GB2101261A - Plugging and cutting a gas line without excavation - Google Patents

Abstract

An underground pipe (10), such as a gas line is sealed at or near a point where it joins onto a main (12) by a radially expansible plug (24) which may be inserted in the line without the need to excavate to obtain access to the point of sealing. The plug comprises a thermally stabilized cross-linked preshrunk material e.g. polythene and is inserted into the pipe (10) on a heater (28). The plug may be inserted from a point where the pipe emerges from the earth. Once the plug, placed on the end of the heater is appropriately positioned by manipulating a flexible shaft (52), the heater is energized, causing the plug to radially expand, fitting it tightly inside the pipe (10) at or near the main (12). The heater (28) is then withdrawn, and the pipe (10) may thereafter be cut adjacent the inserted plug by inserting a powered cutting device on the end of a flexible shaft similar to the shaft (52). <IMAGE>

Description

SPECIFICATION Method and apparatus for plugging and cutting a gas line or the like without excavation The present invention relates to a method of sealing an underground pipe or the like at or near the point where it joins onto a main.

There exists a serious problem in the gas industry with respect to the time-consuming and expensive cutting off of gas and the removing of gas lines from premises which have been abandoned. Frequently, regulations require the gas line to be plugged at or near the main and the gas line cut when a premise has been abandoned for six months or more. These are safety regulations in order to prevent explosions and other possible problems caused by the leakage of gas.

The regulations often not only require the plugging of the line, but also the cutting of the line at or near the gas main after it has been plugged so that future excavations by means of heavy equipment will not rip the line from the gas main, causing a substantial gas leak. These steps may be desirable even where they may not be required by regulation.

The cost to the utility Companies in terms of time and expense to perform the plugging and cutting is very substantial. Prior to the present invention, the gas utility would have to excavate at the point where the gas line joins onto the main.

This is usually in the roadway or the sidewalk.

There is substantial expense in this excavation and the necessary refilling and re-paving operations.

An object of the present invention is to enable a gas pipe, or any other similar type of pipe, to be plugged at or near the main without the need of excavation.

The present invention provides a method of sealing an underground pipe or the like at or near a point where it joins onto a main, without excavation to obtain access to the pipe, in which a thermally stabilized radially preshrunk plug is mounted on a heater, said heater being mounted on a flexible elongate shaft having a diameter less than the diameter of the pipe and said plug is inserted into said pipeline at an access point beyond where the pipe emerges from the earth, and is positioned in said line at or near said main by feeding said shaft into said line; and in which the heater is thereafter energised, causing said preshrunk plug to expand radially to its unshrunk condition and to seal said pipe; and said heater and said shaft are thereafter separated from the plug and are withdrawn.

Thus, the invention enables the sealing of the underground pipe, such as a gas line or the like, at or near the point where it joins onto a main without having to excavate, by obtaining access through the pipe itself to the point where it joins onto the main. This results in a substantial cost saving. This is especially important where it is noted that the cutting off of the gas or other similar utility to an abandoned property does not result in the production future income. The substantial expense of excavating, plugging the line, refilling and repaving is a total loss to a utility.

Access to the pipe is obtained at a point where it emerges from the earth. This point may be in the basement of the abandoned premises.

The plug is preferably a thermally stabilized cross-linked preshrunk polymer plug.

The invention includes apparatus for sealing an underground gas pipe or the like at or near the point where it joins onto a main, without excavation to obtain access to the pipe, comprising: a heat conductive tubular element adapted to fit over a heater; a resilient sheet member coiled about at least a portion of said tubular member for exerting a radially outward force; a layer of thermally stabilized material mounted over said resilient sheet member, said material having been radially preshrunk to form a smaller diameter tubular plug, whereby said layer is radially expansible to the unshrunk condition of its material upon being heated; and a layer of bonding material mounted over said expansible layer to provide a bond between said expansible layer and said pipe.

The heater may be mounted on a flexible elongate shaft having a diameter less than the diameter of the pipe into which it is to be inserted.

The plug is placed on the heater and is inserted into the pipe and positioned at or near the point where the line joins the main. The heater is then energized, preferably by an electric line running through the flexible elongate shaft, causing the preshrunk cross-linked material or polymer to expand to its original cross-linked condition, thereby sealing the pipe. The heater may then be withdrawn.

In a preferred embodiment, the elongate shaft is fitted with resilient washers about its circumference so that a substantial amount of gas does not leak from the opening of the gas pipe where the plug was inserted during the sealing process.

After the plug has been expanded in position, a cutting tool mounted on an elongate flexible shaft may be inserted into the pipe. The cutting tool is positioned near the inserted plug and energized.

The cutting tool cuts the pipe from the inside of the pipe. After the pipe is completely cut, the cutting tool and the elongate flexible shaft are withdrawn from the line and the operation of sealing and cutting the pipe is complete.

The invention is further described, by way of example with reference to the drawings, in which: Figure 1 is a cross-sectional elevation view of a plug inserted in a line and the line being cut carrying out a preferred embodiment of the invention in accordance with the present invention, Figure 2 is an elevation view of a plug mounted on the end of a heater being inserted into a pipeline in carrying out the method in accordance with the present invention, Figure 3 is a cross-sectional view taken along the centre line of the plug and shown along line 3-3 of Figure 2, but also showing the plug being inserted in the line which has been broken away in Figure 2, Figure 4 is a detailed cross-sectional view of a plug installed ir a line with the heater and tubular insertion element being withdrawn, and Figure 5 is a cross-sectional view taken along line 5-5 of Figure 3.

Referring now to the drawings in detail wherein like numerals indicate like elements, there is shown in Figure 1 a line 10 running between a main 12 and the interior of the building wall 1 4.

The line may be any type of a line which is to be sealed and cut without excavation. However, for purposes of illustration, and without intending to be limiting, the invention herein will be described with respect to the plugging and cutting of a gas line running from a gas main. It is understood that other types of lines may be plugged and cut, such as water lines, in accordance with the present invention.

The line 10 and the main 12 are shown buried in the earth 16, as is conventional. A typical sidewalk 18, kerb 20 and roadway 22 are shown for illustration purposes.

By means of the present invention, a line 10 may be plugged at or near the main 12 without having to excavate the roadway 22 and/or the kerb 20. Excavation and replacement of items such as road surface, kerbs and sidewalks is extremely expensive. Even the excavation and refilling of unimproved earth is very expensive.

The line 10, with which the present invention may be used may be of conventional steel, copper or synthetic plastics pipe. In carrying out the present invention, a plug 24 is installed in line 10 at or near the point where line 10 connects with main 12, as shown in Fig. 1.

The line 10 is cut or opened, such as by removing a fitting, at point 26, which is a point where line 10 emerges from the earth and is accessible, such as inside the basement of the building from which gas service is being discontinued. A heat expansible plug 24, as shown in Figure 2, is inserted into line 10 on the end of a heater 28.

As may be best seen from Figures 3. 4 and 5 taken together, the plug 24 includes a resilient sheet member 30 which may be of stainless spring steel, beryllium copper or other suitable resilient material. Resilient sheet member 30 is provided with an inwardly directed flange 32 along its innermost edge. Flange 32 slidably fits into a slot 34 in a tubular insertion element 36.

The tubular insertion element 36 preferably comprises a good heat conductor, such as copper.

The flange 32 of the resilient sheet member 30 is inserted into slot 34 of the tubular insertion element 36 and the resilient sheet member 30 is wrapped tightly around tubular insertion element 36 with the inner end of resilient sheet member 30 being held at the flange 32 in slot 34.

Preferably, the resilient sheet member 32 is wrapped twice around turbular insertion element 36. However, it is understood that the resilient sheet member 30 may be wrapped around the tubular insertion element 36 a greater or lesser number of times depending upon the resilience of the material, the thickness of the material and the desired degree of outwardly directed force to be caused by the coiled resilient sheet member 30.

Preferably, the plugs 24 are manufactured in a form in which they are supplied to the user mounted on the tubular insertion element 36.

However, once the plug has been installed in the line, the tubular insertion element 36 is preferably withdrawn owing to its attachment to the heater element by a locking means such as set screw 38.

The rear end 40 of the tubular insertion element 36 fits into a slot 42 of the heater element 28 where it is locked by set screw 38 or other suitable locking means.

Formed on the outside of the resilient sheet member 30 is a layer of thermally stabilized crosslinked preshrunk material 44. The thermally stabilized cross-linked layer 44 may be a polymer and may preferably be cross-linked polyolefin such as thermally stabilized cross-linked preshrunk polyethylene, although other cross-linked polymers may be used, such as cross-linked polyvinyl chlorides, ABS (acrylonitrile-butadienestyrene copolymers), polyurethanes, polyolefins with a metal ion added such as that commercially available from E. l. duPont de Nemours 8 Co.

under the trademark "SURLYN" and/or most rubbers. Although the term cross-linked polyolefin or polyethylene may be used herein as specific examples of preferred embodiments, other crosslinked polymers or other materials may be used in practising the present invention. The#crnss-linking of the polyolefin may be preformed by ultra-violet light, chemical means such as the use of dicumal peroxide or by radiation. As is known in the art, cross-linked polyolefin, or other thermally stabilized material, tends to return to its size or condition at which it was cross-linked. Crosslinked tubing, such as cross-linked polyethylene tubing, may be heated and axially stretched to reduce its radial dimension. The axially stretched cross-linked polymer may then be used to form the layer 44 of the plug 24.Upon reheating of the plug 24, by means of heater 28, when it is inserted in the desired position in the line, the cross-linked material layer 44 tends to expand radially back to its normal cross-linked condition.

This radial expansion causes an expansion of the plug in the line causing it to become fixed firmly in place.

Outside the layer 44 of the plug 24, there is provided a relatively soft outer tacky surface layer 48 which will bond to the inner surface 50 of the line 10. The layer 48 may comprise a mastic which is aggressive in its ability to stick to the inner surface 50 of line 10. The layer 48 need not form a chemical or molecular bond with the line 10, but a strong mechanical bond with the inner surface 50 of line 10 is sufficient when the bond is formed by an aggressive sticky mastic. The resilient sheet member 30 provides a radially outward force on layers 44 and 48 helping the polymer layer 44 to expand radially when heated and providing reinforcement for layers 44 and 48 thereby ensuring a long life for the plug 24 when inserted into a line.

In inserting the plug 24 into a line 10, the plug 24, which is preferably already attached to a tubular insertion element 36, is slid over a heater 28 with rear end 40 of tubular insertion element 36 received in slot 42 of the heater 28. The set screw 38, or other suitable locking means, is tightened to lock the tubular insertion element 36 to the heater 28. The heater 28 is attached to an elongate flexible tubular shaft 52. The flexible tubular shaft 52 has sufficient stiffness to enable the pushing of plug 24 along the inside of the line yet sufficient flexibility to enable the shaft to bend in conformity with curves in the pipe to enable insertion for considerable distances up to 46 metres from the point 26 of access. However, even greater distances may be achieved. The tubular element 52 may be coiled on a holding stand 54 as shown.Preferably, an electric cable 56 runs through the centre of tubular shaft 52 supplying electric power for heating elements 58 and 60 (shown in Figure 5) of the heater 28. The electric cable 56 is connected at its opposite end to an electrical controller 62 which may be used to regulate the current in the heater elements 58 and 60 to control their temperature. The electric controller 62 may be connected by means of plug 64 to any convenient socket, such as socket 66 shown in Figure 1 for illustration purposes.

Several washers 68 (Fig. 2) are preferably provided on shaft 52, preferably immediately behind the heater 28. Washers 68 are selected to fit snuggly to the inside wall of line 10 thereby preventing substantial loss of fluid, such as gas, during the time that the line 10 is opened at point 26 and the plug 24 on the front end of the heater 28 on shaft 52 is being inserted.

Once the plug 24 on the heater 28 is inserted in the line 10 to a position substantially at or near the main 12, the controller 62 is energized, causing the controlled heating of the plug 24 by means of the heater 28. When the plug 24 is heated, the polyolefin expands causing the plug to become tightly lodged within the line 10 at the desired location. The controller 62 is then turned off, and the plug is allowed to cool. The shaft 52, with the heater 28 and tubular insertion element 36 thereon, is then withdrawn back through the line 10 and out of the opening 26.

in accordance with a preferred method of the present invention a cutting device 70 mounted on the end of a flexible tubular shaft 72 is inserted into the line to a point substantially adjacent plug 24, as shown in Fig. 1. The tubular shaft 72 may be similar to the flexible tubular shaft 52 and both of these shafts may be made of any suitable flexible material which has a predetermined degree of stiffness. In a preferred embodiment, resin-bonded glass fibre tubing can be used. The flexible tubular shaft 72 is provided with an electric cord 74 running therethrough which supplies electrical power to a motor 76 of the cutting device 70. The power to the motor 76 is supplied by an electrical controller 78, which may be plugged into the socket 66.The cutting device 70 is provided with retractable or foldable blades which may be retracted or folded for insertion into the line, extended for cutting, and then again retracted for withdrawal of the cutting device 70 from the line. In this manner, the line 10 may be cut immediately behind the inserted plug 24 thereby completing the process of plugging the line and cutting the line without the need for excavation. The cutting of the line prevents damage to the main 12 and the connection to the main 12 in the event that the line 10 is contacted or ripped up by future excavation.

In summary, the present invention includes the method and apparatus for plugging and sealing an underground line without having to excavate to obtain access to the line. The plugging and cutting of the line are done at a substantial distance from the building, at or near the point where the line joins a main. This distance may be at a substantial distance from an access point to the line. The plugs are preferably constructed on a slitted tubular insertion element. The tubular insertion element, which is of a heat conductive material, is installed and locked to the end of a heater. The heater is inserted by means of an elongate flexible shaft having electrical connections running therethrough.The elongate flexible shaft is also provided with sealing means to prevent the significant loss of gas or other fluid back through the line while the plug is being inserted and installed in place. Once the plug is installed in place, preferably at or near the main, the flexible elongate shaft is withdrawn along with the heater and the attached tubular insertion element. The plug remains in place and acts as a seal for extended periods of time. The plug is reinforced by a resilient sheet spring member. Once the plug is installed, the cutting device is inserted in the line in a similar manner and the line is cut immediately adjacent to and behind the installed plug. The cutting device is then withdrawn and the operation has been completed without the need for expensive and time-consuming excavation and back filling operations.

The present invention may be embodied in other specific forms without departing from the scope of the invention.

Claims (17)

1. A method of sealing an underground pipe or the like at or near a point where it joins onto a main, without excavation to obtain access to the pipe, in which a thermally stabilized radially preshrunk plug is mounted on a heater, said heater being mounted on a flexible elongate shaft having a diameter less than the diameter of the pipe and said plug is inserted into said pipeline at an access point beyond where the pipe engages from the earth, and is positioned in said line at or near said main by feeding said shaft into said line; and in which the heater is thereafter energised, causing said preshrunk plug to expand radially to its unshrunk condition and to seal said pipe; and said heater and said shaft are thereafter separated from the plug and are withdrawn.

2. A method as claimed in claim 1, in which the plug comprises a cross-linked material.

3. A method as claimed in claim 1 or 2, in which, after withdrawl of the heater, a power cutting tool mounted on an elongate flexible shaft is inserted into said pipeline and is positioned adjacent said installed plug by feeding such shaft into the pipe, and in which said cutting tool is energised to cut said pipe: and said cutting tool and said shaft are thereafter withdrawn.

4. Apparatus for sealing an underground gas pipe or the like at or near the point where it joins onto a main, without excavation to obtain access to the pipe, comprising: a heat conductive tubular element adapted to fit over a heater; a resilient sheet member coiled about at least a portion of said tubular member for exerting a radially outward force; a layer of thermally stabilized material mounted over said resilient sheet member, said material having been radially preshrunk to form a smaller diameter tubular plug, whereby said layer is radially expansible to the unshrunk condition of its material upon being heated; and a layer of bonding material mounted over said expansible layer to provide a bond between said expansible layer and said pipe.

5. Apparatus for sealing an underground gas pipe or the like as claimed in claim 4, further comprising a heater mounted on one end of an elongate flexible shaft, said heater being adapted to fit into said tubular element, said shaft having sufficient stiffness to push said heater through said pipe and sufficient flexibility to bend in conformity with curves in the pipe.

6. Apparatus for sealing an underground gas pipe or the like as claimed in claim 4 or 5, wherein said heater is cylindrical and is adapted to fit into said tubular member, and is provided with means for locking said tubular member to said heater.

7. Apparatus for sealing an underground gas pipeline or the like as claimed in claim 6 wherein said tubular element is removable from the inside of said resilient sheet member after said expansible layer has been expanded in the pipe.

8. Apparatus for sealing an underground gas pipe or the like as claimed in claim 5. 6 or 7, wherein said shaft comprises resin-bonded glass fibre.

9. Apparatus for sealing an underground gas pipe or the like as claimed in any of claims 5 to 8, wherein said shaft is provided with one or more resilient washers fitted to the outer surface of said shaft behind said heater, said resilient washers providing a tight fit with the inner wall of the pipe, whereby gas or other fluid is substantially prevented from escaping from the open end of the pipe where the plug was initially inserted.

10. Apparatus for sealing an underground gas pipe or the like as claimed in any of claims 5 to 9, wherein said shaft is hollow.

11. Apparatus for sealing an underground gas pipe or the like as claimed in any of claims 5 to 10, wherein said heater is electrically powered and electrical control circuitry is provided for controlling the temperature of said heater.

12. Apparatus for sealing an underground gas pipe or the like as claimed in claims 10 and 11, wherein an electrical cable for connecting the electrical heater to the electrical control circuitry is run through the hollow shaft.

13. Apparatus for sealing an underground gas pipe or the like as claimed in any of claims 4 to 12, wherein said resilient sheet member is provided with a radially inwardly directed flange formed longitudinally along its innermost end, said flange being fitted into a longitudinal slit in said tubular element.

14. Apparatus for sealing an underground gas pipe or the like as claimed in any of claims 4 to 13, wherein said thermally stabilized material is thermally stabilized cross-linked polyolefin.

1 5. Apparatus for sealing an underground gas pipe or the like as claimed in claim 14, wherein said polyolefin is thermally stabilized cross-linked polyethylene.

16. A method of sealing an underground pipe or the like substantially as herein described with reference to the drawings.

17. Apparatus for sealing an underground gas pipe or the like, constructed and adapted to be used substantially as herein described with reference to and as illustrated in the drawings.