WTO Equipment Maintenance & Troubleshooting 2 — Questions and Answers
Question 1: A centrifugal pump is experiencing cavitation. Which symptom is most characteristic of this condition?
- Steady high discharge pressure
- Rattling or crackling noise with fluctuating flow (Correct answer)
- Overheating of the motor windings
- Excessive seal leakage
Correct answer: Rattling or crackling noise with fluctuating flow
Cavitation causes vapor bubbles to collapse violently, producing a rattling or crackling noise accompanied by erratic flow and reduced pump efficiency.
Question 2: When performing a routine inspection of a chemical metering pump, the operator notices the diaphragm is cracked. What is the appropriate immediate action?
- Continue operation at reduced feed rate
- Replace the diaphragm before resuming chemical feed (Correct answer)
- Seal the crack with epoxy and monitor closely
- Switch to gravity feed as a temporary measure
Correct answer: Replace the diaphragm before resuming chemical feed
A cracked diaphragm will leak chemical and deliver inaccurate doses, so it must be replaced immediately before the pump is returned to service.
Question 3: Which type of valve is best suited for throttling flow in a water treatment plant pipeline?
- Gate valve
- Globe valve (Correct answer)
- Ball valve
- Check valve
Correct answer: Globe valve
Globe valves are designed for throttling because their disc and seat arrangement allows precise flow control with minimal turbulence.
Question 4: A turbidity meter at the filter effluent is reading consistently higher than expected. Which maintenance step should be performed first?
- Backwash the filter immediately
- Clean and calibrate the turbidimeter using standards (Correct answer)
- Increase coagulant dosage
- Replace the filter media
Correct answer: Clean and calibrate the turbidimeter using standards
Before making operational changes, the turbidimeter should be cleaned and verified with calibration standards to confirm the reading is accurate.
Question 5: What does a high amperage reading on a pump motor most likely indicate?
- The pump is running below its design flow
- The impeller is oversized or there is mechanical binding (Correct answer)
- The suction head is too high
- The discharge valve is fully closed
Correct answer: The impeller is oversized or there is mechanical binding
High amperage indicates the motor is working harder than normal, which can result from an oversized impeller, mechanical binding, or excessive back pressure.
Question 6: A pressure gauge on the filter influent line reads zero during normal operation. What is the most likely cause?
- The filter is operating at design capacity
- The gauge is faulty, clogged, or the isolation valve is closed (Correct answer)
- Inlet pressure has been deliberately reduced
- The filter backwash cycle is active
Correct answer: The gauge is faulty, clogged, or the isolation valve is closed
A zero reading on an in-service pressure gauge typically indicates a faulty gauge, a plugged gauge connection, or a closed isolation valve rather than true zero pressure.
Question 7: Which lubrication practice is recommended for most water treatment pump bearings?
- Lubricate as frequently as possible to prevent wear
- Follow the manufacturer's schedule and avoid over-greasing (Correct answer)
- Use only water-soluble lubricants for potable water applications
- Lubricate only when bearing temperature exceeds 200°F
Correct answer: Follow the manufacturer's schedule and avoid over-greasing
Over-greasing can damage seals and cause overheating; manufacturers' lubrication schedules are designed to provide adequate protection without excess.
WTO Equipment Maintenance & Troubleshooting 2
A centrifugal pump is experiencing cavitation.
Which symptom is most characteristic of this condition?