What to do


Belt running to one side at a given point

Idler(s) behind a trouble point are not at right angle

Advance the end(s) of the idler(s) in the direction of belt travel.

Blocked idler(s)

Lubricate or replace idler(s)

Crooked conveyor structure

Make corrections

Buildup of material on idlers

Clean, and improve maintenance

Particular section of belt running to one side at all points

Belt not joined squarely

Refasten resp. replace splice

Crooked textile belt

If the textile belt is new, it might straighten out after a couple of days under full load.

Crooked steel cord belt,

because of

- wrong lay of steel cords,

- transverse thickness difference,

- tension difference of steel cords,

- height difference of steel cords.

Measures to be discussed with belt manufacturer.

In most cases, a replacement is inevitable.


Belt runs to one side for a longer distance

Idlers out of square

Align idlers

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

Material build-up on idler

Premature wear or abrasion of belt bottom cover

Dirty, frozen or misaligned idlers

Clean, improve maintenance

Overload in horizontal or convex curves


Transition length too short

Check, and extend, if possible.

Slippage on drive pulley

Check pulley for correct lagging. Consider to use ceramic

Material spillage between belt and pulley

Improve loading conditions. Install plows or scraper before the tail pulley.

Impressions from aggressive ceramic lagging

Replace lagging

Excessive abrasion of pipe belt outer side

Correct position of tilted training idlers.

Transition length
Impression of pulley lagging

Insufficient traction between belt and pulley

Belt slips


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.

Drive pulley

Excessive elongation of belt

Tension too high

Reduce tonnage; reduce counterweight.

Belt strength too low.

Replace by stronger belt

High-elongation carcass

Replace by lower elongation belt, for instance with polyester warp.

Buildup of material on idlers

Clean idlers, improve scraper systems

Splice starting to open

Dangerous. Check splices (X-ray).

Grooving, gouging of top cover

Skirt board seals are pressed against the belt

Leave enough clearance b etween seal and belt.

Skirtboard seals too hard

Use proper sealing material (no old conveyor belts...).

Material impact

Improve chute design for smoother feeding; install impact idlers.

Material trapped under seals

Install cushion idlers to hold belt up towards skirts.

Impact cover damage

Grooving, gouging of bottom cover

Frozen (or even broken?) idlers

Free the idlers and lubricate them

Material buildup

Install or improve cleaning devices, avoid spillage, improve maintenance


Usually causing longitudinal grooves.

Worn pulley lagging

Replace it

Broken idler

Hard and/or cracking cover

Compound too hard

Compound contains too many sulfur bridges. No repair possible.


Sulfur bridges replaced by oxygen bridges. No repair possible

Exposure to heat, temperature of conveyed material is too high

Use high temperature resistant belt type.

Lack of ozone protection

No repair possible. Monitor the crack progression

Cracked cover

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.

Steel cord impact damage

Splice failure

External damage,

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.

How to make a proper splice.

Note: For longer, important conveyors it is recommended to have state-of-the-art belt 24/7 scanning by an X-ray system.

Torn steel cord belt splice

Lack of adhesion or overloading

Cover-ply separatation

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.


Opened splice ramp

Damage by external body or jammed conveyor part

Longitudinal rip

Usually a cold or hot repair is required. Temporarily, mechanical fasteners may be used.

In many cases, replacement of the belt is unavoidable.

Groove in cover

Mistracking belt

Edge damage

Critical especially with steel cord conveyor belts. Adjust pulleys and idlers for straight tracking. Severe damage should be repaired by hot vulcanization.


See animations on top of this page.

Edge damage




"Other" problems

Transportation accident

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