Case studies

The increasing demand for energy by Tasmanian industrial, residential and commercial consumers led to the development and construction of the Tasmania Natural Gas Pipeline. This pipeline runs from the Gippsland Basin in Victoria across Bass Strait and onshore through Tasmania, a distance of some 732 kilometres. The pipeline became operational in late 2002.

BlueScope Steel's Port Kembla plant in New South Wales supplied 17,300 tonnes of steel to this project, for conversion to API 5L X70 and X65 strength pipe. The steel was of consistent quality, and delivered at a rate that matched OneSteel's production schedule, dovetailing with project requirements.

Location

The pipeline's route includes a 302 kilometre section on the sea floor in Bass Strait. It emerges onshore at Five Mile Bluff, north east of George Town in Tasmania, then continues onto Bell Bay where it supplies the Aurora Energy Tamar Valley Power Station and Rio Tinto Aluminium smelter before continuing south-west to Rosevale. It then divides into two laterals, one continuing northwest through Burnie and onto Port Latta, where it supplies the Grange Resources pelletising plant and the other continuing south to Hobart. The combined length of the Tasmanian onshore segment is approximately 430 kilometres.

Construction

Duke Energy Australia Pty Ltd was the pipeline developer. Construction was undertaken by KT Pipelines for the onshore Victorian sector of the pipeline, McConnell Dowell and Nacap for the Tasmanian onshore sector of the pipeline and Allseas Construction Contractors for the Bass Strait submarine sector of the pipeline. Construction of the pipeline commenced in October 2001 and was completed in September 2002 at a cost of AUD440 Million. The Tasmanian Gas Pipeline (TGP) is managed by Tas Gas Networks on behalf of the asset owner Tasmanian Gas Pipeline Pty. Ltd.

Varying pipe diameters, wall thicknesses and grades were utilised in this project, with the offshore sector requiring 355 millimetre (14") diameter pipe and onshore sector comprising 355 millimetre (14"), 219 millimetre (8") and 168 millimetre (6") diameter API 5L X70 and X65 grade pipe. Pipe for the onshore sectors of this project were manufactured by OneSteel Oil & Gas at Kembla Grange in NSW using raw coil feed produced by BlueScope Steel's Port Kembla plant. In particular, BlueScope Steel supplied;

• 4,700 tonnes of steel for the manufacture of 355mm (14") diameter API 5L X70 grade pipe
• 6,900 tonnes of steel for the manufacture of 219mm (8") diameter API 5L X65 grade pipe
• 5,700 tonnes of steel for the manufacture of 168mm (6") diameter API 5L X65 grade pipe.

Technical

BlueScope Steel employs a range of stringent quality control measures to ensure the quality of its steel products.

The production of 17,300 tonnes of steel with specific steel conversion and casting practices utilised BlueScope Steel's internationally accepted quality practices to provide a narrow band of chemical composition and internal cleanness ratings. The internal cleanness of the steel was particularly important for this project as the majority of the coil supplied was centre slit prior to pipe forming. Centre-line cleanness promotes weld line integrity.

The quality control aspects continued through the hot strip mill rolling cycle where stringent reheat practices, surface quality and finishing and coiling temperatures were closely monitored. This resulted in very uniform steel of excellent quality, with mechanical properties restricted to a narrow range of strength levels.

The production of steel for the Tasmania Natural Gas Pipeline is a typical example of the quality standards imposed by BlueScope Steel in its production of steel for the pipeline industry.