Trelleborg overhauls energy inefficient hydraulic power packs

10 August 2010

An aerospace manufacturer claims to have cut its energy bill by £12,000 (€14,000) after implementing ABB variable speed drives. Trelleborg Sealing Solutions has designed the drives into hydraulic systems at its Burton-on-Trent, UK plant.

The company manufactures solutions and products that seal, protect and dampen vibrations in a wide range of industries, including sealing products for both civil and military aircraft.

Staff had pinpointed high energy use in the hydraulic power packs, which supply hydraulic fluid to a number of presses used to bond fabric to rubber.

The hydraulic pressure in the system is maintained by a motor where if the presses had no demand for hydraulic power, the motors would simply continue to build the hydraulic pressure. At a certain point, known as the unload value; the pressure would need to be relieved. The motors would be switched to recirculating the hydraulic fluid in the system resulting energy wastage as the motors were doing no useful work in this phase.

Andy Lamb, process, facilities and safety manager at the plant, contacted ABB Drives Alliance member Inverter Drives Systems (IDS) to investigate and prove how variable speed drives could improve the system’s energy use: “We had been challenged to save 10 percent on our energy costs and felt that variable speed drives could help us achieve this,” said Lamb.

IDS performed an energy appraisal on the power pack installation, which uses four 18.5 kW motors. The motors run for 126 hours per week and 51 weeks per annum. Monitoring over a week gave a calculated energy consumption of 15.8 kW, using a power factor of 0.75. Based on a figure of nine pence per kWh, this equates to an annual consumption of £9,137 per motor, or £36,551 for all four motors.

To improve these costs, IDS installed four 18.5 kW ABB standard drives to automatically maintain the system pressure just below the system unload value, using a pressure transducer to feed back to the drive’s internal PID control. Energy savings achieved on this application are £2,742 per motor, or £10,960 for the four motors, with a payback time of 11 months.

A further power pack had an average power consumption was 7.1 kW. With half of its time spent unloading and half loading, the machine cost £4,100 per year in electricity.

The energy use was also monitored over a week, during which time average energy consumption was recorded as 4.8 kW, a saving of 2.3 kW or 30 percent. This gave an annual cost saving of £1,230 with a payback time of 18 months.

This gives a total energy saving for both applications of over £12,000 a year.

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