GB2205551A

GB2205551A - An automatic sampler for flowing liquid

Info

Publication number: GB2205551A
Application number: GB08713603A
Authority: GB
Inventors: Roy Jenkins
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-06-10
Filing date: 1987-06-10
Publication date: 1988-12-14
Anticipated expiration: 2007-06-10
Also published as: GB2205551B; GB8713603D0

Abstract

An automatic sampler has a shuttle (p) with a space (j) to contain an aliquot of fluid to be sampled. This shuttle moves axially within a cylinder (q) so that the space communicates with either primary ports (o and e) or secondary ports (a and n) in the cylinder wall. The fluid to be sampled flows via the primary ports and a space (k) irrespective of the position of the shuttle with respect to the primary ports. To take a sample, the shuttle is moved axially so that the aliquot contained in the shuttle space (j) is transfered to, and flows out of a secondary port (n). This outflow may be assisted by the application of compressed gas to a secondary port (a). Axial leakage is prevented by seals at (b, c, d, f). Provision is made for the application of compressed gas at (g) or (m) to move the shuttle. <IMAGE>

Description

AN AUTOMATIC SAMPLER.

This invention relates to method and means for taking samples of fluids.

It is often necessary to obtain samples of fluids for analysis or other evaluation. In the case of a fluid whose constituents or charateristics vary with time it is necessary to obtain these samples in such a way that the totality of samples is truly representative of the bulk of the liquid. One well known method is to take a number of aliquots, each of a fixed volume.

These aliquots are bulked to provide a sample for examination. The aliquots may be taken at fixed intervals of time or may be taken, for instance, at a frequency depending on the rate of flow of fluid in a pipeline.

It is sometimes necessary to take aliquots automatically in such a way that the fluid cannot escape into the environment either because it is dangerous or otherwise undesirable or because, for instance, exposure to the air would damage the sample.

According to the present invention there is provided a cylindrical shuttle fitted into a cylinder. The shuttle is provided with a space which can contain a fixed volume of fluid when the shuttle is fitted into the cylinder. Seals are provided to prevent the fluid from flowing axially in the annular space between the shuttle and cylinder. Ports are provided in the cylinder wall to allow the fluid to flow into and out of the space in the shuttle. The shuttle is arranged to move axially backwards and forwards along the cylinder so that the space is alternatively open to ports accepting the fluid to be sampled and open to ports connected to means for containing the bulk sample.

In order that the invention may be more fully understood a specific embodiment will now be described by way of example.

Refering to Fig.l, the shuttle (p) consists of a stainless steel piston with an annular groove (j) formed at its centre. This groove forms the space to contain the aliquots. The various edges of the shuttle are chamfered and smoothed to allow easy passage through '0' ring seals described below.

This shuttle oscilates in the plastics cylinder shown in Fig.2. The cylinder is here shown made in five parts for ease of manufacture. In the cylinder are four annular grooves (b,c,d,e) into which are fitted '0' rings to act as the seals. Also in the cylinder are annular grooves (i and k) whose function will be described below.

In the ends of the cylinder are ports (g and m) to allow compressed air to be applied to move the shuttle (p) backwards and forwards in the cylinder (q).

One method of using these means is illustrated in Figs.

3,4 and 5.

The shuttle normally rests to the right hand end of the cylinder (1). In this position the fluid to be sampled flows in via the the port (o), through the space formed between the groove in the piston (j) and the groove in the cylinder (k) and out via the port (e).

Fluid cannot flow from ports (o and e) axially along the cylinder towards the ports (a and n) because of the '0' ring seals (c and d).

When a sample is to be taken, compressed air is applied to the port (m) and port (g) is opened to the atmosphere. The shuttle then moves to the left.

As shown in Fig.4, when the shuttle (p) is half way along the cylinder, the aliquot of sample is trapped in the groove in the shuttle (j). It is isolated from the ports (a,e,n and o) in the cylinder by the two '0' ring seals (c and d). Fluid can still flow from port (o) to port (e) by virtue of the annular groove in the cylinder (k).

The situation at the end of the shuttle movement to the left is illustrated in Fig. 5. The groove in the shuttle (j) is now open to port (n). In the case of sampling a liquid, a supply of compressed gas may be applied to port (a) to assist the removal of the aliquot from the groove into collecting means connected to port (n).

After allowing sufficient time for the collection of the aliquot, the shuttle is returned to the position shown in Fig.3 by applying compressed air to port (g) and opening port (m) to the atmosphere.

By virtue of the groove formed in the cylinder (i) the flow of compressed gas continues after the shuttle has returned to the position of Fig.3. This ensures that the aliquot is conveyed to the collecting means.

An alternative method of using these means is to allow the shuttle to rest normally in the position shown in Fig.5 and to move it momentarily to the position of Fig.3 when an aliquot is to be taken.

In this case, the fluid to be sampled is constrained to flow normally in the annular groove (k) formed in the cylinder. The size of this groove may be chosen to avoid a substantial reduction in velocity of the fluid.

This method is appropriate when the fluid to be sampled is a liquid containing suspended solids in which case a reduction in velocity may cause depositing of the solids in such a way as to give a false sample.

According to an alternative embodiment, the space in the shuttle for containing the aliquots is in the form of a hole or holes formed in the shuttle on diameters or radii in such a way that, when adjacent to the ports, these holes (or hole) always connect the opposite ports via the annular groove in the cylinder notwithstanding any random rotation of the shuttle.

The ends of the holes at the surface of the shuttle are shaped so as not to damage the seals as the shuttle moves backwards and forwards.

In order to reduce inertia, the shuttle may be constructed so as to be hollow but without an axial through passage for compressed air. In this embodiment it is desirable that the hollow shuttle should be filled with rigid, lightweight material or have its ends sealed. This allows air to be trapped at the two ends of the movement allowing controlled deceleration.

In some applications (such as control by microprocessor) it is necessary for the controlling system to be imformed of the position of the shuttle.

In this case detecting means are provided in the cylinder.

According to further embodiments the shuttle is moved by direct mechanical means or by magnetic means.

Claims

CLAIMS.

1. A method of taking samples of fluid which comprises providing a shuttle capable of axial movement within a cylinder, providing a space in the shuttle to contain an aliquot of the fluid to be sampled, providing primary port means in the cylinder wall and allowing the fluid to be sampled to flow into and out of this space via these primary port means, preventing the axial leakage of the fluid to be sampled between the shuttle and cylinder, axially moving the shuttle within the cylinder so that the space communicates with secondary port means in the cylinder wall, allowing the aliquot of the fluid to be sampled contained in the space in the shuttle to flow out of the space via the secondary port means, providing a space to allow the fluid to be sampled to continue to flow via the primary port means irrespective of the position of the shuttle within the cylinder and axially returning the shuttle so that the space communicates with the primary port means in readiness for taking another sample.

2. A method according to claim 1 wherein the axial movement of the shuttle is caused by the application of compressed gas alternately to its two ends.

3. A method according to claim 1 wherein the axial movement of the shuttle is caused by the provision of mechanical means.

4. A method according to claim 1 wherein the axial movement of the shuttle is caused by the provision of magnetic means.

5. A method according to claim 1 wherein the removal of the aliquots of fluid to be sampled from the space in the shuttle is assisted by the application of compressed gas to a secondary port.

6. A method according to claim 1 wherein the movement of the shuttle within the cylinder is controlled by the provision of detecting means.

7. Means for taking samples of fluid which comprises a shuttle provided with a space to hold an aliquot of the fluid to be sampled, a cylinder within which the shuttle may move axially, primary port means in the cylinder wall to allow the fluid to be sampled to flow into and out of this space, means for moving the shuttle axially within the cylinder so that the space in the shuttle may communicate with ether the primary port means or secondary port means, sealing means for preventing the axial leakage of fluid to be sampled between the shuttle and cylinder, secondary port means in the cylinder wall to allow aliquots of sample to flow out of the space within the shuttle and a space to allow the fluid to be sampled to continue to flow via the primary port means irrespective of the position of the shuttle within the cylinder.

8. Means according to claim 7 wherein the means for moving the shuttle comprises means for applying compressed gas alternately to the two ends of the shuttle.

9. Means according to claim 7 wherein the means for moving the shuttle comprises mechanical means.

10. Means according to claim 7 wherein the means for moving the shuttle comprises magnetic means.

10. Means according to claim 7 wherein detecting means are provided to allow control of the movement of the shuttle within the cylinder.

11. Means according to claim 7 wherein the flow of liquid to be sampled from the space in the shuttle is assisted by the provision of means for the application of compressed gas to a primary port.

12. Means according to claim 7 wherein the means for moving the shuttle axially are controlled by the provision of detecting means to detect the position of the shuttle within the cylinder.

13. A method for taking samples of fluids substantially as hereinbefore described.

14. Means for taking samples of fluids substantially as hereinbefore described.