What is the typical reason a ball mill trunnion needs to be replaced unexpectedly?
It is unclear if the trunnion damage was known ahead of time and planned for a change-out during the shell reline or if it was discovered during the reline work.
While, not knowing if this is the feed or discharge end trunnion, there could be a number of things causing this emergency repair job and plant downtime:
- Dropped charge can cause stress fractures and/or deformation
- Metallurgical quality issues from foundry (e.g. slag inclusion stress riser can initiate fatigue cracking)
- Slurry racing behind trunnion liner or center discharge cones due to leak – erosion thins the metal and causes weakness.
- Dirt/grit contaminates bearing – causes deep scoring of journal surface and poor lube pressure retention (lift)
- Wearing through trunnion liner can cause localized erosion/weakness
- Lube or operational failure may have caused overheating and/or galling damage of journal surface.
Other Typical, and maybe similar, reason is:
- Poor maintenance or operation! Contamination of lube.
- Washing/hosing dirt into trunnion when the feed chute leaks is another big one.
- The cyclone underflow tube somehow sanded and plugged to the point of overflowing and spilled over the trunnion, causing slurry to enter.