BACKGROUND OF THE INVENTION

This invention relates generally to a method for installing a replacement pipe within an existing, conduit, and more particularly to a method for installing the pipe by inserting an uncured resinous replacement pipe into an existing conduit to be relined and then curing the replacement pipe with ultrasonic energy.

The need for rehabilitating existing pipelines and conduits is growing as existing pipelines continue to deteriorate. However, it is undesirable to remove the existing pipelines and replace them with new pipe. More preferred is to install a new pipe within the existing pipeline without excavation and destroying any existing structures. One of the most widely practiced systems for accomplishing this is referred to as a "soft-lining" system or the "Insituform" process in which a soft felt tube impregnated with a curable resin and tailored to match the size of the existing pipeline, is inserted into an existing pipeline. The tube is then expanded to the interior dimension of the existing pipeline and the resin is cured to yield a new rigid and durable resin pipe within the existing pipeline.

The "Insituform" method is described in greater detail United Kingdom Patent No. 1,340,068 the contents of which are incorporated herein by reference. This method employs a flexible multi-layer tube including a fibrous carrier layer disposed between two membranes. The inner membrane is relatively impermeable to fluids. The carrier layer is impregnated with thermosetting resin mixed with catalyst and promoter and the tube is inserted into the existing pipeline. It is then inflated by internal pressure such as by application of a fluid, such as water, within the tube. To cure the resin stored in the fibrous carrier material, hot water, hot air or steam is typically circulated through the expanded tube to initiate accelerated curing of the resin.

Further embodiments of that process are described in United Kingdom Patent No. 1,449,455, the contents of which are

incorporated herein by reference. As described therein, the flexible replacement tube is inserted into the existing pipeline, one end thereof is anchored and the remainder of the tube is everted through the anchored end so that the tube everts into the pipeline to be relined. The everting medium is usually a liquid and when the eversion process is completed, the liquid remains inside the everted tube under pressure to maintain the shape of the replacement pipe while the resin cures. In another embodiment of the Insituform process, the replacement pipe is not everted, but is inserted into the existing pipeline and then inflated with heated fluid, such as water, air or steam to the shape of the existing pipeline surface. The internal membrane should be impermeable to the inflation fluid.

Although these methods are successful, they can be expensive in view of the high energy costs involved in heating sufficient fluid to cure the resin. Furthermore, the heated fluid only accelerates the curing process which begins as soon as the thermosetting resin is mixed with catalyst and promoter. Accordingly, the replacement pipeline will slowly begin to harden over time. The use of ultraviolet curable resins to increase shelf life are discussed in U.S. Patent Nos. 4,581,247 and 4,680,066. However, the use of UV-curable resins can be inconvenient to handle and must be protected from exposure to sunlight.

UV-curable pipe has other disadvantages. The resin and felt resin carrier have to be transparent to UV light and the water within the pipeline must be clean and transparent to the UV rays. Furthermore, the process is limited by the ability of the UV radiation to penetrate sufficiently and the cooling effects of water present.

Rehabilitation of sewer lines can present additional rehabilitation problems because fluid tends to be flowing through the existing pipeline. Typically, the naturally flowing fluid must be bypassed to enable the traditional installation method to be carried out in an empty pipe. This is not always practical or acceptable.

Accordingly, it is desirable to develop an improved method for installing a replacement pipe, formed with fibers holding curable resinous material, within an existing pipeline, which avoids the shortcomings of the prior art.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the invention, a replacement pipe and method of installation are provided in which flexible replacement pipe including curable resinous material is installed in an existing pipeline and the resinous material is cured ultrasonically to yield a rigid replacement pipe within the existing pipeline. The replacement pipe is preferably formed with a fibrous carrier layer including curable resinous material disposed between two liner layers.

The replacement pipe is installed to have a tubular shape within the existing pipeline and is maintained in an expanded shape by application of internal pressure, such as from fluid.

In one embodiment of the invention, the replacement pipe is inserted into an existing pipeline in a collapsed condition having dimensions less than those of the existing pipeline. It is then inflated by application of fluid under pressure so that the replacement pipe conforms to the inner dimensions of the existing pipeline. In another embodiment of the invention, the pipe is inverted as it is introduced into the existing pipeline and then maintained in an expanded shape by application of internal pressure. At least the inner liner of the replacement pipe should be impervious to the fluid. The fluid can be liquid already flowing through the existing pipeline. The replacement pipe should be fitted with a suitable device at its downstream end to insure that the naturally flowing fluid will provide sufficient pressure to inflate the replacement pipe.

An ultrasonic device is moved through the fluid inside the replacement pipe tube and applies ultrasonic energy to cure the resinous material.

Accordingly, it is an object of the invention to provide an improved replacement pipe and method and apparatus for installing the replacement pipe in an existing pipeline.

Another object of the invention is to install a replacement pipe without having to bypass fluid naturally flowing through an existing pipeline.

Still another object of the invention is to provide a replacement pipe that can be cured by application of ultrasonic energy.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus and pipe embodying features of construction, combinations of elements and arrangements of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIGS. 1A, IB and 1C are schematic diagrams illustrating steps of installing replacement pipe in an existing pipeline in accordance with an embodiment of the invention;

FIGS. 2A, 2B and 2C are schematic diagrams illustrating steps of installing replacement pipe in an existing pipeline in accordance with another embodiment of the invention;

FIGS. 3A, 3B and 3C are schematic diagrams illustrating steps of installing replacement pipe in an existing pipeline in accordance with another embodiment of the invention;

FIGS. 4A, 4B and 4C are schematic diagrams illustrating steps of installing replacement pipe in an existing pipeline in accordance with another embodiment of the invention;

FIG. 5 is a plan view of an ultrasonic curing device suitable for use in curing in accordance with the invention; and

FIG. 6 is a plan view of a multiple transducer ultrasonic curing device for use in curing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A replacement pipe in accordance with an embodiment of the invention is formed with a resin section disposed on one or between two lining layers. At least the inner liner should be an impermeable membrane. The resin section can include a carrier impregnated with curable resin material. Thermosetting resin compositions, such as allyl, bismaleimide, epoxy, phenolic, polyester, polyamide, polyurethane or silicone resins and combinations thereof that will cure upon application of ultrasonic energy are acceptable. The carrier can be any acceptable fibrous material, such as felt and the like and the resin section will become rigid and strong when the resin is cured.

Thermosetting unsaturated polyester resin compositions are particularly well suited to be included in the resin section of replacement pipe constructed in accordance with the invention. Unsaturated polyesters are extremely versatile and can be acceptably rigid, corrosion resistant and weather resistant for pipe applications. Such unsaturated polyesters have been used in widely diverse applications, such as in constructing boats, exterior automotive parts and bowling balls.

Commercial unsaturated polyester resins consist of an unsaturated polyester dissolved in cross-linking monomer and containing an inhibitor to prevent cross-linking until the resin is to be cured. Unsaturated polyester is the condensation product of an unsaturated dibasic acid (typically maleic anhydride) and a glycol. The degree of unsaturation is varied by including a saturated dibasic acid such as phthalic anhydride, isophthalic acid, or adipic acid. The glycol is usually propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol and combinations thereof.

Styrene is a particularly well suited cross-linking monomer. Other acceptable cross-linking monomers include vinyl toluene, methacrylate, alpha methyl styrene and diallyl phthalate. Conventional inhibitors include hydroquinone, parabenzoquinone and tertiary butyl catechol.

Depending on the application for the replacement pipe, chemical resistance can be achieved by using isophthalic acid, neopentyl glycol, trimethyl pentanediol and hydrogenated bisphenol A. Weathering resistance can be improved by using neopentyl glycol, methyl methacrylate and ultraviolet absorbers such as benzophenones and benzotriazoles.

The polyester resin material is cured by a free radical addition reaction. An organic peroxide can serve as a catalyst and can be the source of the free radicals. At elevated temperatures, heat decomposes the peroxide to produce the free radicals. Peroxyesters and benzoyl peroxide are organic peroxides used at elevated temperatures.

The resin component can also include a curing promoter. The promoter causes the organic peroxide to decompose and form free radicals. Cobalt octoate is an appropriate promoter, especially when methyl ethyl ketone peroxide (MEKP) is used as the catalyst. Diethylaniline or dimethylaniline are acceptable promoters when benzoyl peroxide is used as the catalyst.

Epoxy resins are also well suited to be included in the resin section of replacement pipe constructed in accordance with the invention. The term epoxy resin refers to a variety of cross-linking materials that contain the epoxy or oxirane group. The epoxy group is reactive with a wide variety of curing agents or hardeners. The curing reaction converts the low molecular weight resin into a three dimensional thermoset structure. Standard epoxy resins are based on bisphenol A and epichlorohydrin as raw materials. Other types are based on the epoxidation of multifunctional structures derived from phenols and formaldehyde or aromatic amines and aminophenols.

Epoxy resins can be cured at low temperatures with aliphatic polyamines or polyamides. Cures at elevated

temperatures can occur with anhydrides, carboxylic acids, phenol novolac resins, aromatic amines or melamine, urea and phenol-formaldehyde condensates. Cures at lower temperatures generally require a two component system including resin separated from hardener prior to the curing reaction. Cures at elevated temperatures can be performed with a one component mixture of ingredients which will be stable at ambient temperatures. These are more suitable for increasing the pot- life of the resin.

Intermediate molecular weight solid epoxy resins can be cured through both the terminal epoxy group and the pendant hydroxyl group in the polymer backbone. Typical cross-linking agents include dicyandiamide or phenolic group terminated poly(hydroxyethers) with imidazole accelerators. Medium molecular weight resins can also be utilized to form epoxy esthers by reaction with fatty acids at high temperatures, whereby both the terminal epoxy groups and the secondary hydroxyl groups are converted to ester linkages, the latter by azeotropic removal of water. Other intermediate molecular weight epoxy resins are prepared by chain extension of liquid epoxy resins and brominated bisphenol A.

High molecular weight epoxy resins, which can be classified as poly(hydroxy ethers) , contain low concentrations of epoxy end groups. They are cured via the hydroxyl groups, typically with aminoplasts (melamine or urea-formaldehyde resins) or phenoplasts (phenol-formaldehyde resins) at elevated temperatures.

It has been discovered that thermosetting resin compositions, formulated without initiators or retardants, provide a particularly well suited resin material for replacement pipes having long pot-life and can be cured by application of ultrasonic waves. Alternatively, the pot-life of a resin composition used in conventional replacement pipes can be increased significantly by using considerably less, such as less than 50% of a conventional amount of initiator.

Accordingly, cure initiators should be chosen to give the resin a long pot-life and for their chemical sensitivity to

ultrasound. Conventional resin formulations for replacement pipes include initiators having activation temperatures in the range of about 40-60°C. However, pot-life can be increased by employing initiators having activation temperatures in the range of 100-200 ^β C and more preferably 100-150"C. The resin should not be heated to the extent that it will begin to degrade. This will enable the replacement pipe liner to be wet out in quality controlled factory conditions and to be safe from curing until activated with ultrasound.

The carrier portion of the resin section preferably has a fibrous sheet structure including a mat, a web or randomly oriented fibers. The fibers can include glass and/or natural and synthetic fibers and the fibers may be of differing denier. A felt-like mat or web of randomly oriented fibers is particularly well suited for storing acceptable quantities of resin so that a wetted out web or mat absorbs a maximum amount of resin. A preferable carrier includes a needled felt of synthetic plastics material fibers which may optionally include filament reinforcement.

The carrier can be combined with the resin material by charging a quantity of resin into the inside portion of a carrier tube and if necessary, by applying vacuum to the tube to remove air from the carrier. The tube can then be compressed, such as by passing the tube through nip rollers in order to insure even distribution of the resin in the carrier material.

After the flexible resinous pipe is installed in a tubular shape in the pipeline, it is maintained in an expanded condition by application of fluid, such as water flowing naturally through the existing pipeline or added from an external source. The pipe can include liners on both the interior and exterior sides thereof. The inner liner should be impervious to fluids.

It is preferable to ultrasonically cure the resin in the replacement pipe which can be done in the presence of the usual fluid in the conduit. Sonochemistry utilizes high power ultrasound in the frequency range between 20 and 100 kHz to

influence chemical activity in liquids. The effect of the high power ultrasound is to create cavitation bubbles throughout the liquid medium during sonication. Ultrasound is transmitted through a medium by waves which alternately compress and stretch the molecular structure of the medium through which the waves pass. This stretching action during the rarefaction cycle of the wave is so powerful that the structure of a liquid medium will be literally torn apart to form microbubbles. During the subsequent collapse of these bubbles in the succeeding compression cycle, extremely high energies are generated inside the bubbles. These involve pressures of hundreds of atmospheres and temperatures of thousands of degrees. The mechanical and chemical effects of the collapsing bubbles are complex, but the end result is often the significant enhancement of chemical activity.

The generation of ultrasound waves is normally by electrically driven transducers employing piezoelectric ceramic elements. These piezoelectric elements, such as PZT disks, expand and contract when subjected to reversing electric voltage. The piezoelectric elements can be sandwiched between metallic disks to form transducers that can be tuned to generate particular frequencies of ultrasound. A 25 kHz transducer immersed in water will transmit an ultrasonic wave at 1450 m/s having a wavelength of 5.8 cm for hundreds of meters. If the transducer is positioned in a pipe filled with water, reflections will take place at the pipe walls and complex propagation will take place within the pipe, including guided and standing waves. It can be advantageous to line the walls of the existing pipeline with high density material to enhance the ultrasound cure effectiveness.

High power ultrasound can be generated by multiple transducers mounted on a suitable mandrel or by special cylinders energized by push-pull transducer arrangements. The several kilowatts of power ultrasound requires to induce chemical activity in significant quantities of material can be attained with conventional ultrasound technology.

When the pipe is cured ultrasonically, curing takes place throughout the thickness of the resin. This provides a high quality cure. Curing progresses down the length of pipe as the ultrasonic cure device travels through the length of pipe. This leads to less longitudinal tension, compared to pipe that is cured all at once by application of heat throughout the length of pipe.

The method of installing replacement pipe in accordance with the invention can be applied to virtually any situation in which a pipeline, conduit or other passageway is to be repaired. However, the process is best illustrated by describing the rehabilitation of sewer pipelines. Sewer pipes can vary in diameter from 6 inches to several feet and are normally laid at a gradient with manholes at junctions and bends.

Damage to existing sewer pipelines occurs due to ground movement, chemical attack or age. A soft-liner replacement pipe formed with thermosetting resin material and felt is manufactured, with reinforcement or other composite materials if required, to match the internal dimensions of the pipe. At least the inside of the replacement pipe will include an impervious membrane to seal the replacement pipe during the installation procedure. The replacement pipe is then taken to the installation cite and installed by either a pull-in or an inversion method.

The length of existing pipeline to be repaired is cleaned by access through local manholes. The natural flow of liquid through the pipeline is typically bypassed so that installation can be accomplished in an empty pipe. However, this is not always practical or acceptable and installation methods in accordance with the invention are advantageous when this cannot be accomplished.

Referring to FIG. 1A, a supply of replacement pipe 10 is delivered to a manhole 15 in a layered condition on a roll 11 or on a pallet, which can include a winching system. Alternatively, replacement pipe 10 can be delivered to manhole 15 in a folded pack. An existing pipeline 20 to be relined can

have liquid such as water flowing therethrough in the direction of an arrow A. If fluids are to continue to flow through existing pipeline 20 during installation of replacement pipe 10, pipe 10 should be installed in the direction of fluid flow.

FIGS. 1A-1C illustrate steps of the pull-in installation method in accordance with an embodiment of the invention. A rope 13 is fed from a leading end 18 of replacement pipe 10, down manhole 15, through existing pipeline 20 and out through a downstream manhole 16 where it is pulled by a takeup winch 12. Replacement pipe 10 is then pulled into position between manholes 15 and 16 as shown in FIG. IB.

At a trailing end 17 of replacement pipe 10 a sealing ring 17a is provided for securing pipe 10 in position after insertion into existing pipeline 20. Fluid flowing in the direction of arrow A will inflate replacement pipe 10. An inflatable or mechanical valve device 21 is positioned at downstream manhole 16 to control fluid pressure and thereby control the inflation of replacement pipe 10. During inflation, fluid will back-up in manhole 15 as the pressure within replacement pipe 10 builds up.

Referring to FIG. 1C, after replacement pipe 10 is inflated, it is maintained in an expanded tubular shape by application of internal pressure from fluid within pipe 10. Rope 13 can then be used to pull an ultrasonic transducer 25 through replacement pipe 10 to ultrasonically cure replacement pipe 10. This yields rigid replacement pipe 10'. It has been found that it is advantageous to pull the ultrasonic transducer through replacement pipe 10 at about 1 meter per minute as this permits sufficient time to initiate curing of the resin. After one pass of ultrasonic transducer 25, rigid replacement pipe 10* will be a smooth and shiny structural liner that is resistant to wear and chemical action. The ends of rigid replacement pipe 10 ^» are finished and any necessary lateral connections can be cut, such as by robots.

An alternative embodiment of the pull-in method is illustrated in FIGS. 2A-2C. Throughout the application, similar structures shown in the figures will be assigned the

same reference numerals. Leading end 18 of replacement pipe 10 is pulled through existing pipeline 20 and up into upstream manhole 16. Trailing end 17 is kept in manhole 15 and fluid from a pump 50 is pumped into replacement pipe 10. Trailing end 17 is kept above a height required for sufficient pressure to build up and to inflate pipe 10. Leading end 18 is kept at a spill level so that appropriate fluid pressure will be available to inflate pipe 10. Ultrasonic transducer 25 is then pulled through pipe 10 while proper inflation pressure is maintained.

FIGS. 3A, 3B and 3C illustrate an inversion lining method in accordance with the invention. A leading end 18 ^■ of resin impregnated replacement pipe 10a is fed down manhole 15. A seal 17• is formed at leading end 18* and existing pipeline 20. Fluid begins backing up in manhole 15 to create a pressure head for inverting replacement pipe 10a. The outside of replacement pipe 10a, as it is removed from roll 11, should have a membrane that is impermeable to fluids, as it is the outside that comes into contact with fluid naturally flowing through pipeline 20 as pipe 10 becomes inverted. The impermeable membrane reports to the inside of pipe 10.

As pressure begins building up, it inverts replacement pipe 10a which will become fully extended and inflated, as shown in FIG. 3C. A fluid control device 21' is included to maintain the pressure head. After replacement pipe 10a is fully everted, ultrasonic transducer 25 is pulled through the pipe at about 1 meter per minute to allow the ultrasound sufficient time to initiate curing of the resin.

Another embodiment of the inversion-liner method is shown in FIGS. 4A-4C. An inversion collar 60 is positioned in upstream manhole 15 at a height above that which is required to supply sufficient pressure to inflate replacement pipe 10a. Pump 50 pumps fluid into the interior 110a of replacement pipe 10a to invert pipe 10a towards downstream manhole 16. Referring to FIG. 4C, the downstream end of replacement pipe 10a is positioned at a spill level high enough to keep

replacement pipe 10a inflated as it is cured by transducer device 25.

Installing replacement pipe in accordance with the invention can also be accomplished by either conventional pull- in or inversion methods, in which the existing flow is bypassed. For example, the installation methods described in U.S. Patent Nos. 4,680,066 and 4,581,247 or British Patent Nos. 1,340,068 and 1,449,455 can be employed and the description thereof is incorporated herein by reference. After the replacement pipe is installed, the ultrasonic transducer is pulled therethrough to cure the replacement pipe.

FIG. 5 illustrates an axial transducer ultrasound device 100 for curing replacement pipe 10 in accordance with the invention. Ultrasound device 100 includes an axial transducer having a piezoelectric transducer 103 at each end of a titanium cylinder 104. Transducers 103 are connected to a power source by a power cable 101. Device 100 radiates a uniform field of ultrasound radially throughout the water within replacement pipe 10 without attenuation and onto and through replacement pipe 10. Replacement pipe 10 will absorb some of the ultrasound energy by chemical reaction and conversion to heat and the remainder will be transmitted. Axial transducer ultrasound device 100 also includes a plurality of guide springs 102 for correctly positioning device 100 within inflated replacement pipe 10.

Much of the energy transmitted by axial transducer ultrasound device 100 is reflected back into the pipe by the density discontinuity at the interface of replacement pipe 10 and existing pipeline 20 and will be added to the primary intensity. Energy levels depend on the pipe diameter and thickness.

A multiple transducer ultrasound device 200 is shown in FIG. 6. Multiple transducer device 200 includes a plurality of ultrasound transducers 201. Multiple transducer device 200 can provide larger power although the field pattern may not be as uniform. Another alternative transducer arrangement is to focus the ultrasound field onto a narrow circumferential band

by a profiled axial transducer. This can reduce the energy requirements needed for curing the resin. Suitable devices can be obtained from Martin Walter Ulteraschalltechnic GMBH, HardtstraBe 13-Postfach 6, Ortsteil Conweiler D-7541 Straubenhardt 5.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the pipe and apparatus set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Particularly it is to be understood that in said claims, ingredients or compounds recited in the singular are intended to include compatible mixtures of such ingredients wherever the sense permits.