Vibrating screen bearings: arrangement, lubrication and failures
A vibrating screen shakes on purpose. A shaft with an eccentric weight spins in the exciter and the whole box vibrates with it. The bearing sees a load that turns with the shaft, which is the opposite of the normal case, and it sees large accelerations as well.
Typical duty
| Speed | Load | Temperature | Typical life |
|---|---|---|---|
| 700 – 1,000 rpm | High, rotating with the shaft | 70 – 100 °C at the bearing | Dedicated vibratory bearings, short relube interval |
How the bearings are arranged
Circular-motion screen · exciter shaft
Used when: Mining, quarry and aggregate screens
The weights are mounted on the shaft, so the heavy load circles with the shaft instead of staying in one direction. In a normal bearing the outer ring is stationary relative to a fixed load. Here the inner ring has the unusual job of rotating with the load, and the outer ring sees the load rotating around it. That, plus the shaking, is why a special bearing is used.
Common failures and how to prevent them
| Failure | What you see | Why it happens | Prevention |
|---|---|---|---|
| Cage fracture Cage damage | Broken cage pieces, scored rollers, sudden heat. | Standard cage under high acceleration, or lack of lubrication. | Use the vibratory-duty bearing with a hardened window cage and keep relubrication on time. |
| Fretting in the loose fit Fretting corrosion | Brown-red powder and polished patches on the bore or outer ring. | Small movements at the non-locating fit under constant vibration. | Use the coated bore version (VA406) or a PTFE-coated outer ring at the floating end. |
| Heat from over-greasing or too little grease Overheating & lubricant breakdown | Hot bearing, discoloured rings. | Too much grease churns, too little grease runs dry. | Stick to the quantity and interval in the bearing selection. Do not fill the housing completely. |
| Dust and fines Abrasive wear | Dull raceways, gritty grease. | Worn seals in a dusty plant. | Replace seals, keep clean grease coming through the labyrinth. |
| Fatigue from overload Subsurface-initiated fatigue | Spalling at the load zone. | Overfilled screen box, excess exciter weight, or running off-resonance. | Keep within the load in the screen maker’s documentation. |
| Distorted housing Misalignment & distorted seats (edge loading) | Uneven wear. | Cracked side plate, bolts loose, or bad housing seats. | Inspect the side plate around the housings at every service. |
Lubrication
Grease
EP grease with a viscosity ratio around 4 at working temperature. The catalogue example is 30 g every 75 h.
Oil bath
Some exciters run in an oil bath instead. Keep the level right and the oil clean.
Sealing
- Labyrinth seals: Grease-filled labyrinth rings at each housing. Short regreasing pushes dust out.
- Exciter housing: Oil-tight in oil-lubricated designs; a vent keeps it from building pressure.
What to watch
- Bearing temperature on both sides, and the difference between them.
- Greasing log. Missed intervals are the most common cause of failure.
- Cracks around the bearing housings and the stroke of the screen.
Questions
Which bearings are used in vibrating screens?
Circular-motion screen · exciter shaft: Mining, quarry and aggregate screens.
What are the common bearing failures in vibrating screens?
Cage fracture: Standard cage under high acceleration, or lack of lubrication. Fretting in the loose fit: Small movements at the non-locating fit under constant vibration. Heat from over-greasing or too little grease: Too much grease churns, too little grease runs dry.
How should vibrating screens bearings be lubricated?
Grease: EP grease with a viscosity ratio around 4 at working temperature. The catalogue example is 30 g every 75 h. Oil bath: Some exciters run in an oil bath instead. Keep the level right and the oil clean.