Patent Application
20160178108
This application relates generally to piping and pipe construction. More specifically, this application relates to methods and apparatus for reinforcement and/or repair of pressurized pipes, using inner liners.
The drawings, when considered in connection with the following description, are presented for the purpose of facilitating an understanding of the subject matter sought to be protected.
While the present disclosure is described with reference to several illustrative embodiments described herein, it should be clear that the present disclosure should not be limited to such embodiments. Therefore, the description of the embodiments provided herein is illustrative of the present disclosure and should not limit the scope of the disclosure as claimed. In addition, while the following description mostly references using a flexible braided tube, an overlapped inner tube, and a collapsible tube, it will be appreciated that the disclosure may include other types of expandable tubes such as unbraided tubes or braided overlapped tubes, and the like.
Pipelines often corrode and deteriorate with age, requiring repairs. An example is the recent San Bruno, Calif. gas pipe failure of a 30-inch steel pipe that killed eight and caused millions of dollars of damage. The NTSB (National Transportation Safety Board) investigation following the explosion concluded that faulty welds in the 50+ year old pipe were a major cause of failure. There are thousands of miles of such pipelines that must be repaired. As reported by San Francisco Chronicle, PG&E officials estimated the cost of the mandated repairs to be around $11.3 billion. Clearly, in many cases removal and replacement of these transmission lines is not feasible. Economic methods and products for repair of such pipes that minimize digging are needed.
In addition, there are cases where the pipe is not damaged but may require strengthening so the gases or fluids can be transported at a higher pressure which would allow a larger volume of materials to be transported through the pipe per hour. The methods presented in the present disclosure can be used to repair and/or strengthen such pipes and allow larger put-through volumes. Furthermore, there are leaking pipes which can be repaired by the presented methods to make them watertight and to stop the leakage.
The existing technologies for repair of pipelines have many limitations and shortcomings. Some companies use fiberglass tubes that are made to match the exact diameter of the pipe being repaired. Pieces of these tubes, about 1000 feet or so long, are placed in a thin plastic bag and are saturated with various resins. Then the entire assembly is forced into the pipe by an inversion process which places the resin-saturated fiberglass tube against the host pipe and keeps the dry and clean face of the plastic bag facing the inside of the pipe. Steam, hot air, or UV light is then used to cure the fiberglass tube in place, against the host pipe. Such techniques have several shortcomings such as:
To overcome the above shortcomings and provide additional functions and uses, new methods for repairing and/or reinforcement of pipes are disclosed herein.
Briefly described, methods and articles of manufacture are disclosed for internally reinforcing various pipes that are constructed from different materials including but not limited to steel, concrete, masonry, wood, fiberglass, plastics, and the like. Some of the various pipes may be used to carry pressurized water, gas, oil, and the like. In an embodiment of these methods at least a layer of a flexible, bendable, radially expandable tube is first inserted into or is pulled through the inside of a desired pipe. These tubes, for example, may be braided (such as those supplied by A&P Technology, Cincinnati, Ohio), woven, or unwoven tubes or overlapped sheets of materials or longitudinally-folded or longitudinally collapsed tubes that are made of carbon, glass, basalt, Kevlar or other fibers. In various embodiments the inserted radially expandable tube may be pre-saturated in epoxy.
In a subsequent step an expansion apparatus, such as a balloon, is passed through the radially expandable tube which forces the radially expandable tube to touch all around the inside wall of the pipe. In embodiments in which the radially expandable tube is not pre-saturated with epoxy, an epoxy spray may be attached to the leading side of the expansion apparatus/balloon or be moved in front of the apparatus and spray epoxy on the radially expandable tube ahead of the expansion of the tube. In either case, when the epoxy smeared expandable tube comes in contact with the inside surface of the pipe and adheres to it, a strong and integrated liner is formed inside the pipe and becomes an integral part of the pipe. Depending on the designed characteristics of this liner, it can add strength to the pipe in multiple directions, including radial, longitudinal, and transverse, and/or prevent any leakage of the content of the pipe.
The presented methods also work well on large diameter pipes where man entry is possible and the crew can enter the pipe through access ports and apply the radially expandable tube to the pipe's inside surface manually or using a device. The described methods are equally suitable for small-diameter pipes where man entry is not feasible and the radially expandable tube must be installed using mechanical devices. These methods can be utilized to repair long portions of a pipe or to repair and reinforce only certain spots (typically shorter lengths) that require repair.
In various embodiments, the radially expandable tube may be a woven or braided tube made of high strength strands, such as the one shown in
The radially expandable carbon biaxial tubes or sleeves have the cosmetically desirable appearance of a 2×2 Twill pattern but as a tube they can be slid over a prepared mandrel or tube to create straight or tapered tubing. Similarly, they can be saturated with resin and slid inside a tube or pipe and pressed and cured while being pressed against the pipe surface to repair and strengthen the pipe. Some radially expandable tubes can be increased from their base diameter up to 30% and decreased up to 70%. This means that a 20″ diameter radially expandable tube can be used in a single application to fit inside a pipe with variable diameter ranging from 6″ to 26″. Laying up radially expandable tubes is predictable, repeatable, and suitable for precise manufacture of composite parts. Expandable carbon biaxial tubes are extremely resistant to cracks between layers created by multiple concentric tubes, reducing the possibility of delaminating and increasing the strength of the product. This is very helpful when more than one layer of the tube is used to repair a pipe. When inflated, braided reinforcement orients itself to the direction of force. This actually strengthens its outer skin, enabling it to withstand pressure and carry load, and to tolerate damage and fatigue. If a puncture does occur, the tube provides a slow, controlled failure, rather than a more damaging and potentially catastrophic blowup. Expandable tubes also completely conform to the shape of products with changing geometries. The expandable tubes may have the following features:
A dry expandable tube may be saturated with a resin such as an epoxy to form, for example, a Fiber Reinforced Polymer (FRP) tube capable of resisting loads. There are several ways to saturate an expandable tube including but not limited to:
In some embodiments, the expandable tube is saturated with epoxy before entering the pipe. The preferred epoxy is QuakeBond™ Heat Cured Resin that has a very long shelf life (more than 24 hours) at ambient temperature. This allows the saturation of the expandable tube several hours before it is installed and provides a higher efficiency and shorter installation time. This resin cures in only 2-5 minutes when it is subjected to a temperature of 250-300 degrees Fahrenheit.
Some of the advantages of the present methods are:
In one embodiment, such as the one illustrated in
As shown in
Linings of adjacent pipe sections are overlapped by a few inches or feet to create a continuous lining within the pipe. Preferably, the overlap is in the direction of the flow (like shingles on a roof) to make sure that the fluids flowing in the pipe will not seep between the lining and the host pipe.
Examples of the heating elements are those manufactured by LaminaHeat in Massachusetts that are very thin and can provide uniform high temperatures, in the range of 200-350 F, that are required for the curing of the epoxy. In some embodiments the bladder itself can be filled with hot air, steam or gas so that as the bladder (or packer) pushes the expandable tube against the host pipe, it will also cure it.
In various embodiments, such as the one shown in
In some embodiments the heating surfaces 540 may be coated with a resin mixed with carbon nanotubes such as those manufactured by Boyce Components (Phoenix, Ariz.). These products cure to form a coating on the surface of the heating element and when an electrical current is passed through them, they provide a uniformly heated surface that can efficiently cure the resin applied to the expandable tube.
In some embodiments the cylindrical device 560 can include a motor to make it move/travel inside the flexible tube 510 at a desired speed. Such devices 560 can be either directly connected to an electrical cable (tethered mode) or operated remotely, for example by an operator who is outside the pipe. In another embodiment the cylindrical device 560 can be pulled with a winch or similar devices containing a cable, rope, chain 530, and the like.
The above tools can also be used when the pipe is large enough for man entry. In such cases the crew can use these devices in addition to their own tools to saturate and push the flexible tube against the host pipe. In some embodiments the crew working inside the pipe can move the cylindrical device at the desired speed to cure the resin-saturated flexible tube.
In some embodiments the primary method of curing the resin is to use heating blankets to heat a flexible tube saturated with special resin [QuakeBond™ 350HC (Heat Cured) Resin]. This resin cures in 2 minutes when it is heated to a temperature of 350 F. In other embodiments, resins that are cured in ambient condition, which may take up to a few hours to cure, can be used. In other embodiments, UV-Cured resin, or hot steam and the like can be used to cure the resin.
In various embodiments the entire lining procedure can be repeated as many times as desired. For example, the first flexible tube may have most of the fibers in the longitudinal direction (along the length of the pipe to resist thrust loads) and the next flexible tube(s) may have most of their fibers in the hoop direction (to resist hoop stresses that are generated when the pipe is pressurized). The number of flexible tubes and the orientation of fibers within each flexible tube is a task that engineers determine based on the loading and strength requirements of the pipe.
In other embodiments the flexible tube can be incorporated with a 3D fabric or a honeycomb sheet. Such 3D fabric or honeycomb core can be applied between layers of flexible tube and add significant stiffness and strength to the repair liner. These combinations are particularly useful when a pipe repair has to be designed to resist external gravity loads in addition to the internal pressure.
In another embodiment one or more thin layers of a fabric or tube called a “veil” can be installed between the pipe and the flexible tube and/or on the inside surface of the flexible tube. This veil has multipurpose such as preventing galvanic corrosion, creating an impervious and watertight membrane inside the pipe, etc. The veil is typically made from a lightweight glass or polyester chopped mat or twisted yarn or biaxial fabric.
In other embodiments additional coatings can be applied on top of the installed flexible tube for further resistance to chemicals or for added durability, abrasion resistance, water tightness and the like. Those skilled in the art realize that numerous such products are available in the market and can be incorporated in the repair methods described here. Such coatings can be applied by brushing, rolling or spraying methods and the like.
In yet other embodiments, it may be required to drill or otherwise tap into the pipe to connect other pipes and fittings to the repaired pipe. As known to those skilled in the art, there are currently techniques for performing such tasks. In one example, the coordinates of these connections are accurately mapped and recorded before the repair and once the flexible tube is installed robotics drills can cut those holes from inside the pipe, allowing the connections to be re-made. Likewise, if the pipe is accessible from outside, the pipe and the flexible tube liner can be drilled through from the outside surface of the pipe to accommodate installation of connections and fittings.
In another embodiment, the techniques detailed above can be used to construct a new pipe. As an example, a lightweight form/tube or mold such as a cardboard sonotube can be used as a mold (instead of a pipe) and the procedure above can be followed to cure one or more layers of flexible tube inside the mold. This creates a cylindrical structure (a pipe) that can be removed by slipping it off of the mold. In some embodiments, the mold can be torn to expose the pipe; this has the disadvantage that the mold will be destroyed and not useable after its first use. In other embodiments, a layer of bond breaker can be applied to the inside of the mold, allowing the finished pipe to be slid off the mold without damaging it, allowing the mold to be reused.
In another embodiment the mold can be made of several sections of a more durable material such as steel or fiberglass that are connected or bolted together to form a mold. Once the pipe has been constructed inside the mold using one or more layers of flexible tube, then the mold can be taken apart and the finished pipe is removed. Such molds can be used repeatedly. With these methods any desired curved shape sections (rather than a straight cylinder segment) can be produces to construct fittings such as 45 degree bends and the like. These fittings (constructed in various angles) can be connected to the straight pipe segments to create any desired pipe geometry and alignment for any project.
In some other embodiment, the pipe may be constructed without the need for an external mold. One example is to use the inflatable bladder as the device determining the final diameter and shape of the pipe. For example, if a 20-ft long×12-inch diameter pipe is to be constructed, a piece of the flexible tube longer than 20 feet is saturated. This flexible tube will be designed to have a diameter of approximately 12 inches when it is stretched. The resin saturated flexible tube is pulled over the deflated bladder and then the bladder is inflated to form a cylinder 20-ft long×12-inches in diameter. The flexible tube is cured in that condition and then the bladder is deflated and pulled out, leaving the newly-constructed pipe behind. In such a case, it may be easier to heat and cure the flexible tube from outside since the outside face is readily accessible. In some embodiments, the bladder can provide the heat for curing by hot water, air, steam, hot gas and the like. The ends of such a pipe can be trimmed for future connection to other pipe segments.
In another embodiment, a collapsible rigid mandrel constructed of such materials like steel or fiberglass and the like can be used. The resin-saturated flexible tube can be pulled on top of (i.e. the outside surface of) the collapsible mandrel and the mandrel is activated to expand outwards to the desired diameter (or size if the mandrel is not cylindrical, for example when making a 45 degree bend fitting). Then the resin is cured from outside or from heating elements that are a part of the skin of the collapsible mandrel. Once the resin is cured, the mandrel is collapsed and pulled away, leaving the finished tube, pipe, fitting or shape behind.
The tubular structure can be further enhanced by including one or more layers of 3D fabric or honeycomb core saturated with resin and subsequently cured. In one embodiment, for example a tube can be made with a single layer of flexible tube, and then additional layers of 3D fabric and/or honeycomb core can be wrapped around that to create a much stiffer structure. Such a stiff tubular structure can be used as a stay-in-place form in construction where it can be filled with concrete and or reinforcing steel to create a column, a pile for marine construction, a utility pole, etc.
The expandable tubes can be designed to be directly attached to the inside surface of the pipe and resist the loads jointly with the pipe material. On the other hand a thin layer of compressible material may be added between the pipe and the expandable tube to transfer all or most stresses resulting from all or most loads (both internal pressure and external loads from traffic, soil, etc.) to the expandable tube material. This is because while the tube expands as a result of internal forces of the pipe, the expansion of the tube deforms the compressible material layer which will not transfer the forces to the pipe. In other words, while calculating the allowable pressure in pipes repaired with the mentioned liner tubes, it is important to recognize the fact that the liner tube will stretch as it is subjected to internal pressure. Therefore, it is possible to first line the pipe with a thin coat of a compressible material. This material can be sprayed on the pipe surface. Depending on the pipe diameter, a small thickness, such as 0.05 inch, may be sufficient. With such an arrangement, the liner tube can be designed to take the entire operating pressure of the pipeline, relieving the old steel pipe of any internal pressure. As the liner tube is pressurized, its expansion will cause a reduction in thickness of the sprayed compressible coating without transferring any or very small amount of the pressure to the host pipe. This method creates “a pipe inside a pipe” and fully protects the outer pipe since the original/outer pipe may not be relied upon for any future operations once the lining is complete.
Those skilled in the art realize that while the main concepts have been introduced here using pipe as an example, the application of these embodiments goes much further. For example, the tubes described above can be used as a pipe but also in a smaller scale as structural elements (tubes) that are used to construct bicycle frames, motorcycles, automotive parts, structural tubing for columns and supports in buildings, bridges, piles, utility poles and the like.
Those skilled in the art will appreciate that many other honeycomb type layers, hollow structures, or laminate structures are possible without departing from the spirit of the present disclosures. For example, the honeycomb cells may be constructed in any geometric form, such as rectangle, hexagon, and the like to serve the same purpose. Likewise, other spacer materials such as foams, polyurea and the like can be used to achieve higher strength and stiffness.
Changes can be made to the claimed invention in light of the above Detailed Description. While the above description details certain embodiments of the invention and describes the best mode contemplated, no matter how detailed the above appears in text, the claimed invention can be practiced in many ways. Details of the system may vary considerably in its implementation details, while still being encompassed by the claimed invention disclosed herein.
Particular terminology used when describing certain features or aspects of the disclosure should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the disclosure with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the claimed invention to the specific embodiments disclosed in the specification, unless the above Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the claimed invention encompasses not only the disclosed embodiments, but also all equivalent ways of practicing or implementing the claimed invention.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
The above specification, examples, and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. It is further understood that this disclosure is not limited to the disclosed embodiments, but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
While the present disclosure has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this disclosure is not limited to the disclosed embodiments, but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
This non-provisional application is related to U.S. provisional patent applications No. 61/962,358 filed on Nov. 06, 2013, entitled “CONSTRUCTION AND REPAIR OF PIPES WITH BRAIDED FRP TUBE,” the disclosure of which is hereby expressly incorporated in its entirety by reference.
