Inclined Screen Maintenance
Why would I change the rotation of the screen?
The ability to change the direction of eccentric shaft rotation will enable you to choose between flow and counterflow conditions. Flow rotation increases the rate of travel of material over the screen deck and increases capacities. Counterflow rotation at the same screen slope decreases screen capacity but increases screening efficiency. Box motion with counterflow shaft rotation may have a tendency to plug screen openings with near size particles.
What should I inspect before startup?
Before starting up the screen each day, check the following items:
- Check the oil level in the bearing housing by removing the oil plug on the vibrator unit's oil level block. If no oil is visible, add oil following the instructions in the Installation, Operation and Maintenance Manual.
- Check for a visible grease slick around the labyrinth seal at each end of the vibrator shaft. Grease must extrude slightly from the seals to make an effective dust and moisture seal for the bearing housings.
- Check the condition of the feed box and discharge-lip liner. Note any excessive wear in your log book and replace the affected parts as soon as possible.
- Check the wire cloth for holes or excessive wear.
- Keep the wire cloth taut between the screen side plates. Tighten the new wire cloth, as needed, after the first one or two days of operation. Whipping, caused by loose wire cloth, greatly reduces the life of the wire.
- Inspect the drive assembly for signs of V-belt stretching or cracking.
- Make sure all coil springs are free of rock and other foreign material.
- Make sure all guards are in place and in good condition.
Why the violent startup and shutdown?
When starting or stopping the inclined screen, the screen basket has a tendency to surge on its supports during the interval of slow vibrator-shaft speed. This is a normal action that stops when the vibrator unit reaches operating speed or stops completely.
How important is the feed box?
The feed box is designed to receive material and spread it across the full width of the screen. To
increase the efficiency of the screen and give more uniform wear, maintain a uniform feed rate to the center of the feed box.
What do I check during normal operation?
During daily operation, check for unusual sounds or signs of excessive vibration. Make sure you know the cause of any abnormality. Correcting problems when they first appear can often save you expensive downtime later.
Watch for product spillage due to damage or wear in the feed-end curtain, feed box, or discharge-lip liner. Record any observations about the system in your log book.
What should we do at shutdown?
At the end of the shift (or workday), always clear the system of product. To make sure the screen is empty at the next startup, stop the in-feed and watch the system run until the last of the rock material has been cycled through the screen and discharged, then shut down. Observe the surging as the vibrator shaft decelerates. If surging is extreme, the rubber snubbers may need adjustment.
How often should I check the tension on the V-belts or sheaves?
For any new V-belts or sheaves, check the belt tension after two, eight and 40 hours of operation. Adjust to the V-belt manufacturer's specifications. Failure to do so may result in belts damaged beyond use and costly downtime.
Important: For any new V-belts or sheaves, check the belt tension after two, eight, and 40 hours of operation. Adjust to the V-belt manufacturer’s specifications. Failure to do so may result in belts damaged beyond use, and costly downtime.
Operational Best Practices
Can I cut or weld on the screen box?
It is not recommended.
How should I feed the screen for optimum performance?
The feed should be spread evenly across the width of the screen.
How important is the clearance around the screen?
Clearance around the screen is especially important during initial startup and during shutdown.
How deep should the material bed be?
Bed depth should not exceed four times the screen opening at the discharge end of the deck.
How often should I check the speed and throw?
Conduct regular checks on speed and throw.