Is it necessary to provide an effective net positive suction head?
Thread Content
When selecting a pump, one of the factors to consider is the effective net positive suction head. Each pump has a required net positive suction head; therefore, shouldn’t the user provide the effective net positive suction head, so that the manufacturer can check whether the difference meets the requirements? But the manufacturer said we don’t need to provide it. . . . . . So does our user group or the design department need to provide this important parameter?
It is advisable to provide media that are easy to vaporize or special operating conditions! Generally, as long as there is inlet pressure and temperature, there’s no problem!
The value of NPSHa must be provided by the user or the design institute.
The NPSHa design institute can provide the most accurate value directly; or it is possible to approximate the value by using the inlet pressure, the vaporization pressure of the medium at the operating temperature, and the specific gravity of the medium.
The effective net positive suction head available, NPSHa, is provided by the designer to the pump supplier after taking into account the layout of the equipment and pipelines. Before shipping the pumps, the pump supplier can only determine the required net positive suction head, NPSHr, by conducting tests with clean water. The designer should require that the NPSHr of the pump be less than NPSHa; the detailed calculation method for NPSHa is specified in HG/T-20570.5 \"Calculation of System Characteristics of Pumps\"