Question

At which of the following conditions is it easy to control Net Positive Suction Head (NPSH) of a centrifugal pump?

• A. \(\text{greater than the vapour pressure of the liquid}\)
• B. \(\text{less than the vapour pressure of the liquid}\)
• C. \(\text{equal to the vapour pressure of the liquid}\)
• D. \(\text{less than barometric pressure}\)

Hint:

To avoid cavitation, always ensure NPSH>vapour pressure of the liquid.

Answer 1

The Correct Option is A

Step 1: Understanding Net Positive Suction Head (NPSH).
- NPSH is a measure of available pressure above the liquid’s vapour pressure.
- For proper pump operation, NPSH must be greater than vapour pressure to prevent cavitation.
Step 2: Explanation of incorrect options.
- (B) and (C): If NPSH is less than or equal to vapour pressure, cavitation occurs, damaging the pump.
- (D): Less than barometric pressure is irrelevant to NPSH control.
Step 3: Selecting the correct option. Since NPSH must be greater than vapour pressure to prevent cavitation, the correct answer is (A) greater than the vapour pressure of the liquid.