Representative case · 06
Yaw bearing wear: metal in the purged grease
The turbine is producing. Dark, metallic grease from some purge points; a rubbing noise at one nacelle position.
Representative case. This page describes a fault pattern that is common in the field, as a diagnostic sequence. It does not describe a specific wind farm, turbine or date; numbers are examples only and limits vary by turbine type. On your own turbine the OEM instructions, LOTO procedure and safety rules apply; work near energised equipment is for authorised personnel only.
Symptom
The turbine is producing. Dark, metallic grease from some purge points; a rubbing noise at one nacelle position.
What was measured
Grease collected point by point; metal concentrated at three neighbouring points, a magnet test confirmed steel particles.
Root cause
A blocked lubrication line left one sector of the bearing without grease.
Fix and verification
Line cleared, distributor replaced, sector greased; close follow-up at short intervals.
Lesson
A running pump does not mean grease reaches every point.
Full version
The complete diagnostic sequence — possible causes table, step-by-step checks, maintenance checklist and common mistakes — is in the Turkish version of this case.