The Fundamental Tracking Principle
A conveyor belt tracks toward the high-tension side of a pulley or the leading edge of a skewed idler. When an idler is skewed (rotated in plan view), the belt is steered toward the lead end. When one side of a pulley has higher tension, the belt migrates to that side.
The belt tracks to the same side consistently — the drift direction tells you the cause.
Diagnosis Before Adjustment
Before touching any adjustment, observe and record:
- Where does the belt drift? — Head end, tail end, or middle section?
- On which strand? — Carry (top) strand, return (bottom) strand, or both?
- When does it occur? — Loaded, empty, or both?
- Does it drift consistently or oscillate?
Common Causes and Fixes
| Symptom | Cause | Fix |
|---|---|---|
| Belt drifts at tail end only | Tail pulley not square to conveyor centreline | Adjust tail pulley — advance the side the belt runs toward |
| Belt drifts at head end only | Head/drive pulley misalignment | Align drive pulley; check for material build-up on pulley |
| Drift in middle of carry strand | Idler frame misalignment; bent idler roll | Re-align carry idlers; replace bent rolls |
| Drift when loaded but not empty | Off-centre loading; spillage build-up on return idlers | Correct chute position to centre-load the belt; clean return idlers |
| Belt wanders from side to side | Splice camber (belt permanently curved); loose splice | Cut and re-vulcanise splice square; check splice tension |
| Belt tracks well then drifts off | Material build-up on idler or pulley lagging | Clean build-up; increase cleaning frequency; check scraper adjustment |
Idler Adjustment Procedure
The rule: to move the belt to the right (when viewed in the direction of belt travel), advance the right end of the idler in the direction of belt travel. This steers the belt toward the advancing end.
- Identify the section where tracking needs correction
- Begin at the problem zone — adjust the idlers 2–3 frame positions upstream from where the drift becomes visible
- Advance the idler frame on the side the belt needs to move toward — typically 1–3 mm at a time
- Run the belt for several passes before observing effect — changes work gradually
- Work upstream from the problem area, one set of idlers at a time
Never adjust more than 3–4 idlers at once — over-correction causes the belt to track to the opposite side. Patience is essential. Allow several belt revolutions after each adjustment before re-assessing.
Preventive Measures
- Install self-aligning (training) idlers — one every 10–15 m on long conveyors
- Ensure loading is centred — chute centreline aligned with belt centreline
- Keep pulleys and idlers free of material build-up with effective belt scrapers
- Use rubber-lagged pulleys (diamond or herringbone pattern) for better traction and tracking
- Check idler frame alignment when installing new belt or after any structural work