YB Series self priming rotary vane pump with internal by-pass valve . The pumps use a rotor with sliding vanes to draw the liquid. The material of construction is nodular iron with sliding vanes built in a special self lubricat-ing material Due to its efficiency the pumps can handle viscous and also volatile liquids and require less horsepower than other equivalent pumps. The pumps are capable of higher flow-rates at lower number of revolutions than other designs.