Cherry Valley freezes out £30,000 on variable-speed drives 14 May 2014

Cherry Valley Farms, one of the UK's largest producers of duck products, now expects to save £30,000 a year from its freezing costs, following the installation of ABB variable-speed drives on its blast chiller.

The Lincolnshire-based firm rears 8 million ducks every year and processes 45,000 a day, most of which are frozen in 10 blast chiller bays. Each has two 4kW motors driving fans that blow air over refrigeration coils, freezing a full day's production overnight.

However, Cherry Valley factory engineering manager Rob Stevens explains that although freezing only takes place four days a week, the fans operate 24/7, because switching them off would cause them to ice up.

Stevens says that it was not possible to simply to control blast chiller temperatures through PI (proportional-integral) control as the bays go through regular de-frost cycles. There is also a significant air exchange between bays, making temperature feedback unreliable, he adds.

Stevens says he turned to ABB partner IDS because "we have worked with IDS on several other projects".

IDS installed 20 ABB HVAC drives, two for each blast chill bay. In production, the drives now run the motors at 45Hz, giving a 25% energy saving during the freezing period. Outside production hours, the motors are slowed further to 30 Hz, producing a further 60—70% saving.

"As well as the energy saving, we expect that the slower start up achievable by the drives could lead to fewer fans breaking up, which we sometimes experienced with the direct-on-line method used previously," comments Stevens.

Brian Tinham

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