Level 4 · Expert sample questions
5 free sample questions on pumps and hydraulics for the Level 4 · Expert wastewater treatment operator exam. Try each one, then open the answer to check your work.
At peak flow, three influent pumps run at 55% speed and deliver 9 MGD using 210 kW. A controlled test shows two pumps at 78% also deliver 9 MGD using 165 kW, with stable wet-well level and required minimum pump flow. What change should be evaluated for normal peak operation?
Answer: B. Stage two pumps and verify level and energy use
The test delivered the same flow with stable level, acceptable pump flow, and 45 kW less demand. A controlled two-pump staging change should be verified under normal peaks before it becomes the standard sequence.
A duty sludge pump develops strong discharge pulsation after maintenance. Average flow is normal, the relief setting is unchanged, the discharge check valve passes, and dampener charge is near zero. A standby pump is available. What is the best plan?
Answer: B. Transfer duty and restore the dampener charge
The standby allows safe isolation, while restoring the failed dampener and verifying pressure protection addresses both the fault and return-to-service risk.
A variable-speed influent pump shows scattered vibration readings, but the readings were taken at different speeds and flows. Management wants a trend that can support planned maintenance without waiting for an alarm. What should the reliability program do?
Answer: C. Trend matched-duty vibration readings and spectra against the pump's baseline at consistent speed and flow.
Readings taken at comparable duty points make a real change easier to separate from normal speed and load effects, and spectra help identify the changing fault pattern. It is like comparing fuel use on the same route instead of mixing city and highway trips. A trends unlike conditions before checking an alarm value, B compares readings taken at unmatched conditions, and D builds a moving baseline from mixed duties and delays investigation.
Three duty pumps still meet station flow, but only one can be removed during a planned outage. Pump 1 has elevated vibration that has stayed stable for six months; a check found correctable soft foot. Pump 2 bearing-envelope vibration doubled in two weeks, and ferrous debris in its oil is increasing. Pump 3 efficiency is down 10%, with stable vibration and high wear-ring clearance. Which work should be done first?
Answer: D. Inspect and overhaul Pump 2 bearings
Two approved tubing types are tested in a peristaltic phosphorus-feed pump. Type 1 costs less but loses 15% output after three days and needs weekly replacement. Type 2 holds calibration for four weeks at the same pressure and chemical strength. Both meet the pump rating. What should control the selection?
Answer: D. Use verified tubing life and total operating cost
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