What to do
Idler(s) behind a trouble point are not at right angle
Belt running to one side at a given point
Buildup of material on idlers
Crooked conveyor structure
Advance the end(s) of the idler(s) in the direction of belt travel.
Clean, and improve maintenance
Lubricate or replace idler(s)
Belt not joined squarely
Particular section of belt running to one side at all points
Crooked steel cord belt,
- wrong lay of steel cords,
- transverse thickness difference,
- tension difference of steel cords,
- height difference of steel cords.
Crooked textile belt
Refasten resp. replace splice
Measures to be discussed with belt manufacturer.
In most cases, a replacement is inevitable.
If the textile belt is new, it might straighten out after a couple of days under full load.
Belt runs to one side for a longer distance
Idlers out of square
Off-center material feeding
Adjust chute and loading conditions.
Belt runs off-center around the tail pulley and in the loading area
Misaligned pulley or belt camber
Align the pulley
Dirt build-up on pulley
Clean the pulley or ...
install training idlers
Scraper pressed too hard on belt
Premature wear or abrasion of belt top cover
High speed differential between belt and conveyed material
Material build-up on return idlers
Adjust the scraper
Reconsider chute/feeding layout.
The chute should deliver the conveyed material to the belt as closely as possible to its speed and direction.
Use cleaning device.
Install (some) disc type return idlers
Dirty, frozen or misaligned idlers
Premature wear or abrasion of belt bottom cover
Slippage on drive pulley
Transition length too short
Overload in horizontal or convex curves
Clean, improve maintenance
Check pulley for correct lagging. Consider to use ceramic
Check, and extend, if possible.
Excessive abrasion of pipe belt outer side
Impressions from aggressive ceramic lagging
Material spillage between belt and pulley
Correct position of tilted training idlers.
Improve loading conditions. Install plows or scraper before the tail pulley.
Insufficient traction between belt and pulley
Counterweight too light or blocked
Worn pulley lagging
Increase belt wrap (contact length between belt and pulleys); improve belt cleaning.
Add counterweight or increase screw take-up tension or eliminate blocking.
Replace lagging. Consider to use ceramic.
Tension too high
Excessive elongation of belt
Buildup of material on idlers
Belt strength too low.
Reduce tonnage; reduce counterweight.
Clean idlers, improve scraper systems
Replace by lower elongation belt, for instance with polyester warp.
Replace by stronger belt
Splice starting to open
Dangerous. Check splices (X-ray).
Skirt board seals are pressed against the belt
Grooving, gouging of top cover
Material trapped under seals
Skirtboard seals too hard
Leave enough clearance b etween seal and belt.
Install cushion idlers to hold belt up towards skirts.
Improve chute design for smoother feeding; install impact idlers.
Use proper sealing material (no old conveyor belts...).
Grooving, gouging of bottom cover
Frozen (or even broken?) idlers
Free the idlers and lubricate them
Install or improve cleaning devices, avoid spillage, improve maintenance
Usually causing longitudinal grooves.
Worn pulley lagging
Compound too hard
Hard and/or cracking cover
Lack of ozone protection
Exposure to heat, temperature of conveyed material is too high
Compound contains too many sulfur bridges. No repair possible.
Use high temperature resistant belt type.
Sulfur bridges replaced by oxygen bridges. No repair possible
No repair possible. Monitor the crack progression
Impact of material falling onto belt, or foreign body clamped between belt and pulley
Holes or breaks in belt
Reduce impact; use cushion idlers; use belt with impact protection system; repair the spots.
If you want to increase strength and thickness of the belt, check the pulley diameters and motor power first
Note: For larger holes check the repair procedure with the belt supplier, because the safety factor may have become critically low.
improper splice manufacturing
Splice failure is most critical and needs immediate professional care.
In case of damaged steel cords or even excessive movements of steel cord ends (see also "Excessive elongation of belt"), the splice has to be cut out and removed.
Note: For longer, important conveyors it is recommended to have state-of-the-art belt 24/7 scanning by an X-ray system.
Lack of adhesion or overloading
Check whether adhesion between cover and carcass of the belt is sufficient and whether pulley diameters are big enough.
Random cracks in the top cover rubber perpendicular to the direction of belt travel can also be an indication of too small pulley diameters.
Damage by external body or jammed conveyor part
Usually a cold or hot repair is required. Temporarily, mechanical fasteners may be used.
In many cases, replacement of the belt is unavoidable.
Critical especially with steel cord conveyor belts. Adjust pulleys and idlers for straight tracking. Severe damage should be repaired by hot vulcanization.
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