otal head is the pressure available out of the pump that result from the change in the mechanical input energy into kinetic and potential energy, i.e. the energy that the pump transfers to the liquid. On the pump curve, the total head is the difference between the discharge head and the suction head. The total head for a liquid is dependent on rotation speed and capacity. Thus, the total head for is independent of the fluid that is being pumped and is constant for different fluid under the same capacity and rotational speed. The total head, as seen in Figure 2, decreases as the capacity increases.The efficiency of the pump can be obtained from the brake horsepower, the power required by the pump or the horsepower input to the pump, and the liquid horsepower, energy delivered by the pump to the fluid. As seen in the theoretical performance curve in figure one, the pump efficiency increases as the capacity of the pump increases.The net positive suction head (NPSH) is the absolute pressure available at the pump suction flange and is above the vapor pressure of the liquid. The NPSH ensures that sufficient head of the liquid at the entrance of the pump impeller is present to overcome internal flow losses of the pump. This allows the pump to operate free of vapor bubbles created by the boiling action of the liquid.Figure 2: Theoretical Pump Performance CurveTo study the performance of the motor, the following parameters are studied: current to the motor, motor shaft rotational speed, motor efficiency, and the power factor against the load. The current supplied to the motor is the current that would be supplied if the voltage were at the rated voltage of the motor. The motor efficiency is the ratio of the HP output from the motor to the HP input to the motor. Figure 3 shows the theoretical trends of the motor performance curves.A friction factor chart represents friction versus Reynolds number for a wide range of roughness parameter...
