Overhead Crane Common Faults and Troubleshooting: Complete Guide
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Overhead cranes (also called bridge cranes) are among the most widely used lifting machines in workshops, warehouses and stockyards. They operate under frequent start-stop cycles and heavy loads, so faults can occur in the mechanical drive, electrical control and metal structure systems at any time.
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Correctly identifying the cause of a fault and applying the right fix is essential for safe crane operation and long service life. This guide covers the most common overhead crane faults, their causes and troubleshooting methods.
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Table of Contents

1. Brake Fails to Hold (Insufficient Braking Torque)
2. Brake Does Not Release
3. Brake Lining Overheats and Wears Rapidly
4. Unstable Braking Torque
5. Gearbox Vibration on the Bridge
6. Trolley Runs “On Three Wheels”
7. Trolley Wheel Slipping During Travel
8. Trolley Sways Violently on Starting
9. Bridge Wheel Flange Rubbing (Rail Gnawing)
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1. Brake Fails to Hold (Insufficient Braking Torque)

Symptoms: The hoist drifts — the load drops by gravity — and the trolley or crane drifts along the runway after stopping.

Causes and fixes:

1. Oil or grease on the brake wheel surface reduces the friction coefficient and braking torque. Fix: Clean the brake wheel surface with kerosene or gasoline.
2. The brake lining is badly worn and the rivets are exposed; during braking the rivets contact the brake wheel, reducing braking torque and scoring the wheel surface. Fix: Replace the brake lining.
3. The main spring is incorrectly adjusted with insufficient tension. Fix: Re-adjust the brake to increase main spring tension.
4. The main spring is fatigued, aged or cracked, losing elasticity and tension. Fix: Replace the spring and re-adjust the brake.
5. The brake is incorrectly installed — the brake frame is off-center or skewed relative to the brake wheel. Fix: Loosen the frame anchor bolts, tighten the brake until the shoes grip the wheel, pack the gap under the frame, then re-tighten the bolts so the frame and wheel are concentric.
6. The solenoid stroke is wrongly adjusted, or an obstruction sits under the horizontal lever of a long-stroke brake solenoid. Fix: Re-adjust the solenoid stroke or remove the obstruction.
7. The hydraulic brake thruster impeller turns stiffly, reducing braking torque. Fix: Adjust the impeller, remove binding and let it rotate freely.
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2. Brake Does Not Release
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Symptoms: The brake fails to open, so the mechanism cannot start.

Causes and fixes:

1. Main spring tension is too high and the solenoid pull force is lower than the spring force. Fix: Re-adjust the brake to reduce main spring tension.
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2. The brake lever linkage is binding, blocking the release force. Fix: Inspect the linkage and remove the binding.
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3. The brake push rod is bent and its tip cannot reach the solenoid armature, so the shoes cannot be pushed open. Fix: Straighten or replace the push rod.
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4. The brake lining sticks to the dirty brake wheel surface. Fix: Clean the brake wheel surface.
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5. The solenoid coil is burned out or the wiring is broken, leaving no magnetic pull force. Fix: Replace the coil or reconnect the wiring.
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6. The hydraulic thruster impeller is stuck. Fix: Clear the impeller binding.
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7. Excessive voltage drop brings the coil voltage below 80% of rated voltage, so the magnetic pull is weaker than the spring force. Fix: Eliminate the cause of the voltage drop and restore normal voltage.
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3. Brake Lining Overheats, Smokes and Wears Rapidly
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Symptoms: The brake lining heats up, smokes, smells burnt and wears away quickly.
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Causes and fixes:

1. The clearance between the lining and the brake wheel is too small, so the lining contacts the wheel during normal operation. Fix: Re-adjust the clearance evenly so the lining fully disengages when the brake is released.
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2. The auxiliary spring of a short-stroke brake has failed and cannot push the shoes away from the wheel. Fix: Replace the auxiliary spring and re-adjust the brake.
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3. The brake frame is not concentric with the brake wheel, so the lining edge never disengages. Fix: Reinstall the brake and achieve concentricity.
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4. The brake wheel surface is rough or mismatched with the lining. Fix: Re-machine the brake wheel or replace it.
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4. Unstable Braking Torque
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Symptoms: Braking torque fluctuates and braking is inconsistent.

Causes and fixes:

1. The brake wheel is out of round with excessive radial runout, so it periodically strikes the brake shoes during braking. Fix: Re-machine the brake wheel to specification or replace it with a qualified one.
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2. The brake frame is not concentric with the brake wheel, and the wheel strikes the shoe during braking. Fix: Reinstall and re-adjust the brake frame.
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5. Gearbox Vibration on the Bridge
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Symptoms: The gearbox vibrates on the bridge frame during operation.
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Causes and fixes:

1. The gearbox anchor bolts are loose. Fix: Tighten the anchor bolts.
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2. The gearbox input shaft is misaligned with the motor shaft, or the output shaft is misaligned with the driven shaft. Fix: Re-align the gearbox to the required concentricity.
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3. The supporting steel structure under the gearbox is not rigid enough and deforms under load. Fix: Reinforce the supports to increase rigidity.
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6. Trolley Runs “On Three Wheels”
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Symptoms: Only three trolley wheels contact the rail; one wheel is suspended in the air.
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Case 1 — The same wheel (Wheel A) is always suspended wherever the trolley is on the bridge:
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1. Wheel A is out of tolerance with a smaller diameter, so it hangs when all axle mounting axes are in one horizontal plane. Fix: Replace the wheel, or lower its axle mounting position to eliminate the gap.
2. The wheels are within tolerance, but mounting precision is poor — the four axles are not in one plane and Wheel A’s axle is high. Fix: Lower Wheel A’s axle so all four axles are in the same plane.
3. The trolley frame is defective or deformed, and the corner warps upward. Fix: Straighten the trolley frame to eliminate the warp.
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Case 2 — “Three-wheel” running appears only at one or two to three positions on the bridge:
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1. The elevation difference between the two main girders at the same cross-section exceeds tolerance, so the wheel above the lower girder is suspended. Fix: Adjust the girder elevations to within tolerance.
2. The trolley rail installation is poor and the rail top elevations at the same cross-section differ beyond tolerance. Fix: Adjust the rails so both rail tops are level or within tolerance at that cross-section.
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7. Trolley Wheel Slipping During Travel
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Symptoms: The trolley wheels slip while the trolley is travelling.

Causes and fixes:

1. Oil, sand or (for outdoor cranes) frost and ice on the rail tops. Fix: Clean the rail tops.
2. Poor wheel mounting with a suspended wheel — especially a driving wheel — or too little wheel load. Fix: Adjust the wheel mounting positions and increase the driving-wheel load.
3. The rail top elevation difference at one cross-section is too large, causing unequal driving-wheel loads. Fix: Adjust the trolley rails to the installation standard.
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8. Trolley Sways Violently on Starting
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Symptoms: The trolley body sways and vibrates severely at startup.

Cause and fix:

1. With a squirrel-cage motor, the trolley starts too abruptly when driving-wheel loads are uneven or one wheel is suspended. Fix: Adjust the wheel mounting precision or the trolley rails to the installation standard.
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9. Bridge Wheel Flange Rubbing (Rail Gnawing)
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Symptoms: The wheel flanges wear severely; the crane may occasionally run off the rail.

Causes and fixes:

1. The wheels are out of specification — especially when the two driving wheels differ greatly in diameter, producing unequal linear speeds on the two sides so the crane runs skewed. Fix: Measure the driving wheel diameters, remove the larger wheel and re-machine it to match the other before reinstalling.
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2. The drive backlash differs too much between the two drive trains, so the crane starts asynchronously and also skews during braking. Fix: Inspect both drive trains and remove the excessive backlash so both shafts meet the technical requirements.
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3. Poor wheel mounting precision — wheels tilted in the horizontal direction steer the crane into a skew and cause severe flange rubbing. Fix: Check and re-align the tilted wheels so the horizontal deviation is less than L/1000 (L is the measured chord length).
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4. The bridge frame is deformed and the diagonal dimensions are out of tolerance (diamond shape). Fix: Straighten the frame with flame straightening, or adjust the wheel positions so the diagonal difference meets the standard.
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5. Poor runway installation — excessive elevation differences or span out of tolerance. Fix: Adjust the runway rails to the installation standard.
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6. With individually driven ends, the brakes are incorrectly adjusted — if one brake is not fully released, the resistance differs between the two sides. Fix: Adjust both brakes so they release fully during travel and produce equal braking torque when stopping.
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7. The two drive motors run at different speeds, so the linear speeds on both sides differ. Fix: Replace the motor to achieve synchronization.
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8. Oil, frost or debris on the rail tops. Fix: Clean the rails.
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Frequently Asked Questions (FAQ)
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1. Why does my overhead crane brake fail to hold the load?
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The most common causes are oil or grease on the brake wheel, worn brake linings with exposed rivets, an incorrectly adjusted or fatigued main spring, brake misalignment, or a stiff hydraulic thruster impeller. Clean the wheel, replace worn linings or springs, and re-adjust the brake.
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2. Why won’t the crane brake release?
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The main spring may be too strong, the lever linkage binding, the push rod bent, the thruster impeller stuck, the solenoid coil burned out, or the coil voltage below 80% of rated voltage due to voltage drop. Check each of these in order.
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3. Why does the trolley run on three wheels?
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Either one wheel is out of tolerance, the four wheel axles are not in one horizontal plane, the trolley frame is warped, or the main girder / rail top elevations differ beyond tolerance at a cross-section. Fix the specific cause to restore four-point contact.
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4. What is crane rail gnawing (wheel flange rubbing)?
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Rail gnawing is when the wheel flanges grind against the rail sides, usually caused by unequal driving-wheel diameters, differing drive backlash, tilted wheels, frame deformation, poor runway installation, or uneven brakes and motor speeds. If left uncorrected it can cause severe flange wear and even derailment.
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5. Why does the crane gearbox vibrate?
Loose anchor bolts, misalignment between the gearbox shafts and the motor or driven shafts, or a weak supporting structure are the usual causes. Tighten, re-align and reinforce as required.

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