Limits on suction lift: The achievable suction lift of a centrifugal pump depends primarily on which factors?

Introduction / Context:
The maximum suction lift of pumps is limited by available Net Positive Suction Head (NPSH), which is a function of ambient conditions and hydraulic losses. Misjudging these factors leads to cavitation and performance loss.

Given Data / Assumptions:

• Pump drawing water from a sump via a suction line.
• Standard atmospheric conditions unless otherwise stated.

Concept / Approach:
NPSH available = (atmospheric head − vapour pressure head) − static suction lift − entrance/friction losses − velocity head at pump eye. Higher atmospheric pressure increases available suction head; higher water temperature raises vapour pressure and reduces margin; higher velocities and friction losses reduce available head at the impeller eye.

Step-by-Step Solution:
Account for atmospheric pressure: sets absolute ceiling on suction head.Account for water temperature: vapour pressure increases with temperature, lowering allowable lift.Account for velocity and friction: losses in suction line reduce pressure at pump inlet.Conclusion: all listed factors govern suction lift.

Verification / Alternative check:
Applying the NPSH formula confirms changes in any of these variables alter cavitation margin and thus safe suction lift.

Why Other Options Are Wrong:
Considering only one factor leads to incorrect prediction of permissible suction conditions; the phenomenon is multi-factorial.

Common Pitfalls:

• Placing pumps far above water level and ignoring summer temperature effects.
• Using undersized suction lines causing high entrance/pipe losses.

Final Answer:
all the above