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Troubleshooting GuideCrane Brake Not Holding
The most critical safety element in lifting; the crane must not be run under load until diagnosis is complete.
How the brake works
Crane brakes are spring-applied, electromagnetically released. The spring keeps the brake closed at all times; when power reaches the motor, the coil overcomes the spring and opens the brake. When power is removed the brake closes on its own — the load stays suspended.
That is why a "brake not holding" complaint is usually not about the brake staying open, but about it failing to close fully. As the air gap between lining and disc grows, the spring's closing travel becomes insufficient.
Possible causes
| Possible cause | Symptom | What to do |
|---|---|---|
| Air gap has grown | Brake engages late, noise has increased | Measure the gap, adjust to the manufacturer's value |
| Lining below limit | Cannot be adjusted any further | Replace the lining |
| Lining contaminated | Soft brake, silent slippage | Fix the leak, replace the lining |
| Brake spring fatigued | Adjustment does not hold | Replace the spring |
| Coil permanently energised | Brake never closes | Check the control circuit and contactor |
| Disc worn/warped | Judder when engaging | Replace the disc |
| Overload | Slippage only under heavy load | Check capacity and the limiter |
Step-by-step diagnosis
- Make the crane safeLower the load, clear the area, isolate and lock out power.
- Measure lining thicknessCompare against the manufacturer's limit value.
- Measure the air gapMeasure with a feeler gauge and compare to the adjustment value.
- Look for contaminationCheck the lining and disc surface for oil, and the gearbox seal for leaks.
- Check the springSpring length and force; a fatigued spring cannot be compensated by adjustment.
- Check the control circuitCoil supply, contactor sticking, timing.
- Adjust and testAfter adjustment, verify brake engagement unloaded, then with a stepped load.
Lasting fix and root cause
If the fault returns soon after the brake is adjusted, the problem is not the brake itself. If the lining wears faster than expected, the crane may be operating above its duty class: daily cycle count and average load should be measured.
If the lining keeps getting contaminated, the source is the gearbox seal or a bearing; replacing the lining without replacing the seal is money wasted.
If the brake coil burns out repeatedly, check the supply voltage, the timing in the control circuit, and whether the contactor is sticking.
Technical terms
| Term | What it means |
|---|---|
| Air gap | The set clearance between the lining and the disc. |
| Spring-applied brake | A brake type that closes by spring force and opens electrically. |
| Brake coil | The electromagnetic winding that opens the brake. |
| Feeler gauge | A set of thin blades used to measure small gaps. |
Frequently asked questions
Can I adjust the brake myself?
The brake is the most critical safety element in lifting. Adjustment must be done by a competent person and verified afterwards with a stepped load test.
How long does a lining last?
It depends on cycle count and load, not time. The same crane can wear out a lining at very different rates at two different sites; that is why measurement is part of periodic maintenance.
Is a second brake required?
Not mandatory, but it is a common safety choice for heavy-duty or higher-risk loads; the need is determined by risk assessment.