October 18, 2017

Plastic pipe systems – up to the challenge

There can be few environments more challenging than mining, particularly in extreme climates, and it is essential that any materials specified for critical infrastructure work are up to that challenge. Philip Wood, International Business Development Manager for Polypipe, the UK’s leading manufacturer of plastic piping and water management systems, explains that plastic is a material that is more than fit for purpose.

 Plastic piping systems can be manufactured from a variety of different types of plastics, ranging from high-density polyethylene (HDPE) to polypropylene, PVC or ABS. While the chemical constituents of each may vary, they share a number of qualities which make them suitable for a wide range of applications in the mining industry and for other major civil engineering projects. These applications can encompass surface and sub-surface draining, cellular crate systems to capture and store water and filtration systems.

Polypipe’s Ridgidrain HDPE system has been deployed at several major African mining projects, from Banro Corporation’s Namoya mine in the Democratic Republic of Congo (DRC), to the Tonkolili and Marampa mines in Sierra Leone and the Western Ranges Iron Ore Mine in Liberia. A perfect solution for surface and sub-surface water drainage, Ridgidrain is currently in use in de-watering and tailings management applications as well as transport infrastructure and general mine water supply. Ridgidrain’s structured twinwall design delivers inherent robustness and strength – giving it the flexibility to resist high traffic loads without cracking or leaking, which is essential in ensuring the chemicals frequently used in mining do not enter the water table.

Polyethylene (PE) systems, such as Polypipe’s PE100 system, could have been tailor-made for use in some of the toughest conditions. Used widely in applications such as recirculation pipelines for heap leaching operations, solution mining, process slurry pipelines and process water, PE is both chemical and corrosion resistant. It performs well when handling the most aggressive materials from abrasive slurries to corrosive acids, bases and salts making it suitable for use in tailings pipelines, mineral extraction and treatment applications. PE is also resistant to thermal shock and will stand up to the harshest of environmental conditions, operating between -40°C and +60°C. Both HDPE and PE pipes have inherent strength and impact resistance, but are flexible enough to cope with ground settlement after installation. With an extremely smooth bore, they are less likely to block and so are more easily maintained. If large volumes of liquid are being transported, there is very low friction, meaning less drag or turbulence at high flow rates and greater resistance to scaling than water absorbent materials.

For above-ground applications, black PE systems have the additional benefit of being UV-stabilised and therefore do not need to be buried and are inherently resistant to weathering. PE is also non-conductive and is therefore not at risk of electrolytic corrosion, subject to the correct precautions being taken to avoid the build-up of static discharge.

Installation benefits

Modern manufacturing processes have brought many additional benefits to PE and HDPE pipework systems. With ongoing technological innovation, they have become thinner, lighter and more robust than most rigid materials – typically they weigh 94% less than their concrete equivalent.

This brings benefits from at every stage from production line to ultimate installation. Production flexibility enables us to tailor make pipeline packages to customer’s specific requirements. So, when looking at transporting materials from Polypipe’s state-of-the-art UK manufacturing facility for overseas shipment, we are able to supply pipes at lengths that allow for the internal dimensions of the shipping containers and maximise their capacity. Once at site, plastic pipes are lighter and easier to handle and so minimise the need for the use of heavy lifting equipment, representing a benefit both in terms of cost and in health and safety.

A key consideration in undergound systems is the elimination of leakage. As PE pipes are typically supplied in 6m lengths, this reduces the number of joints required which not only reduces the potential for leakage but also speeds the installation process. PE pipes can also be jointed using electro-fusion or butt-welding techniques which form a continuous homogenous pipeline which eliminates leakage and pipes can be designed in bespoke lengths and angles to enable them to fit around existing infrastructure or difficult terrain.

Serving the infrastructure

As well as the operations directly associated with extraction and processing, mining infrastructure also includes a wide range of social or welfare structures – housing and community facilities being a key part of this. Water management systems are equally important in dealing with capture, treatment, re-use, attenuation, soakaway and drainage.

Above ground plastic drainage systems can be manufactured from HDPE, PVC or ABS and PVC offers a flexible and adaptable solution for below ground drainage. Again, these pipes are lightweight and easy to handle and install. Systems benefit from push-fit mechanisms which require no special tools or expertise and there are multiple options for pipe length, diameter and fixings.

Other aspects of infrastructure water management that can benefit from the qualities of plastics systems are large expanses of hard landscaping where extremes of rainfall may need to be allowed for. Cellular systems, such as Polypipe’s Polystorm offer considerable advantages over traditional soakaway systems based on the use of aggregates to ensure that surface water is cleared quickly and efficiently.

These systems of made from polypropylene which, although it has similar properties to polythylene, also has distinct differences. It does not present stress-cracking problems and has excellent electrical and chemical resistance and can be injection moulded to produce extremely tough but lightweight modular units. Such a system is ideal for de-watering and storage and transport infrastructure. Offering a 95% void ratio, the systems deliver maximum water capture and retention and can be used for attenuation through the use of an impermeable outer skin or for soakaway with a permeable membrane allowing the controlled release of water to surrounding subsoil. Systems are available with load bearing capacities from 20 tonnes/m² for lightly trafficked or pedestrian areas to 80 tonnes/m² for lorry parks or roadways.

The environmental aspect

A key factor of mining and civil engineering projects is that they are expected to have multi-generational lifespans and sustainability is a major consideration for materials used in the construction of their permanent infrastructures.

Plastics have the advantage of excellent environmental credentials. This shows through the previously mentioned technological developments which have resulted in hugely reduced materials content without compromise to strength, performance and longevity. Modern production techniques also see a high percentage of re-cycled material being used and the finished products are ultimately recyclable.

Other environmental benefits include reduction of carbon footprint from transportation because of light weights and the ability to maximise consignments. In fact, in terms of total life cycle, plastics can be considered to be one of the most energy-efficient materials.

In summary, the use of plastic pipework systems on major projects can result in high quality, reliable and sustainable solutions across a wide range of applications, in civil engineering projects, mining processes and associated infrastructure developments.

To find out more, visit www.polypipe.com/mining

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