Required net positive suction head NPSHr for centrifugal pumps
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Generally, the required net positive suction head ratio NPSHr for centrifugal pumps is determined through testing. So, how is the NPSHr value on the centrifugal pump curve provided by pump manufacturers to the design agencies obtained? By the time the final data in the form of that pump curve is submitted, the pump has not yet been put into operation. Please provide an explanation. Thank you!
1. The pump manufacturer has produced a similar pump, and therefore knows the NPSH value for that pump. 2. The manufacturer has its own design software or empirical values. 3. What is provided to the design institute are approximate values
The value provided by the design institute is the design value; the manufacturer selects the appropriate model based on these parameters. If a NPSH test is required, the measured NPSHr is compared with the value given by the design institute – if it is ≤ the value specified by the design institute, then it is considered acceptable.
The manual states that it was obtained by the pump manufacturer using clean water at 20°C for testing