A Refinery in Oklahoma, having been experiencing capacity problems with its charge pump, called in Pumping Machinery, LLC, to increase pump capacity. After increasing production requirements in 1998, the steam turbine-driven United TCM-B centrifugal pump, installed in 1953, was unable to cope. The refinery hoped to avoid replacing the pump completely, and after six years of trying to increase the capacity, unsuccessfully, the refinery contacted Pumping Machinery, LLC. Based in Atlanta, GA, USA, Pumping Machinery, LLC is a consulting company, specializing in solving tough pump problems, troubleshooting, training and upgrades. The analysis revealed multiple issues. The volute design was limiting the flow, and the impeller inlet was causing cavitation and NPSH problems, starving the pump above 400 gpm. It was then decided to modify the impellers and the volute, thus simultaneously solving a volute capacity limitation, as well as improve impeller NPSH characteristics. Modifications have proven effective, and, after the pump was brought on-line, it ran at a higher flow then it ever had, smoothly and quietly without NPSH problems.