ABC Pumping Systems and Hydraulics 3

Question 1

When installing a vertical turbine pump in a wet well, the minimum submergence of the intake bell should be maintained primarily to prevent:

Accepted Answer

Air entrainment and vortexing

Answer

Insufficient submergence allows air vortices to form at the intake, causing air entrainment that can lead to cavitation and loss of prime.

Question 2

A pump's best efficiency point (BEP) is important because operating far from BEP causes:

Accepted Answer

Increased radial thrust, bearing wear, and reduced pump life

Answer

Operating far from BEP increases radial hydraulic forces on the impeller shaft, accelerating bearing and seal wear and shortening pump life.

Question 3

In a series pump configuration, what happens to the total head and flow compared to a single pump?

Accepted Answer

Head doubles, flow remains approximately the same

Answer

Pumps in series add their heads at the same flow rate, allowing the system to overcome higher total head while flow stays approximately constant.

Question 4

Which formula correctly expresses hydraulic horsepower (WHP) for a pump?

Accepted Answer

WHP = Flow (gpm) × Head (ft) / 3,960

Answer

Water horsepower is calculated as WHP = (Flow in gpm × Head in feet) / 3,960, derived from unit conversions of flow, pressure, and power.

Question 5

A pump experiencing excessive vibration and noise is most likely suffering from which problem?

Accepted Answer

Impeller wear ring clearance that is too large, or cavitation

Answer

Worn impeller wear rings or cavitation cause hydraulic imbalance and bubble collapse that produce vibration and noise in centrifugal pumps.

(ABC) Association of Boards of Certification Practice Test