Pumps and Hydraulics Practice Questions for Level 2 · Intermediate

1. Question 1

   A sludge pump's seal area becomes warmer while seal-water pressure falls below normal. What should the operator inspect first?

   1. Seal-water valve, strainer, tubing, and supply pressure.
   2. Pump suction valve, wet-well level, and vacuum gauge.
   3. Pump discharge valve, check valve, and pressure gauge.
   4. Motor current, coupling guard, and vibration trend.
   Show the answer

   Answer: A. Seal-water valve, strainer, tubing, and supply pressure.

   The paired seal temperature and seal-water pressure changes point directly to the seal-water path.

2. Question 2

   A primary-clarifier blanket rises while the sludge pump runs, but measured withdrawal flow falls and suction vacuum increases. What should the operator inspect first?

   1. Pump discharge valve, check valve, and force-main pressure.
   2. Collector torque, scraper movement, and drive condition.
   3. Suction piping, withdrawal valve, and possible obstruction.
   4. Feedwell distribution, surface loading, and influent pattern.
   Show the answer

   Answer: C. Suction piping, withdrawal valve, and possible obstruction.

   Higher suction vacuum with lower withdrawal flow indicates restriction before the pump.

3. Question 3

   A scum pump repeatedly loses prime while the collection pit contains adequate liquid. What should the operator inspect first?

   1. Discharge valve, check valve, and downstream pressure.
   2. Motor current, overload history, and speed command.
   3. Suction line, foot valve, fittings, and air leakage.
   4. Seal-water pressure, bearing temperature, and vibration.
   Show the answer

   Answer: C. Suction line, foot valve, fittings, and air leakage.

   Adequate pit level with repeated prime loss points first to air entry or loss of suction-side sealing.

4. Question 4

   Influent flow through a primary clarifier increases sharply while influent solids concentration and sludge withdrawal remain stable. Which immediate performance change is most likely?

   1. Primary-effluent suspended solids increase as settling opportunity decreases.
   2. Primary-effluent suspended solids decrease as surface overflow rate increases.
   3. Sludge blanket depth decreases because more detention time becomes available.
   4. Solids-removal efficiency remains unchanged because feed concentration is stable.
   Show the answer

   Answer: A. Primary-effluent suspended solids increase as settling opportunity decreases.

   Higher hydraulic loading reduces effective settling time and can carry more settleable solids into the effluent.

5. Question 5

   A variable-frequency drive lowers the speed of a centrifugal pump while system conditions remain otherwise similar. What response is generally expected?

   1. Flow decreases and discharge head decreases.
   2. Flow decreases and discharge head increases.
   3. Flow increases and discharge head decreases.
   4. Flow increases and discharge head increases.
   Show the answer

   Answer: A. Flow decreases and discharge head decreases.

   For a centrifugal pump operating in a similar system, reducing speed generally reduces both delivered flow and developed head.

Operator Master has 21 Level 2 · Intermediate pumps and hydraulics questions, free.

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