Liquid sampling apparatus

A sampling apparatus for taking a liquid sample includes an inlet, a sample housing defining a sampling chamber for the liquid sample, and a sampling tube through which, in use, a flow of liquid to be sampled flows from the inlet into the sampling chamber. The sampling tube extends a predetermined distance within the sampling chamber, and defines a fluid pathway between the inlet and the sampling chamber.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus for liquid sampling. In particular, it relates to an apparatus for obtaining a liquid sample from a body of liquid along a depth range, which is representative of the liquid along the entire depth range.

When a liquid, for example oil, is stored in large volumes, the properties and composition of the liquid can vary significantly at different depths. A sample removed from a single point within such a body of liquid will only provide information on the composition at that specific depth within the liquid, and does not provide an accurate representation of the entire body of liquid. Therefore, to obtain accurate readings relating to, and representative of an entire body of liquid, it is necessary to obtain a sample taken along the entire depth of the liquid. Furthermore, it is not sufficient to merely take multiple samples from a number of specified depth points as important variations in the liquid properties along the depth may be ignored. This is particularly important in liquid such as oils in which stratified layers may form.

Accordingly, a number of current sampling systems continuously sample liquid whilst traversing the depth of a body of liquid. Such systems generally comprise a sampling container having multiple sampling apertures located at the top of chamber. As the sampling chamber is lowered through the liquid, the liquid pressure forces liquid into the chamber via one or some of the apertures, while the remaining apertures allow air from within the chamber to escape. However, as the sampling chamber descends within the liquid, the liquid pressure increases, resulting in an increase in flow rate of the liquid into the chamber. Hence, the sampling flow rate is not constant as the container descends along the sampled depth range. As a result, the liquid sample will generally contain a greater volume of liquid from the lower end of the sampling range than from the upper end. Therefore, whilst such systems improve on single depth sampling techniques, they fail to provide samples which are representative of the entire depth range sampled. In addition, as such samplers are raised back through the body of liquid once the sampling has been completed, at least the upper levels of the sample are contaminated as liquid continues to enter the chamber and mix with the sample already taken.

It is therefore desirable to provide an improved system for sampling liquids which addresses the above problems, and provides a sample representative of the entire sample depth range, and/or which provides improvement generally.

SUMMARY OF THE INVENTION

According to the present invention there is provided a liquid sampling apparatus, as described in the accompanying claims.

In a first aspect of an embodiment of the invention there is provided a sampling apparatus for taking a liquid sample. The apparatus comprises an inlet, a sample housing defining a sampling chamber for the liquid sample, and an inner sampling tube through which in use a flow of liquid to be sampled flows from the inlet into the sampling chamber. The inner sampling tube is located and extends a predetermined distance into and within the sampling chamber.

Preferably the inner sampling tube has an outlet spaced a predetermined distance from the inlet and through which in use the liquid sample flows into the sampling chamber.

In preferred embodiment of the invention, the sampling apparatus is arranged such that the outlet of the inner sampling tube is in use vertically disposed above the inlet. The inner sampling tube in use thereby defines a fixed constant inlet pressure head for fluid flowing into the sampling apparatus.

The inlet preferably further comprises an inlet valve assembly. The inlet valve assembly comprises an inlet aperture and a non-return valve.

The sampling apparatus may further comprise an outlet. Preferably, the outlet comprises an outlet valve assembly. The outlet valve assembly has an outlet aperture and a non-return valve.

The sampling apparatus preferably comprises a base cap and an end cap, connected to opposing ends of the sample housing. The base cap comprises a base cap section and an inlet valve assembly comprising the inlet, and the end cap comprises an end cap section and an outlet valve assembly comprising the outlet. The sampling apparatus is oriented in use such that the end cap is vertically disposed above the base cap. The inlet is therefore in use at a greater liquid pressure than the outlet, thereby forcing liquid to flow into the sampling chamber through the inlet.

The sampling apparatus is preferably arranged such that the flow rate of liquid into the sampling chamber is constant and independent of the external liquid pressure.

In another aspect of an embodiment of the invention, there is provided a sampling apparatus for taking a liquid sample. The apparatus comprises a sample housing defining a sampling chamber for the liquid sample, and an inlet comprising an inlet valve assembly, through which the liquid to be sampled flows into the sampling chamber. The inlet valve assembly comprises an inlet aperture, a body section and a collar. The collar is slidably attached to the body section, and is slidable between a first position and a second position. In the first position the collar covers the inlet aperture, thereby preventing in use the passage of liquid therethrough. In the second position, the inlet aperture is uncovered, such that in use passage of liquid therethrough is enabled. The collar thereby in use only permits liquid to enter the inlet aperture when the sampling apparatus is descending within liquid. When in use the sampling apparatus is stationary or moving upwardly, the collar seals the inlet aperture.

The collar is preferably biased to the first position. The collar may be biased to the first position by its own weight. Alternatively, a resilient means is provided to bias the collar to the first position.

In another aspect of an embodiment of the invention, there is provided a sampling apparatus for taking a liquid sample. The apparatus comprises an inlet, a sample housing defining a sampling chamber for the liquid sample, and an outlet valve assembly. The outlet valve assembly comprises a valve having a sealing member, and a resilient member, the valve being biased to a closed position by the resilient member, and a key member having a pin. The key member is attachable to the valve by a screw thread such that the pin extends towards the sealing member of the valve. The key member may turned within the thread of the valve is use, such that the pin engages the sealing member thereby opening the valve. The key member thereby enables in use the valve to be selectively opened or closed by insertion or removal of the key member therein or therefrom.

DETAILED DESCRIPTION

Referring toFIG. 1, the sampling apparatus comprises a sample housing1defining a sampling chamber, a base cap6, and an end cap3. In use, the sampling apparatus8is lowered vertically into a body of liquid to obtain a sample thereof. The base cap is located at the base of the sample housing1and the end cap3is located at the top of the sample housing1. The main body of the sample housing1is preferably cylindrical, although such is not essential. The sample housing1is preferably made of stainless steel, although it may be made of any other suitable material.

The sample housing1is provided with an aperture10at the top of the sample housing1, and an aperture9at the base of the sample housing1. A threaded section7is provided at the base of the sample housing1for attachment of the base cap6. The base of the sample housing1is preferably reduced in diameter, such that the outer diameter of the base of the housing is less than the outer diameter of the main body of the housing. The top of the sample housing1is also provided with a threaded section11for attachment of the end cap3.

The end cap3comprises an outlet valve assembly, and cap section26. An aperture29is formed in cap section26. The outlet valve assembly comprises key member12and valve13. Valve13comprises a resilient member, for example a spring, a sealing member25, for example a ball, and apertures30and18. Cap section26is threaded for attachment to sample housing1, a resilient sealing member15is provided in a radially extended groove within cap member26, for providing an air tight seal with the sample housing1. Aperture29is threaded to permit attachment thereto of key member12. A pin member17extends from the base of key member12, and an internal bore14is provided within pin member17, which interconnects with internal bore31of key member12.

When the sampling apparatus is not in use, the key member12remains separate from cap section26, such that non return valve13is closed. Prior to the commencement of sampling, the key member12is attached to cap section26. As key member12is threaded into aperture29the pin member17progressively extends further within aperture29until it begins to push against sealing member25of the non return valve13. As pin member17is forced against sealing member25, the resilient member of the non return valve13is compressed such that the seal between sealing member25and aperture30is broken. A pathway is thereby provided for air to exit from the sampling chamber via apertures18and30, and then through internal bores14and31of key member12. In this way, air is able to escape from the sampling chamber as it fills during liquid sampling. Once sampling is completed, the key member12is removed from cap member26, thereby allowing the non return valve13to close. In this way, the sampled liquid contained within the sampling chamber is sealed within the sampling chamber, which is essential for preventing escape of liquid or gases from the chamber once sampling is completed. In addition, key member12comprises a lug28for attachment of a supporting cable or wire, which is used to lower the sampling apparatus during sampling.

Base cap6consists of a cap section34and a valve section35. The cap section34attaches to the base of sample housing1via a threaded section21. A resilient sealing member16is provided within a radial groove in cap section34to provide an air tight seal between cap section34and the sample housing1. An inner bore32extends within base cap6. The inner bore32extends from the cap section34into the valve section35where it is restricted before continuing to the inlet aperture5. A sealing member20is provided within the wider section of the inner bore32such that the combination of the restricted bore section and the sealing member20form a non-return valve which allows fluid to flow into the sampling chamber, but prevents fluid from exiting the sampling chamber once sampling has stopped. A collar2surrounds, and is slidably engageable with, the valve section35. The collar member2comprises a main body36and a flange section33which radially extends therefrom. Alternatively, the collar may comprise a relatively thick disc member which covers and extends over. The collar member2is preferably made of nylon, although it may be made of any other suitable material.

The collar member2covers and seals the inlet aperture5such that liquids or gases are prevented from entering or leaving said aperture5. The outer diameter of the valve section5is increased at its base, such that the outer diameter of the base of valve section35is greater than the inner diameter of the collar member2, thereby acting as an end cap an preventing the collar member2from sliding off the end of the valve section35. Preferably, the outer diameter of the valve section35is increased by providing a retaining nut4at the base of the inlet valve6, although any suitable means for locating the collar section in the closed position could be provided. The collar2is slidable from the closed position, to an open position, wherein the aperture5is uncovered. The collar2is biased towards the closed position. Preferably, the collar2is biased towards the closed position by its own weight, or by the force of liquid on the its upper surface. Alternatively, the collar may be biased towards the closed position by a resilient member such as a spring.

An inner sampling tube22is inserted into the inner bore32of base cap6such that the inner sampling tube22extends upwardly from the base cap6. The inner sampling tube is preferable cylindrical, and extends within the sampling chamber from the base cap6. When the base cap6is connected to the sample housing1, the inner sampling tube22extends vertically within the sampling chamber. The inner sampling tube22does not extend along the full internal height of the sampling chamber1, such that when the end cap3is connected to the top of the sample housing1a gap is defined between the end cap3and the outlet24of the sampling chamber22.

In operation, the end cap3and base cap6are firstly connected to the sample housing1. The key section12is screwed into the cap section26of the end cap3such that the valve13is opened. The sampling apparatus8is then lowered into the body of the liquid to be sampled by a supporting cable or wire connected to the key member12of the end cap3. A drive mechanism is provided to provide constant release of the supporting and cable, thereby enabling the sampling apparatus8to be lowered through the liquid at a steady rate. As the sampling apparatus8is lowered through the liquid, a fluid pressure is applied to the lower surface of the flange section33of the collar member2. This causes the collar member2to slide upwardly relative to the inlet aperture5, thereby exposing the inlet aperture5. Fluid pressure forces liquid into the aperture5. As the liquid enters the inner bore of valve section35it forces upwards the sealing member20to provide a fluid pathway from the aperture5to the inner sampling tube22. The liquid continues to rise within inner sampling tube22until it reaches the apex24. At this point, the liquid overflows from the outlet24of the inner sampling tube22into the base of the sampling chamber.

Liquid continues to enter the sampling chamber at a constant flow rate as the sampling apparatus8descends within the body of liquid, thereby providing a sample which is representative of the entire sampling depth. The constant flow rate is achieved through the arrangement of the sampling apparatus8to provide a constant pressure differential between the outlet24of the inner sampling tube22and the outlet aperture18of the end cap3. As the sampling apparatus8descends within the liquid the fluid pressure at inlet aperture5increases, as does the pressure at the outlet aperture18. The pressure at the outlet24of the inner sampling tube22is less than the pressure at inlet aperture5by an amount equivalent to the hydrostatic head provided by the volume of liquid contained within the inner sampling tube22and inner bore of the inlet valve6. Although the pressure at the outlet24of the inner sampling tube22increases with depth, the difference between this pressure and the pressure at the inlet aperture5remains constant irrespective of the depth. As the increase in pressure at the outlet aperture18is directly proportional to the increase in pressure at inlet aperture5the difference between the pressure at the outlet24of the inner sampling tube22and the pressure at the outlet aperture18also remains constant.

The pressure differential between the outlet24of inner sampling tube22and the outlet aperture18determines the flow rate of liquid into sampling chamber. Therefore, as this differential remains constant, so does the flow rate of liquid into the sampling chamber. As such, sampling flow rate is independent of external fluid pressure, and hence depth, and therefore remains constant along the entire sampling depth. The sampling depth will usually be the entire depth of a body of liquid, although the descent of the sampling apparatus8may be controlled to sample a specified depth from the surface to a point within, but not at the bottom of, the depth of the liquid.

Once a sample has been completed, the sampling apparatus8is retracted from the liquid. As the sampling apparatus8travels upwards within the liquid, fluid pressure acts downwards on the upper surface of the flange member33of collar member2, thereby returning it to the closed position. The weight of the collar member2also acts to return it to the closed position. The closed position is defined as any position in which the collar member covers the inlet aperture5. The collar member also returns to the closed position whenever the sampling apparatus8is stationery within the liquid. In this way, the inlet aperture5is permanently open during sampling to provide a continuous and constant sample, but is closed as soon as sampling is ceased to prevent further liquid entering the sampling chamber. Once the sampling apparatus8is stationery or moving upwardly, the sealing member20also returns to the closed position, thereby also preventing release of liquid from the sampling apparatus8. As the sampling apparatus8is raised within liquid, the pressure within the sampling chamber prevents the liquid from entering the chamber via the end cap3.

Once the sampling apparatus8has been retrieved from the liquid, the key member12is removed from the cap section26, thereby closing the valve13and preventing the release of liquid or gases from the sampling chamber. Sealing the end cap3enables the sampling apparatus to be turned upside down to enable the base cap6to be removed from the sample housing1. The base cap6may then be replaced by a sealing cap for storage and transit of the sample.

Once the sample has been taken, it must subsequently be removed from the sampling chamber for analysis. In the simplest scenario, the end cap could be removed and the liquid decanted for analysis. However, for certain sampling techniques, for example Reid Vapour Pressure (RVP) sampling, it is preferable to avoid decanting the liquid as this results in gases such as the light end gases for oil samples, being lost. Additional valve means39is provided to enable the removal of the sample from the sampling chamber1without decanting.

Once the sampling chamber has been capped, the valve13ensures that the sampling chamber is sealed. When it is required to analyse the sample, the sampling valve39is screwed into cap section26, similarly to the key member12. Sampling valve39comprises an internal bore48running through the centre of the main valve body47and a secondary internal bore41connecting with internal bore48. The central internal bore48is narrow at the top of the main body47and widens towards the base of the main valve body47. An end shaft49is inserted into the wider section of central internal bore48, which is threaded at its tip allowing it to be screwed into corresponding threaded section43on the internal bore48. A tightening member42is provided at the base of the pin shaft49. A resilient sealing member46is compressed by a spring45which acts against a washer44, and the tightening member42. A pin38extends from pin shaft49upwardly within inner bore48. As tightening member42is turned, the pin shaft49turns within the threaded section43such that the pin38is forced upwardly against the sealing member25thereby breaking the seal of the valve. In this way a fluid path way is opened from outlet aperture18through the central internal bore48and additional internal bore41. A sampling tube40is connected to internal bore41to transport the sampled liquid from the sampling valve39to a suitable analysis apparatus. When a suitable volume of the liquid has been removed from the sampling chamber1, the tightening member42may be turned in the opposite direction thereby retracting the pin38and once again sealing the sampling chamber.

Therefore, there is advantageously provided a sampling apparatus which enables a continuous sample to be taken along a specified depth of a liquid, with the sampling flow rate remaining constant along the entire sampling depth, thereby providing a sample which is representative of the liquid along the entire sample depth. An inlet valve is provided which enables liquid to enter the sampling apparatus while the sampling apparatus is moving downwardly within a liquid, and which prevents liquid from entering or exiting the sampling apparatus once the sampling apparatus becomes stationery or moves upwardly. There is also provided means for sealing the chamber once a sample has been taken to permit transit of the sample. Furthermore, there is advantageously provided a sampling valve to enable removing of the sample from the sampling chamber without the need to decant the sample, as is necessary for sampling techniques such as RVP sampling.

It will be appreciated that in further embodiments various modifications to the specific arrangements described above and shown in the drawings may be made. For example, whilst it is described that the main body of the sample housing1is preferably cylindrical, it will be appreciated that a housing having a square cross section may also be provided.