Pumping Systems & Pump Selection Flashcards

A pump operating at a higher flow rate than its BEP is said to be running:

Answer: On the right side of the curve (toward runout)

Running to the right of the BEP (runout condition) results in reduced efficiency, increased NPSH requirements, and potential motor overload.

What is the purpose of a pressure relief valve on an irrigation pump discharge?

Answer: To protect the system from over-pressure caused by water hammer or valve closure

A pressure relief valve opens automatically when system pressure exceeds a set point, protecting pipes, fittings, and emitters from damage.

In a submersible well pump system, what determines the maximum practical depth for a single-stage centrifugal pump?

Answer: The pump's maximum shutoff head

A single-stage centrifugal pump can only lift water up to its shutoff head; for deeper wells, multi-stage submersible pumps are required.

The affinity laws for centrifugal pumps state that when pump speed doubles, flow rate:

Answer: Doubles

By the affinity laws, flow is directly proportional to speed: doubling RPM doubles GPM.

A variable frequency drive (VFD) on an irrigation pump motor is used primarily to:

Answer: Adjust pump speed to match system demand and save energy

A VFD modulates pump speed to maintain a target pressure or flow, reducing energy consumption significantly compared to throttling or cycling.

Water hammer in irrigation pipelines is best mitigated by:

Answer: Using slow-closing valves and/or pressure relief valves

Slow-closing valves reduce the rate of velocity change that causes pressure transients; pressure relief or surge relief valves absorb residual pressure waves.