Danfoss cuts costs on pump operation

01 June 2007

An automotive gearbox manufacturer claims to have cut costs by £17,000 a year by reducing energy consumption of pumps driving its machine tool cooling fluid circuits.

Wyko, a Danfoss Drives Partner, conducted an energy survey of the machine tool coolant circuits which feed the machine shops with coolant solution. Wastewater is mixed with oil to create a low viscosity cooling solution that is sprayed over the cutting edges. This cooling emulsion is pumped round the machine shops to feed the various machine tools. There is a low pressure ring operating at approximately three bar pressure. Some high volume production tools require substantially more coolant than others do. A four bar pressure ring, boosted by a second pump feeds these particular tools. Both the 37kW low-pressure and 30kW booster pump motors were being run continuously at full, fixed speed.

The survey and measurements conducted by Wyko revealed that the 37kW pump, running continuously at full speed, was itself delivering in excess of the high pressure requirement, meaning the low pressure ring was over-pressurised, while the high pressure pump, working and absorbing energy, was not contributing in any meaningful way.

The system was retrofitted with Danfoss VLT 8000 AQUA drives. Danfoss 4-20ma pressure transducers were fitted to both low and high pressure rings, immediately on the output of the pumps. This controlled the pressures at the design level, irrespective of coolant demand on the shop floor, and the integral PID controllers within the drives were set up using Danfoss’ MCT10 programming software. Danfoss claims that total installation and commissioning barely disrupted production and added minimal costs to the project.

The manufacturer said that results had exceeded predictions. Annual running costs fell to £7.5k, a saving of over 70%, delivering a financial payback in less than 8 months.

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