WTT Preventive Maintenance Procedures 3 — Questions and Answers
Question 1: During a tower interior inspection, a technician finds corrosion on the internal flange surfaces. What is the first corrective action?
- Immediately decommission the tower
- Document with photos, remove corrosion, apply approved coating, and report to engineering (Correct answer)
- Paint over corrosion without removal
- Ignore if corrosion is less than 10mm deep
Correct answer: Document with photos, remove corrosion, apply approved coating, and report to engineering
Proper corrosion remediation requires documentation, mechanical removal, application of an approved protective coating, and engineering notification for structural evaluation.
Question 2: Which instrument is used to verify insulation resistance of the generator windings during PM electrical inspections?
- Clamp meter
- Megohmmeter (megger) (Correct answer)
- Oscilloscope
- Multimeter set to AC volts
Correct answer: Megohmmeter (megger)
A megohmmeter applies high voltage to measure insulation resistance in megaohms, revealing moisture intrusion or winding degradation.
Question 3: What is the minimum safe distance a ground crew member should maintain from a wind turbine during rotor rotation when ice shedding conditions exist?
- 1.5× rotor diameter
- Rotor diameter + hub height (Correct answer)
- 50 meters
- 10 meters
Correct answer: Rotor diameter + hub height
Ice throw distance calculations typically use rotor diameter plus hub height as the minimum exclusion zone during icing conditions.
Question 4: During PM, a technician checks the cooling system of a liquid-cooled generator and finds coolant level low. What should be done before adding coolant?
- Add coolant immediately and document
- Inspect for leaks, identify and repair the source, then refill to specified level (Correct answer)
- Drain and refill the entire system
- Only top off if below the minimum mark by more than 20%
Correct answer: Inspect for leaks, identify and repair the source, then refill to specified level
Low coolant always indicates a potential leak; the source must be identified and repaired before refilling to prevent recurrence and coolant loss.
Question 5: What does checking 'backlash' in a wind turbine yaw drive gearbox assess?
- Yaw motor current draw
- The amount of play between meshing gear teeth (Correct answer)
- Yaw brake holding force
- Number of yaw errors in the SCADA log
Correct answer: The amount of play between meshing gear teeth
Backlash is the clearance between mating gear teeth; excessive backlash indicates gear wear that can cause imprecise yaw control and increased impact loading.
Question 6: A PM checklist requires verifying that all nacelle emergency exit hatches open freely. Why is this critical?
- To allow drone inspections
- To ensure technicians can evacuate quickly in a fire or emergency (Correct answer)
- To verify hatch seal integrity for weather exclusion
- To comply with noise emission standards
Correct answer: To ensure technicians can evacuate quickly in a fire or emergency
Emergency egress must be unobstructed so technicians can exit the nacelle rapidly in the event of a fire, medical emergency, or other life-threatening situation.
Question 7: When performing an ultrasonic thickness test on a wind turbine blade shell during PM, what condition is being assessed?
- Internal temperature of the blade
- Wall thickness to detect delamination or erosion thinning (Correct answer)
- Blade natural frequency
- Surface roughness coefficient
Correct answer: Wall thickness to detect delamination or erosion thinning
Ultrasonic thickness testing measures the laminate wall thickness to detect material loss from erosion or internal delamination without cutting the blade.
WTT Preventive Maintenance Procedures 3
During a tower interior inspection, a technician finds corrosion on the internal flange surfaces.
What is the first corrective action?