Essential Series on Pump Selection and Piping(1)

I. Basic Basis

1. Flow rate is one of the key performance parameters for pump selection, directly impacting the overall production and pumping capacity of the entire system. In process design by design institutes, three flow rates—normal, minimum, and maximum—are typically calculated. When selecting a pump, the maximum flow rate serves as the primary basis, while the normal flow rate is also considered. If the maximum flow rate is unavailable, it is common practice to set it at 1.1 times the normal flow rate.

2. The required head for the device system is another crucial performance parameter for pump selection, and the head should typically be chosen with a 5%~10% margin.

3. Liquid properties, including the name of the liquid medium, physical properties, chemical properties, and other characteristics. Physical properties encompass temperature, density, viscosity, the diameter of solid particles in the medium, and the content of gases, which are relevant to the system's head, net positive suction head calculation, and the selection of appropriate pump types. Chemical properties primarily refer to the corrosiveness and toxicity of the liquid medium, serving as a crucial basis for selecting pump materials and determining the type of shaft seal.

4. The pipeline arrangement conditions of the system refer to the liquid delivery height, delivery distance, delivery direction, the minimum liquid level on the suction side, the maximum liquid level on the discharge side, as well as pipeline specifications, lengths, materials, pipe fitting specifications, and quantities, in order to perform system head calculation and net positive suction head (NPSH) verification.

5. The operational conditions involve numerous factors, such as the operating temperature of the liquid, the saturated vapor pressure, the suction side pressure (absolute), the discharge side container pressure, altitude, ambient temperature, whether the operation is intermittent or continuous, and whether the pump is fixed or mobile in position.