The document discusses the use of HDD technology for stripping de-laminated HDPE liners from pipes, particularly in a Pima County project. It describes the failure of the original HDPE liner due to various factors leading to turbulent flow and associated problems, prompting the development of a new trenchless methodology for efficient removal. The methodology involves a innovative robotic stripping device that prepares pipes for the installation of new liners, resulting in the effective cleaning of approximately 5,700 feet of pipe over two and a half months.

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

2. 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.

3. 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.

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

5. Inspection Results
Liner failure
indicated by the
camera operator.

6. Inspection Results
HDPE liner folded
into the flow stream.

7. Inspection Results
Liner has completely
pulled away from host
pipe
Creates turbulence
downstream
By-product of
turbulence is hydrogen
sulfide gas that
escalates degradation
of pipe.

8. Inspection Video

9. Problems in Pima County
De-lamination disrupted flow.
Caused back ups
In Pima County, fine granular soil is
susceptible to erosion.
Backups lead to ground erosion
Sinkholes follow
Emergency repairs were required

10. 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

11. Methodology

12. Benefits of HDD Technology
Proven existing
technology
Un-intrusive
Rotational ability
to use stripper
technology
Connect to
pump for water
pressure

13. How the Stripper Works
Urethane radial
Stripper or triangular pilot
arms are was used as a
deployed centering plug
using water
pressure
Rotation of the drill
string allows the
cutting blades to
strip the lining
material away
from the host pipe

14. The Liner Stripping Method

15. Access to the Line
For the directional
drill to access the
sewer main, a
fifteen foot section
was removed from
the top of the pipe.

16. 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.

17. Coordination of Drill and Stripper
Mobile camera
inspection truck
controls the camera
and communicates
to the drill operator.

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

19. Installation of Stripping Device
The stripping device
is lowered down
hole in sections and
assembled in the
manhole.

20. 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.

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

22. Bypass
To prevent
customer
interruption, the
working section on
the sewer line was
bypassed using a
pump to maintain
sewer flow.

23. Removal of Debris from Line
WSU used a
vacuum truck to
clean the entry
manhole and
remove the cut
lining chips and
other debris.

24. 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

25. 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.

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