Question

The amount of energy required to move the water into the eye of an impeller is called as

• A. Net positive suction head required
• B. Net positive suction head available
• C. Total energy head
• D. Pressure head

Hint:

NPSHR = Energy required by the pump design.
NPSHA = Energy available from installation system. To prevent cavitation: $\text{NPSHA} > \text{NPSHR}$.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Net Positive Suction Head (NPSH) is the absolute total hydraulic head required at the suction flange to prevent cavitation.
Key Formula or Approach:
\[ \text{NPSHA} \ge \text{NPSHR} + \text{Safety Margin (0.5--1.0 m)} \]

Step 2: Detailed Explanation:
In centrifugal pump hydraulics:
1. Net Positive Suction Head Required (NPSHR): The minimum absolute hydraulic energy head (above the liquid vapour pressure) required by the pump design at the suction eye to overcome friction, entrance turbulence, and impeller blade acceleration without causing localized liquid vaporization (cavitation). It is an intrinsic characteristic of the pump design specified by manufacturers.
2. Net Positive Suction Head Available (NPSHA): The actual absolute suction head provided by the external suction piping system.

Step 3: Final Answer:
Thus, the energy required by the pump to draw water into the impeller eye is Net positive suction head required, matching option (A).