Gearbox Manufacturer Saves GBP 17,000 a Year

Gearbox Manufacturer Saves GBP 17,000 a Year A major automotive gearbox manufacturer has realised energy savings of over GBP 17,000 per annum on the pumps driving one of its machine tool cooling fluid circuits. The local branch of Wyko, a Danfoss Drives Partner, was recently called upon to conduct an energy survey of the machine tool coolant circuits which feed the machine shops with coolant solution. Waste water is mixed with oil to create a low-viscosity cooling solution that is sprayed over the cutting tools to cool and lubricate the cutting edges, thereby prolonging their lives. This cooling emulsion is pumped round the machine shops to feed the various machine tools.Some high-volume production tools require substantially more coolant than others. A low-pressure ring operates at approximately 3 bar, but fed off that, there is also a 4 bar high-pressure ring, boosted by a second pump, feeding the high-volume production machines. 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 that 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 operational in that it was delivering coolant to the machines but could not have been said to have been working within design parameters. Wyko identified that retrofitting Danfoss variable speed drives with pressure control feedback from the cooling circuits would bring the system under control and save sufficient energy to easily recoup the investment within one year.The system was retrofitted simply and quickly with new Danfoss VLT 8000 Aqua drives. Their compact size meant they fitted comfortably into the existing control cabinet and were easily integrated into the system, leaving the existing star / delta starters as an emergency bypass facility. Danfoss 4-20mA pressure transducers were fitted to both low and high-pressure rings, immediately on the output of the pumps, to control the pressures at the design level, irrespective of coolant demand on the shop floor, and the integral PID controllers within the drives were quickly set up using Danfoss' MCT10 programming software. Total installation and commissioning barely disrupted production and added only minimally to the project cost.When commissioned the results exceeded predictions.Annual running costs fell to a projected GBP 7500, a saving of over 70%, delivering a financial payback in less than eight months. As energy costs continue to rise, even greater savings will continuously be delivered to the plant's bottom line and the savings represent a significant carbon reduction in the fight against global warming.