Energy saving benefits of low-friction pipes

14 September 2016

Rich Pedley discusses the improved pump efficiencies that are possible when coupled with  plastic pipework systems.

Energy efficiency has become increasingly important in the manufacturing industry, with contractors, consultants and end users keen to select products that are able to demonstrate clear energy savings. This applies to all products in the supply chain – pumps and pipework are no exception. 

The majority of plant and manufacturing facilities require large volumes of water and industrial fluids. A reliable network of pumps and pipes are integral to the effective distribution and operation of water and fluid supplies. The energy efficiency of pipework systems are coming under increased scrutiny and, while there is a belief that plastic pipe systems are more energy efficient than metal alternatives, there has previously been little evidence to confirm the theory. 

This is why Durapipe UK embarked on a joint project with pump manufacturer, Wilo, to undertake research into the energy required to pump water through a plastic pipe network, compared with a traditional carbon steel system. 

The energy used to pump fluid around a pipe network will come down to the level of frictional head loss; when a liquid flows through a pipe. Friction between the pipe wall and the liquid causes a head loss, an irreversible loss of the fluid’s potential energy. Calculating this loss is fundamental to the design of any pipework system for industrial applications, with the internal roughness of a pipe being an important factor when considering friction los

The absolute roughness of a pipe material is provided in mm, with the smooth bore of plastic pipes providing a much lower surface roughness than carbon steel. The lower the surface roughness value, the lower the frictional head loss experienced, which in turn means reduced pump duties, smaller pumps and resulting ultimately in energy and cost savings.

Plastic versus steel
The research project compared the pump duty requirement using both plastic and steel pipe materials. The test was carried out based on an installation of 200m of straight 32mm pipe, 20 elbows and two isolation valves, assuming a flow rate of 1.0 litre per second. 

The results revealed a total frictional head loss of 8.23m for the plastic pipe system, compared with 15.71m for the steel installation. Due to the reduced power needed to operate a plastic pipe installation, a lower duty, more cost effective pump can be selected to work with the pipe network. The cost for the most appropriate pump to effectively service this application was £1,717.02 for the steel pipe system and £676.20 for the plastic pipe option, offering a cost saving of 60%. 

More importantly, the smaller pump required for the plastic pipe network would generate energy cost savings of 75%, compared with the pump required for the carbon steel pipe network.

In addition to the initial reductions in installed costs, the energy cost savings for a plastic pipe material will increase over the lifetime of the system. Suffering from scaling and corrosion, the surface of steel pipework deteriorates over time, which restricts flow through the pipework, seeing increased pump duties needed to pump the fluid through the pipe and delivering rising energy costs. In comparison, the smooth bore of plastic pipe sees a consistent flow rate maintained over the lifetime of the system offering stable pump energy costs, while also benefiting from reduced maintenance requirements and costs. 

Every manufacturer in the supply chain needs to be able to communicate the energy efficiency credentials of their products if they are to continue competing for new projects. It is, therefore, important to consider that mechanical services, such as pump and pipe networks can have a significant effect on energy consumption.

Rich Pedley is industrial brand manager at Durapipe.

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