A major pumping systems used in refineries is overhung centrifugal pump. Some of them, which were manufactured before 80 s, are still being used in refineries in Brazil. Usually theses equipments have flexible rotors since the ratio L/D is high and the packing, that offers stiffness, was replaced by mechanical seals in order to get more safety. As consequence, the dynamic response of these pumps is very sensitive to any variation of the wear ring clearance.Weariness due to erosion and surfaces in contact increase the diametral clearance of the wear ring, that increases the vibration and reduces the efficiency of the pump since the flow through the seals rises. So, in order to solve these two concerns (vibration and efficiency) this study investigated the feasibility of replacing the static ring by the floating wear ring through rotordynamic analyses using the following software: ROMAC and XLTRC2. Floating wear ring reduces the erosion and increases the efficiency of the pump since it permits to minimize the radial clearance. The disadvantage of using floating wear ring is that each one has to be designed for a specific operation condition.