Engineeringtalk.com reported that steel manufacturer Corus Colors has reduced the energy consumption of one of its hydraulic systems by 70% by installing an ABB variable speed drive. The hydraulic system used during the trial is located on a production line used for retreating and inspecting strip material, driving actuators and web guiding systems in a 24 hour process.
Hydraulic systems typically waste much of their energy because an amount of fluid circulates at all times, although the work is only carried out in short bursts. In addition, the pressure for the hydraulic system is normally provided with a positive displacement pump, a type of pump that offers far less potential to save energy than the more common centrifugal pump.
Corus Colors, with the help of Phil Tomkinson from Radway Control Systems, saved energy by retrofitting the existing system with a variable speed drive. The pump speed was reduced when the system was in neutral and during actuation of the cylinders. When in neutral, power consumption was initially around 9kW. Under drive control, power consumption was reduced to 2kW, a reduction of 77%.
The reduced energy consumption will allow a payback time of just 18 months and reduce the company's carbon footprint by 33 tonnes of CO2 a year. The reduction in energy consumption under load initially surprised Corus's engineers, as it should take the same amount of energy to move a hydraulic cylinder a given distance, regardless of whether a drive or direct on line operation is used.
However, further tests showed that the drive used a lower motor speed to achieve the required pressure. The drive automatically adjusts the pump speed to maintain system pressure. Pressure feedback is returned to the drive from a transducer.
The ABB industrial drive supplied by Radway Control Systems has built in PID control that helps keep external values, such as pressure, under control. The desired system pressure is 90bar. As in all hydraulic systems, the on load times are short.
(Sourced from www.engineeringtalk.com)
