Electric tractors save energy at Astra car plant 13 December 2010

General Motors says has saved energy, improved productivity and optimised line-side delivery operations at its Astra cars manufacturing plant in Ellesmere Port by switching to electric tow tractors.

Richie Mellor, senior engineer at the worldwide facilities group, Ellesmere Port, states that the tractors are powered by Hawker batteries from EnerSys, and replace gas-powered units.

"We can use the new tractors right through the shift to deliver parts to the production line, without any disruption to the operations," he says. "EnerSys and the tractor manufacturer have supplied us with a complete package that met our specification, delivered operational benefits and a number of savings."

Mellor explains that, as part of the plant's ongoing investment programme, it approached a number of suppliers and, after testing equipment on site for a year, decided on a combination of 25 Linde P602 tow tractors and Hawker batteries with LifeSpeed high speed chargers.

The choice of battery and charger was crucial to the project, he says, because these allow the trucks to be top-up charged for short periods during scheduled work breaks, to maintain enough power to operate right through the shift.

"This saves a lot of time each day," says Mellor. "With the old tractors it took around 10 minutes to leave the working area to replace the gas bottle but with the new electric tractors we don't need to do this."

One disadvantage in switching from gas to electric power was the wiring needed to supply the chargers. Mellor concedes that there was a cost, but estimates it is saving around 50% on fuel, which will offset the investment well within the lifetime of the tractors and batteries, even without taking into account savings in maintenance, cleaning and heating.

As for the location of the chargers, Mellor explains that the Astra plant's kanban operation relies on tractors working in dedicated store areas to feed specific parts of the line. Hence, the most efficient position was adjacent to the storage racking.

For dolly delivery, where the trucks are wider-roaming, the more efficient option was to group charging points close to where the drivers take their breaks. This, he says, maximises the amount of time available for charging.

Brian Tinham

Related Companies
EnerSys Ltd
Linde Material Handling (UK) Ltd

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