WTT Preventive Maintenance Procedures 2 — Questions and Answers
Question 1: What is the recommended interval for inspecting wind turbine blade leading edge erosion under standard operating conditions?
- Every 6 months
- Annually (Correct answer)
- Every 2 years
- Every 5 years
Correct answer: Annually
Annual blade inspections are the industry standard for detecting leading edge erosion before it significantly reduces aerodynamic efficiency.
Question 2: During a gearbox oil change, a technician notices the drained oil contains fine metallic particles but no chunks. What is the appropriate next step?
- Immediately shut down the turbine and call for major repair
- Refill with new oil and flag for increased monitoring interval (Correct answer)
- Ignore it as normal wear debris
- Replace the gearbox immediately
Correct answer: Refill with new oil and flag for increased monitoring interval
Fine metallic particles are a normal byproduct of gear wear; the correct response is to refill and shorten the monitoring interval to watch for progression.
Question 3: Which torque method is preferred when re-torquing main flange bolts during preventive maintenance?
- Impact wrench to feel method
- Torque wrench to manufacturer-specified values (Correct answer)
- Hand tightening until snug
- Hydraulic tensioner only on bolts above 1" diameter
Correct answer: Torque wrench to manufacturer-specified values
Manufacturer-specified torque values applied with a calibrated torque wrench ensure proper clamp load and prevent bolt fatigue or joint loosening.
Question 4: What does a rising trend in vibration amplitude on the main bearing during consecutive PM readings typically indicate?
- Normal load fluctuation
- Progressive bearing wear requiring attention (Correct answer)
- Sensor calibration error only
- Improved rotor balance
Correct answer: Progressive bearing wear requiring attention
A consistent upward trend in vibration amplitude is a classic condition-monitoring signal of progressive bearing degradation.
Question 5: Before performing any work inside the nacelle, which safety interlock must a technician verify is engaged?
- Pitch lock pin
- Rotor lock (rotor brake + lock pin) (Correct answer)
- Yaw brake only
- Generator circuit breaker only
Correct answer: Rotor lock (rotor brake + lock pin)
The rotor must be secured with both the mechanical rotor brake engaged and the rotor lock pin inserted to prevent unexpected rotation.
Question 6: How should a technician dispose of used gearbox oil collected during a preventive maintenance oil change on a wind turbine?
- Pour it onto the ground away from waterways
- Store in labeled containers and deliver to a licensed waste oil recycler (Correct answer)
- Burn it on site to reduce volume
- Flush with water and discharge
Correct answer: Store in labeled containers and deliver to a licensed waste oil recycler
Used oil is a regulated hazardous waste and must be collected, labeled, and delivered to a licensed recycling or disposal facility per EPA regulations.
Question 7: What is the purpose of checking the pitch bearing grease nipple fittings during a scheduled PM?
- To verify bearing temperature
- To ensure grease can be injected and the old grease is being purged (Correct answer)
- To measure bearing play
- To confirm blade angle accuracy
Correct answer: To ensure grease can be injected and the old grease is being purged
Checking grease nipples confirms fittings are unblocked and that fresh grease is displacing degraded grease from the bearing raceway.
WTT Preventive Maintenance Procedures 2
What is the recommended interval for inspecting wind turbine blade leading edge erosion under standard operating conditions?