Power and free conveyors are reliable, but they have more moving parts than simple chain conveyors: dogs, stops, switches and accumulating trolleys. When something goes wrong, a structured approach finds the cause quickly.
Before you start
Symptoms, causes and fixes
| Symptom | Likely causes | What to do |
|---|---|---|
| Carrier does not stop at a stop | Stop blade not extending; worn trolley lever; sensor fault | Check air and valve, inspect lever and blade, test sensor |
| Carrier does not release | Stop not retracting; trolley dog not rising; worn pusher dogs | Check stop function; inspect trolley dog spring and pusher dogs |
| Carriers collide in queues | Accumulating levers worn or bent | Inspect and replace front trolley levers |
| Jams at switches | Tongue not in end position; misalignment; worn tongue | Check end-position sensors, alignment and wear |
| Jerky chain or surging | Poor lubrication; tight spots; take-up too slack | Lubricate, inspect curves, adjust take-up |
| Drive overload trips | Jam, excessive load, worn chain, cold oven start | Find the jam; check chain elongation and load |
| Trolley derails | Damaged track joint, worn wheel, debris | Inspect track joints and wheels; clean track |
| Noisy section | Dry or failed bearings; worn curve rollers | Locate by listening; replace bearings or rollers |
A structured approach
- Note where and when the fault happens: always at one spot, or anywhere?
- Check the HMI alarm history for patterns.
- Watch the carrier through the problem area at low speed.
- Inspect the mechanical parts involved; measure wear.
- Fix the cause, not only the symptom, and record what you found.
Preventing repeat faults
- Follow a lubrication and inspection schedule
- Measure chain elongation regularly
- Keep spare levers, dogs, stop blades and sensors on site
- Train operators to report unusual noise early
Read how power and free works, switches and the maintenance checklist. HITREE offers service and spare parts.
Spare parts that shorten troubleshooting
| Part | Typical fault it solves |
|---|---|
| Front trolley levers | Carriers that do not accumulate or release |
| Pusher dogs | Carriers not picked up |
| Stop blades and cylinders | Carriers not stopping |
| Proximity sensors | Missed stop or switch signals |
| Switch tongues | Jams and derailments at switches |
Common mistakes to avoid
- Resetting faults repeatedly without finding the cause
- Clearing jams with the chain running
- Replacing parts without recording which and why
