AC power dynamometer provides the system power, drive the diesel engine fire pump work, and the experimental data is transmitted to the measurement and control system in real time. Through the acquisition, including rated conditions, three different operating points pump flow, rotational speed, inlet pressure value, impeller pressure value, the atmospheric pressure value, the experimental temperature etc. the data calculation, each operating point of the pump NPSH and impeller head value is obtained. To the impeller head value dropped to no cavitation head value of 3% of NPSH as judge standard of critical cavitation allowance, drawing three conditions under the critical NPSH discriminating curve, and then draw the diesel fire pump cavitation characteristic curve, and according to the allowable suction pipe line of hydraulic
