Setyr worked example — WTG-07 Gearbox Inspection and Hub Entry Not approved for use. Version 1 · 2026-09-04
Worked example only — your site must author, review and approve its own
procedure under 29 CFR 1910.147(c)(4). setyr.com/procedures
WTG-07 Gearbox Inspection and Hub Entry
Wind energy
Nacelle gearbox inspection with hub entry for pitch bearing check. Rotor lock mandatory before hub entry.
This is a worked example, not a procedure you can adopt. It describes equipment that does not exist, with illustrative tag numbers.
29 CFR 1910.147(c)(4) requires the employer to develop, document and
utilise energy control procedures specific to their own machines, and (c)(6)
requires the employer to inspect those procedures periodically. Neither duty
can be delegated to a vendor or discharged by this document.
Other standards 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.
Isolation points
| # | Tag (illustrative) | Type | Disposition | What it does and why | Dwell |
|---|---|---|---|---|---|
| 10 | WTG-07-BLADE-FEA | Block | Apply & verify | All three blades feathered to 90 degrees and confirmed. Reduces rotor torque from wind. | — |
| 20 | WTG-07-GRID-DISC | Disconnect | Isolate & lock | MV grid disconnect at the tower base. Isolates the turbine from the collector circuit. | — |
| 30 | WTG-07-CONV-DC | Bleed | Isolate & lock | Converter DC link bus discharge. STORED ELECTRICAL - link capacitors hold charge after the grid opens. | — |
| 40 | WTG-07-XFMR-LV | Disconnect | Isolate & lock | LV distribution transformer isolation. Feeds nacelle services, yaw and pitch controllers. | — |
| 50 | WTG-07-YAW-DRIVE | Disconnect | Isolate & lock | Yaw drive motor isolation. Nacelle can slew under wind load if the yaw drives are live. | — |
| 60 | WTG-07-PITCH-HYD | Valve | Isolate & lock | Pitch hydraulic supply to the blade pitch cylinders in the hub. | — |
| 70 | WTG-07-PITCH-ACC | Bleed | Isolate & lock | Pitch accumulator bleed. Holds pressure to feather blades on power loss - bleed and confirm the gauge. | — |
| 80 | WTG-07-ROTOR-LOCK | Block | Apply & verify | Rotor lock security bolt engaged in the disc brake. MUST be fitted before anyone enters the hub. | — |
| 90 | WTG-07-PITCH-UPS | Disconnect | KEEP ENERGISED | Pitch backup UPS. Must REMAIN LIVE so the blades can feather in an emergency while work is underway. | — |
| 100 | WTG-07-LIFT-EMRG | Disconnect | KEEP ENERGISED | Service lift and tower emergency lighting. Must REMAIN LIVE - the only means of descent and rescue. | — |
| 110 | WTG-07-SVC-SWITCH | Switch | Not an isolation device | Service switch tag in the nacelle. A TAG ONLY - tagging the service switch is NOT part of the lockout. | — |
| 120 | WTG-07-LIGHTNING | Chain | CANNOT BE ISOLATED | Blade lightning receptors and tower down-conductor. NO isolating device - a strike energises this path regardless of turbine state. | — |
What your site must supply
- 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.
Authorship and validation
This example was authored by Setyr for domain validation. It is not derived from any customer's controlled documents. It illustrates the elements 29 CFR 1910.147(c)(4)(ii) requires a procedure to contain — it does not certify compliance, which is a property of an employer's programme rather than of any document.