Method and apparatus for removing a pipe lining
An apparatus for removing a lining from a pipe includes a collapsible stripping tool having a plurality of extensible arms with an abrading tool mounted on each arm that is deployed by inserting the apparatus into the pipeline, supplying pressurized fluid to a cylinder to extend the arms and force the abrading tools into engagement with the lining and rotating and pulling the tool down the pipe without destroying the pipe.
The invention related to an apparatus and method for removing a lining from an underground pipe.
BACKGROUND OF THE INVENTIONUnderground pipelines used to convey water, gas, sewage and other fluids have, in the past been constructed of clay tile, concrete, cast iron, ductile iron, steel or even wood. These pipelines have limited useful service lives due to deterioration of mechanical properties leading to leakage, collapse, ingress of external matter (soil), or blockages due to foreign matter buildup as a result of internal discontinuities. In some cases, deterioration of mechanical properties may be due to chemical attack. For example, concrete pipe and cast iron and/or ductile iron pipe is susceptible to interior degradation, particularly at the “crown” of the pipe, due to the effect of hydrogen sulfide gas. In other cases mechanical or environmental factors may cause the deterioration. For example, tree roots may accelerate or cause degradation or blockages of underground lines. Deterioration may occur throughout the body of the pipe or at the connections between pipe segments.
Pipe lining is a process that was developed to enhance or prolong the useful life of pipelines, in particular, underground lines. The lining is typically installed in-situ in cases wherein the mechanical and physical properties of the pipe have degraded, but before total collapse. In some cases, the lining is installed when the pipe is new during the manufacturing process with the intention of providing a barrier between the conveyed product and the host pipe material.
A number of different materials have been used in pipe lining applications. Materials originally used to form in-situ type linings included PVC (Poly Vinyl Chloride), HDPE (High Density Poly Ethylene) and CIPP (Cured In Place Pipe) materials. Additionally polyethylene lining was optionally applied to the inside surface of ductile iron pipe at the time of manufacture.
These linings provided enhanced performance and service life. However, just as the host pipes had a limited life span, typically measured in decades, so did many of the early lining systems. Many linings that slowed or stopped deterioration of the host pipes are now suffering from the same ills that plagued the original host pipes. In some cases blockages due to lining collapse have resulted where the bond between the lining and host pipe has failed or where foreign material has entered between the lining and host pipe.
Lining technology and materials have improved over time. Currently, PVC linings are only used where appropriate, HDPE linings are used in heavier walls or tighter fits than previously attempted. Poor CIPP chemistries and processes have fallen by the wayside to allow only the best CIPP methods and materials to be used. Ductile iron is no longer lined with polyethylene; rather epoxy compounds are used. These improvements will result in extended useful life for the pipelines into which the linings are installed. However in most cases, the improved methods and materials cannot be used to repair previously lined pipes without removing portions of the previously installed linings that have separated from the host pipe or otherwise degraded.
Failure of a pipe lining presents a dilemma to the owners of pipe systems that have previously been lined using early technology lining systems. In most instances, the failing lining prevents the use of new lining technologies to repair the existing host pipe, leaving the owners with two options. The lined pipe may be burst (see Streatfield et al., U.S. Pat. No. 4,738,565) and a new pipe pulled in, with some added difficulty due to the lining. Alternatively, the entire length of the pipe may be excavated to remove and replace the existing pipe. However, the host pipe holds value in that it could possibly be lined by utilizing one of the new and improved technologies.
The use of mechanical devices to clean pipes has been limited to the removal of relatively loose or soft scale and other debris from pipe lines. For example, “pigging” devices have been used in attempts to clean to steel pipelines, especially those used to transport natural gas and oil. The device is propelled through the pipe line using pressurized gas or liquid applied to one end of the pig. The pig moves axially only, brushes or scrapers mounted on the pig have one chance to remove modest amounts of scale or loose debris from the pipe. The use of a pig to clean pipe lines in this manner is typically done in a maintenance mode. Another mechanical device for cleaning pipe lines is disclosed in commonly assigned U.S. Pat. No. 6,792,820 issued Sep. 21, 2004 to Wentworth et al. The '820 patent discloses a mechanical cleaning device propelled with a rotating drill string. The device is used preparation for replacement of the buried pipe, in particular prior to bursting the host pipe and pulling in new replacement pipe. See also Harr U.S. Patent Application 20050097689, May 12, 2005, for a culvert cleaning tool and method. A need remains for a process and apparatus suitable for removing a lining or liner from an existing pipeline sufficiently to allow a new lining to be installed, as opposed to merely cleaning the inside of the pipeline leaving the existing lining in place.
SUMMARY OF THE INVENTIONA method of removing a lining from an underground pipe according to the invention includes the steps of mechanically fragmenting the lining without destroying the underground pipe, and removing the resulting lining fragments from the pipe, typically with a pressure fluid. With the lining removed, the pipe may be relined using known techniques. The existing lining will usually consist of a tubular layer of plastic bonded to the inside surface of the pipe, but with loose portions that are either unbonded from the pipe, or weakly bonded to it. For purposes of relining, it is preferred to remove these loose portions of the existing lining before covering the remnant of the old lining with a new lining.
According to another aspect of the invention, a method of removing a lining from an underground pipe includes the steps of moving a stripping tool axially through the inside of the pipe, and operating the stripping tool in a manner effective to substantially remove the lining without destroying the underground pipe. For purposes of the invention, “substantially remove the lining” means sufficient removal of loose portions so that the pipeline can be relined. The stripping tool is preferably rotated as it is moved axially through the pipe as one or more abrading tools attached to the stripper are forcibly urged in a radial direction. The abrading tool may be one or more of a stiff wire brush, serrated scraper blade, a series of knife blades mounted in a common frame, or similar devices. In one embodiment, the stripping tool includes a plurality of plurality of stripping assemblies each mounting an abrading tool and connected to a central shaft that is coaxial with the pipe, and the method includes extending the stripping assemblies in a radial direction away from the shaft and into engagement with the inside of the pipe.
In another aspect, the invention provides a collapsible rotary apparatus for removing material from the inside of a pipe. Such an apparatus includes a shaft, at least one arm mounted on the shaft, an extension and retraction mechanism connected to the arm which moves the arm in a radial direction, which mechanism includes at least one pivot about which the arm moves during extension and retraction, and an abrading tool mounted on the arm in a position for circular movement along the inside of the pipe upon rotation of the shaft. Radial extension of the arm(s) from a collapsed position to an extended position using the extension and retraction mechanism moves the abrading tool against the inside of the pipe. These and other aspects of the invention are discussed further in the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGSThe invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements, and wherein:
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Joints 12 and 16 are replaceable and, as illustrated in
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The pressurized fluid used to actuate piston 76, typically drilling fluid or water, flows through drill string 54 (
A variety of abrading tools such as scrapers, knives, perforators and brushes may be mounted on arms 40, 42 of stripping tool 18 for removing lining 52 from a pipe line.
Holder 112 is welded or otherwise fastened to a mounting bracket 116 including a pair of opposed legs 124 with a section of square rod 126 welded to an inside surface of leg 124 that aids in positioning the bracket on mounting plate 64 and in retaining the bracket in position on the plate. Tool holder 112 is mounted one of arms 40, 42 by sliding mounting bracket 116 over mounting plate 64 and fastening the tool holder to the mounting plate with a bolt 130 (
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Each of knives 134 includes a scalloped cutting end 142 and a mounting end 144 having a pin hole 146. As best illustrated in
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During the lining removal process, stripping tool 18 applies force to lining 52 in three directions. A cutting, scraping or brushing tool mounted on arms 40, 42 applies a radially directed force against the lining when arms 40, 42 are deployed. Tools mounted on arms 40, 42 also apply an axial force on lining 52 as lining removal apparatus 10 is pulled through pipe line 50. Additionally, as stripping tool 18 is rotated, tools mounted on arms 40, 42 apply a force tangential to the circumference of pipe line 50 to lining 52. In this manner, lining 52 may be cut, scraped, brushed, scored or perforated to remove loose or degraded portions of the lining and/or prepare the lining for the application of addition lining material without destroying the host pipe. Fragments of lining 52 that would tend to clog the cutting or scraping tools or otherwise interfere with the removal of lining 52 or with the re-lining operation are washed away with water or drilling fluid ejected through nozzles 104 in stripping tool 18.
One device suitable for pulling apparatus 10 through pipe 50 while rotating stripping tool 18 is a Horizontal Directional Drill (HDD) such as a D24x40 Navigator produced by Vermeer Manufacturing of Pella Iowa. While lining removal apparatus 10 is particularly suited for use with a HHD, the apparatus may be used with other machines capable of passing torque through a rod extended through a pipe, for example the HB5058 Pipe Bursting Machine manufactured and sold by Earth Tool Company LLC of Oconomowoc, Wis. Lining removal apparatus 10 may also be employed with a non-rotating drill string or rod, in which case, apparatus 10 is configured to rotate stripping tool 18 under power independently of a rod or drill string. Such rotary motion could be produced by mounting a hydraulic motor on the tool or rod and actuating it by hydraulic supply hoses towed behind the tool, thus providing the required torque to turn the tool.
In a further variation, a large cylindrical brush with radially extending bristles may be employed, wherein the bristles are made of a resilient steel or similar material and are sized so that they are distorted (bent) when pulled into the pipeline, so that a radial force is exerted against the lining. This arrangement is simple and easy to make, but would lose performance as the bristle tips break off due to the constant abrasion, and the number of pipe sizes a given brush attachment could be used in would be limited. While certain embodiments of the invention have been illustrated for the purposes of this disclosure, numerous changes in the method and apparatus of the invention presented herein may be made by those skilled in the art, such changes being embodied within the scope and spirit of the present invention as defined in the appended claims.
Claims
1. A method of removing a lining from an underground pipe, comprising:
- mechanically fragmenting the lining without destroying the underground pipe by removing substantially all loose portions of the lining along a length of the underground pipe; and
- removing resulting lining fragments from the pipe.
2. The method of claim 1, wherein the lining comprises a tubular layer of plastic bonded to an inner peripheral surface of the underground pipe, and the loose portions comprise portions of the plastic layer weakly bonded or unbonded to the inner peripheral surface of the underground pipe.
3. The method of claim 2, further comprising relining the underground pipe along the length of the underground pipe to be relined after the lining fragments have been removed.
4. A method of removing a lining from an underground pipe, comprising:
- moving a stripping tool axially through the inside of the pipe; and
- operating the stripping tool in a manner effective to substantially remove the lining without destroying the underground pipe.
5. The method of claim 4, wherein the stripping tool comprises a mechanism that rotates the stripping tool along the inside of the pipe so that the tool engages and fragments the lining.
6. The method of claim 5, wherein the stripping tool is forcibly urged in a radial direction against the inside of the pipeline as it rotates.
7. The method of claim 5, wherein the stripping tool is pulled through the pipeline as the stripping tool rotates.
8. The method of claim 6, wherein the stripping tool is pulled through the pipeline as the stripping tool rotates and forcibly engages the inside of the pipeline.
9. The method of claim 5, wherein the stripping tool comprises a stiff wire brush.
10. The method of claim 5, wherein the stripping tool comprises a serrated scraper blade.
11. The method of claim 5, wherein the stripping tool comprises a series of knife blades mounted in a common frame.
12. The method of claim 4, wherein the lining comprises a tubular layer of plastic.
13. The method of claim 6, wherein the stripping tool comprises a plurality of stripping assemblies connected to a central shaft that is coaxial with the pipe.
14. The method of claim 13, further comprising extending the stripping assemblies in a radial direction away from the shaft and into engagement with the inside of the pipe.
15. A collapsible rotary apparatus for removing material from the inside of a pipe, the apparatus being configured to rotate inside the pipe as the apparatus is pulled through the pipe, comprising:
- a shaft;
- at least one arm mounted on the shaft;
- an extension and retraction mechanism connected to the arm which moves the arm in a radial direction, which mechanism includes at least one pivot about which the arm moves during extension and retraction; and
- an abrading tool mounted on the arm in a position for circular movement along the inside of the pipe upon rotation of the shaft, wherein radial extension of the arm from a collapsed position to an extended position using the extension and retraction mechanism moves the abrading tool against the inside of the pipe.
16. The apparatus of claim 15 further comprising a cylinder connected to extending the extensible arms and maintain the scraping tools in contact with the inside of the pipe under a force applied by the cylinder.
17. The apparatus of claim 15 further comprising a plurality of extensible arms mounting abrading tools thereon coupled to the shaft at spaced intervals around the circumference of the shaft.
18. The apparatus of claim 15 wherein the abrading tool comprises one of a brush, knife and scraper.
19. The apparatus of claim 17 wherein at least one of the arms is axially offset from the adjacent arms.
Type: Application
Filed: Dec 30, 2005
Publication Date: Jul 12, 2007
Inventors: Steven Wentworth (Brookfield, WI), Harry Baum (Frisco, CO)
Application Number: 11/324,018
International Classification: B24B 1/00 (20060101);