New Australian technology restores large Melbourne stormwater pipelines 

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
had suffered abrasion and corrosion, with sections of the pipe wall missing. Partial collapses had occurred at some locations.  

The project called for rehabilitation of over 500m of pipe (with diameters ranging from 900mm to 1500mm) to restore their structural and hydraulic capacity. Replacement was not feasible as they were under more than 3m of cover, beneath houses and adjacent to major roads.

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.

Last Updated on 11 May 2002