From the magazine

Trenchless in the loop

On 13 January 2015, Victorian drilling contractor Pezzimenti Trenchless commenced a month-long drilling operation in support of the Victorian Northern Interconnect Expansion Project. Working in clay ground conditions for client Nacap Australia – which in turn were contracted by APA Gasnet Australia – Pezzimenti Trenchless completed a total of three bores followed by pipe jacking, pipe insertion and pull back.

The VNIE Project

The Victorian Northern Interconnect Expansion, also known as the VNIE project, involves the construction of a 135 km looping pipeline from Wandong to Broadford and from Mangalore to Glenrowen in Northern Victoria.

The VNIE project is comprised of three main sections: Construction of a 68.4 km pipeline loop from Euroa Compressor Station Discharge to Glenrowan, including the installation of cross tie connections at Euroa and Glenrowan; construction of a 17.4 km pipeline loop from Wandong to Broadford including a tie-in at Wandong and cross tie connection at Broadford; and, construction of a 49.8 km pipeline loop from Mangalore to Euroa Compressor Station Suction.

Accuracy the name of the game

Working to a 28-day straight work cycle, Pezzimenti Trenchless completed three bores as part of the VNIE project, each with a diameter of 700 mm and crossing beneath rail lines. Measuring 45 m, 60 m and 117 m in length, respectively, the bores crossed beneath the Benalla to Yarrawonga Railway, the North Eastern Railway and the Goulburn Valley Railway.

Following boring, 500 mm diameter Humes RC jacking pipe was inserted via the pipe jacking method in order to accommodate the 406 mm diameter steel gas pipe. Once inserted, pull-back of the coated steel gas pipe was completed.

According to Pezzimenti Trenchless Director Joe Pezzimenti, the primary challenge of the project was to ensure the accuracy of the bore along its length within a tolerance of 10-15 mm. This was due to having to pull back the gas pipe in one continuous string with just 18 mm clearance between the gas pipe, centralisers, and the internal diameter of the RC jacking pipe. To further centralise the pipe, kwik-ZIP HDX 38 spacers were used.

Throughout the project, the client was very impressed with the accuracy of Pezzimenti Trenchless’s laserbore system to maintain lines and levels throughout the bore, added Mr Pezzimenti.

“Through careful planning and preparation, a great result was achieved,” he concluded.

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