IA Pumping Systems & Pump Selection 2

Question 1

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

Accepted Answer

On the right side of the curve (toward runout)

Answer

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

Question 2

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

Accepted Answer

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

Answer

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

Question 3

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

Accepted Answer

The pump's maximum shutoff head

Answer

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

Question 4

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

Accepted Answer

Doubles

Answer

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

Question 5

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

Accepted Answer

Adjust pump speed to match system demand and save energy

Answer

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

IA - Irrigation Association Certification Practice Test