North American Special - Trenchless International

projects
April 2009 - Trenchless International
Rehabilitation of a return
line for cooling water
An innovative low pressure pipeline repair technique has been tested at a power plant in Berlin.
Michael Roeling describes the procedure and successful outcome of the test.
With a capacity of 600 MW, Reuter
West is the most powerful heat and power
plant in Berlin, Germany. It consists of
two equal units, each with an output of
300 MW (block D and E), which were put
into operation in 1987 and 1989 respectively
and located next to the existing old
power plant, Reuter.
During recent routine maintenance
checks it was noticed that two of the four
return pipes connecting the side coolers
with the main cooling return line between
the cooling tower and unit E were showing
leakages caused by pitting corrosion. The
leaking pipes are made of welded steel,
with a nominal diameter of 600 mm and are
operated with a maximum pressure of 29
psi. The pipeline had been partly assembled
by welding half pipes together on site,
causing tolerances in diameter, an unusual
trait for steel pipelines.
The return lines, together with many other
lines, are installed in a service duct below a
pavement designed for heavy-duty trucks.
The replacement of larger pipe sections
would have required the opening of the
pavement, digging a trench and removing
the reinforced concrete floor. This method
was rejected from the beginning; primarily
due to the obstruction it would cause to
internal plant traffic, but also for cost reasons.
The replacement of small sections
inside the closed service duct by hand was
also discussed as a possible alternative.
However, the cost would have been quite
high. In either case, the replacement could
never have been executed within the time
frame.
BKP Berolina Polyester GmbH & Co
offered to install the new Berolina-LP-Liner,
the first field test of the product. This
renovation solution promised cost advantages
for the power plant’s owner Vattenfall
Europe. Plant management decided to
renovate a test section using the liner and
await a result before making a final decision
about the method of renovation or
replacement.
Preparation
As the condition of the leaking pipes —
except the pitting holes — was generally
still good, the final decision on method was
postponed for several months. The leakages
were closed by welding steel plates
over the holes. A 40 metre test section was
left for the liner renovation test. This section
was limited by a 90 degree bend with a
wall duct that followed on one side. On the
other side of the section, and an additional
90 degree bend led into an extension section.
The distance between the upper pipe,
which had to be renovated, and the ceiling
measured only 3 to 5 cm. First the bends
were removed because the liner installation,
and subsequent curing by using
UV-light, required reasonably straight sections.
Afterwards the section was scheduled
to be cleaned by high pressure jetting.
Unfortunately this was not sufficient as the
pipe was encrusted with a hardened buildup
that could have damaged the liner.
An intensive cleaning and levelling of the
pipe’s inner surface was carried out using
a special scraper known as a ‘go-devil’
(pictured).
The insertion of the light train.
Installation of the liner
The liners were fibre reinforced plastics
(FRP), using several layers of glass-fibre
mesh reinforcement together with polyester
resin which is cured by using UVA-light.
So far the Berolina-Liners have been used
for renovation of storm water or sewer
pipes. The water tightness test in those
cases followed the procedures of EN 1610
with a maximum test pressure of 7.25 psi
when using water and 1.45-2.90 psi when
using air as a pressure medium. Based on
the existing liner products the company
ventured into a new product line to enable
the renovation of pressure pipes.
In this project, the liner for low pressure
pipes was chosen to complete the test.
Following the pipe cleaning, a polyethylene
gliding foil was pulled in the pipe to
protect the liner from damage by welding
burrs or any remaining hardened build-up
when being pulled in.
Then the liner was pulled into the pipe
with a hydraulic winch and closed with
end caps.
The liner was then inflated by air pressure
in order to insert the UVA-light source.
The light source consisted of a light train
with eight metal halide lamps. The light
spectrum was synchronised to the photo
catalysts in the polyester resin. A curing
unit, type Compact and made by HC
PipeTech, was used for curing the liner.
Due to the very small external dimensions
of this equipment, the installation crew
was able to bring the unit into the service
duct by hand and through a door only 90
cm wide.
After the insertion of the light train, the
liner was expanded close fit to the inner
wall of the host pipe. The special design
of the liner allows it to dialate over a
relatively wide range of diameters – from
5 per cent under measurement up to 5
per cent over measurement compared
with the specified size of the host pipe.
Therefore, the large tolerances in diameter
of the host pipe were not an issue for
the liner.
After dilatation, the light source was
ignited and pulled through the liner at a
defined speed. The UVA-light enabled the
polymerisation of the polyester resin.
After the curing had been completed
the liner ends were cut with precision and
the installed liner could be examined. The
smoothness of the inner liner surface was
striking. In a public sewer system the job
would have been completed by this stage.
In this case, the connection to the existing
pipeline had to be made. Flange collars,
also made of FRP, were bonded to the
protruding liner ends and the continuing
pipeline components with flange joints
attached. This design was necessary for
two reasons. Firstly, the design allowed for
the opening of the test section for future
inspections without destroying any part of
the pipeline. Secondly, a joint by laminating
was not possible because of the very
narrow distance between the pipeline
and the reinforced concrete ceiling. Even
for the flange type of connection used in
this project, the concrete cover had to
be removed at some locations to allow
enough working space.
Summary
The project described above has been
accomplished in an extremely short time
frame, especially considering the very
tight working space. The renovation of the
straight section, including cleaning with
the ‘go-devil’, pulling in of gliding foil and
liner, curing and exact cutting was done
in a single day. The replacement of the
pipe section with half pipes would have
taken three to four weeks. The time taken
for connecting the liner with the rest of
the pipeline, as well as for the preparing
works for removing the old steel bends,
was within the normal time frame for this
kind work. The pipe section renovated by
ID 150 mm (~ 6‘‘) up to
ID 1000 mm (~ 40‘‘)
Glass fibre and/or polyester
webs impregnated with resin
Brief installation time
Bridging of profile
differences and cross
sections
Chemical resistant
Suitable for all profiles
Seamless construction
Smooth surface
Ready for installation
Berolina-Liner System
®
Lightspeed sewer rehabilitation in 5 continents
CIPP with UV-light
The renovated pipe section.
using the Berolina-LP Liner has been in
full and unrestricted operation for over six
months at the time of writing. From testing
so far the Berolina-LP-Liner can be
rated as reliable for this kind of pipeline
renovation in power plants and other low
pressure pipes.
BKP Berolina Polyester GmbH & Co. KG, Berlin, Germany. For more information visit www.bkp-berolina.de or
contact +49-30-36471-400 email info@bkp-berolina.de
BKP Berolina Polyester GmbH & Co. KG
Am Zeppelinpark 22
13591 Berlin, Germany
®
UV-light source
Tel.: +49 (0) 30 / 36471-400
Fax: +49 (0) 30 / 36471-410
info@bkp-berolina.de
UVA-light in action.
Insertion of the Berolina-LP-Liner.
Less space required
projects
April 2009 - Trenchless International
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