Primus Line® Breathes New Life into Historic Trunk Main in Brisbane
Aug 18, 2021
Urban Utilities relies on trenchless technology for 2.2 km section
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 litres of water per second flow 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. Many car dealerships, restaurants, hotels, offices, residential buildings and several bus stops line the traffic route.
As with many water utilities, replacing water mains in heavily congested urban environments can be a costly and disruptive process. In this case, trenchless technology was the key to success.
Trenchless technologies allow utilities to rehabilitate water pipes that are nearing the end of their service life and "turn back the clock". In this way, security of supply can be ensured for future generations while minimising disruption to existing residents, businesses and traffic – and with significantly less investment than conventional methods.
Given the location of the pipe, flexible lining solution 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 traffic impact.
Physical and economic evaluation in advance
The large-scale project at Ann Street was preceded by a detailed condition assessment of the host pipe and economic evaluation, to ensure that 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.
Primus Line® as selected method
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.
In a single day shift, 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, demonstrating the speed and versatility of the system.
Start of the major project
The successful completion of the trial marked the start of the implementation of the "Ann Street" project. 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.
The installation phase due to its complexity and challenging site conditions, 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. Urban Utilities previously installed Primus Line® on other rehabilitation projects in its service region. At the time, Urban Utilities engaged Primus Line® to provide training to its capital delivery team. Urban Utilities also keeps necessary tools and spare parts in stock to perform Primus Line® installations and to be able to do possible repairs and maintenance in-house. The Primus Line team provided engineering support and accompanied the beginning of the measure with a supervisor.
Special DN 500 connectors with a DN 600 flange on the pipeline side ensure the connection to the flange on the host pipe while keeping the pits as small as possible. After commissioning, the pipeline can be operated with an operating pressure of up to 11.3 bar.
Primus Line delivered the four liner sections pre-folded in a U-shape and wound onto drums. The liner insertion into the old pipe is done with a winch. In the process, it also 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.
A pressure test concluded the successful installation before the main was disinfected and returned to operation.
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