Borstar® PE materials bring added value to the utility and industrial pipe sectors

Since its introduction, polyethylene (PE) from Borealis’ proprietary Borstar® process has set the industry standard for pipeline construction in technical performance and delivered value to the pipe producers, pipeline installers, operators and end users.

To the pipe producer Borstar PE has improved process efficiency, reduced production costs and increased the effective plant capacity, as well as extending the range of pipe sizes that can be produced from PE. Through its superior balance of properties, Borstar PE enables engineers and system designers to utilise PE where they would previously have had to specify more costly steel or iron pipes. The advantages and benefits they bring to system managers include lower installation costs, simplified installation with reduced disruption to residential communities and, importantly, they provide reliable long-term performance.

Borstar® medium density PE80

Borstar PE has proven it can meet the needs of a wide range of pipeline projects using many different installation technologies including insertion, pipe bursting and directional drilling. Borstar bimodal medium density (MD) PE80’s special properties produce tough flexible pipes for challenging projects such as renovating gas pipe systems in congested urban environments. The bimodal process provides a higher resistance to crack growth than previously possible, which enables pipes produced from Borstar MDPE PE80 to be used for difficult insertion projects and operated at a higher pressure than other MDPE pipes.

In Milan, Italy, AEM Gas had used bitumen coated steel pipes for its medium pressure gas distribution system but the highly corrosive conditions meant that a number of these mains needed to be renovated by inserting a smaller diameter PE pipe. To carry out the work in the centre of Milan it was essential to minimise disruption to normal street activity and this was best achieved with a flexible MDPE pipe. Borstar ME3441 was specified for its high flexibility and its high resistance to slow crack growth and rapid crack propagation.

In the first project, which was undertaken in 2003, a 400mm SDR11 pipe was inserted into the 500mm, 160m long steel main in just four days with a minimum of disruption to Milan’s busy Via Stresa. Moreover, AEM Gas was able to use their own equipment and workforce to replace the main and made an overall saving of 20% compared to replacing the mains by other means.

Transco, the major gas distribution company in the United Kingdom, are conducting a major renovation of the gas system in response to demands from the UK Health & Safety Executive to replace all metal pipes within 30 metres of buildings. One such pipeline was a 24 inch cast iron main in Bethnal Green, London. While renovation by insertion of a PE pipe was an option, a close fit method was necessary to retain the maximum flow capacity of the pipeline and therefore the “Subline” renovation technique was chosen.

In order to reduce the risk of failure from surface damage induced in the inserted pipe, a PE material with a high resistance to crack growth was required and Borstar ME3441 specified.

The 595mm SDR33 pipe was welded on site into continuous lengths and fed through the Subline forming unit to form a “C” shape (see photograph). As the pipe exited the machine, an automatic strapping unit located and friction welded the polyester straps at regular intervals to keep the pipe in shape.

A winch cable was connected to the front end of the liner pipe and the pipe pulled into position. Because the cross sectional area was reduced by approximately 40%, the winch load was low and an insertion rate of one metre per minute was achieved. Once the liner pipe was in place the winch cable was de-coupled and the pipe reverted to circular form using cold water at a pressure of 2 bar. As the pipe reformed the restraining straps broke and remain trapped between the liner pipe and the cast iron host pipe.

The whole renovation process was completed in a remarkably short time with minimal disruption, providing Transco wit

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