Find the Symptom. Fix the Cause.
Most conveyor faults get "fixed" two or three times before anyone finds what is actually causing them. Start from what you can see on the line, and work back to the reason.
Ten Faults, and What Is Usually Behind Them
Every line below links to a guide that goes the whole way through that fault — cause by cause, with what to check before you order anything.
| What you see | What is usually behind it | Check this first | Guide |
|---|---|---|---|
| The belt drifts to one side | Build-up on pulleys or idlers, off-centre loading, a structure out of square, or a seized roller. Rarely just one of them. | Look at the pulley faces for packed material before touching any alignment. | Belt tracking → |
| Rollers have stopped turning | Seizure, not wear. Seal mismatch, wrong grease, water ingress or overspeed — the bearing fails before its fatigue life is used. | Spin it by hand and listen. Rough or dry means the seal let contamination in. | Bearing failure → |
| Material under the return side | Carry-back. Wrong cleaner type, wrong blade tension, or a cleaner mounted in the wrong place. | Where the blade meets the belt, and whether it is still holding tension. | Cleaner selection → |
| Rollers wear out too soon | The L10 figure is a bearing rating, not a promise about your duty. Speed, load, environment and sealing all cut it. | Check the real belt speed against the roller rpm the life class assumes. | Service life → |
| The belt slips at the drive pulley | Lagging type, groove pattern or thickness not matched to the belt tension and wrap angle. | Whether the lagging has glazed over or worn smooth. | Lagging selection → |
| Replacement rollers do not fit | A measurement was missed — most often the shaft end type, or the overall length rather than the shell length. | Take all six measurements; do not trust the old part number. | How to measure → |
| Two quotations look the same, prices differ | Different standard, bearing class, wall thickness or seal. The spec sheet usually does not say which. | Ask which standard and which life class each one is built to. | Standards → |
| Imported rollers disappointed last time | A price gap comes from somewhere: tube, bearing, seal, machining, or packing for the voyage. | Inspect before shipment, not after it arrives. | Sourcing checklist → |
| Not sure whether to ask for an idler or a roller | The words are used loosely across the industry. What matters is whether the unit is driven or free-turning. | Describe what it does, not what you call it. | Terminology → |
| Specifying idlers for a new line | Starting from diameter instead of duty. Environment and failure cost decide the build; diameter follows. | Answer duty, environment and failure cost before anything else. | Selection guide → |
The Three Numbers Behind Most of These Faults
A quotation that only lists diameter and length tells you nothing about whether the roller will survive your duty. These three do.
| Number | What it actually tells you | Limit in the standard |
|---|---|---|
| Radial runout | How far the roller surface wanders as it turns. High runout is felt as vibration, heard as noise, and shows up as premature bearing and belt wear. | At most 0.5 mm — GB/T 10595 Table 13. The limit varies with belt speed and roll length. |
| Rotational resistance | How much drag the roller adds. Multiplied across hundreds of idlers it is a real share of your drive power — and the first sign of a seal or bearing problem. | At most 2.5 N dust-duty and 3.6 N water-duty — GB/T 10595 Table 15. |
| Load rating | What the roller carries before the bearing, the tube or the shaft gives up, and against which life class it is rated. | 10 to 20 kN axial load by shaft diameter — GB/T 10595 Table 14. |
The figures above are the limits in GB/T 10595 (current edition 2017) — what a roller has to meet, tested in a defined way, not a generic claim from a catalogue. They are also the numbers to check when a batch arrives.
Most of our orders are built to a drawing rather than selected from a catalogue, so we quote these against your duty and agree the acceptance criteria with you before production — the number on the quotation is the number you can test on arrival. If you buy to DIN, CEMA or your own specification, the tests are comparable even where the limits differ. Full tolerances and test conditions →
What to Send Us
Three things, and we can usually tell you whether the fault is in the component or in the specification.
What you are seeing
Photos if you can — the fault itself, plus one wider shot showing where on the line it happens.
The duty it happens under
Material, belt speed, tonnage, and whether the section runs wet or dry.
What you have already tried
Saves us proposing the same fix, and often points straight at the cause.
Six measurements
Diameter, length, shaft diameter, shaft end type, bearing size, mounting type — the full method.
A drawing, if you have one
Non-standard rollers are routine for us. We build to your drawing rather than sell you the nearest catalogue item.
Which standard you buy to
GB/T, DIN, CEMA or your own — it decides the class, the tolerances and the comparison.
Frequently Asked Questions
Which conveyor fault costs the most to leave alone?
Carry-back. Material that rides back on the return side packs into idlers and pulleys, which is how a cleaning problem turns into seized rollers, belt drift and edge damage. It is cheap to fix at the cleaner and expensive to fix three components later.
Will self-aligning idlers fix a tracking problem?
Sometimes — and that is exactly the risk. A self-aligning idler corrects the symptom at one point on the line. If the real cause is off-centre loading, a structure out of square, or build-up on the pulley faces, the idler hides the cause until it shows up somewhere worse. Find the cause first.
One roller has seized. Do I replace one, or the whole set?
It depends on whether the failure is random or systematic. One seized roller among many that are still sound is usually a single defect. Seizures arriving in batches, or clustered at one point on the line, mean the duty is defeating the build — and then spot replacement just buys you the same failure again.
Do you need the old part to quote a replacement?
No. Six measurements are enough: roller diameter, overall length, shaft diameter, shaft end type, bearing size and mounting type. A photograph of the shaft end and of the roller in its frame settles the rest. You do not need to ship the old roller to us.
What if our roller is not in any standard table?
Send the drawing — or send the sample and we will measure it. Non-standard diameters, shaft ends and seals are routine for us; we build to your drawing rather than asking you to accept the nearest catalogue item.
What should I send to get a useful answer back?
Three things: what you are seeing (photos if possible), the duty it happens under, and what you have already tried. That is usually enough for us to say whether the fault is in the component or in the specification.
Tell Us What You Are Seeing
Describe the symptom and the duty. We will tell you what we think is causing it — and what we would build instead.
Describe Your Problem