ENERGY MANAGEMENT | PRODUCTION Make more from less
Energy is a major cost in any compounding plant but it is not a fixed one. Mark Holmes talks to some leading energy and equipment specialists to find out how to cut energy bills
There are plenty of steps that can be taken in the compounding plant to minimise and manage energy usage but the compounding extruder motor is a good place to start. Motors typically use around two-thirds of the energy at a compounding plant so it is really important to implement a motor management programme, according to Dr Robin Kent, Managing Director of UK-based Tangram Technology, a consulting engineer for energy management in plastics processing. He has developed a simple step-by-step programme (outlined in Figure 1) that is designed to reduce motor energy costs throughout the motor system, not just in the motor itself. The first stage of the programme is focused on
demand. “Minimising the demand is not about removing services that are necessary for opera- tion,” says Kent. “It is about providing the appropri- ate service when needed.”
He says the best method — and the first step in
his programme — to reduce the cost of motor energy is to stop motors operating when not required or when not producing valuable output. The second step is to reduce transmission losses, which he says are often a major component of the losses in the motor system and can easily exceed
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losses in the motor itself. Step three is to reduce the driven load. This can be achieved through measures such as improving the control system, better maintenance, and examining the load to identify methods of reduction. The second stage in Kent’s programme is to optimise the supply, which means getting the right size motor. “Motors are often too large for the application. This can lead to higher-than-needed operational costs if the motor is operating at full load. If a large motor is operating at low loads, then the efficiency will drop dramatically and again add to operational costs. Getting the right size motor for the application is a key issue,” he says. “The next step is to improve the motor efficiency.
The efficiency of a motor will vary with the motor type, the load and the demand profile but new high-efficiency motors are available to save energy.” Kent says that installation of high-efficiency motors is now required by EU and US law for new installations but many old and hidden motors will be IE 1 rated or less. These motors can easily be upgraded to IE 3 (equivalent to NEMA Premium efficiency in the US) to give energy savings across the loading range and the payback will generally be less than a year. The sixth and final step is to slow the motor
February 2021 | COMPOUNDING WORLD 29
Main image: The route to improved energy efficien- cy moves through simple management strategies as well as plant upgrade and equipment investment
IMAGE: SHUTTERSTOCK
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