Troubleshooting Failures

Roll Wear

Cause - Idler misaligned to belt travel causing scuffing between belt and roll.
Repair - Ensure roll is at right angles to direction of belt travel.
Cause - Contamination between belt and roll.
Repair - Ensure belt is clean on contact surface.
Cause - Idler set not sitting at right angles to belt. ie. tilted.
Repair - Set idler frame at right angles to belt by shimming, if necessary.

Idler seizure

Cause - Material lodged between frame and roll.
Repair - Clean idlers.
Cause - Load on idler in excess of design load.
Repair - Introduce additional idlers to reduce individual loads per idler set. Also, check vertical tolerance to ensure idlers are not too high.
Cause - Impact of material on roll.
Repair - Check tensions to ensure the belt sag is not excessive.

Frame buckle

Cause - Frame members too light.
Repair - Replace frames.
Cause - Inadequate frame stiffeners.
Repair - Replace frames.
Cause - Alignment of frame incorrect.
Repair - Align frames.
Cause - Excessive belt sag.
Repair - Check and adjust belt tensions.

Reduced idler bearing life

Cause - Idler loads in excess of design loads.
Repair - Decrease conveyor capacity. Change idler specification.
Cause - Idlers misaligned to belt.
Repair - Align idlers.
Cause - Belt tensions too low.
Repair - Check and adjust belt tensions.
Cause - Belt vibrating (flap).
Repair - Identify reason / source of belt flapping and eliminate. Check for build- up on idler rolls.

High power absorbed

Cause - Roll diameter too small.
Repair - Change idler diameter.
Cause - Excessive misalignment of idler sets.
Repair - Check and align all idler sets.
Cause - To many idlers used.
Repair - Check design and increase idler pitch if possible.

Belt edge damage

Cause - Bad belt training causing belt to miss track and run into steelwork.
Repair - Check loading is centralised. Realign belt empty and loaded.
Cause - Belt radius incorrect causing over stressing of belt edge.
Repair - Install additional idlers in vertical convex curves.

Belt damage in center

Cause - Belt pulled into nip point between rolls.
Repair - Change idler frames. Increase guage length.
Cause - Transitions incorrect.
Repair - Introduce additional idlers and/or increase length of transition zones.

Belt overfill

Cause - Design capacity of idler set exceeded.
Repair - Reduce feed rate or increase belt speed.

Excessive belt sag between idlers

Cause - Take up tensions too low.
Repair - Recheck conveyor design and increase take up mass if possible.
Cause - Idler spacing too high.
Repair - Adjust idler pitch to limit sag to 1% to 3% of pitch.
Cause - Erratic loading of belt causing high load points.
Repair - Improve feed system. Regulate feed. Maintain clean feed chutes.

Belt miss tracking

Cause - Idler frames not at right angles to belt.
Repair - Adjust frames to ensure rollers are 90° to belt travel.
Cause - Idler frames out of level across stringers.
Repair - Install shimms beneath frames one side.
Cause - Idler frames tilted backwards towards tail.
Repair - Install shimms under low side.
Cause - Idler rolls seize.
Repair - Replace seized rolls.

Seal "pop"

Cause - Idler shaft deflection too high.
Repair - Introduce additional idlers to reduce shaft deflection per roll.
Cause - Seal housing incorrect tolerance.
Repair - Replace idlers.

Bearing grease contamination

Cause - End cap seal ineffective.
Repair - Replace idlers.
Cause - Contamination from water jet.
Repair - Prevent unnecessary washdown, reduce hose pressure.
Cause - Excessive dust in the area.
Repair - Install de-dusting. Check skirt seals.
Cause - High temperature variation causing roll to breathe through seal.
Repair - Investigate alternative seal design or breathing holes.

Impact idler rubber failure

Cause - Poor chute design.
Repair - Re-design chute to reduce impact height and/or use grizzly to load fines before large lumps.
Cause - Rubber hardness incorrect (must be in excess of 60 shore).
Repair - Replace "soft" impact idlers.

Transition idler failure

Cause - Excessive distance between idlers.
Repair - Install additional idlers to distribute load.
Cause - Incorrect idler trough angle.
Repair - Change idler frames to improve trough angle.

End cap/disk failure

Cause - Weld between roll and end cap being worn away by belt.
Repair - Check idler alignment. Check load and idler pitch.
Cause - End cap plate thickness incorrect.
Repair - Replace idlers.

Roll buckle

Cause - Incorrect roll shell thickness.
Repair - Replace idlers.
Cause - Excessive load on idler.
Repair - Reduce conveyor throughput. Increase belt speed.

Roll vibrating

Cause - Incorrect alignment between shaft, bearings and end cap.
Repair - Replace idlers.
Cause - Seam weld in tube not removed.
Repair - Replace idlers. Apply coating.
Cause - Build-up on idler shell
Repair - Remove and clean idlers. Improve belt cleaning / scraper setting.