The pump's full performance test system is a full performance test bench that can accurately test all the performance parameters of the pump through precision instruments.
The national standard accuracy is Class B. The flow rate was measured with a precision worm gear flowmeter, and the lift was measured with a precision pressure gauge. The suction stroke was measured with a precision vacuum gauge. The power is measured with a precision shaft power machine. The speed is measured with a tachometer. The efficiency is calculated based on the measured value: n = rQ102. The characteristic curve of the pump, including the content and function. The curve representing the relationship between the main performance parameters is usually called the performance curve or characteristic curve of the centrifugal pump. The centrifugal pump performance curve is the external expression of the movement law of the liquid in the pump. The actual measurement is obtained. The characteristic curves include: flow-head curve (QH), flow-efficiency curve (Q-η), flow-power curve (QN), flow-cavitation curve (Q-NPSHr), and the performance curve is arbitrary for the pump. The flow point can find a set of heads, power, efficiency and NPSH values on the curve. This set of parameters is called the working state, which is called the working condition or working point, and the highest efficiency point of the centrifugal pump. The working condition is called the best operating point, and the best working point is generally the design operating point.
Generally, the rated parameters of the centrifugal pump, that is, the design operating point and the optimum operating point coincide or are close. In the practice selection efficiency range, that is, energy saving, and can ensure the normal operation of the pump, it is very important to understand the performance parameters of the pump. The NPSH of the pump, the suction stroke and the respective unit of measurement and the letter pump are generated at the inlet of the impeller due to a certain vacuum pressure. The vaporized bubbles move under the impact of the liquid mass, on the impeller, etc. The surface of the component is ablated, thereby destroying the components such as the impeller. At this time, the vacuum pressure is called vaporization pressure, and the NPSH is the excess energy exceeding the vaporization pressure per unit weight of liquid at the pump suction port. The unit is marked with meters and (NPSH)r. The suction stroke is the required NPSH Δh: the vacuum that the pump is allowed to absorb, that is, the allowable installation height of the pump, in meters. Suction stroke = standard atmospheric pressure (10.33 m) - NPSH - safety (0.5 m) The standard atmospheric pressure energy pipeline vacuum height is 10.33 m. For example: a pump must have a NPSH of 4.0 meters, and ask for a suction Δh? Solution: Δh=10.33-4.0-0.5=5.83m. Why should the outlet valve be closed when the centrifugal pump starts? When the centrifugal pump starts, there is no water in the outlet pipe of the pump, so there is no pipe resistance and lifting height resistance. After the pump is started, the pump head is very low and the flow rate is very large. At this time, the output of the pump motor (shaft power) is very large (according to the pump performance curve), and it is easy to overload, which will damage the motor and circuit of the pump, so it should be turned off at startup. The outlet valve is required for the pump to operate normally.
