Food producer drives down its energy costs.
Food producer drives down its energy costs.
Accurate end-product sizing, lower maintenance costs, quieter operation and reduced energy bills are the results of replacing DC drives and motors with ABB variable speed inverter drives on two extruder lines used in the production of the breakfast cereal, Weetos.
As part of The Weetabix Food Company’s ongoing improvements program, energy and productivity reviews are undertaken on various aspects of the electrical, mechanical, control and automation systems throughout the year. It was suggested carrying out an energy appraisal.
Portable energy loggers were installed to the incoming supply to monitor and measure kW, kVA, kVAr, power factor, current and voltage. One area identified as a high energy user was the extruders, which consumed up to 30 percent of the site’s energy consumption.
Extruder use 30% of site consumption
Product is fed into a hopper and is measured into the extruder screw. The extruder mixer transfers the product forward through the barrel under a controlled temperature and pressure through a faceplate. From here it is extruded into a long hollow tube before being cut into short lengths prior to cooking. There are two types of extruders using DC motors: one uses two motors rated at 250 kW and 132 kW, and the other uses four 64 kW and two 90 kW motors.
During the plant shutdown period, the DC drives were replaced with eight ABB industrial drives, five ABB general purpose drives, and low voltage ABB motors rated from 0.75 kW to 250 kW were installed. Following the installation, further measurements were taken and a 20 percent drop in energy consumption was observed. The results showed that by changing to AC drives, Weetabix has saved some £28,000 per year, with a payback within three years.
£48,000 pa SAVINGS
From an engineering perspective Weetabix have eliminated maintenance on the drive train, as there are no carbon brushes to replace, no forced cooling, and feedback devices are eliminated as the gearboxes are protected by implementing a torque limit control on the AC drive. It is estimated that engineering maintenance cost and plant downtime are reduced amounting to nearly £20,000 per year to provide total savings estimated to be £48,000 p.a. Other benefits included:
OTHER BENEFITS
– The new AC drive technology brings greater torque control and speed accuracy, thanks primarily to the motor control platform, direct torque control (DTC). The control system was simplified as DTC removes the need for encoder feedback is needed
– Improved repeatability has led to product quality improvements resulting in the cooking time of the end-product is optimised; there is minimal temperature fluctuation which further saves energy.
– Scheduled maintenance has reduced and noise levels have fallen from 130 to within the regulation 80 dBA.
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