Subtopic: Remedial measures against pump cavitation
Question Statement:
Which of the following practical measures will effectively increase $NPSH_A$ and suppress cavitation in an agricultural pump?
Options:
(A) Lowering the pump closer to the water sump surface (reducing static suction lift $h_s$)
(B) Increasing the diameter of the suction pipe to minimize friction losses
(C) Eliminating unnecessary sharp bends and elbows in the suction pipeline
(D) Operating the pump at water temperatures near boiling point
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. Lowering $h_s$ directly increases $NPSH_A = H_{atm} - H_v - h_s - h_{fs}$ (A is true).
2. Larger suction pipe diameter slashes velocity and friction loss $h_{fs} \propto 1/D^5$ (B is true).
3. Fewer fittings reduces minor losses in suction line (C is true).
4. Higher water temperature dramatically raises vapor pressure $P_v$, slashing $NPSH_A$ and accelerating cavitation (D is false).