No over-load centrifugal pump is able to shut down in the head to the zero head range of any operating point of operation, are not overloaded or burnt due to overload the prime mover centrifugal pump, and at the point, the pump power reserve factor K≈ 1.0. Without overload centrifugal pump can also be called full head pump, full flow pump, with generalized saturated shaft power characteristics of the centrifugal pump, the shaft power of the extreme centrifugal pumps. Can be seen that the essence of non-overload centrifugal pump, the pump shaft power curve peak or shaft power with the flow rate increases and have smaller changes, the shaft power curve is relatively flat, so that the pump shaft power in the dead head to zero Head (ie from zero flow to maximum flow) are less than or equal to the prime mover's power. Abroad, although there was a company that produced no-load centrifugal pump as early as the beginning of this century, that is, a centrifugal pump with a saturated shaft power, no overload pump has not been widely produced and used under the environment of focusing on pump efficiency and size. In recent years, with the development of science and technology and the increasing awareness of reliability, in many applications, in order to improve the reliability of operation, people once again attach importance to this type of centrifugal pump with saturated shaft power. Matching single units should take into account the maximum power and safety margins that may be present in the pump in order to meet frequently varying or adverse operating conditions and an increase in shaft power due to efficiency over long periods of time. China's research on no-load centrifugal pump is in the initial stage, there is no mature hydraulic model, there is no mature design methods and procedures.