Page 17
Contractors World - International Vol 4 No 3
Sewer Back in Shape
for Decades to Come
Last year, quick rehabilitation was needed for 150 metres of sewage pipe
with diameters of 300 mm on the shores of Lake Attersee, a popular holiday
destination in the Salzkammergut region of Austria.
The contractors, SPR Europe, proposed to us the Close-Fit liner system
to provide the optimal solution.
The Close-Fit method has existed for 20 years as an alternative to other
trenchless pipe rehabilitation technologies, such as CIPP or spiral-wound pipelining.
With the pipe-in-pipe method, pressure pipes as well as gravity pipes of various diameters and lengths can be
rehabilitated cost-efficiently and quickly, extending the service life of the pipes by at least 50 years.
Some 150 metres of pipe-in-pipe and a defect wastewater sewer in the network of the Attersee Region was
rehabilitated in no time at all.
The sewer with diameters 300 mm,were showing signs of breaks and cracks in the brickwork after a pipe
inspection. At the location directly on the shores of the tourist destination Lake Attersee trenchless renovation
was the economical and technical best solution for rehabilitating the sewer in the specified narrow time frame and
without major impact on the heavy daily traffic.
Taking into account the criteria – time frame, condition of the existing pipe, construction site surroundings,
nominal width and length of the rehabilitation section, the Close-Fit method presented the ideal solution. The
breaks and cracks would normally make preliminary sealing necessary. With the chosen liner system this step is not
necessary and installation of the liner could be started without delay.
Structurally self-supporting pipe-in-pipe
With the help of a traction limited winch and using a normal manhole, a four-man team from the Rabmer
construction company, a subsidiary of SPR Europe, installed the pre-shaped PE pipe in the 150 metre length of
sewer in two days.
The deformation reduces the diameter of the new pipe by 25-30%, making it much easier to pull it into the
damaged pipe. With the help of hot steam and pressure, the liner was brought back into its original circular shape
and pressed against the host pipe, without an annular gap. The new structurally self-supporting pipe within the
pipe can withstand operating pressures of up to 12 bar and can withstand even higher pressures in combination
with the host pipe.
In the following two days, rehabilitation was performed manually on the manholes as well as the connections to
the manholes, where pressure was applied to eliminate the annular gap between the liner and the host pipe.
For the installation of the Close-Fit liner, a
cutting device is used to taper off the tip of
the liner. Holes are drilled into the tip for
attaching the winch cable.
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