Francis vane impellers consist of double-curvature vanes extending over the full vane surface. They have a characteristic between the radial and mixed flow classes. This impeller is a most popular impeller shape with a specific speed between 1500 and 4000. Inlet losses are reduced and high suction lifts are capable as a result of this Francis vane impeller design. In high temperature pumps, fully enclosed Francis vane impeller design is keyed to the shaft and secured by an impeller bolt and washer to remain rigidly in place under all load conditions. The design is hydraulically balanced to extend bearing and seal life.