GB2263325A

GB2263325A - Apparatus for and method of removing liquids

Info

Publication number: GB2263325A
Application number: GB9200205A
Authority: GB
Inventors: Peter William Lawrence
Original assignee: British Gas PLC
Current assignee: British Gas PLC
Priority date: 1992-01-07
Filing date: 1992-01-07
Publication date: 1993-07-21
Anticipated expiration: 2012-01-07
Also published as: GB9200205D0; GB2263325B; EP0578792A1; CA2105383A1; WO1993014388A1; RU2075739C1; PL170128B1

Abstract

Apparatus for detecting the presence of a liquid, such as water which has collected as a pool in gas pipes, and thereafter removing the detected liquid from the pipes comprises a conduit 2, a liquid detector 3 mounted within a nose cone 4 connected to an end of the conduit 2, an indicator 5 which indicates when the detector has detected liquid, and a pump 9 which is connected to the conduit 2 and operated to pump the detected liquid along the conduit away from the detector. <IMAGE>

Description

APPARATUS FOR AND METHOD OF REMOVING LIQUIDS The present invention relates to the removal of liquids and, more particularly though not exclusively, to the removal of liquids, such as water or monoethylene glycol (MEG), from gas pipelines.

The UK gas distribution system for distributing natural gas to premises comprises many miles of low pressure gas mains pipework.

Where these low pressure gas mains are laid in areas with high water tables, water may enter the mains where joints between adjacent lengths of pipe develop leaks.

The distribution system still includes many miles of the old style cast iron mains which were installed before natural gas was used in the system. These mains are gradually being replaced by polyethylene pipe. Adjacent cast iron mains pipes have lead/yarn joints, and in order for such joints to remain gas tight, the packing material (jute or hemp fibres) should be maintained in a swollen state. However, natural gas is a dry gas which tends to cause the packing material to dry out and shrink and possibly result in some gas leakage at the joints. To prevent this problem occurring the natural gas is conditioned with MEG which may be introduced continuously in vapour form into the pipework by "fogging units". The MEG serves as a yarn swellant. Where excess MEG is present it may condense as droplets on the pipe walls and form pools of liquid MEG which it may be desirable to remove.

Leaks may also occur between newly laid lengths of polyethylene pipe and old cast iron pipe and thus allow the ingress of water into the pipework.

It will therefore be appreciated that pools of water or MEG may collect in low points of the pipework. The presence of a pool of water or MEG may cause a loss of pressure or even a blockage in the main and should therefore be removed. However, the location and removal of the liquid may be difficult.

An object of this invention is to provide an apparatus for, and a method of, detecting and removing liquid.

From one aspect the invention provides apparatus for detecting the presence of a liquid and removing the detected liquid, comprising a conduit, a liquid detector which is carried by the conduit, an indicator which is responsive to the detector detecting liquid, and pump means connected to the conduit for pumping detected liquid along the conduit away from the detector.

Conveniently, the detector is located within a housing comprising one or more apertures via which liquid can enter the housing and enter the conduit. The housing may comprise a portion of the conduit itself, but preferably, the housing is in the form of a tube, for example in the form of a nose cone, which is mounted on one end of the conduit. With this latter arrangement it is possible that the tube together with the detector located therein may be adapted to be readily removable from the conduit and replaced by a new unit should, for example, the detector develop a fault.

Preferably, the tube, or a portion of the conduit in the vicinity of the detector, is weighted or made of a sufficiently dense material to facilitate the maintenance of contact between the tube or said conduit portion with a surface towards which it is urged by gravity. Thus, for example, when the conduit is moved lengthwise through a generally horizontal gas mains pipe the tube tends to move along the lower portion or bottom of the pipe where any pools of liquid would collect.

Conveniently, the conduit is flexible. This allows the conduit, for example, to follow bends in a pipe as the conduit is moved through the pipe. However, preferably, the conduit is sufficiently rigid to permit it to be fed forwardly in stages from one end along a generally horizontal path in a generally lengthwise direction such that the one end remains ahead of the remaining portion of the conduit being fed along.

The detector may be a liquid level switch detector, for example an optical liquid level switch detector. Alternatively, the detector may comprise two electrical contacts which when bridged by an electrically conducting liquid causes the completion of an electric circuit and activates the indicator. However, the optical switch detector is preferred because it is capable of detecting non-conducting liquids as well as electrically conducting liquids. Thus, this form of detector is suitable for detecting the presence of a pool of MEG.

Advantageously, the housing or conduit contains a one-way valve which acts in a manner to prevent liquid which has been pumped away through the conduit from draining back past the valve to the source of the liquid. In one embodiment, the detector is secured to the valve to form a combined assembly or unit. The assembly may be provided with openings via which liquid can reach the detector. Conveniently the assembly may be of generally tubular form with the openings being disposed around the peripheral wall of the assembly and communicating with an interior region of the assembly between the detector and the valve part of the assembly.

The tubular assembly may be removably located in the tubular housing (or casing) and the housing may have apertures provided around its periphery which overlap, or are in alignment with, the openings around the tubular assembly.

The indicator means may provide a visual and/or audible signal in response to the detector detecting liquid.

From another aspect the invention provides a method of detecting the presence of a liquid and removing detected liquid, comprising moving a conduit carrying a liquid detector over regions to detect the presence of liquid overlying such regions, observing the detection of liquid by the detector by means of an indicator which is responsive to the detector detecting liquid, and pumping liquid through the conduit away from the detector.

The method may be employed to detect and remove pools of liquid, such as MEG or water, from pipes; in which case the conduit is moved along or through a pipe.

The conduit may be introduced into the pipe via an entry device which incorporates a seal between the conduit and the pipe wall.

This facilitates use of the method, for example, on a live gas main.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which : Figure 1 is a schematic view of one embodiment of apparatus according to the invention, Figure 2 is an axial section view, on a larger scale, through the leading end of the conduit and the attached nose cone of the apparatus in Figure 1, Figure 3 is a cross-sectional view through the nose cone taken on the line III-III in Figure 2, and Figure 4 shows schematically another form of nose cone and detector at the leading end of the conduit.

With reference to Figures 1 to 3 of the drawings, apparatus 1 for detecting the presence of a liquid and for removing detected liquid comprises a portable length of conduit 2 and a liquid detector or sensor 3 located within a metal nose cone 4 which is fitted to the leading end 2a of the conduit. An electrical meter/buzzer indicator device 5 is connected to the detector 3 via leads 6 which are connected to a cable 7 from the indicator device 5. The cable 7 passes into the conduit, to connect with the leads 6, through a gland or seal 8 provided in the wall of the hose at a point remote from the leading end. A pump 9 which can be activated by a generator 10 is connected to the conduit for drawing or sucking liquid through the conduit from the nose cone.

The back or rear end of the conduit is connected to a flame trap 11 and a vessel 12 for collecting liquid which has been pumped along the conduit from the nose cone.

Between the pump 9 and the gland 8 the conduit 2 incorporates a filter 13 and a main on/off valve 14, and is connected to a pressure gauge 15 for indicating the pressure within the conduit.

The conduit may be made of a flexible plastics material which is also sufficiently rigid or self-supporting to permit the conduit to be fed forwardly in stages, for example by hand, from the leading end connected to the nose cone along the interior of a generally horizontally extending pipe such that the nose cone remains ahead of the remaining portion of the conduit which is fed along the pipe.

The nose cone 4 is generally in the form of a tube 16 closed at the front end 17 and having the rear end 18 open and fitting securely into the leading end 2a of the conduit. The front portion of the nose cone contains a lead weight filling 19 which assists, as the conduit is fed along the pipe, in keeping the nose cone and conduit 2 on the bottom or lower portion of the pipe where pools of liquid may have collected.

The tubular portion 16a of the tube 16 behind the lead weight fitting 19 serves as a housing or casing for locating both the liquid detector 3 and a one-way or non-return valve 20. The valve 20 functions in a manner to prevent liquid which has been pumped away from the nose cone through the conduit from draining or running back past the valve into the pipe when the pump has been switched off.

The valve comprises a tubular body 22 which defines an annular valve seat 23 and houses a valve member 24 which is slidably movable within the body 22. The valve member 24 is biased towards the valve seat 23 by a helical compression spring 25 which acts against a shoulder 26a provided by an externally threaded ring member 26 which is screwed into one end of the body.

The detector 3 used by the applicants in their experiments with this embodiment was a solid state optical liquid level switch supplied by RS (Radio Spares) Components Limited. The detector, as supplied, was modified so as to screw into the opposite end of the tubular body 22 of the valve to form therewith an assembly, with the liquid sensing part of the detector generally facing the valve member 24. The portion of the tubular body between the valve seat 23 and the detector 3 is provided with equispaced openings 30 around its periphery. These openings are aligned with corresponding apertures 31 provided in the peripheral wall of the nose cone. Alignment between the tubular body 22 and the casing 16 is maintained by means of a grub or set screw 32 which screws through the casing and is tightened against the tubular body.The openings 30 and apertures 31 allow liquid to flow through the nose cone 4 and into the tubular body 22 into the vicinity of the liquid detector 3. It will be appreciated that when the pump 9 is in operation the valve member 24 moves away from the valve seat 23 to allow access therethrough into the conduit.

As can be seen from Figure 2 the electrical leads 6 extend from the front end of the detector 3. The leads pass along inwardly facing channels 35,36 on opposite sides of the valve/detector assembly provided in the tubular peripheral wall of the nose cone housing portion 16a. The leads 6 extend rearwardly of the valve/detector assembly and are connected by connectors 37 to an electrical cable 7 (not shown in Figure 2) contained within a semi-rigid glass-fibre tube 39 (shown in broken lines) which extends along the inside of the conduit. Remote from the nose cone the cable 7 emerges from the end of the glass-fibre tube 39 and passes through the gland 7 and out of the conduit to the meter/buzzer indicator device 5.

When the conduit 2 is pushed through a pipe and a pool of liquid, such as a pool of water is encountered by the nose cone 4, then if the liquid is of sufficient depth to enter the tube 16 and tubular body 22 and be detected by the detector 3 the electrical circuit incorporating the detector and meter/buzzer device 5 is completed. The position of the indicator needle 5a of the meter will then provide a visual indication of the presence of liquid in the pipe, whilst the buzzer will sound to provide an audible indication of the presence of liquid. With the valve 14 open, the generator 10 can then be switched on to activate the pump 9 to draw or suck the water past the valve 20 into the conduit, past the filter 13 and (open) valve 14, and into the vessel 12 where the water is collected.

Where the apparatus is used in a live gas main the conduit may be introduced into the main via an entry device (not shown), incorporating a gland or like sealing arrangement, mounted on the main over a hole which has previously been tapped through the wall of the main.

If gas is removed from the main through the conduit it separates from the liquid and is vented via the flame trap 11.

Conveniently, the apparatus described above (apart from the liquid collection vessel 12) may be mounted on a transportable supporting frame, with the conduit stored in a wound up condition when not in use (not shown), so that the apparatus can readily be moved from one location to another as required. The collection vessel may be mounted on the frame when the apparatus is being used but is removed when the frame is moved around on site.

In the form shown in Figure 4, the nose cone 4 has a single aperture 40 at the front end. An electrical contact in the form of a ring 41 is fitted into the aperture 40. At the junction between the nose cone 4 and the front end of the conduit 2 another electrical ring contact 42 encircles the nose cone.

Leads 43 connect the contacts to the meter/buzzer device. When an electrically conducting liquid, such as water which may have collected as a pool in gas mains, bridges the two contacts an electrical circuit is completed as before and the meter and buzzer indicate the presence of water. The pump can then be activated to draw the water through the hole in the ring contact 41 and into and through the conduit. The two electrical contacts 41,42 thus serve as the sensing means of the liquid detector.

In Figure 4, a one-way valve is not incorporated into the apparatus although it will be appreciated that this embodiment could be modified to include such a valve.

Claims

1. Apparatus for detecting the presence of a liquid and removing detected liquid, comprising a conduit, a liquid detector which is carried by the conduit, an indicator which is responsive to the detector detecting liquid, and pump means connected to the conduit for pumping detected liquid along the conduit away from the detector.

2. Apparatus as claimed in claim 1, in which the detector is located within a housing comprising one or more apertures via which liquid can enter the housing and enter the conduit.

3. Apparatus as claimed in claim 2, in which the housing is in the form of a tube which is mounted on one end of the conduit.

4. Apparatus as claimed in claim 3, in which a plurality of said apertures are provided around the periphery of the tube.

5. Apparatus as claimed in claim 3 or 4, in which the tube is in the form of a nose cone.

6. Apparatus as claimed in any of claims 2 to 5, in which the tube or a portion of the conduit in the vicinity of the detector is weighted or made of a sufficiently dense material to facilitate maintenance of contact between the tube or said conduit portion with a surface towards which it is urged by gravity.

7. Apparatus as claimed in any of the preceding claims, in which the conduit is flexible.

8. Apparatus as claimed in claim 7, in which the conduit is sufficiently rigid to permit it to be fed forwardly in stages from one end along a generally horizontal path in a generally lengthwise direction such that said one end remains ahead of the remaining portion of the conduit being fed along.

9. Apparatus as claimed in any of the preceding cla -s, in which the detector is a liquid level switch detector.

10. Apparatus as claimed in claim 9, in which the deter is an optical switch detector.

11. Apparatus as claimed in any of the preceding cIa: s, in which the casing or conduit contains a one-way valve which acts in a manner to prevent liquid which has been pumped away tough the conduit from draining back past the valve to the so z of the liquid.

12. Apparatus as claimed in claim 11, in which the detector is secured to the valve to form an assembly.

13. Apparatus as claimed in claim 12, in which the assembly has openings via which liquid can reach the detector.

14. Apparatus as claimed in claim 13, in which the assembly is of generally tubular form with the openings being disposed around the peripheral wall of the tubular assembly and communicating with an interior region of the assembly between the detector and the valve part of the assembly.

15. Apparatus as claimed in any of the preceding claims, mounted on a movable support means.

16. Apparatus substantially as hereinbefore described with reference to Figures 1 to 3 or Figures 1 and 4 of the accompanying drawings.

17. A method of detecting the presence of a liquid and removing detected liquid, comprising moving a conduit carrying a liquid detector over regions to detect the presence of liquid overlying such regions, observing the detection of liquid by the detector by means of an indicator which is responsive to the detector detecting liquid, and pumping liquid through the conduit away from the detector.

18. A method as claimed in claim 16, in which the conduit is moved through a pipe.

19. A method as claimed in claim 17, in which the conduit is introduced into the pipe via an entry device which incorporates a seal between the conduit and the pipe wall.

20. A method as claimed in any of claims 17 to 19, employing apparatus as claimed in any of claims 1 to 16.