An ounce of prevention
Even though the OK mill is very sturdy, you should still be sure to:
- Stop wear from air blasting in good time
- Keep seals in good condition to avoid wear and false air
- Change filters and keep lubrication systems in good condition
- Adjust roller stoppers to avoid roller table contact
- Change nitrogen pressure in hydraulic accumulators according to grinding pressure
- Fix oil spills/leakages and change hoses as needed
Normal maintenance
We recommend visually inspecting the mill every two weeks, both while running and stopped.
Major maintenance Major jobs include reversal/change of segments and/or hardfacing. A full hardfacing usually takes 3-4 days. For clinker grinding, hardfacing is usually required annually; for slag grinding, expect to hardface every 3-4 months.
The mill’s swing-in/out roller support system makes it easy to maintain the rollers and suspension system.
Swinging one roller out and changing the seals takes 24 hours, while changing a hydraulic cylinder takes 10-16 hours.
The mills have 2 access doors for ease of maintenance, and entry is possible as soon as the mill is stopped. Any jobs done inside the mill have to wait until it is cooled down – typically 3-4 hours.
Watch the Mill Maintenance animation:
Rollers and wear liners
The rollers and the wear liners of the grinding table are segmented and therefore easy to replace when worn out. Roller wear segments can easily be reversed or replaced while inside the mill – that is, without taking rollers out of the mill. The separator reject cone is provided with rail and trolley for that purpose.
By reversing the wear segments of the rollers to use both sides of the segments, you can achieve higher utilisation.
In case of instability
Instability in the grinding process may occur in the case of: 1. Excessive material in the mill; 2. Lack of material in the mill; 3. Extremely dusty feed; 4. Worn segments.
Solve it by: 1. Adjusting mill feed; 2. Increasing mill gas flow; 3. Adjusting dam ring height and 4. Ultimately, re-welding or replacing segments.
Watch Hardfacing a vertical roller mill: