ABB drives halve Pfizer pump energy costs on chiller plant 01 October 2010

Pfizer is reporting savings of €28,000 a year on electricity costs for chiller applications at its Ringaskiddy plant, in Ireland, since installing variable speed drives.

Sean Lee, of energy consultancy EMSA, says that Pfizer had identified its plant chillers as prime targets for improving energy efficiency, because of the then fixed-speed circulation pumps that manage heat transfer fluid to and from the plant's cold storage tank.

Lee explains that an energy appraisal found that the application included three 45kW motors and one 37kW motor, all with soft starters. For best efficiency of the process, however, the pumps needed to maintain a constant flow rate of 185m3/hr, but the pumps were rated for 240185m3/hr – so gate valves were being used to throttle the pumps.

"In conjunction with Pfizer Process Engineering, we decided that the best way of achieving both the optimum flow and energy saving was to open the valves fully and use variable speed drives to maintain the optimum flow. We found that we could achieve the desired flow rate by running the motors at 35Hz, rather than 50Hz."

EMSA used ABB's Pumpsave energy saving calculation programme, which predicted an energy saving of 50% per motor, with cost savings for each motor of around €7,200 per year. Based on a running time of 4,360 hours, this would give a payback time of two and a half years.

ABB partner integrator carried out the work, installing and commissioning new ABB variable speed drives and new, high efficiency ABB EEx de IE2 motors, which were laser aligned with the pumps.

Says Lee: "Reliability will also be improved as high efficiency motors are less likely to break down and also should not require rewinding or need their bearings replaced for many years. Their cooler running temperature will also mean less mechanical stress."

Brian Tinham

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