TL;DR

A leaking trunnion seal lets cement dust contaminate the bearing and the work area. Replace the seal during the next planned stop. Inspect the trunnion running surface for scoring before fitting a new seal.

What you might see

cement dust leaking at the trunnion seal
mill ventilation air escaping the trunnion end
seal lip visibly worn or cracked
dust accumulation on the trunnion bearing housing

Likely causes

Tap to mark as ruled out

Trunnion seal lip worn through normal service life
Trunnion surface scored or corroded under the seal, preventing lip contact
Seal clamp ring loose allowing the seal to shift and break contact
Mill running at positive internal pressure pushing material through any seal gap

Required tools

Clamp ring tools
Replacement seal
Torque wrench
Abrasive cloth (for minor surface defects)
LOTO kit

Safety first

Cement dust is a respiratory and explosion hazard. Use respiratory PPE when working near a leaking seal.
Lock out all drives before removing the seal clamp ring.

Procedure

7 steps · ~45 min

1
Stop the mill and lock out the main drive and auxiliary drive.
2
Inspect the trunnion seal lip condition. Look for cracks, wear-through, or hardening of the seal material.[1]
3
Inspect the trunnion running surface for scoring, pitting, or corrosion under the seal contact zone.[1]
4
Check the seal clamp ring bolt torque. Retighten any loose bolts to the specified value.
5
If the seal is worn, remove the clamp ring and replace the seal. Match the new seal lip material and profile to the original.
6
If the trunnion surface is scored, assess whether the scores are shallow enough to polish out with abrasive cloth, or whether the trunnion needs machining.
7
After seal replacement, run the mill for 2 hours and inspect the seal area for leakage.

Sources

FLSmidth FLSmidth UMS / TMS Cement / Ball Mill general technical documentation, FLSmidth
FLSmidth ball mill trunnion seal maintenance documentation (general)

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