GB2291403A

GB2291403A - Sampling water pipe debris

Info

Publication number: GB2291403A
Application number: GB9514978A
Authority: GB
Inventors: Susan M Williams
Original assignee: North West Water Group PLC
Current assignee: North West Water Group PLC
Priority date: 1994-07-21
Filing date: 1995-07-21
Publication date: 1996-01-24
Anticipated expiration: 2015-07-21
Also published as: GB9414689D0; GB9514978D0; GB2291403B

Abstract

A method and apparatus for sampling debris present in a mains water pipe. A sampling device is inserted into a water pipe, the device comprising an open ended head which is brought into contact with and forms a closed chamber with the pipe wall. A jet of water is directed at accumulated debris in the chamber and dislodged debris is flushed from the chamber for sampling purposes. <IMAGE>

Description

SAMPLING WATER PIPE DEBRIS This invention relates to a method and apparatus for sampling debris present in pipes, for example mains water pipes, to assess whether or not the pipes should be cleaned.

Mains water pipes often contain sediments which, under normal flow conditions, remain at the bottom of the pipe. However, abnormal flow conditions such as flow reversals, or burst water mains, may cause the sediment to lift and become suspended in the flow of water, causing discoloured water. It is thus sometimes necessary to clean mains water pipes, in order to avoid water quality problems.

The amount of sediment which collects in a given pipe cannot be predicted and is partly a function of the location, material and diameter of the pipe. This difficulty in predicting sediment build up can lead to the situation where a pipe that is relatively free of sediment is cleaned, while a heavily soiled pipe is not cleaned when necessary.

Currently, no easy method exists to assess sediment build up in mains water pipes and hence assess the need for cleaning. It would be preferable that any such method was able to assess sediment levels without interrupting supplies to customers and without causing discoloured water problems.

It is and object of the present invention to obviate or mitigate the problems outlined above.

According to the present invention there is provided a method for sampling debris present in a pipe, the method comprising inserting a sampling device into the pipe so that it contacts a wall of the pipe and forms a closed chamber with the pipe wall pumping fluid into the sampling device to dislodge any debris from that part of the pipe wall which is within the chamber, and removing the dislodged debris from the chamber for sampling purposes.

By removing the debris for sampling purposes, not only can an indication of the amount of debris present be obtained, but also the type of debris can be assessed.

Preferably, the debris is removed from the pipe by flushing it out with fluid. The fluid is typically water. A plurality of samples may be taken of the debris at intervals along the pipe. The sampling device may be rotated relative to the pipe wall to improve contact therewith.

The invention also provides apparatus for sampling debris present in a pipe using the above method, the apparatus comprising a sampling device having and open-ended head which may be brought into contact with the pipe wall to be sampled so as to form a closed chamber with the pipe wall, means for delivering fluid to the chamber to dislodge debris from the pipe which is within the chamber, and means for removing the dislodged debris from the chamber.

The sampling device head may be of generally cylindrical shape, or may be conical.

The head may be spring-mounted on a support tube, a release mechanism being provided to cause the head to spring into contact with the pipe wall. Preferably, a resilient seal is provided around the open end of the sampling device head. The sampling device may be collapsible to enable it to be collapsed for passage through an aperture in the wall of the pipe.

Preferably the sampling device head is rotatable relative to the pipe wall to assist in formation of a seal therewith. The sampling device may comprise two coaxial tubes defining fluid passageways to and from the head.

Specific embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic cross-sectional view showing a first embodiment of the present invention Figure 2 is a schematic view of an alternative type of sampling device head for use with the apparatus of Fig.1; Figure 3 is a schematic cross-sectional side view showing a second embodiment of the present invention; and Figure 4 is a sectional view illustrating details of the head of the apparatus of Fig. 3.

Referring to Figure 1 of the drawings, there is illustrated an apparatus for sampling the amount of debris present in a water pipe 1. The water pipe 1 is provided at intervals along its length with a number of tapping points 2, each having a gate valve 3 provided therein.

Each tapping point 2 is 2" in diameter and is already provided on water pipes to allow access to the pipe 1 for flow and pressure measurements. The water pipe 1 may range in diameter from 8" to 48" and may have a water pressure between 0 and 10 bar. Water may flow along the pipe at a flow rate of 0-2 ms~l.

The apparatus comprises a steel shaft 4 having a sampling device head 5 on one end thereof. The shaft 4 fits through the tapping point 2 to enable it to be inserted into the pipe 1.

The sampling device head 5 is of a hollow cylindrical shape, with one of its ends connected to the shaft 4 and its other end left open. A rubber seal 6 is provided around the free end of the head 5. Two hoses 7,8 are provided within shaft 4. Hose 7 extends into the sampling device head 5 and has a tapered end whilst hose 8 only extends to the end of shaft 4 attached to head 5.

With reference to Fig.2, there is illustrated and alternative style of sampling device head 11 which works on the same principle. The device 11 is conical and is formed of stiff rubber, with a rubber seal 12 around its lower edge. The device 11 may be formed so as to be collapsible by retracting it into the shaft 4 thereby enabling the diameter of the seal 12 to be larger than the diameter of the tapping point. The area encompassed by the sampling device head should be as large as possible so that localised variations in the amount of debris within the pipe 1 are less likely to result in measurements being taken which do not truly represent the conditions within the pipe. The device of Fig.2, is used in the same way as the device of Fig.l, and will not be described further.

A gland 9 is provided around the shaft 4 and may be attached to the tapping point 2 by means of a screw thread 10. The gland allows the mains pressure in the pipe 1 to be accommodated without significant leakage of water from the pipe 1. The shaft 4 may be moved up and down within tapping point 2 through the gland.

A portable pump (not shown) is provided to pump water into hose 7.

In order to sample the debris in the pipe 1, a cover (not shown) is removed from the tapping point 2 and the gland 9 is fastened onto the tapping point. The shaft 4 is inserted into the gland, and the valve 3 is opened. The shaft 4 is slowly lowered until the seal 6 of the sampling device head 5 contacts the bottom of pipe 1. The shaft is pressed down against the pipe wall so that a good seal is made by seal 6 to the bottom of the pipe 1. As a result, a closed chamber is formed between head 5 and the bottom of the pipe.

Water is then pumped into hose 7 at a higher pressure than that of the water in the pipe and issues from the tapered end of hose 7 as a jet into the interior of sampling device head 5. The jet of water causes any debris lodged on the bottom of the pipe within the chamber defined by the head 5 to become dislodged. The dislodged debris is flushed through the hose 8 into a sample bottle (not shown).

Several samples of the debris may be taken at intervals along the pipe wherever tapping points are provided, the samples giving information as to the amount of debris present in the pipe and the type of debris. The method does suffer from the disadvantage that debris is sometimes not evenly spread over the bottom of the pipe. There is thus a chance that the sampling device will take a sample of an area of pipe having a lower or greater amount of debris. This problem may be mitigated to some extent by making the area encompassed by the sampling device as large as possible, for example by using a device of the type shown in Fig.2.

Figures 3 and 4 illustrate in some detail an apparatus in accordance with the invention which works on the same principle as the apparatus sketched in simple terms in Figure 1.

The apparatus in Figure 3 comprises a barrel nipple 13 which in use is inserted into a gate valve on a mains pipe line. A union 14 connects the barrel nipple 13 to a gear box housing 15 supporting a lead screw housing 16. A lead screw 17 mounted within the housing 16 supports a drive nut 18a. Rotation of a shaft 19 is transmitted via sprockets 20a and 20b to the lead screw 17 to cause the nut 1 8a to move axially along the screw 17.

The nut 18 is coupled to the upper end of a tube assembly comprising a support tube 18b, an outer tube 21 and an inner tube 22. The annular space between the two tubes is in communication with a hose 23 that is coupled through a valve 24 and the gear box housing 15 to the interior of the barrel nipple 13. Thus once the apparatus is mounted on a gate valve and that valve is opened water within the main can flow via the valve 24 to the annular space between the tubes 21 and 22. The inner tube 22 is in communication with a hose 25 via a valve 26. The outer tube 21 may be moved axially and may rotate relative to a block 27 supported in the gear box housing. The outer tube 21 may also rotate relative to the tube 1 8b which is coupled to the drive nut 1 8a but is not movable axially relative thereto.

As shown in greater detail in Figure 4, the lower end of the outer tube 21 supports a head assembly comprising a body 28 on which an outer casing 29 s slidably supported. A spring 30 biases the outer casing 29 downwards. A grub screw 30a in the outer casing is received in an elongate slot 31 which limits the axial movement of the outer casing relative to the body 28. The grub screw 30a also prevents relative rotation between the body and outer casing.

A blind bore 32 extends parallel to the axis of the body 28 and receives a probe 33.

The probe 33 supports a short tube 34, which is a close but sliding fit within the bore 32. In the configuration shown in Figure 4, the tube 34, which cannot slide relative to the probe 33, displaces a ball bearing 35 into a groove 36 formed on the inner surface of the outer casing 29. The probe is retained within the bore 34 by a backing plate 37 secured to the lower end of the body 28.

If the probe 33 is pushed upwards (in the configuration shown in Figure 4) the tube 34 clears the ball bearing 35 which is then free to move readily inwards in a radial hole within the body 28. As a result the ball 35 is moved clear of the groove 36 and the outer casing 29 is forced downwards by the spring 30. The device can be reset simply by pulling the outer casing 29 upwards against the spring 30 and pulling the probe 33 downwards until the ball bearing 35 is forced into the groove 36.

In use, the device in Figure 3 is mounted on the gate valve and the gate valve is then opened whilst the valves 24 and 25 are closed. A tool is then connected to the shaft 19 and rotated to drive the nut 18 downwards which carries with it the tube 21 and the sampling head supported on that tube. As the sampling head approaches the far wall of the pipe into which it has been inserted, the probe 33 strikes that wall and is pushed into the bore 32. The ball 35 is then release from the groove 36 and the sampling head is forced rapidly downwards by the spring 30. A resilient seal 38 formed around the cylindrical end of the outer casing of the sampling head then forms a seal with the pipe wall. Rotation of the shaft continues until the spring 30 has again been compressed. thereby ensuring that the sealing head is pressed firmly against the pipe wall.

In the event that any debris is trapped between the seal 38 around the bottom edge of the head and the pipe wall in a manner which would prevent a good seal being formed, it is advisable to rotate the sealing head relative to the pipe wall simply by rotating the tube 21.

This ensures a good seal is formed. Thereafter the valve 26 can be opened to release the pressure within the chamber defined by the head against the pipe wall. Only a small amount of liquid should escape and may be collected in a sample bottle. Assuming that the seal has been reliable formed no further fluid will escape until such time as the valve 24 is opened to cause water to be forced into the annular space between the tubes 21 and 22. That annular space communicates through passageways (not shown) in the body 28 of the sealing head with the chamber defined between the sealing head and the pipe wall. Thus water is forced into that chamber, dislodging any debris therein and flushing the debris through the tube 22, the valve 26 and the hose 25 into the sampling bottle. A reliable indication of the volume and type of debris within the pipe can thus be obtained.

It will be appreciated that the present invention may be used to assess the distribution of debris in any fluid-conveying pipes, not just water pipes.

Claims

1. A method for sampling debris present in a pipe, the method comprising inserting a sampling device into the pipe so that it contacts a wall of the pipe and forms a closed chamber with the pipe wall, pumping fluid into the sampling device to dislodge any debris from that part of the pipe wall which is within the chamber, and removing the dislodged debris from the chamber for sampling purposes.

2. A method as claimed in claim 1, wherein the debris is removed from the pipe by flushing it out with the fluid.

3. A method as claimed in claim 1 or 2, wherein the fluid is water.

4. A method as claimed in any preceding claim, wherein the sampling device is rotated relative to the pipe wall to improve contact between the sampling device and the pipe wall.

5. A method as claimed in any preceding claim, wherein a plurality of samples of the debris are taken at intervals along the pipe.

6. Apparatus for sampling debris present in a pipe using the method according to any one of claims 1 to 5, comprising a sampling device having an open-ended head which may be brought into contact with the pipe wall to be sampled so as to form a closed chamber with the pipe wall, means for delivering fluid to the chamber to dislodge debris from the pipe wall which is within the chamber, and means for removing the dislodged debris from the chamber.

7. Apparatus as claimed in claim 6, wherein the sampling device head is of generally cylindrical shape.

8. Apparatus as claimed in claim 6, wherein the sampling device head is conical.

9. Apparatus as claimed in any one of claims 6 to 8, wherein the head is spring loaded and a release mechanism is provided to cause the head to spring into contact with the pipe wall.

10. Apparatus as claimed in any one of claims 6 to 9, wherein a resilient seal is provided around an open end of the sampling device head to form a seal between the sampling device and the pipe wall.

11. Apparatus as claimed in any one of claims 6 to 10, wherein the sampling device head is collapsible to enable it to be collapsed for passage through an aperture in the wall of the pipe.

12. Apparatus as claimed in any one of the claims 6 to 11, wherein the sampling device head is rotatable relative to the pipe wall to assist in the formation of a seal therewith.

13. Apparatus as claimed in any one of claims 6 to 12, wherein the sampling device comprises two coaxial tubes defining fluid passageways to and from the head.

14. A method of sampling debris present in a pipe substantially as hereinbefore described, with reference to the accompanying drawings.

15. Apparatus for sampling debris present in a pipe substantially as hereinbefore described, with reference to the accompanying drawings.