WTG-07 Gearbox Inspection and Hub Entry
Nacelle gearbox inspection with hub entry for pitch bearing check. Rotor lock mandatory before hub entry.
It refers to equipment that does not exist and illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain. It is not a document to adopt. Under (c)(4)(i) the employer must develop and document energy control procedures specific to their own machines, and under (c)(6) must inspect them at least annually.
Other standards also apply to this work
- NFPA 70E — arc flash, for work at the MV disconnect and converter.
- 29 CFR 1910.146 — hub entry is a confined space in most programmes.
12 points, in sequence
All three blades feathered to 90 degrees and confirmed. Reduces rotor torque from wind.
MV grid disconnect at the tower base. Isolates the turbine from the collector circuit.
Converter DC link bus discharge. STORED ELECTRICAL - link capacitors hold charge after the grid opens.
LV distribution transformer isolation. Feeds nacelle services, yaw and pitch controllers.
Yaw drive motor isolation. Nacelle can slew under wind load if the yaw drives are live.
Pitch hydraulic supply to the blade pitch cylinders in the hub.
Pitch accumulator bleed. Holds pressure to feather blades on power loss - bleed and confirm the gauge.
Rotor lock security bolt engaged in the disc brake. MUST be fitted before anyone enters the hub.
Pitch backup UPS. Must REMAIN LIVE so the blades can feather in an emergency while work is underway.
Service lift and tower emergency lighting. Must REMAIN LIVE - the only means of descent and rescue.
Service switch tag in the nacelle. A TAG ONLY - tagging the service switch is NOT part of the lockout.
Blade lightning receptors and tower down-conductor. NO isolating device - a strike energises this path regardless of turbine state.
What your site must supply
This example is structurally complete and factually generic. The things below are the things only you can know — and they are exactly what makes a procedure yours.
- Your own asset and isolation-point tag numbers. The tags shown are illustrative and refer to equipment that does not exist.
- The actual location of every disconnect, valve and vent on your equipment.
- Measured stored-energy magnitudes and the dwell time required to dissipate them.
- Your verification method for each point, and who is authorised to perform it.
- Any additional energy sources present on your equipment and absent here.
Author this properly, once
Setyr holds procedures like this as living documents — bound to real isolation points, with lock registries, group lockout, person-in-charge custody and periodic review built in.