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Product category: Industrial Drives/Controls
News Release from: ABB Automation Tech (Drives and Motors) | Subject: Variable speed drives
Edited by the Engineeringtalk Editorial Team on 07 July 2005

Variable speed drives cut food cooling
costs

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Food manufacturer Northern Foods is saving over GBP 30,000 a year in electricity costs thanks to the installation of three ABB variable speed drives at its Riverside Bakery in Nottingham.

Food manufacturer Northern Foods is saving over GBP 30,000 a year in electricity costs thanks to the installation of three ABB variable speed drives at its Riverside Bakery in Nottingham The plant, which produces chilled preprepared foods for customers such as Marks and Spencer and Sainsbury, uses large refrigeration units to store both the ingredients and the finished products

The refrigeration units are fed by cooling water pumped by three 75kW motors.

Soft-start control panels have been used to control the motors since the plant was built 22 years ago, but as part of a wide-ranging energy saving plan, Northern Foods was keen to find a way to improve the energy efficiency of the pumping system.

Says Northern Foods' Engineering Manager Vernon Humphries: "We looked at various options from several companies".

"Inverter Drive Systems here in Nottingham was the only company that could offer a satisfactory turnkey solution".

"I don't have the engineering staff to tackle this project and Inverter Drive Systems could handle the whole thing, from investigating and justifying the project, to supplying, installing and commissioning".

Inverter Drive Systems, an ABB Drives Alliance partner, conducted a preliminary energy survey of the motors.

Once the project had been agreed with Northern Foods, Inverter Drive Systems removed the existing soft-start control panels and supplied three 55kW ABB industrial drives in control panels.

Also supplied by Inverter Drive Systems was a 4-20mA analogue temperature sensor connected to the inverter's integral PID controller, which uses the return temperature of the chilled water as its feedback signal.

When the plant is working hard, the requirement for chilled water increases and the pumps run faster.

When the plant is idling at weekends and holidays, the pumps run at a minimum speed, as the return temperature of the chilled water is already cool.

Installing the drives turned out to be a challenge.

All the services for the plant, including the chillers, are installed in the roof space, which meant lifting them 6m through a hatch in the roof from the production floor.

To save space, the inverters are side mounted inside the control panels.

The inverters were installed individually which meant no lost production time as two out of three ran at any one time.

Inverter Drive Systems also performed post-installation energy monitoring.

Average power reduction was found to be of 65.2% per pump, giving estimated energy cost savings per year of GBP 30,000 with a payback time of 10 months.

As well as the energy saving benefits, the system also provides accurate control of the chilled water temperature to the plant.

Says Humphries: "We are very pleased with the ABB drives and they have performed above expectations since installation".

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