GB2206173A

GB2206173A - Method of buried pipe replacement

Info

Publication number: GB2206173A
Application number: GB08806638A
Authority: GB
Inventors: Yoshitaka Niki; Masataka Fukami; Kenji Kondo
Original assignee: Kurimoto Ltd
Current assignee: Kurimoto Ltd
Priority date: 1987-06-26
Filing date: 1988-03-21
Publication date: 1988-12-29
Anticipated expiration: 2008-03-21
Also published as: JPH0378513B2; JPS646590A; DE3835901C2; GB8806638D0; GB2206173B; DE3835901A1; CA1321479C

Description

1 2206173 11Method of pipe replacementlf THIS INVENTION relates to a

method of replacing an existing old pipe, such as water service pipe, gas pipe or the like, with a new pipe and, in particular, to a method of replacing an old pipe with a new one without digging up the ground.

When an old pipey in particular a cast iron pipe, has deteriorated with age and become unable satis factorily to perform its function or when it is required to replace the old pipe with a new due to new requirements, it is desirable to replace the old pipe by a new one without digging up the ground, because great labour and cost is involved in excavating the old pipe and because such digging work unavoidably obstructs traffic or affects means of transport and communication.

According to a known method of pipe replacement called "pipe-in-pipell, a new pipe is simply inserted into the old one under the ground, but this inevitably means that the internal diameter of the new pipe must be smaller than that of the old pipe, resulting in a reduction in the capacity for transporting gas or water.

An attempt has already been made to overcome the above-discussed drawback of the Hpipe-in-pipell method, as disclosed in UK Patents GB 215262B "Pipe Replacement System", GB 2124325B and GB 2092701B "Mains Insertion".

Apparatus in accordance with these prior proposals is illustrated in detail in Figure 7 of the accompanying drawings, Figures 8 and 9 illustrating a manner of actual use of this prior apparatus.

The aforesaid prior art discloses a method and an apparatus for pipe replacement in which a new pipe is attached to a rear end of a bursting mole having a cylindrical body with an external diameter which is larger than an old pipe to be replaced. The bursting mole and the new pipe move forward together, and a front end or head of the bursting mole intrudes into the old pipe and progressively burst the old pipe to form an enlarged space to receive the new pipe following behind the bursting mole, so that the old pipe is replaced with the new one.

As shown in Figure 7, a rear end of a mole 4a having a body with a larger external diameter than that of an old pipe la is connected to either a new pipe 9a for directly replacing the old pipe or to a sheath 14 for receiving and protecting the new pipe.

In Figures 8 and 9, the mole 4a incorporates an air cylinder serving as a drive unit for the mole, and an air hose 7a for actuating the air cylinder is connected to a pressure source (compressor 8a) and passes through the new pipe or sheath. A cable 3a attached to the tip end of the mole passes through the old pipe and is connected to a winch 2a.

The mole 4a is impulsively driven forward by the driving force applied by the pressure source while being subjected to a tractive force by the winch thereby bursting the old pipe. Since the maximum external diameter of the mole body is larger than the external diameter of the old pipe, the fragments of the old pipe are pushed outwardly to form a space larger than the external diameter of the new pipe or the sheath which follows the mole. In this manner, by utilising the gap corresponding to the difference in the external diameters of the mole and the new pipe, the pipe replacement can be smoothly carried out using a new pipe of substantially the same diameter as the old pipe.

The known method described above may be said to constitute a rational way of replacing bu.ried pipes. However, when the above known method -is studied in detail, several drawbacks are found therein. That is, the following drawbacks exist whether a new pipe or a sheath is towed into position by the mole:

1. When no sheath is used (i.e., a new pipe is connected to the rear end of the mole for direct renewal):

(a) Because an air hose and possibly other items are inserted through the new pipe, any paintwork or lining on the internal surface of the new pipe may be damaged by the coupling of the hose at the time of working or drawing the hose.

(b) Because exhaust air is discharged inside the new pipe, lubricating oil in the air (mixing of lubricating oil with the air is necessary for sliding motion of piston) may adhere to the internal surface of the new pipe and soil it. If an exhaust air hose is provided in an attempt to obviate this problem, not only is the working efficiency lowered but the performance of the air cylinder is also affected due to the reduced discharge cross-section. Moreover, an increased number of hoses is then required, and the danger of damage to the internal surface of the new pipe may increase corres- pondingly.

2. When a sheath is used (i.e., a new pipe is inserted i into a sheath after the sheath is installed in place of the old pipe):

Because the. sheath attached to the mole should have an internal diameter which is larger than the external diameter of the new pipe, the external diameter of the mole is obliged to be rather large as compared with the former case where no sheath is used. Accordingly, greater pressure has to be applied to the surrounding ground and working efficiency is thereby lowered.

Further, the consequences of such greater pressure on the surrounding ground (pressure, vibration) cannot be ignored. In particular, where there is another existing buried pipe line in the vicinity, then is a serious possibility of dislocating the other pipe line or loosening a pipe joint thereof due to such pressure.

The present invention aims to solve the abovediscussed problems and to provide an improved pipe replacement method by which the internal surface of the new pipe is protected from damage, stain or pollution, while minimizing the adverse consequences on the corresponding ground.

Accordingly, the invention provides a method of replacing an old buried pipe with a new pipe, comprising attaching a temporary pipe having an external diameter which is substantially the same as the new pipe to the rear end of a bursting mole having a cylindrical body whose external diameter is larger than the old pipe moving the mole forward so that a head of the mole intrudes into the old pipe and bursts it to provide an enlarged space for receiving the temporary pipe following the mole, applying the new pipe to one end of the temporary pipe, and withdrawing the temporary pipe such that it is progressively replaced by the new pipe.

11 A method embodying the invention obviates such problems as damage to the paintwork and lining of the internal surface of the new pipe with which the old pipe is replaced. Even when the drive unit is equipped with an air cylinder, the internal surface of the new pipe is prevented from stain and damage due to the adherence of foreign materials (lubricating oil in the exhaust air)y and cleaning of the new pipe after the replacement is not required.

Mo.reover7 since a temporary pipe having an external diameter almost the same as the new pipe is used in the replacementy the external diameter of the temporary pipe can be one size smaller than a comparable sheath for the same size of new pipe, so that the driving force necessary for the forward movement can be correspondingly smaller. As a result, detrimental influences on the surrounding ground can be reduced.

Furthermore, the temporary pipe once used can be repeatedly used for future replacements, and therefore the method according to the invention may be said to be more economical as compared with a sheath which is used only once and left buried.

In order that the invention may be more readily understood, embodiment thereof will now be described by way of example with reference to the accompanying drawings, in which:

Figures 1 and 2 are diagrammatic sectional views illustrating a method of pipe replacement embodying the present invention; Figure 2 is a diagrammatic sectional view illustrating an example of a temporary pipe employed in the method of Figures 1 and 2; Figure 4 is a sectional view illustrating the wall construction and coupling arrangement of an example of a new pipe; Figures 5 and 6 are diagrammatic sectional views illustrating respective further embodiments of the invention; and Figures 7 to 9 are diagrammatic sectional views illustrating a prior art pipe replacement method.

An embodiment of the invention will now be described with reference to Figure 1 (showing the replacement of an old pipe with a temporary pipe) and Figure 2 (showing the replacement of the temporary pipe with a new pipe).

The steps involved in the illustrated pipe replacement method are as follows:

1. A starting pit K1 and a destination pit K2 are dug at respective ends section of an old buried pipe which is to be replaced and existing pipe members in the pits are removed.

2. A winch is installed at the destination pit, and a cable 3 of the winch is passed from the destination pit K2 to the starting pit K1 through the inside of the old pipe 1.

3. A temporary pipe 5 composed of interconnected temporary pipe members and having almost the same length as the section of the old pipe to be replaced is attached to the rear end of a mole 4, and the mole and the temporary pipe are coupled together by means of a wire 6 inserted through the temporary pipe 5. The wire is tensioned between the rear end of the mole and the 1 1k 1 r rear end of the temporary pipe. At this timey an air hose 7 is inserted through the inside of the temporary pipe, and the ends of the air hose are connected to the mole 4 and a compressor 8 respectively.

The cable 3 of the winch is connected to the front end of the mole to guide the mole to the end of the existing pipe in the starting pit.

5. The existing buried pipe is burst by a head of the mole as a result of forward motion of the mole 4 under the action of the tractive force of the winch and the impulsive drive of the air cylinder disposed in the mole, whereby the temporary pipe towed by the mole is progressively installed within the fragmented old pipe as the mole progresses from the starting pit to the destination pit.

6. Upon reaching the destination pit, the mole 4 is uncoupled from the temporary pipe 5 and the air supply hose and others inside the temporary pipe are also removed. The foregoing steps 1 to 6 correspond to Figure 1.

7. A new pipe member 9 is connected to the end of the temporary pipe in the starting pit and is pushed in toward the destination pit by means of a jacking device 10 disposed in the starting pit, whereby the temporary pipe 5 is thrust out of the ground at the destination pit by a corresponding amount as the new pipe is inserted.

8. New pipe members are inserted one by one from the starting pit and pushed toward the destination pit, whereby the temporary pipe is progressively replaced with the new pipe extending from the starting pit to the destination pit. When short temporary pipe members are 1.

used, as illustrated, they are removed one by one at the destination pit. The foregoing steps 7 to 8 correspond to Figure 2.

The above steps remain almost unchanged when a device other than an air cylinder is used as a drive unit incorporated in the mole, because a drive source is required to be connected to any such device by way of a hose or cable.

Figure 3 illustrates the construction of a temporary pipe 5 which may be used in the above descrIbed method. As can be seen, the temporary pipe 5 is composed of interconnected members each having a reduced diameter spigot portion at one end and an enlarged diameter socket portion at the other end for receiving the spigot portion of an adjacent pipe member. Because the temporary pipe moves under the ground, it is preferable for the external surface of the pipe to be smooth, although the configuration and material of the temporary pipe does not matter so far as it is durable enough against traction applied by the mole, compressive force applied by the jacking device as the new pipe is inserted, and pressure from the surrounding ground.

Figure 4 is a view illustrating an example of a nut and bolt joint between adjacent pipe members of the new pipe 9. The body of the pipes composed of a ductile cast iron processes by centrifugal casting, the internal surface of the pipe is lined with a cement mortar 11, and the external surface of the pipe is coated with an armoured concrete 13 which includ.es reinforcing basket members 12 (composed of welded steel bars), both internal and external surfaces composing of a ductile cast iron pipe for use in propulsion working for the replacement, which is the most preferable embodiment of the invention.

4 In another embodiment of the method according to the invention illustrated in Figure 5, the new pipe 9 is connected to the rear end of the temporary pipe 5 so as to be pulled through the ground to the destination pit K2 behind the temporary pipe 5 at the latter is pulled out of the ground by the winch 2, thereby obviating the head for a jacking device in the starting pit K1. In this embodiment, since the temporary pipe and the new pipe move forward through the space left by the passage of the mole 4, an advantage is that no large propulsion (i.e. jacking device) is needed in addition to the propulsion system for the temporary pipe.

Figure 6 illustrates a further embodiment of the pipe replacement method, in which the temporary pipe members are successively connected together within the starting pit K1 where there is insufficient space for the connection to take place at ground level.

Claims

CLAIMS:

1. A method of replacing an old buried pipe with a new pipe, comprising attaching a temporary pipe having an external diameter which is substantially the same as the new pipe to the rear end of a bursting mole having a cylindrical body whose external diameter is larger than the old pipe, moving the mole forward so that a head of the mole intrudes into the old pipe and bursts it to provide an enlarged space for receiving the temporary pipe following the mole, applying the new pipe to one end of the temporary pipe, and withdrawing the temporary pipe such that it is progressively replaced by the new pipe.

2. A method according to claim 1, wehrein the mole is moved forwardly impulsively.

3. A method according to dlaim 1 or 2, wherein the new pipe is thrust into the ground behind the temporary pipe by a jacking device installed in a pit dug to expose one end of the old pipe.

4. A method according to claim 1 or 2, wherein the temporary pipe is pulled from the ground by a winch, thereby towing the new pipe into place.

5. A method of replacing an old buried pipe with a new pipe substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

6. A method according to claim 5, substantially as modified with reference to Figure 5 or Figure 6 of the accompanying drawings.

7. Any novel feature or combination of features described herein.

Published 198 3 at The Patent Office. State House, 66.71 High Holborn. London WC1R 4TP Further copies may be obtained from The Patent Office, Sales Branch, St Me::,' Cra3V. Orpington, Kent BR.55 3RD Printed by Multiplex techiuTles ltd. St Mary Crky. Kent. Con, 187.