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Stripping of liners from pipes using hdd technology (2007)
Stripping of liners from pipes using hdd technology (2007)
Stripping of liners from pipes using hdd technology (2007)
Stripping of liners from pipes using hdd technology (2007)
Stripping of liners from pipes using hdd technology (2007)
Stripping of liners from pipes using hdd technology (2007)
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Stripping of liners from pipes using hdd technology (2007)

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In the Spring of 2007 Harry Baum made a presentation at the annual North American Society for Trenchless Technology convention, which was held in San Diego, California. Harry originally contacted …

In the Spring of 2007 Harry Baum made a presentation at the annual North American Society for Trenchless Technology convention, which was held in San Diego, California. Harry originally contacted Steve Wentworth about his concept--a process/tool to strip failed polyethylene liners from the inside of buried pipes.Steve and Harry perfected that concept and filed for patent protection on the tool. Harry then hired Fishel Co. as a sub-contractor to assist with the work.

Learn more about Western Pipeway at http://www.westernpipeway.com

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  • 1. North American Society for Trenchless Technology (NASTT) NO-DIG 2006 Nashville, TN March 15-20, 2007STRIPPING OF LINERS FROM PIPES USING HDD TECHNOLOGYHarry Baum and Kwigs Bowen21 President, W.S.U. Inc.., Breckenridge, Colorado2 Area Manager, Team Fishel, Chandler, ArizonaABSTRACTHorizontal directional drilling is a non-intrusive method for installing utility lines, gas pipes, water pipes,sewer lines or fiber-optic conduit below the ground without the need to open trench. Horizontal directionaldrills “bore” a tunnel using fixed-length drill rods that are threaded together to create what’s called a drillstring. This drill string is advanced or drilled through the ground from an entrance to an exit location. Thisdrilled bore can be drilled to precise locations because of the drilling tool’s slanted steering plate. Theorientation of the tool and its slanted steering plate is what determines the direction the drill headnavigates. The directional path will move when pushed through the ground without rotation. A transmitterenclosed in the drill heads housing transmits depth, digital clock rotation position, temperature and angleto a remote receiver on the surface. Maximum depth depends upon the style of the transmitter butnormally 50 feet is average.Because of the flexibility HDD offers, Harry Baum, owner of W.S.U. Inc. and Steve Wentworth of EarthTool Company LLC (manufacturer of HammerHead trenchless products) began conversations on theconcept to remotely remove linings from the inside of sewer lines. As a novel concept inventionWentworth designed an umbrella like mechanical device which is attached to a directional drill.Wentworth had already designed tooling for other directional drilling uses and was able to quickly offerBaum solutions. Baum was very familiar with failed liners and the problems caused where open cut wasoften the only solution for removing linings. Removal of factory installed linings using custom designedtooling, deployed and actuated by a directional drill rig, is a new method. Having the ability to attachdifferent tools to the end of rigid drill pipe opens the opportunity for other remotely operated mechanicaldevices. Just as a surgical tool is used to open arteries the stripping tool could open the clogged sewerarteries without open cutting the entire section.Ductile iron pipe with factory applied high density polyethylene (HDPE) liner has been widely used forsanitary sewer installations where high hydrogen sulfide gas concentrations exist. Failure of the pipesprotective HDPE liner from hydrogen sulfide corrosion caused the liner to delaminate in sheets. Thiscreated the potential for problematic system backups. It was clear that the failing liner had to be removed.The removal was intended to simultaneously eliminate the potential for backup and produce a surfaceappropriate for relining using cured in place pipe (CIPP) methods.This paper will review a highly successful 1st attempt at using a new trenchless technology, LinerStripping, in cooperation with Pima County Wastewater Management, Tucson Arizona. System ownerengineers, contractor, sub-contractor and equipment manufacturer joined to make the job possible withthe custom developed technology.The job success highlights the potential HDD drills have to service non-man entry or difficult man entrylocations with custom engineered tooling. The method of “Liner Stripping,” as with all trenchless methods,will be less disruptive and less invasive than previously accepted methods or remedies to service a pipe’s Paper E-2-04
  • 2. interior spaces. The results demonstrate that servicing the interior of buried pipes with the attributes of anHDD drill stem is a concept that has profound potential.INTRODUCTIONRecently, the Pima County Wastewater Management (PCWM) in Tucson, Arizona found itself with aperplexing problem when it tried to rehabilitate one of its ductile HDPE lined sanitary sewer pipes. Inweighing possible solutions, PCWM officials permitted “Liner Stripping” of the HDPE using a horizontaldirectional drill HDD rig followed by CIPP lining of the sewer main. Normally HDD is used for thetrenchless installation of new underground utilities not rehabilitation so this application is quite a novelconcept.The Pima County wastewater conveyance system consists of nearly 3,300 miles of public separatesanitary sewers, ranging in size from 6- to 78-in. pipe diameters with an 84-in. box culvert. The OldNogales Highway trunk sewer consists of more than 16,000 ft of 18-in ductile iron pipe with apolyethylene liner. The liner has de-laminated from the host pipe to some degree on roughly one-third ofthe total length of the trunk sewer line. The de-lamination on some stretches was severe enoughwarranting an emergency repair to remove the liner from the flow line. Pima County surrounds the highdesert city of Tucson and land south to the Mexico border. Tucson sits on a remarkably flat planeconsisting of fine granular soil that is susceptible to erosion. Blockage backups must be avoided whenoperating a pipeline or ground erosion can case sinkholes.In the 1980’s corrosion of ductile iron pipe was avoided by using a factory installed polyethylene lining.The liner .06 to .10” (1.524 to 2.54 mm) thick was intended to prevent hydrogen sulfide gas, fromcontacting the ductile iron sealing the odiferous gas from the iron atmosphere. Hydrogen sulfide gas is anormal byproduct of decomposition in sanitary systems.Damage to the HDPE liner around the bell and spigot may have occurred during installation or some timeafterward allowing hydrogen sulfide to attack the ductile iron pipe. Oxidization built up between the linerand the interior surface of the ductile iron which caused de-bonding of the liner from the pipe. This de-bonding of the liner caused the liner to hang down inside the pipe like poorly applied wallpaper fallingfrom the ceiling. Sewer flow velocity between the de-lamination accelerates the sewer liner degradation.This was evident when an inspection camera (figure 1) was used to inspect the line. The hanging liner(figures 2-5) reduces the annular circumferential area stalling the flow of solids which had causedbackups and could continue to do so.Figure 1 - The mobile camera inspection truckcontrols the operation and recording of a roboticcamera. The camera documents real timeinformation which becomes a permanent record forfuture use. Paper E-2-04
  • 3. Figure 2 - Shown from the robotic camera, is a Figure 3 - The arrow indicates the early stages ofseparated HDPE liner folded into the flow stream. HDPE lining separation at the ductile iron pipe joint.Figure 4 - The circle indicates liner that has Figure 5 - Liner failure indicated by the cameracompletely pulled away from the host pipe creating operator.turbulence downstream. A by-product of thisturbulence is hydrogen sulfide gas which escalatesthe degradation of the pipe.Pima County has the additional stress of having the possibility of the backup inducing a sinkhole in one ormore locations. For this reason, county officials had to find a solution that would eliminate the hangingliner and find a solution to protect the perfectly serviceable ductile iron portion of their pipe.W.S.U. Inc., in Breckenridge, Colorado, was contracted by Pima County engineers to rehabilitate theductile iron sewer line using the custom stripping tool developed by Earth Tool Company, LLC, andmanufacturer of HammerHead trenchless products based out of Oconomowoc, Wisconsin. The proximityof the line, within a railroad right of way made open-cut a daunting and undesirable method. PCWMDengineers chose the less invasive technology HDD knowing that open cut methodologies would not beacceptable.After the HDPE liner was completely removed a new CIPP liner would be applied to the bare ductile ironpipe which would produce the corrosion barrier need to make the pipe last. To insure complete removal ofthe HDPE liner a sewer camera recorded instantaneous progress inspection behind the rotating liningstriping mechanism.HDD SOLUTIONThe HDD rig is setback from the intersection from the intended path end point (figure 6). This setback isdetermined by HDD rig rod radius specifications and the desired depth end point. The midsize HDD rig Paper E-2-04
  • 4. chosen for this application can develop 24,000 pounds of tensile and 4,000 ft. lbs. of torque. However,only a small portion of this power is required to accomplish the stripping liner removal process. A drill rodaccess point is excavated and the top section of pipe removed (figure 7) An inflatable plug was insertedinto the sewer line and the sewer flow was by-passed around the working section (figure 8).Figure 6 - On the surface, thedirectional drill operator receivesradio confirmation from the Figure 8 - To prevent customercamera operator to access interruption, the working section on Figure 7 - For the the sewer line was bypassed using aprogress in the sewer line. If a directional drill to accesssection requires further stripping, pump to maintain sewer flow. the sewer main, a fifteenthe camera operator alerts the drill (15) foot section wasoperator to back up and give removed from the top of theadditional attention that section of pipe.pipe.After the trenchless bore path intersected the sewer line, the drill stem was pushed out so as to extendinto a downstream manhole where the Poly Stripper mechanism was installed (figure 9). To control thelong unsupported drill string a soft urethane radial or triangular pilot was used as a centering plug (figure10) with marginal diametrical clearance. With rotation bearings housed at both ends of the centering plugstabilized the rod during high speed rotation.Figure 9 - The stripping device is lowered down Figure 10 - The liner stripping device is assembledhole in sections and assembled in the manhole. above ground to instruct crew members of the proper joint assembly connection down hole.The Poly Stripper was attached just behind the centering plug. Using the HDD rig’s water pump pressure,the deployment of the radial stripper arms are controlled via bias pressure within the strippers operating Paper E-2-04
  • 5. piston mechanism (figure 11). Water pressure controls the stripper arms’ force when deployed against theliner host pipe (figure 12). Some water is bypassed around the piston chamber flushing away cuttingscontinuously. At the entry manhole, a screen was placed in the flow path, separating cuttings from theflow. These chips of the liner were then vacuumed up and disposed of (figure 13).Figure 11 - The stripping arms Figure 12 - The robotic camera Figure 13 - WSU used a vacuumare deployed using water trails the stripping device truck to clean the entry manholepressure supplied by through the showing where the pipe has and remove the cut lining chipsdrill stem by a water pump been stripped of the HDPE and other debris.connected to the directional drill. lining.Once the arms are deployed, thedrill string is rotated and the lineris scraped from the pipe,preparing it for lining.HDPE liner is scraped away from the adjacent host pipe during rotational arm deployment. Followed bythe inspection camera the Poly Strippers’ progress is monitored as rotational speed is variable toapproximately 250 rpm. Radio contact between the HDD rig operator and the camera operator was all thedirection necessary to achieve production speed of approximately 10ft/min. By inspecting with thecamera, the operator was alerted to sections that required further stripping. In addition, the cameraoperator could communicate the need to retract the stripper arms to de-tangle portions of the HDPE linerthat had entangled the stripper arms.Several attachment cutting tools were developed, a .125” (3.175 mm) thick spring steel scraper provedsuperior to other designs. Each of the three stripper arms held one scraper blade which was angledslightly away from the clock wise rotation center line. Water used to make drilling fluid is common practicewhen directional drilling underground utilities so additional rig operator training is minimal. Repeatedly,the operator turned on the water pump, waited for water pressure to rise at the rig then began rotating thedrill stripping tool. He then pulled drill pipe toward the rig until again removing drill stem and repeating theprocess.CONCLUSIONHDD machines can provide huge economic potential to service non-man entry or difficult man entrylocations with custom engineered tooling. Engineers basic working knowleadge of HDD capabilities cansolve a myriad of sewer line issues. Pima County Arizona engineers were more than satisfied with thefirst successful performance of this experimental method. Coordination between engineers, contractor,sub-contractor and equipment manufacturer was essential in providing planning through job completion. Information supplied by Dan Cohen of WSU, a licensee of Inliner Technologies, installed ~ 5,720 lf of18 inch ∅, 7.4mm thick CIPP using the Pulled-In-Place method of insertion per ASTM F 1743, PCWMDspecifications and WSU, ISO protocol. Individual runs of CIPP were resin impregnated at WSU’s wetoutfacility located near Fairplay, Colorado just prior to it’s scheduled installation date. The wetout tube alongwith it’s corresponding calibration hose was shipped to the job site in Tucson, Arizona inside atemperature controlled, refrigerated reefer truck. The lining tube was winched into place followed by anair inversion of the calibration hose. The CIPP was then cured using steam for pressure and heat. Paper E-2-04
  • 6. Independent third party testing was performed by HTS, Inc. of Houston, TX for thickness (ASTM D 5813),flexural properties (ASTM D 790) and tensile strength (ASTM D 638). Each CIPP installation exceededthe required minimum properties in every instance.In all, the Poly-Stripper was used to clean about 5,700 feet of pipe over a two and half month period.Afterward, WSU went in and rehabbed the pipe using CIPP with the comfort in knowing the loose linerwas completely removed as video proved. To date the project is considered by all involved to have beena very succuessful method for removing de-bonded liner from ductile iron pipe. Because the liner wasremoved completely, the corresponding CIPP liner was installed normally without any intrusive obstacles. Paper E-2-04

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