41 as appended to claim 36, the passageway communicates via a flexible tube or pipe with a receptacle for receiving fluid discharged from the sampler.

43. A fluid sampler according to claim 36 or any one of claims 37 to 41 as appended to claim 36, the passageway terminates in an elongated aperture which throughout the stroke of the piston is always in communication with a conduit capable of being connected to a receptacle for receiving fluid discharged from the sampler.

44. A fluid sampler according to any one of claims 14 to 43, wherein the actuator means comprises a pneumatic, double-acting actuator.