Outoseal, a new main bearing housing sealing system from Outotec keeps the grinding mills at mine-sites free of contamination to maintain safety and prevent main bearing failure.
Equipment at mine sites is subjected to continuous contamination and debris such as dust, oil, water and slurry.
It is especially important to keep the grinding mill well-maintained and free from contaminants that are hazardous to safe and efficient operation.
One important mill component, which must stay contaminant-free is the lubrication system for the main supporting bearings wherein contamination can lead to:
- Premature wear of the lubrication system components
- High levels of water in the lubricant
- Main bearing failure
In addition to affecting performance and lifespan of equipment, lubricant leaks also cause compliance issues with modern environmental legislation.
According to Jeff Belke, Chief Application Engineer - Grinding Mills at Outotec, the main bearing housing sealing system must therefore not only avoid contamination of the lubrication system but also avoid any leaking of lubricant into the environment.
These dual sealing requirements have been a significant challenge for mill builders and mill owners, since the main bearing housings are often very large with high sealing velocities.
Several factors need to be considered for an effective sealing solution:
- Ensure contaminants are kept out and lubricants are kept in
- Ensure the seal speed capacity is well in excess of the installed velocity
- Seal should not cause wear to critical mill components
- Seal materials must be tolerant of operating temperature, lubricant type, process fluids and UV
- Seal design must be easily adjustable for modifications during the commissioning process
- Seal must be suitable to retrofits and greenfield installations
Outotec has factored in these considerations to design a new main bearing housing sealing system called the Outoseal.
Key features of Outotec’s Outoseal:
- Based on Outotec’s proven traditional tip-to-tip shaft mounted v-ring seal arrangement of a v-ring seal tip sealing against the front and back of a static plate
- Design ensures the sealing direction is axial rather than radial
- Combines a number of separate parts including the two separate v-seals into one robust arrangement, using internal forces to reduce detrimental seal movement to almost zero
- Uses a simple-to-install O-ring cord to change the seal lip pressure
- Oil for lubrication is supplied via the main bearing lubrication system
- Incorporates integrated ‘flingers’ on the inboard and outboard sides of the seal
Key benefits of Outoseal main bearing housing sealing system:
- Lips have minimised contact area with seal plates, whilst still providing sufficient contact pressure and area to ensure a good seal
- O-ring cord can be used to vary the contact pressure of the lip on the plate, enabling installation variations simply by changing the O-ring cord diameter
- Single arrangement mitigates the movement of individual v-seals, which can impact seal performance
- Axial sealing direction ensures high tolerance of geometric run-outs and prevents wear of mill journal
- Flexible arrangement can be retrofitted to existing mills
Optimised lubrication systems
Outotec’s Outoseals use oil supplied via the main bearing lubrication system, dispensing with the need for a standalone seal lubrication system.
Key advantages include:
- Eliminates grease contamination from the main bearing lubricant
- No maintenance as there is no need to clean or dispose off grease purged from the seals
- Reduced waste and costs since oil is recycled back to the bearing lubrication system and re-used
- Oil is conditioned with the main flow of returning bearing oil, removing any contaminants before the oil is reused
- Integrated ‘flingers’ use rotational forces to centrifugally spin fluids on the seal away from the sealing surface
- Inboard flinger keeps bearing lubrication oil away from the inside lip of the seal
- Outboard flinger, in combination with the stationary outer labyrinth angle protects the outer seal lip from wash down water, rain, dust, slurry leakage and other contaminants