Time to belt up and save energy
December 1st 2007

A factory's plan to save energy by upgrading from v-belts to timing belts on air handling drives has been expanded to include a wide range of automation equipment.This has cut €140,000 from the annual energy bill, improved the working environment and suggested further savings

Stryker Orthopaedics manufacture a range of orthopaedic implants,bone cements and bone substitute materials at it's facility in Limerick, Ireland. Like many other companies it has become increasingly aware of energy cost increases and has undertaken several initiatives to reduce energy usage/costs and to protect the environment.

Maintenance manager Robert McKillican calculated that changing from v-belts to timing belts would reduce energy consumption by about 10% and called in Michael Dineen of Dickson Bearings to discuss the idea.

It was soon realised that slippage of the v-belts gave a soft starting effect,which would be lost with a toothed belt.The two briefly considered the use of electronic soft starts, but soon decided that variable speed drives would be better because they could be used to tune the air handling to exactly match demand.

The plant's eight extraction fans all worked quite hard to ensure complete extraction of dust particles.

Initial calculations suggested that significant energy savings could be made if each were tuned to exact local demand, rather than run faster than necessary.Additionally, staff numbers and production levels vary during Stryker's two-shift day so there was potential to further slow down the air handling at different times throughout the shifts.

There were a number of practical issues to be addressed, not least which drive to use.Michael recommended the L300P Series from Hitachi, three at 55kW and five at 37kW, which are suitable for fan drive applications.

Meanwhile Robert was unearthing some practical considerations.The control panels, for instance, had to be designed to fit into a small control room.As they would be close to some sensitive equipment, chokes would be required on every input and output to minimise noise generation and harmonics onto the mains.With the Hitachi drives it was also possible to set a maximum total output, so that penalty charges from the electricity supplier could be avoided. A PLC would be required to control the system, and it seemed logical to stick with Hitachi and use an EH150 series.This communicates with the plant's existing building management system to make the whole installation interactive.

Finally it was realised that security staff as well as control engineers would need access to the system.

Therefore it was decided to install two touch screen HMIs, again Hitachi, one in the control room the other in the security office, and to use clear graphical displays to make use as intuitive as possible.

Within days of completing the installation, energy meters strategically located around the system were confirming that considerable savings were being made.No detrimental effect on machine performance or other production compromises were identified. Initially the drives were configured to give the fans three set speeds, but the intention is to upgrade this with PID pressure sensor feedback so that load matching becomes exact.

"For many years we were able to ignore energy issues, but once we started monitoring usage our attitude changed completely," says Robert McKillican.

"This is now filtering out to the whole workforce. The lesson is that monitoring energy consumption leads to a constant drive for more savings."