FI104625B - Method for lining pipes - Google Patents

Description

104625

The present invention relates to a method of lining pipes as set forth in the preamble of claim 1. The invention will be described in connection with gas, oil and water supply pipes, but it is obvious that the invention can be applied to all types of pipes.

When lining installed pipes (which are embedded in the ground tend to crack due to ground movements), it is known to pass a heated plastic pipe liner through a nozzle or press to reduce the diameter and then to an existing pipe for a certain length.

The present invention relates to an improved method of lining an installed pipe line when a tension clamp is used to reduce the diameter of the lining pipe prior to being drawn into an existing pipe line. "Installed" pipeline means a pipeline that has already been installed for its intended purpose, such as submerged pipelines for gas, oil, water or waste water, pipelines forming part of a larger facility, such as oil / gas refineries or storage facilities. , or t · * ·· 'pipelines resting on the ground and installed to connect the access point to the receiver, such as an oil pipe, • · · V; which connects the oil source to the refinery or port.

For a submerged pipeline, it is evident that the normal system when passing through such a process will include a winch placed adjacent to the trench

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at the other end of the length of pipe to be lined, from which a cable or similar flexible connection passes through the pipe to another trench, on one side of which it is attached to the front end of a plastic lining pipe. The second trench next to the # 104625 2 has a heating and compression device comprising a heater and a size reduction device. The downstream end of this device may have a reciprocating "pusher" that can grab onto and pull the tube and force it toward the lining tube.

Characteristic features of the present invention will be apparent from the characterizing part of the appended claim 1. Thus, there is provided a method of lining tubes comprising the steps of providing a liner tube of a certain length having an outside diameter greater than the inside diameter of the tube to be lined and made of polyethylene or a copolymer of polyethylene and at least one alpha olefin of up to ten carbon atoms. The liner tube is drawn through a tension clamp mounted directly or indirectly to the liner tube using a tensile stress puller which is attached to the front end of the liner tube and is threaded through the tube to reduce the outside diameter of the liner tube by up to 15%. The liner is drawn through an installed pipeline with the outer diameter reduced in size and / or maintained less than the inside diameter of the liner, with tension applied by the drive device that partially limits the outside of the liner:. radial expansion at the exit of the press remained f I »·. ··. movement. Thereafter, expansion of the liner tube is allowed within the liner tube by relaxing said tensile stress, followed by memory expansion under normal atmospheric pressure and ambient temperature of the liner tube. The pipe to be lined is installed as a • · · V * submerged pipe and the pipe to be lined and the pipe to be laid are • · · V: at least 10 meters long.

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In one embodiment of the invention, the liner can be heated by methods known per se prior to the tensioning operation: "·· Alternatively or additionally, the liner may be heated as it passes through tensile press 104625 3. In this case, there is a device for heating the inner surface of the tension through it.

According to another embodiment of the invention, the tensile compression operation may be performed at ambient temperature. For example, the choice of liner tubes for tension extraction at ambient temperature will depend, for example, on the dimensioning of the liner, its SDR ratio and the characteristics of the material of which the liner is made. If the liner can be successfully pulled at ambient temperature under certain conditions, it is an easy task for the user to find out by trial and error.

The present invention contemplates, in a suitable embodiment, the use of a tension press provided with a surface inclined at or between 6 ° to 32 °, wherein no part forms an angle greater than 32 ° with the tension of the tension press and extends at least 70% of the axial distance between the part where the liner tube meets this surface and the part where the liner tube exits the tension press.

: According to prior art tube extraction methods .. the tensile presses used are practically comprised of two parts, · · the first being a sloping pressing surface which reduces the diameter to a minimum value and the other an axial * · * 'extension of the tensioner interior. corresponds to this minimum value of «« «V *. We have found that in the practice of the invention there is

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A: it is advantageous to shorten the axial length of said second portion relative to the axial length of the first portion, or

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_ ··, otherwise omit the second part completely. By designing the '** tension press such that the first portion 4 ·:' · extends from an axial distance of at least 70%, preferably more than 80%, and preferably greater than 85%, between the portion of 104625 4 where the liner meets the inclined surface and where the tube leaves the tension press, the tensile stress required to pull the liner tube through the tension press, in particular, is substantially reduced. Another consequence of using such a tension press to carry out the invention is that when a liner tube which is a synthetic hydrocarbon resin such as polyethylene or modified polyethylene which is commonly used in practice has a greater tendency to exert such radial expansion compared to a radial expansion , wherein, as in the prior art, the tension press was provided with a second portion having a substantial length, as described above, typically in the order of 50% of the total length of the tension press. When the tensile stress is relieved, such tendency will result in a greater relative radial expansion compared to the tensile stress used than with prior art tension presses.

This process of the invention is based both on the expansion of the liner tube due to the relaxation of tensile stress in the pipeline and also on the memory effects of the tensile liner tube; enlargement. By using a tension clamp, the axial length of the second portion being reduced relative to the axial length of its first portion, as described above, the relative expansion due to the tensile stress relaxation can be significantly increased, which improves the controllability of the tube lining operation.

• · * • «t · $»:. · 'The above arrangements also provide a considerable advantage over the situation in which they are used. ···. device of the "pusher" type, for example of the type disclosed in our co-pending GB 8806926. The use of this type of pusher is due to the fact that when it grasps the lining tube and forces it towards the liner 5 10462b, there is a temporary reduction in tensile stress at the other end of the pipeline by the puller (such as a winch). It is desirable that the change between maximum and minimum stresses during oscillations is made as uniform as possible with the minimum amount of rapid changes or jerks.

We have found that when tensile presses of the invention are used which require substantially lower tensile stresses to achieve a comparable degree of compression with prior art tension presses, and which are also due to the greater "bounce" and "tensile" tendency of the tube exit the fluctuations themselves become more even. Given the very high forces involved in applying tensile stress, this is again a significant improvement in both operational safety and efficiency.

As a single step, the length of the pipeline to be lined by the method of the invention can typically be 10:. meters upwards. The pipeline boundary length at a given point ···. in the situation may be lined, will depend on the factor combination, including the frictional resistance against the movement of the lining inside the pipeline, the extent to which the lined piping with reduced shear • · »'· *' becomes exposed to deformation ( problem occurring with • t · V * lining pipes of larger diameter having a · · · 'v: relatively high SDR ratio), tensile stress limiting the front end of the lining pipe, beyond which there may be permanent • ·, ··, damage, or permanent extension, the capacity of the drive mechanism (such as the winch) and the uniformity of the diameter and / or orientation of the pipeline: interior. Most appropriate: /! in practice, the length to be lined in a given case can easily be determined by the trial and error method. The method according to the invention makes it possible to line pipelines which can be up to 450 meters in length or more. The surface finishing of the tension press can be accomplished by means known in the art. The surface quality should preferably correspond at least to class N7, typically to class N6, most preferably up to N5, and ideally to about class N4 or better.

It has been found advantageous to use a tension clamp having a slope angle of the tensioning surface of the tension press which is relatively gently relative to the tension of the tension press, so that it is in the range 12 °. . .29 ° and preferably 20 ° ... 25 °. Reducing the angle helps reduce the tensile load required to achieve compression of the liner tube, while at the same time increasing the tensile press surface by any degree of compression. The optimum angle will be that which, in any given situation, minimizes the overall drawbacks caused by the high Jcuorm on the one hand to provide compression and on the other to provide a high friction generating tension surface. The tensile press surface may be in the form of a truncated cone. Alternatively, its inclination angle with respect to the tension of the tension press may be varied within the aforementioned framework. An important and advantageous feature of the present invention is that when using a lining tube made of a deformable memory material according to the method of the invention, the lining tube can be left to expand in the radially lined tube of its material. of the effect from which it is made. With the appropriate • · · V initial liner diameter, compression ratio tensile strength · · ·: during the compression operation and by selecting the tension inlet diameter of the liner, the invention can provide a tightly fitting · After connection) is a consequence of memory expansion of the pipe liner • · at ambient temperature and pressure 104625 7 inside the pipeline. In this context, it is not necessary to rely on prior art methods for expanding pipe liner within the pipeline, such as applying internal overpressure or heat to the liner internally or applying very high stretching forces to the liner during the initial phase to provide initial reduction in liner diameter prior to insertion. The exact operating conditions used to carry out the process of the invention will, in any given situation, depend on a number of factors described above and will vary with the inner diameter and purpose of the pipeline (e.g., water or gas), pipe liner and SDR. (SDR refers to the ratio of the existing diameter of the liner before tension extrusion to the wall thickness of the liner).

According to another embodiment of the present invention, there is provided a device for lining an existing pipe comprising a support structure, a tension clamp disposed in the structure for reducing the diameter of the lining tube passed therethrough, a securing device for securing the structure to the lined tube; for heating the towable lining tube.

The recommended material for the liner is polyethylene, but also other materials with the necessary memory retention properties, such as polyethylene copolymer and at least one alpha olefin with up to ten carbon atoms. • · · V: atom, can also be used. Although the diameter of the liner tube during traction press passage may be as high as>. ··. 15%, a reduction of 5.0 to 9.8% is most appropriate. The shrinkage should be such that the liner tube can be pulled through an existing tube. This is something that is simply required • black is complicated by the fact that the internal dimensions of existing tubes 104625 8 are often not very accurate that the inner diameter The position of the liner may vary with the length of the pipe and the degree of recovery of the liner may vary depending on the environmental conditions and the material of which the liner is made.The liner should have a minimum wall thickness consistent with its intended use and provide reliable internal sealing of the existing pipe. relationship, which is 10 ... 46.

The selected maximum tensile stress for drawing the liner pipe through the existing pipe should preferably be between 45 and 55%, in particular about 50% of the yield limit of the liner in question. The ratio between the die diameter of the drawing press and the diameter of the existing pipe should preferably be between 1.05: 1 and 1.15: 1. A reciprocating pusher may be used to increase tensile stress exerted by said puller to pull the liner tube through the tension press.

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

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Fig. 1 is a sectional side view of an embodiment of the device according to the invention, and

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Figure 2 is a sectional side view of a modified embodiment of the device shown in Figure 1.

Referring to Fig. 1, the apparatus comprises a support structure 1 to which .'j *; includes pipe clamp 2 at one end and «, ·· at the other. end tension clamp 3. The tension clamp 3 is generally cylindrical and comprises a larger diameter: ** part 4 connected to a smaller diameter part 5 · by means of a conical part 6. The tension press is provided with a 104625 9 polished pressing surface which forms an angle of 6 ... 32 ° with the tension of the tension press, the inclination being preferably 12 ... 29 ° and preferably 20 ... 25 °. The surface quality of the polishing is at least of the order N7, typically up to N6, preferably up to N5 and ideally of the order of N4 or better. The ratio of diameters of 4 and 5 is preferably between 1.05: 1 and 1.15: 1. This has been found to provide sufficient clearance between the pipe liner and the inner diameter of the pipe for most normal pipes and is well suited to the framework for material diameter recovery.

The body of the tension press 3 in the illustrated embodiment is hollow and includes an electric heating coil 8 which is supplied with electricity through an electric supply circuit 9. Power is applied to the heating coil to heat the liner tube to a temperature of 35 ° C to 95 ° C and preferably about 50 ° C. When exiting the tension press, the lining tube is cooled by means of an annular heat exchanger 12 located around the tube and which removes heat from the tube. The heat exchange medium may be carbon dioxide, air, water or any other suitable liquid.

The pipe clamp 2 is secured to the free end of the existing pipe and, together with the existing pipe designated 10, forms a stop against which the lining pipe 7 can be pulled. The support structure to which the tube clamp is connected may be tubular or may consist of a plurality of arms connecting the tube clamp 2 and the tension clamp 3.

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When using the device, a liner tube 7 of a certain length of polyethylene or other suitable material may be bevelled or preformed efficiently at one end to form a tip cone at the end on which the notched metal tip cone can be fitted. The preferred ratio between wall thickness and: '' lining tube diameter is considered to be 10 ... 46.

The chamfered portions are formed with holes which are aligned with the holes in the metal cone 10 104625 and through which the cable is connected to the pipe. The cable is threaded through a tension clamp 3 and an existing pipeline and connected to some type of suitably secured pulling device, such as a winch. The power supply is turned on to heat the tension press to the desired temperature and the bevelled end of the lining tube is introduced into the upstream end of the tension press. The cable tension is increased to the required value (usually 45 ... 55%, especially 50% of the yield limit of the liner in question) until the liner begins to move through the tension clamp and retracts into the existing pipeline. In this way, the liner pipe is pulled completely through the existing pipe. The cable is disconnected, and then the memory property of the pipe material may expand the pipe until it comes into contact with the inner surface of the existing pipe.

The passage of the pipe through an existing pipe can be facilitated, if desired, by a liner pusher. Such an arrangement is shown in Figure 2 of the drawing. Referring to this figure, a pusher, which generally comprises a body 21, a hydraulic cylinder 22, a clamping ring 23 and auxiliary devices, is disposed between the tension clamp 3 and the pipe clamp 2.

. ; In use, this machine pulls the liner tube through the tension clamp 3

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. · 1. and push it into an existing pipeline.

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* 1 !! It will be apparent that the foregoing embodiments are described by way of example only, and that many variations are possible without departing from the scope of the invention. For example, the liner * .1 'may be heated prior to being introduced into a tensile press and stretched as described in co-pending application GB-2186340 «.

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Claims (2)

A method of lining tubes, which method comprises the stage of taking a lining tube of a certain length whose outer diameter is greater than the inner diameter of the tube to be fed, pulling the lining tube at the same temperature as the ambient through a draft press using an under tensioning device attached to the front end of the casing and threaded through the pipeline to reduce the outer diameter of the casing by up to 15%, pulling the casing through the casing to be fed with casing where the casing's outer diameter is reduced and / or maintained at a dimension smaller than the inner diameter of the tube to be lined, characterized in that the tensile stress exerted by the pulling device is such that it partially restricts a radial expansion of the outer surface of the liner after it emerges. from the drawing press, that after this an expansion of the lining tube (7) is allowed inside that tube (10) which is to be provided with lining by slackening on said tensile stress, on which follows a memory-related expansion at normal air pressure and the temperature of the environment of the tube (10) to be fed, whereby, the tube (10) to be supplied with lining is mounted as one in |. (| the ground submerged pipeline and this tube (10) and the lining tube i «i! (7) have a length of at least 10 meters, the lining tube (7) being III: made of polyethylene or a copolymer of ethylene and a« · * ··· 1 has at least one alpha olefin of up to ten carbon atoms, and the drawbar (3) is indirectly attached to the tube (10) to be supplied with a support by means of a support means (1) for the press, which means itself is directly attached to the tube (10) which; T: is to be provided with lining or so is the pull press (3) itself: 1 · 1: directly attached to the tube (10) to be supplied with lining. * «Il • II Method according to claim 1, characterized in that the liner (7) is preheated to a temperature of 45 ° to 55 ° C. · · · I ·