Testing procedure Calibration of rotary flow meter In order to measure the flow of water correctly, the rotary flow meter should be calibrated for different flow rates by recording the time required to fill the measuring tank. Performance of a centrifugal pump Before starting the test, the main storage tank was filled and the pump cavity was filled with water through a plug at the top of the pump (a foot valve was installed at the end of the suction pipe). The control valve on the discharge side of pump was closed. The inverter was adjusted to its lowest level (0 Hz). The pump was started and the inverter frequency slowly increased until the pump speed reached about 1,200 rpm based on the tachometer reading. The control valve at the pump discharge was opened slowly to obtain the desired flow rate as shown by the rotary flow meter. The water was allowed to flow for 2-3 min until steady conditions were observed. The 3-way valve was adjusted to let the water flow from the discharge pipe and the
drain valve of the measuring tank was opened to drain the water into the main storage tank until the water was at the lowest level in the measuring glass tube. The drain valve was closed and the highest level of water in the glass tube was recorded.