March 2013 Tube Products International
37
products & developments
Rehabilitation of circulation lines
Often, in addition to cost considerations,
site conditions can make open
construction impossible. For the
rehabilitation of three 900mm circulation
lines at the Berliner Wasserbetriebe
treatment plant in Germany, the constant
hydraulic strain of the pipes prompted a
decision for trenchless rehabilitation.
SPR Europe restored the function and
the corrosion protection of the three
80m-long lines with pipe lining with the
warm-water curing Uniliner™ process.
Sewer networks are typically upstream
of treatment plants, but there are also
sewer networks in the plants themselves,
sometimes with very large diameters
that need to be rehabilitated at some
point. Due to their constant hydraulic
load, repairs cannot be performed using
open construction methods. These
are perfect conditions for the use of
trenchless rehabilitation technology, as
in the case of theBerlinerWasserbetriebe
treatment plant; the lines cross under
the main administration building of the
treatment plant, so no-dig technology
was absolutely necessary.
The three circulation lines connect the
primary clarifier of the treatment plant
with the aeration tanks and have been
under full load since their construction.
The reinforced concrete
pipes in particular
suffered from concrete
corrosion, with some
areas of exposed rebar
and sporadic deposits.
Previously they had
been
rehabilitated
selectively
using
sealing sleeves. To
permanently repair the
concrete pipes, the
sleeves were removed
before installation of
the Uniliner pipe lining
technology.
The three lines connect on both sides
to the circulation shafts, whose special
geometry represented an important
parameter for the rehabilitation. Using
a light-curing system with a draw-in
process was ruled out here for reasons
of safety. From the top edge of the
shaft to the lines, inside the shaft a
construction height of 8.5m needed to
be surmounted. The overhead shaft
was not reachable due to intersecting
pipe bridges. The lower shaft, on the
other hand, protruded 5m above the top
edge, which also had implications for
the implementation of the rehabilitation.
With the Uniliner system a
needled felt liner, impregnated
with thermo-reactive UP resin,
is hydraulically inversed into a
blown up ‘preliner’. The liner is
then cured by the circulation
of warm water. The liner is
characterised by an integral PE
inner coating. A water column
above the shaft was built-up to
ensure the hydrostatic, tight-
fitting inversion of the liner. At the
treatment plant, the water column
was constructed in circulation
shaft 2. From this point, the three
pipes were rehabilitated against
the direction of flow.
An important additional project
condition was that all circulation
lines contained a dimension
change from 900mm to 850mm.
This was accomplished using
the Uniliner, made possible by
its longitudinal seam enabling a
tailored cone section. Otherwise
it would have been necessary
to use a supporting liner, which
would then generate an annular space
that would need to be dammed.
The circulation shaft that protrudes
far above the top edge represented a
special challenge for the installation
procedure. The use of a conveyor belt,
the preferred method for liners of this
dimension, was not possible in this
case, as at the height and diameter
of the shaft, the rolling edge of the
conveyor belt could not be positioned
precisely over the shaft opening and the
liner would have had to be placed on the
shaft edge for the feed-in procedure. For
this reason, a trapezoidal construction
had to be used at the boom of a mobile
crane to be able to lower the six-ton
liner into the shaft and channel.
For curing the water filling, 51 cubic
metres for each channel was supplied
to the liner via a mobile heating system
using a circulation system that heated
the water according to the exact heating
schedule to an inlet temperature of
90°C. During the curing procedure,
which was measured and documented,
the temperature of the liner had to
remain above 50°C for three to five
hours. This led to the complete curing
of the liner, as demonstrated by the
laboratory remote monitoring of the
project, and all testing criteria were
fulfilled completely.
Sekisui SPR Europe GmbH
– Germany
The cured Uniliner system, from the outside
in: old pipe, preliner, polyester needled felt
liner, and integral PE inside coating
Reaching to the sky:
the Uniliner above
circulation shaft 2
