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INNOVATIVE Australian-developed pipe relining technology was recently used in a major project to restore large stormwater pipelines in Stonnington (Melbourne). The
unreinforced concrete pipes of the existing combined storm/sewer pipelines The performance based
project specification prepared by Stonnington City Council allowed a range
of refurbishment methodology alternatives to be considered.
In April 2001 the project
was awarded to prominent Australian pipeline rehabilitation contractor
Interflow Pty Limited, who proposed structural lining using the newly
developed Rib Loc Rotaloc system. This is a “next generation”
development in spirally wound liners from Adelaide based company Rib Loc
Australia Pty Ltd. Like other Rib Loc
processes, Rotaloc installs a liner using a machine that spirally winds a
single strip of uPVC profile. The
fundamental difference is that the Rotaloc winding machine travels along
inside the deteriorated pipeline as it winds the profile.
The profile edges, with
built-in interlocking channels, are locked together by the rotating arms
of the Rotaloc winding machine. The hydraulically operated arms can alter
the diameter of the liner as variations in the diameter of the host pipe
are encountered, thus installing the largest size of liner that can fit
into the deteriorated pipe. Interflow submitted a
type 2 liner in accordance with the WRc Sewer Rehabilitation Manual. This
design assumes that the liner takes all soil, groundwater and live loads,
and any remaining strength in the existing deteriorated pipeline is
ignored. The design does not rely on any bond forming between the liner,
grout or deteriorated pipe. Traditionally the only
way to repair such pipelines without digging them up and replacing them is
to slip line them, involving digging a launch pit and pushing short
lengths of steel, fibreglass or concrete pipe up the inside of the
deteriorated pipe. Launch
pits have to be large enough to accommodate the pushing equipment and at
least one length of lining pipe. Apart from the
inconvenience of digging large holes for launch pits in busy city areas,
storing of short lengths of large pipe above ground is inconvenient and
often dangerous. The Rotaloc option
offered greater hydraulic capacity than other lining options as it
maximised the liner diameter by varying it to contact the host pipe wall.
Flow capacity was further enhanced by the liner’s efficient, circular
shape. The
pipelines were cleaned and cleared of debris (obstructions and loose
material from the pipe wall) before rehabilitation commenced. The first stage of the
project involved rebuilding the stormwater pits, which became the access
points for the Rotaloc lining machine. No excavation was necessary. Installation of a total
of 504 lineal metres of liners was completed during a two-week period.
About 450m of this was 1200mm nominal diameter. The longest pipeline
length between access points was 123m. Liner winding progress
varied depending to the condition of the host pipe, with the best
production rate being relining 50m of 1200mm pipe in just over 2½ hours
from commencement of winding. One
section of pipeline curved 45º through a length of 9m. The Rotaloc liner
was installed in one piece through this bend, without the need for
fabrication. The diameter was gradually reduced over a distance of about
1.5m at the entrance to the bend. The strain capability of the uPVC
profile allowed sufficient deflection of the liner during installation
through the bend. The diameter was then increased to match the host pipe
diameter at the bend exit. Lateral
connections were made as winding progressed. Locations were marked on the
liner then cut and sealed, allowing services to be restored immediately. Authorities often shy away from renewing large diameter stormwater drains and sewers because of a lack of viable rehabilitation options. On this project, Interflow demonstrated a cost-effective solution that restored the structural integrity and hydraulic capacity of the original pipelines. Work was completed without the inconvenience normally caused in densely populated areas by previously available reconstruction methods. Article published with permission from Greg Keane of Construction Contractor.
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