Inactive Thrust Position
Most rotors inside fluid machines have a net axial force acting on them that tends to “push” them in one axial direction or another. This axial force, also called the thrust load, results from an imbalance of all the internal axial hydraulic forces. Fluid machines are usually designed to have a predictable net thrust load for a given set of operating conditions. The thrust bearing face that is not expected to carry the axial load at normal load conditions is called the inactive thrust face. A rotor riding on the inactive thrust face is said to be in the inactive thrust position. The magnitude and direction of the thrust load can change as operating conditions are altered or as the machine wears. A rapid change in thrust position should always be investigated.