Laser hardening of liners

Abstract

To provide a simpler technology for curing a liner in order to rehabilitate a pipe or a canal by laser light.SOLUTION: A process for curing a liner for rehabilitation of a pipe or a canal comprises the steps of: inserting a liner containing at least a resin-impregnated fiber tube into the pipe or the canal; installing the liner by pressing the liner against an inside surface of the pipe or the canal; and curing a resin system in the resin-impregnated fiber tube by moving a device through the installed liner, wherein a laser light impinges on an inner surface of the installed liner, and as a result, the laser light is deflected in the device by at least one optical element at an angle from 0.5 to 179 degrees so as to cure the resin system in the resin-impregnated fiber tube.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a process for curing liners for pipe or canal repair in which a laser beam is used to cure a resin impregnated liner, and to the use of an axicon to generate an annular laser beam profile for curing liners for pipe or canal repair. [Background technology]

[0002] The use of lasers in pipe and canal repair, where a liner is used to cure a resin-impregnated fiber tube, is known, for example from EP 4017906 A1. However, the prior art process was disadvantageous in that it required the laser source to be aimed directly at the inner surface of the liner to be cured. This made the devices required for curing very expensive and complex.

[0003] WO9851960A1 describes curing liners with a laser, where the hardener is encapsulated and the capsules release the hardener upon laser irradiation. The hardener is not a photoinitiator; the capsules will necessarily absorb the laser light.

[0004] Until now, there has been a prejudice that laser curing of liners containing resin-impregnated fiber tubes is particularly difficult. For example, EP 4017906 A1 and WO 9851960 A1 describe that the laser source itself can be directed at the inner surface of the liner, or that the laser light is directed at the inner surface of the liner through a rotating mirror. Until now, these processes have not been able to take the market by storm.

[0005] It is therefore an object of the present invention to provide a simpler technique for laser hardening of liners for pipe or canal repair.

[0006] In a first embodiment, the object of the present invention is to 1. A process for curing a liner for the repair of a pipe or canal, comprising: a. inserting a liner including at least a resin-impregnated fiber tube into the pipe or canal to be repaired; b. installing the liner by pressing the liner against the interior surface of the pipe or canal to be repaired; and c. curing the resin system within the resin-impregnated fiber tube by moving a device through the installed liner, wherein the laser light is deflected within the device by at least one optical element at an angle of 0.5 to 179 degrees relative to the incident laser beam such that laser light is incident on an inner surface of the installed liner, thereby curing the resin system within the fiber tube. is performed and realized by the process.

[0007] For example, this device allows a laser light source to be positioned outside the liner and, in an installed liner, laser light irradiating the liner longitudinally can be deflected onto the inner surface to cure the resin system.

[0008] An important advantage of using laser light in the process according to the invention over processes using conventional light sources (such as mercury lamps without lasers) is that, for example, the intensity loss is approximately linear with distance when using a laser, whereas previously the intensity loss was proportional to the square of the distance. Furthermore, the color of the laser light can be adjusted to the optical conditions for curing the liner in the best possible way. DETAILED DESCRIPTION OF THE INVENTION

[0009] The process according to the invention allows for easier handling, lower investment costs, better control of the curing and better workplace safety (e.g. no longer any risk from electric shock or high pressure lamp explosion).

[0010] [process] Inserting the liner in step a. may be performed either by inserting the liner into the pipe or canal, or alternatively by inverting the liner within the pipe or channel.

[0011] For example, installing the liner in step b. may be performed by pressurizing the liner with a fluid (eg, compressed air, steam, water, or the like).

[0012] In step c, curing can be carried out, for example, thermally or by photocuring. If curing is carried out thermally, for example, a thermal initiator can be included in the resin system. If curing is carried out by photocuring, for example, one or several photoinitiators can be included in the resin system.

[0013] In step c, the device is moved through the liner at a speed preferably in the range of from 0.1 to 5000 cm per minute, particularly preferably from 0.2 to 1000 cm per minute.

[0014] In step c. of the process, the optical element is preferably moved along the liner close to the axis of symmetry of the installed liner, in particular in step c., the central position of the optical element deviates from the axis of symmetry by less than 50%, and very particularly preferably by less than 10% of the inner diameter of the installed liner.

[0015] [Resin-based] Preferably, the resin system according to the present invention is a resin system for curing the liner. For example, the resin system may be a resin system made of unsaturated polyester, vinyl ester, or epoxy resin system. Preferably, the resin system according to the present invention may also contain a thermal initiator, such as an azo compound or peroxide. However, preferably, benzoyl peroxide is not used as the thermal initiator because it is dangerous to the environment.

[0016] Preferably, the resin system contains clay particles in an amount of at most 1% by weight, and more preferably, it contains no clay particles.

[0017] Preferably, the resin system contains natural fibers in an amount of at most 1% by weight, and more preferably contains no natural fibers.

[0018] Additional fillers (eg, aluminum hydroxide or calcium carbonate) may also be included.

[0019] The resin system preferably contains a polymerization initiator in an amount ranging from 0.01 to 5% by weight, particularly preferably from 0.05 to 1% by weight, which may be a photoinitiator or a thermal initiator, or a mixture of a photoinitiator and a thermal initiator.

[0020] Preferably, at least one absorption maximum of the photoinitiator is in the range from 250 to 600 nm, very particularly preferably in the range from 400 to 500 nm.

[0021] [device] The optical element is preferably connected to a light guide, particularly preferably a fiber optic cable, which directs the laser light from the laser source to the optical element.

[0022] The laser source may preferably be located external to the liner.

[0023] The device may be, for example, a drone (e.g., an airborne drone). The optical element is preferably installed on the airborne drone. The optical element on the airborne drone may be connected to a laser source, for example, via a light guide.

[0024] For example, the device may be a carriage on which an optical element is mounted. The carriage may have, for example, wheels. The optical element on the carriage may be connected to a laser source via, for example, a light guide.

[0025] [Laser light] Preferably, the laser light can be generated by at least one laser. Furthermore, several lasers can be used to generate the laser light. When several lasers are used, at least two of the several lasers can emit laser light with different wavelengths. This has the advantage that different initiators or different absorption bands of initiators can be addressed.

[0026] The diameter of the laser beam entering the optical element is preferably in the range of 0.1 to 50 mm (very particularly preferably 1 to 10 mm).

[0027] The wavelength of the laser light (especially the laser light entering the optical element) is preferably in the range of 200 to 2200 nm, particularly preferably in the range of 325 to 600 nm, and very particularly preferably in the range of 400 to 500 nm. This range is particularly preferred because conventional resin systems and liners for pipe and canal repair are optimized to have particularly high transmittance in this narrow wavelength range. Most liners have a maximum transmission loss below about 300 nm. As a result, wavelengths below 325 nm are not advantageous.

[0028] It may be preferable for at least one laser to generate laser light having a wavelength in the range of 975 to 1800 nm, which laser light is converted by a frequency converter to laser light having a wavelength in the range of 325 to 600 nm before entering the optical element.

[0029] Alternatively, it may be preferable for the laser light generated by the at least one laser to have a wavelength in the range of 975 to 1800 μm, particularly preferably in the range of 1200 to 1500 μm. In this case, the laser light is, for example, infrared laser light. The advantage of this alternative lies in the power loss and cost of glass fibers. While fibers for transmitting UV laser light are relatively expensive and do not result in power losses (e.g., 10-30% per 100 m, >6 dB / km), fibers for transmitting infrared laser light are cost-effective and have very low losses (0.1% per 1000 m, <1 dB / km). For the same reasons, infrared laser light and infrared glass fibers are used for telecommunications tasks. Additionally, protection from laser light is less important for infrared laser systems than for UV laser systems. The laser light so generated may then be converted into laser light having a wavelength in the range of 325 to 600 nm, preferably by a frequency converter (such as a nonlinear optical crystal) before the optical element.

[0030] The laser light or at least one laser may, for example, be pulsed or continuous.

[0031] The laser light or at least one laser preferably radiates onto the optical element in the longitudinal direction of the liner.

[0032] Preferably, the intensity of the continuous beam or the average intensity of the pulsed laser light (10 9 From 10 16 W / m 2 Laser light having an intensity in the range of 1000 Hz to 1000 Hz is used in the method according to the invention. Usually, this intensity is measured in terms of power per unit area, i.e., watts per square meter, or W / m 2 The laser pulse duration is preferably in the range of 10 to 350 femtoseconds. The laser pulse energy is preferably in the range of 1 to 20 mJ (millijoules). The laser repetition rate is preferably in the range of 0.1 to 50 kHz.

[0033] [Optical elements] The optical elements may be reflective, refractive and / or diffractive.

[0034] In particular, if the laser light is generated by several lasers, several optical elements may also be used.

[0035] Due to the optics, the laser light preferably propagates on the surface of a cone, which creates an annular illumination on the inner surface of the liner.

[0036] Preferably, this angle may be in the range of from 5 to 150 degrees, very particularly preferably in the range of from 10 to 85 degrees.

[0037] The optical element may include a rotating mirror, which allows the laser beam to be deflected during the movement of the device so that it is incident on the inner surface of the liner where it is placed, thereby curing the resin system. The angle of the mirror relative to the direction of the laser beam in front of the mirror is preferably within the range of ±0.1 to 89.9 degrees, very particularly preferably within the range of 30 to 60 degrees.

[0038] Preferably, the at least one optical element includes at least one axicon, which generates a laser beam with an annular beam profile incident on the inner surface of the installed liner. As a result, the resin system can be cured. Particularly preferably, the optical element does not include galvanometric or rotating elements. The axicon is a conical lens that generates an annular beam profile. Axicons have the advantage that the laser source can actually be located outside the liner when curing the liner, thereby minimizing the risk of an accident with the liner itself during curing. Furthermore, the optical element can be inserted much more easily and quickly than with currently used UV light sources. Furthermore, in contrast to conventional techniques, the light source generates very little heat within the liner. Additionally, this technique makes it possible to cure liners in pipes with significantly smaller diameters. The axicon can be convex or concave. The opening angle of the axicon or the resulting light cone is preferably in the range of 1 to 180 degrees, particularly preferably in the range of 20 to 150 degrees, and more preferably in the range of 40 to 130 degrees. The aperture angle of the axicon is defined as the limiting angle of the emerged light. This aperture angle of the axicon or emerged light cone is therefore twice the angular magnitude of the emerged light relative to the incident laser beam (also designated, e.g., as the deflection angle, as in step c.).

[0039] The optical element may also preferably include at least two axicons. Thus, one axicon may be concave and one axicon may be convex. To optimize the power distribution, the diameter of the ring may be adjusted by varying the distance of both axicons from each other.

[0040] The material of the at least one axicon is preferably glass (in particular quartz glass) or plastic.

[0041] Preferably, the diameter of the axicon is in the range of 2 to 600 mm, very particularly preferably 20 to 50 mm. , or 5 to 50 mm The diameter of the axicon is preferably larger than the diameter of the laser beam.

[0042] The edge thickness of the axicon is preferably in the range of 2 to 10 mm.

[0043] The optical elements may also include at least one diffractive optical element (DOE), which makes it possible to shape, for example, a laser beam.

[0044] [use] In another embodiment, the object of the present invention is realized by the use of at least one axicon for generating an annular beam profile of a laser beam for hardening a liner for repairing a pipe or canal.

[0045] Illustrative Embodiments A commercially available resin-impregnated liner cured by UV light, such as that described in EP 2573442 A1, was used. A pipe with a diameter of 300 mm was fitted with a liner with a wall thickness of 4 mm. The resin system used (e.g., L050-LCW-03 FC made by AOC) contained 0.1 wt.% Irgacure 819 as a photoinitiator. During repair, the liner was inserted into the pipe to be repaired and then inflated using compressed air. Ti with regenerative amplifier 3+ : Al2O3 laser oscillator, and downstream optical parametric oscillator (TOPAS Prime type OPO manufactured by Coherent Inc. company, Astrella Ti:sapphire laser, 6 mJ HE version manufactured by Coherent Inc. company; repetition rate 1 kHz; average power 1 W, pulse peak intensity: 3 × 10 15 W / m 2The laser beam was generated by a 40-fs pulse (pulse duration 40 fs). The wavelength at the OPO output was 450 nm. The laser beam was then guided through a 100 m long fiber optic cable with a 59.8° aperture (twice the deflection angle), which is typical for this purpose, and then guided through an axicon (manufacturer: Thorlabs; type: AX1240-A, diameter 1 / 2", physical angle: 40°, deflection angle: 29.9°, center thickness 10.3 mm, AR coating 350-700 nm, R avg The deflection angle was measured at 532 nm with a laser beam projected annularly onto the inside surface of the installed liner. The carriage pulled the axicon approximately concentrically within the installed liner, through the entire liner, so that the annular laser beam illuminated the entire inside surface of the liner. The speed was set at 3.6 mm per minute.

[0046] Thus, the photoinitiator could be activated and the resin could be cured.

[0047] The features of the invention disclosed in the specification and claims, both individually and in any combination, may be essential for the realization of various embodiments of the invention. The invention is not limited to the described embodiments. Within the scope of the claims, the invention can be modified taking into account the knowledge of a person skilled in the art.

Claims

1. 1. A process for curing a liner for the repair of a pipe or canal, comprising: a. inserting a liner including at least a resin-impregnated fiber tube into the pipe or canal to be repaired; b. Installing the liner by pressing the liner against the interior surface of the pipe or canal to be repaired; c. curing the resin system within the resin-impregnated fiber tube by moving a device through the installed liner, wherein the laser light is deflected within the device by at least one optical element at an angle of 0.5 to 179 degrees such that the laser light is incident on an inner surface of the installed liner, thereby curing the resin system within the resin-impregnated fiber tube. is executed, The process wherein the optical element includes an axicon that generates an annular beam profile of a laser beam incident on the inner surface of the installed liner.

2. The process of claim 1 , wherein the optical element is connected to a laser source via a light guide.

3. 10. The process of claim 1, wherein the diameter of the axicon is in the range of 5 to 50 mm.

4. 10. The process of claim 1, wherein the aperture angle of the at least one axicon is in the range of 20 degrees to 150 degrees.

5. The process of claim 1 , wherein the optical element comprises a diffractive optical element.

6. The process of claim 1 , wherein the optical element comprises at least two axicons.

7. 10. The process of claim 1, wherein the wavelength of the laser light is in the range of 325 to 600 nm.

8. 10. The process of claim 1, wherein the resin system contains a photoinitiator, and wherein one absorption maximum of the photoinitiator is in the range of 325 to 600 nm.

9. 2. The process of claim 1, wherein at least one laser generates laser light having a wavelength in the range of 975 to 1800 nm, and the laser light is converted by a frequency converter to laser light having a wavelength in the range of 325 to 600 nm before entering the optical element.

10. 1. Use of at least one axicon to generate an annular beam profile of a laser beam for hardening a liner for repairing a pipe or canal.