Slow Rolling of Multiple Pump Motors at a Large Petrochemical Complex

Slow rolling of rotating equipment has been used for decades to prevent rotating parts such as shafts of large electric turbines, motors, pumps, and compressors from sagging or bending when not in operation. In industrial facilities, such as large petroleum processing plants, slow rolling is often used with stand-by pumps to prevent pump casing distortion and shaft bending. This paper covers an industrial application of a slow rolling scheme for up to two motors driven simultaneously utilizing a single Adjustable Speed Drive (ASD). The control system has been fully automated using a Programmable Logic Controller (PLC) interfaced with an upstream Distributed Control Systems (DCS). The scheme provides a cost-effective solution for multi-motor applications by reducing the number of ASDs required, minimizing the required footprint in the substation, improving energy efficiency by eliminating electric power conversion losses, and reducing the overall installation costs. Attention will be given to the control systems architecture, automated modes of operation, electrical configuration, and mechanical performance.