GB2606561A - Method of safely accessing ducting pipes - Google Patents

Abstract

A method for gaining access into a ducting pipe, the method comprising: a mechanical cutting of a plurality of paths into the outside wall of the pipe to a depth that does not pierce the internal wall of the pipe; heating of some or all of the remaining pipe wall at the inner section of some or all of the mechanically cut paths; a mechanical rotating, around the axis of the pipe, of a single or plurality of sections of the pipe that are adjacent to one or more of the paths, such as to fully disconnect those sections from any other pipe sections; and the removal of one or more pipe wall sections that are adjacent to a single mechanically cut path or a plurality of the mechanically cut paths, whereby the cutting apparatus comprises: a mechanical cutting device (e.g. routing tool 8) that can locate onto the outside wall of the pipe and move axially and circumferentially and whereby the depth of cut relative to the outside pipe wall can be controlled; and a heating device (e. g. blow torch 16 Fig 5) that creates localised heating to the area of the mechanically cut path.

Description

METHOD OF SAFELY ACCESSING DUCTING PIPES

Technical Field of the Invention

The present invention relates to an efficient method of safely gaining access to a ducting pipe without risking damage to the materials inside.

Background to the Invention

Power and communication cables are increasingly installed below ground houscd within plastic ducting pipes. The correct use of ducts presents many advantages over such alternatives of burying the cables underground unprotected or above surface installations, however they also bring additional engineering and practical challenges.

These ducts are primarily made from robust plastics, including polyethylene and PVC, and can either be straight walled or ribbed. In some applications the ducts can be very thick, often to increase the compressive strength of the pipe or to aid installation. They can either be made from straight sticks of pipe, with an associated jointing method between each joint, or from a single or multiple longer lengths of pipe, normally supplied in coils.

The installation of the ducts can be scheduled and organised somewhat independently to the cable assets, which are subsequently installed via pulling of the cables through the completed ductworks. This can enable longer cable runs thereby reducing the need for expensive cable jointing.

Once installed the ducting acts a protective boundary around the cable, reducing the likelihood of accidental damage to the cables inside during operations such as trench digging or from ground subsidence. Certain ducts can additionally be made watertight, thereby keeping the cables free from potentially damaging water ingress, reducing the likelihood of damage and increasing the lifetime of the cable assets. Further cabling can often be pulled into the ducting at a later date, often with minimal ground operations.

The development of horizontal directional drilling for the installation of cable assets has further accelerated the uptake of long lengths of thick-wall ducting.

This increasing activity further outlines the importance of reliable ducting pipes and the associated installation and maintenance procedures. It is with respect to these procedures that there lies opportunities for improvement.

Cables can occasionally become damaged either during installation or during their working lifetime. This damage may be within the cable core or elements of its sheathing, or possibly associated with a joint, and can prove difficult to accurately locate.

Specialist electronic equipment can sometimes be used to send signals down the cable to estimate the distance to the damaged section, following which an inspection trench can be dug to gain access to the duct. The cables may be isolated to ensure that the cable is safe for the inspection or repair work to be completed.

However there often still exists a possibility that the found duct is the incorrect asset. All ducting pipes should have an associated 'as-laid' drawing which refer to the information required to describe how the new cable assets are positioned upon final construction. Where these exist they can often be inaccurate or insufficiently precise to ensure correct identification of the duct that has been located.

For increased certainty that the exposed cable is made safe the ducting must be removed to allow inspection, repair and often for a 'strike' procedure to be undertaken, whereby a mechanical break is forced in the cable using a destructive method, often using an explosive cartridge.

The safe removing of the ducting around the cable is not currently possible. The cables inside may be damaged, potentially with exposed conductors, creating a very dangerous situation. The cables could be sitting anywhere within the internal dimensions of the duct, not just in the lower portion, and so may well be making contact with any internal surface. Cutting or piercing of the duct with any type of blade risks thrther damage to the cables inside and exposes the operator to the risk of electrocution.

Typical procedures encourage the extending of the inspection trench along the duct until a joint in the ducting pipework is located where the pipes can be forcibly slid apart. This can be very damaging to the surface infrastructure and cause significant disruption, especially where long ducting lengths are used through heavily urbanised or protected areas. In the application of coiled ducting pipes there can be no joints, meaning that no totally safe procedure is possible. For fusion welded pipes, the joints do not present an easier opportunity to access the duct, again adding difficulties for safe operations.

Ducting pipes can also be susceptible to becoming filled with gases, which may be flammable and/or hazardous. Therefore a gas test should ideally be conducted prior to fully opening the duct. A fully safe procedure and efficient for this operation is also not currently present.

Summary of the Invention

The present invention describes a method of gaining safe and expedient access to a ducting pipe (1) in a manner that overcomes many of the challenges highlighted above.

Before the work is undertaken the site must be prepared according to the required specifications and guidance, such as HSG47 for safe work on or near underground services. Once unearthed the ducting pipe (1) should be cleaned and where possible the type, including material and dimensions, should be identified from the markings and cross checked with records. The ducting pipe (1) may be produced from a wide range of materials. Pipes made from thermoplastic materials are particularly well suited for this application.

After inspection the ducting pipe (I) is marked up, for example using a coloured marking pen or chalk, with cut lines that will guide the cutting process. The exact cut details may differ depending upon thc type and size of pipe being access, or the type and size of access required. One mcthod uscs 2 full circumferential lines (2 & 3) of approximately 100nun apart, one of which (3) sits at the edge of the planned access window (6). Another full circumferential line (4) is located at the other end of the access window (6). Two axial lines (5) are located along the length access window, between lines 3 and 4. These axial lines are at approximately opposing sides of the ducting pipe (1). The maximum axial length of the access window possible will depend upon many factors, including reasonable access, ducting pipe material and dimensions, and environmental conditions. Other cut variations may include placing another access window at the other side of line 2, thereby increasing the overall access area.

The ducting details give a target wall thickness of the pipe, however this thickness may sit within a range specified by the associated manufacturing standard, or even outside of it if it was made out of specification. It is therefore good practise to measure the thickness of the pipe wall prior to conducting any cuts. in this described arrangement a selection of locations (7) can be marked and labelled ready for inspection using an ultrasonic thickness meter. These should be across a range of places along each of the cutting paths to get a good assessment of the overall wall thickness.

The electrical routing tool (8) is then set to the correct parameters based on the duct type, size and wall thickness. This ensures that the cut made will not fully penetrate the wall at any point and that it will leave in place a membrane of material that is of the correct thickness. The routing tool (8) connects to a modified attachment clamp (9) which connects to it which closely matches the outside diameter of the ducting pipe (1) to ensure that the tool is held in a radial orientation to the pipe at all times. It may also have a clamping mechanism that firmly attaches the attachment clamp (9) to the ducting pipe (I) such that when installed the routing tool (8) is unable to be lifted away from the outside diameter of the ducting pipe (1) but is still able to transverse around the pipe both axially or circumferentially. Either or both parts of this clamping apparatus may have handles (10) to ensure safe and easy use of the tool.

A pilot plunge is completed with the routing tool (8) once it has been securely attached with the attachment clamp (9). In this described arrangement the hole is located in the pipe segment which will become the first entry into the access window (6) and approximately 20mm away from the circumferential line (3), although other locations are also acceptable. To produce the hole most safely the routing tool (8) is turned on and then the cutting bit (13) is lowered within the depth allowance set on the routing tool (8). Once the full depth is reach the cutting bit (13) is fully retracted and the tool is turned off. The routing tool (8) is removed and the plunge hole is inspected to ensure that the pipe wall has not been broken through and that the remaining membrane is intact.

The remaining membrane is pierced through using a specialised piercing tool (II) which is struck with a hammer (12). This piercing tool (I I) has a non-conductive tip ensure safe use for the operator. It also has a conduit through the long axis of the tool. After the membrane has been pierced the piercing tool (11) is left in the hole and the top section of the piercing tool (11) is removed, along access for a gas meter instrument to be inserted. This is done to identify whether the ducting pipe (I) contains any dangerous or unexpected gases inside whilst not creating a significant leak path. If gases are detected at this stage then the top section can be replaced and the hole plugged whilst further action is organised. If not then the piercing tool (11) can be safely removed and the main access window cutting can begin.

To conduct the cuts the routing tool (8) is positioned over the appropriate marked cutting line and the attachment clamp secured accordingly. The routing tool (8) is then turned on and the cutting bit (13) is plunged to the depth set on the tool. The routing tool (8) is then rotated around or traversed along the ducting pipe (1), following the marked cutting line as closely as possible. Once the cut has been completed the cutting bit (13) is retracted and the routing tool (8) is removed. The cut must be inspected closely to ensure that the membrane is intact through the full length of the cut. If the cut inspection passes the next cut can be made using the same methodology above until they are all completed. The best systematic order of cuts may depend upon the exact type and dimensions of the project.

The remaining membrane is broken using a mixture of externally applied heat and force. This heat can be applied locally typically using a hot air gun or a gas powered blow torch (16). The amount of heat applied must be enough to sufficiently weaken the material in the membrane, but not too much to risk damage to the assets inside the ducting pipe (1) or to risk ignition of the pipe material. In this described arrangement the circumferential cuts (2 & 3) are heated first, although other orders maybe more appropriate for different types or sizes of ducting pipes. Once the heat has been applied the pipe collar (14) that is located between the cuts (2 & 3) is rotated around the axis of the pipe, thereby breaking the membranes and completely detaching the pipe collar (14) from the ducting pipe (1). This twisting action can be applied either by hand or using tools that clamp onto the pipe collar (14). If there are assets inside the ducting pipe (1) such as cables (IS) then the collar can be dropped down onto them. The cuts that are adjacent to the access window panel (17), which may include the two axial cuts (5) and the some of the circumferential cut (4), are then all heated by the blow torch (16). The access window panel (17) can then be peeled away from the ducting pipe (1), starting at the edge adjacent to where the pipe collar (14) previously was. The lifting can be done either by hand or using a tool such as pliers (18), which may be able to utilise the inspection plunge hole. As the lifting is occurring the blow torch (16) or another suitable heating device can continue to apply heat to the cut, especially at the leading edge of the break. The lower access window panel (19) is then easily removed with only heat needed at the remaining section of the full circumferential line (4).

This peeling method can be very success-fill at removing large access window panels (17). On very small or thin walled ducting pipes there can be less requirement for the removal of the pipe collar (14) first, however it significantly eases the process on most common ducting pipes used. It is often required for the access window to be enlarged after the first inspection is complete. Further adjacent access windows can be completed easily with two more axial cuts and one circumferential cut at the far end.

Whilst specific embodiments of the present invention have been described above, it will be appreciated that departures from the described embodiments may still fall within the scope of the present invention.

Throughout the description and claims of this specification, die words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components, integers, processes, methods or steps.

Throughout the description and claims of this specification, die singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers and characteristics described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive The invention is not restricted to the details of any foregoing embodiments.

The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (12)

1. CLAIMS1. A method for gaining access into a ducting pipe, by the removal of one of more side walls of said pipe, die method comprising: a mechanical cutting of a plurality of paths, into the outside wall of the pipe, to a depth that does not pierce the internal wall of the pipe; heating of some or all of the remaining pipe wall at the inner section of some or all of the mechanically cut paths; a mechanical rotating, around die axis of die pipe, of a single or plurality of sections of the pipe that are adjacent to one or more of the paths, such as to fully disconnect those sections from any other pipe sections; and the removal of one or more pipe wall sections that are adjacent to a single mechanically cut path or a plurality of the mechanically cut paths, whereby the cutting apparatus comprises: a mechanical cutting device that can locate onto the outside wall of the pipe and move axially and circumferentially and whereby the depth of cut relative to the outside pipe wall can be controlled; and a heating device that creates localised heating to the area of the mechanically cut path.
2. 2 A method as claimed in claim I wherein the mechanical cutting device is an electrical routing tool.
3. 3 A method as claimed in any of the preceding claims wherein the heating device is a blow torch.
4. 4 A method as claimed in any of the preceding claims wherein the heating device is a hot air gun.
5. A method as claimed in any of the preceding claims wherein an ultrasonic measurement device is used to measure the wall thickness of the pipe in one or more locations to ensure that the mechanical cutting depth is set correctly.
6. 6 A method as claimed in any of the preceding claims wherein a pilot hole is cut with a mechanical cutting device to ensure the cut does not fully penetrate through the pipe wall.
7. 7 A method as claimed in claim 6 wherein a final penetration of the pilot hole is completed using a nonconductive punch tool.
8. 8 A method as claimed in claim 7 wherein a gas detection device can be inserted into said pilot hole.S
9. 9. A method as claimed in ally of the preceding claims wherein one or more pipe sections are mechanically rotated by attaching a clamping tool to one edge of the section and applying a force in a direction predominantly circumferential to the pipe using the said clamping tool.
10. A method as claimed in any of the preceding claims wherein the pipe walls are mechanically removed by attaching a clamping tool to one edge of the wall and applying a force in a direction predominantly radial to the pipe using the said clamping tool.
11. 11 A method as claimed in any of the preceding claims wherein thc pipe walls are folded back along one mechanically cut path, such that the piece is still partially attached to the host pipe or other pipe sections.
12. 12 A method as claimed in any of the preceding claims wherein the pipe walls are fully disconnected from the host pipe or other pipe sections.