Author: Professor, Dr. Dietrich Stein - TrenchlessOnline

INTERNATIONAL
Grouted-in-Place Pipe
Method Used to Reline
German Sewer Lines
By Jens Kirste
Nowadays sewer network owners and operators
are faced with a huge number of different trenchless
methods, materials and suppliers to seal and
rehabilitate their pipes.This applies especially for
cross-sectional pipe dimensions up to approximately 1,000
mm inside diameter (I.D.). Above that size, the number of
approved systems and qualified installers reduces to a comparably
small amount.
Since the early 1990s, Trolining GmbH, Troisdorf,
Germany, has been an internationally recognized expert in
the field of trenchless pipe rehabilitation.Its patented grouted-in-place
pipe (GIPP) method has been successfully
installed in about 20 countries around the globe.The continuously
growing demand for reliable methods for the reinstatement
of large sewers was a clear sign for Trolining to
further increase the effectiveness of its system in that market
segment. Pipe sizes between 800- and 2,000-mm I.D.
today represent Trolining’s main field of application, regardless
of whether the cross-sectional pipe profile to be
rehabbed is circular or a special geometry.
Studded HDPE liner inside the host pipe, just before inflation to adapt to
the host pipe’s egg-shape, sized 1,400 x 2,100 mm.
In the second half of 2006,Trolining completed a project in
the City of Bielefeld, Germany. Bielefeld is a medium-size
town with about 330,000 inhabitants and an urban area of
258 sq km.The total length of public sewers herein is approximately
1,840 km. Regular inspections revealed leaking and a
variety of other damages at one of the main collectors located
along the Mühlen Str., near the city center. Most notably,
the joints of the brick sewer, constructed around 1898, were
found severely eroded.In some areas,the mortar between the
bricks was missing down to a depth of 40 mm.
After assessment of the inspection reports, the municipality
decided that 520 m of the sewer needed urgent repair.
Whereas 310 m showed the standard egg-shape 1,200- x
1,800-mm I.D., further 210 m measured 1,400 x 2,100 mm.
A few months later, Bielefeld’s environmental authority
released a call for tender not only containing the trenchless
rehabilitation of the mentioned sewer lines, but also a number
of other preparatory and adjacent works. Installation of
a bypass line, preliminary sealing of major groundwater infiltration,rehabilitation
of the adjacent manhole chambers and
re-connection of the lateral pipes were just some of the performances
requested from the bidders.
The Trolining System
The Trolining trenchless pipe rehabilitation system is
based on various high-density polyethylene (HDPE) liner
components, which can be combined in a wide range of
alternative configurations. The heart of the system is the
Troliner with its V-shaped embedment studs. The annular
void created by the studs is filled with Trolining Injektor, a
specially engineered injection grout. This high-strength
grout fixes the Troliner liner permanently in place and provides
the load-bearing shell of the system.
Trolining liners are available for pipes ranging from 250to
2,000-mm I.D. Segmental lining sheets are offered for
rehabilitation of lines greater than 2,000-mm I.D. and for
elbows and corners in man-size lines. The rehab system
improves the host pipe’s flow characteristics and provides
exceeding mechanical and chemical resistance.
Every liner is tailor-made according to the exact measurements
taken on the jobsite.That procedure guarantees the
systems “close-fit” characteristics, thus limiting the cross-sectional
reduction to an absolute minimum. Prior to the liner
insertion, the pipe section to be rehabilitated is plugged-off
at both ends, cleaned and visually inspected.A cable winch
is then used to unroll each HDPE liner from its transport
drum and draw it through the line into position.After insertion,
all HDPE liners are welded together at their ends.The
resulting liner — a sandwich — is then inflated with a defined
pressure through passages in the temporary plugs closing
the ends of the liner section.
When the required inflation pressure is attained, the
annular void is filled with Trolining injection grout fed from
the downstream end. The grout’s extremely low viscosity
48 TRENCHLESS TECHNOLOGY September 2007 www.trenchlessonline.com