Stripping of Liners From Pipes Using HDD TechnologyHarry Baum, President, W.S.U. Inc., Breckenridge, Colorado Kwigs Bowen, Area Manager, Team Fishel, Chandler, Arizona

Factory Installed Liners

During the 1980s, an HDPE lining was factory installed on ductile iron pipe to avoid corrosion from hydrogen sulfide gas (a normal byproduct of decomposition in sanitary systems). These pipes were installed throughout the country.

De-lamination of Liners

In the Pima County Project, damage to the HDPE liner around the bell and spigot occurred at some time during installation or afterwards which caused the liner to de-laminate from the pipe it was supposed to protect.

Inspection Results

The arrow indicates the early stages of HDPE lining separation at the ductile iron pipe joint.

Inspection Results

Liner failure indicated by the camera operator.

Inspection Results

HDPE liner folded into the flow stream.

Inspection Results

Liner has completely pulled away from host pipe Creates turbulence downstreamBy-product of turbulence is hydrogen sulfide gas that escalates degradation of pipe.

Inspection Video

Problems in Pima County

De-lamination disrupted flow. Caused back upsIn Pima County, fine granular soil is susceptible to erosion.

Backups lead to ground erosionSinkholes follow

Emergency repairs were required

Methods of Repair

Efficient methods did not exist to remove the liner from the existing pipe for installation of new liners. Conversations between WSU and HammerHead began to design a new trenchless methodology

Methodology

Benefits of HDD Technology

Proven existing technologyUn-intrusiveRotational ability to use stripper technologyConnect to pump for water pressure

How the Stripper Works

Stripper arms are deployed using water pressure

Urethane radial or triangular pilot was used as a centering plug

Rotation of the drill string allows the cutting blades to strip the lining material away from the host pipe

The Liner Stripping Method

Access to the Line

For the directionaldrill to access the sewer main, a fifteen foot section was removed from the top of the pipe.

Coordination of Equipment

Drill operator receives radio confirmation from the camera operator to access progress in the sewer line. If section requires further stripping, the camera operator alerts the drill operator to back up and give additional attention that section of pipe.

Coordination of Drill and Stripper

Mobile camera inspection truck controls the camera and communicates to the drill operator.

The Stripping Device

The liner stripping device is assembled above ground to instruct crew members of the proper joint assembly connection down hole.

Installation of Stripping Device

The stripping device is lowered down hole in sections and assembled in the manhole.

Deployment of Stripping Device

The stripping arms are deployed using water pressure supplied through the drill stem by a water pump connected to the directional drill. Once arms are deployed, drill string is rotated and liner is scraped from pipe, preparing it for lining.

Device in Action

The robotic camera trails the stripping device showing where the pipe has been stripped of the HDPE lining.

Bypass

To preventcustomerinterruption, the working section on the sewer line wasbypassed using a pump to maintainsewer flow.

Removal of Debris from Line

WSU used a vacuum truck to clean the entry manhole and remove the cut lining chips and other debris.

Pipe Ready for New Liner

With the pipe ready to accept a new liner, the pipe is lined with Pulled In Place method.5,720 lf of 18” CIPP installed

Conclusion

In all, the poly stripper method was used to clean about 5,700 feet of pipe over a two and a half month period. With the liner completely removed, the new CIPP liner was installed normally without any intrusive obstacles.

Thank YouHarry Baum, President, W.S.U. Inc., Breckenridge, Colorado Kwigs Bowen, Area Manager, Team Fishel, Chandler, Arizona