Borealis: BorECO™ polypropylene for non-pressure pipe applications

Borealis is at the forefront of polypropylene (PP) material advances. Its long-established relationships with many stakeholders in the pipe industry have enabled Borealis to convert market needs into BorECO™ PP solutions that benefit all members of the value chain: Converters, installers, end-user utilities and communities.

BorECO PP delivers an optimum balance of stiffness and impact properties and good processing characteristics for both extrusion and injection moulding, thereby offering the possibility of a ‘one material’ solution for complete systems in these applications. The performance profile of BorECO PP includes resistance to chemicals, compatibility with all conventional jointing techniques and a potential service life stretching beyond the current industry standards.

This allows simplified logistics through the purchasing, handling and processing of a single material, together with greater cost savings resulting from decreased pipe weight and reduced material consumption, ease of installation and savings in system transportation.

Furthermore, the long-term performance reliability of BorECO PP enables the production of high quality systems that require little or no maintenance or repair over their service life. The total savings generated by BorECO PP-based systems help to reduce waste water disposal fees to commercial and community end users.

Industry leadership
In the late 1990s, Borealis confirmed its industry leadership by bringing to the market the first PP block copolymers with superior stiffness for non-pressure pipe applications, BorECO BA212E. Borealis and its customers have shown an increasing number of community officials, planners and decision makers the benefits of light weight and durable plastics solutions for underground drainage and sewerage systems.

The introduction of BorECO PP allowed an amendment to the standard for ‘Plastics piping systems for non-pressure underground drainage and sewerage – polypropylene’, EN1852-1/A. This related to PP materials with a modulus of elasticity of 1700 MPa or higher (PP-HM), for pipe systems of stiffness class SN8. This new standard made it possible to manufacture thinner walled PP pipes with the same ring stiffness as polyvinyl chloride, polyethylene or conventional PP. Consequently, pipes with an even lower weight per metre could be produced based on the BorECO PP materials.

A new grade, BorECO BA222E with an E-modulus of >1900 MPa and excellent impact strength has been introduced. This new material has been specifically designed for solid wall heavy-duty pipes with increased ring stiffness requirements at reduced weight per metre.

‘One material’, low-weight solution
BorECO PP, BA212E and BA222E grades for solid wall systems offer the lowest pipe weight per metre of commercially available materials for drainage and sewerage.
This translates to a reduction in weight per metre pipe of approximately:

• 15% compared to conventional PP-B (900 kg/m3)
• 27% compared with PVC-U (1530 kg/m3)
• 27% compared with PE (950 kg/m3)

Besides its application in solid wall piping, BorECO PP also brings specific benefits in the production of twin-wall corrugated pipes, ribbed constructions, multilayer and spiral-wound pipes, as well as foamed solutions, injection moulded fittings and inspection chambers. In these applications BorECO PP opens a wider window for more design freedom than is economically achievable with alternative materials.

Increasing benefits
Mainly dominated by concrete, clay and ductile iron, the underground piping sector has over recent years seen the increased acceptance of PP. Growth in the use of PP for gravity-flow pipes has been partly due to the progressively high failure rate of old generation, non-plastic systems.

Common issues centre on brittle failure due to overloading and the lack of flexibility – elimination of this problem is a major advantage of plastics solutions. Furthermore old generation piping material frequently exhibits surface or joint damages, and leakages resulting from ground movement, the sulphuric acid corrosion of concrete, or corrosion of metal reinforcements.

BorECO PP has been applied in a range of different piping systems to overcome these problems and deliver durable, long-term solutions for communities, industrial end users and private house owners.

Solutions in action
The city of Malmö, called the ‘Park City’ of Sweden due to its exceptionally green city design, had a considerable problem with root penetration into the sewerage network. Root penetration can cause leakages in and out of a pipe system. Such leakages can occur in old generation pipe systems that cannot be installed in a completely leak tight manner, and often break shortly after installation due to their lack of flexibility. One consequence of such leakages is that water treatment plants need to be designed and operated at much higher capacity than actually required for the needs of the local population, causing additional costs and resource consumption.

In the early 1990s Malmö installed a test ring of different pipe materials. Trees were planted close to the test ring and television inspections were carried out every two months to see what happened underground. The observations were carried out over six years.

As a result of this investigation, Malmö decided to install fully-welded PP sewerage pipelines in order to overcome the roots penetration problem. The connection technologies used were socket fusion and butt fusion. Since then some 80km of Borealis PP sewerage pipelines have been installed in Malmö.
Malmö city councilor Mr. Bengt Mattsson explained: “Although at installation fully welded systems are around 50% more expensive than the cheapest solutions available, the cost of routine maintenance work over the system’s lifetime is so substantially reduced that the investment is repaid in the short term.”
The experience in Malmö proves how closely economic and ecological benefits are linked together in BorECO PP pipe solutions.

Cold climate performance
BorECO PP grades are especially suited for use, handling and installation in cold climate conditions due to their balanced high stiffness and high impact properties. An installation of spiral wound Weholite pipes made of BorECO PP in the community of Kokkola in Finland was successfully completed in January this year. The large pipe, with an inner diameter of 1600mm, was put into the ground at temperatures well below 0oC.

Further proof of good cold temperature resistance is the installation of a 900mm diameter solid wall pipe, produced by egeplast, in Norway in late autumn 2002. The total pipe length was 2km with pipe sections of 350 metres drawn over forest ground to the final installation position. High flexibility, good abrasion resistance and strength of the pipe were additional requirements related to the harsh handling of the pipe which is not uncommon in the installation process.

Dynamic profile
The high performance profile of BorECO PP gains increasing recognition in high load heavy duty applications. Rehau AWADUKT PP piping has, for example, been selected for the waste water line at the cargo loading section of Cologne-Bonn Airport. In such an environment, resistance to dynamic load in combination with good chemical resistance is especially important. The pipes made of BorECO PP were buried just one metre below the surface and are subjected to continuous dynamic load caused by aircraft carrier traffic. The weight of just one carrier is about 750 tonnes. Cologne-Bonn Airport is the second busiest cargo hub in Germany and handles about half a million tonnes of cargo annually through seven cargo terminals.

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