Rehabilitation

Earlier this year, Urban Utilities completed a multi-million-dollar rehabilitation project on this 130-year-old pipeline.

With the use of the trenchless technology Primus Line®, the project is expected to extend the life of the pipeline by at least 50 years, providing an economical solution with minimal impacts to traffic and nearby businesses and residents. 

The Ann Street pipeline is a cement-lined, cast iron pipe, and helps to supply water to the city centre and the inner-city suburbs.

During the morning and evening peak consumption periods, about 500 L of water per second flows through the pipe. 

Thousands of vehicles a day roll along the four-lane road, which is one of the busiest roads in Brisbane’s central business district, and businesses and bus stops line the traffic route. 

Replacing water mains in heavily congested urban environments can be a costly and disruptive process, so in this case trenchless technology was the key to success.

Given the location of the pipe, Primus Line was chosen as it could pass through several bends in the pipe and be installed using a few small pits, to minimise the impact on traffic. 

Planning 

As Primus Line is a flexible stand-alone pipeline, which is installed with an annulus gap, it can withstand the operating pressures of the water main, but not the external loads from the traffic on the road above. 

The project at Ann Street was preceded by a detailed condition assessment of the host pipe and economic evaluation in order to ensure the existing pipeline could withstand external loads in the future.

The results showed that the pipeline had sufficient load bearing capacity to allow the use of a semi-structural lining system such as Primus Line for the desired service life of at least 50 years. 

The perfect choice 

Due to its unique three-layer structure, the Primus Liner combines flexibility with extremely high material strength.

As a self-supporting pressure pipe liner independent of the old pipe, it absorbs the entire operating pressure, while the old pipe merely functions as a conduit. 

In accordance with ISO 11295, Primus Line is an independent pressure pipe liner capable on its own of resisting without failure all internal loads throughout its design life.

It has the ability to negotiate bends of up to 45 degrees, allows for seasonal movement of the pipeline and ensures the required operating pressure of up to 11.3 bar. 

Despite the reduction in cross-section of the DN 600 pipe, flow calculations showed the client that the installation of a Primus Line DN 500, with its low friction coefficient of only 0.028, would still provide the required flow. 

Before the start of the project, a large- scale trial with a length of 350 m was carried out with the Primus Line system – developed and produced in Germany.

In a single day, the pre-folded liner was pulled into the 350 m field trial section of the Ann Street trunk main, formed into its circular shape with compressed air and successfully connected to the pipeline network.

Start of the major project 

The successful completion of the trial allowed for the commencement of the Ann Street project, where detailed design and construction planning was performed in 2019 by Urban Utilities.

The initial stages of the project also involved cleaning and prepping the existing pipe to make it suitable for installing the liner, while the installation phase began in mid-2020 and was completed in early 2021. 

Most of the work took place at night and the small construction pits were closed during the day with large steel plates, to allow traffic to continue to flow.

The entire project was carried out by Urban Utilities’ own workforce, and the company had previously installed Primus Line on other rehabilitation projects in its service region. 

Urban Utilities had engaged Primus Line to provide training to its team, and kept the required necessary tools and spare parts in stock to perform Primus Line installations and possible repairs and maintenance in-house. 

The Primus Line team provided engineering support and accompanied the beginning of the measure with a supervisor.

Four installation sections were necessary to rehabilitate the 2.2 km long pipeline section, with the Primus Line system DN 500 PN 16 used to rehabilitate the DN 600 water pipeline.

Primus Line delivered the four liner sections pre-folded in a U-shape and wound onto drums.

The liner insertion into the old pipe was done with a winch and in the process passed through some additional smaller intermedia pits to reinstate valves and offtakes.

The liner was pulled through these pits and cut afterwards to install the Primus Line connectors and the necessary valves and t-pieces 

Special DN 500 connectors with a DN 600 flange were used to ensure the connection to the flange on the host pipe while keeping the pits as small as possible. 

A pressure test concluded the successful installation before the main was disinfected and returned to operation.

For more information visit the Primus Line website.

This article was featured in the June 2021 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.