The gear system of manual hoists (such as chain hoists and lever hoists) is their core transmission component, and faults may involve multiple dimensions such as mechanical wear, operational errors, inadequate maintenance, and environmental factors. The following is a systematic explanation from five aspects: fault types, cause analysis, troubleshooting methods, solutions, and preventive measures:

1、 Common types and causes of gear failures

Gear wear/tooth breakage

Performance: laborious lifting, jamming, abnormal noise or sudden failure.

Cause:

Overloading use (causing tooth surface crushing and tooth breakage due to exceeding the rated load);

Poor lubrication (gear oil shortage, poor quality lubricant causing dry friction, tooth surface pitting corrosion);

Long term high-frequency use or accelerated tooth surface wear under impact loads;

Defects in gear material/heat treatment (such as insufficient hardness, uneven quenching).

Gear stuck/jammed

Performance: The chain cannot be pulled and there is a sudden increase in operational resistance.

Cause:

Foreign objects between gears (metal debris, dust embedded in tooth gaps);

Gear shaft bending and bearing damage leading to meshing deviation;

Corrosion inside the gearbox (due to damp environment or failure to prevent rust in a timely manner);

Installation errors (gear center distance deviation, axial displacement).

Transmission failure (slip/self-locking failure)

Performance: Heavy objects are unable to hover or descend uncontrollably.

Cause:

Brake system malfunction (friction plate wear, oil contamination, damaged pawl/ratchet);

Poor meshing between gears and sprockets (chain skipping, sprocket wear);

The failure of the gearbox seal leads to internal contamination (water, dust entering).

2、 Fault diagnosis and troubleshooting methods

Preliminary inspection

Visual/tactile: Observe the wear, breakage, and corrosion of gear tooth surfaces; Check the condition of the lubricating oil (whether it is cloudy or clumped); Touch the gearbox casing to determine temperature rise (abnormal heating may indicate internal malfunction).

No load test: Pull the chain to observe whether the gear rotates smoothly, whether there is any jamming or abnormal noise; Test the brake function (whether the heavy object naturally slides down after stopping pulling).

depth detection

Professional tool: Use a thickness gauge to detect gear wear (if the tooth thickness is reduced by more than 30% compared to the original thickness, it needs to be replaced); Use a gear tester to check the tooth profile error and meshing clearance.

Disassembly and inspection: Disassemble the suspected faulty gearbox, inspect the wear/damage of gears, shafts, bearings, and brakes, and clean up internal foreign objects.

3、 Solution and repair steps

Gear replacement

Replace gears with excessive wear and tear (such as tooth surface pitting, broken teeth, and excessive tooth thickness reduction);

Select gears with the same specifications as the original factory (matching the number of teeth, module, and material);

Adjust the gear mesh clearance during installation (generally controlled at 0.15-0.35mm) to ensure good meshing.

Repair and Adjustment

Gear welding repair: precision machining of locally worn gears after welding to restore tooth profile;

Shaft/bearing replacement: Replace bent shafts and damaged bearings to ensure smooth transmission;

Brake system maintenance: replace worn friction pads, claws/ratchet wheels, clean oil stains, and adjust brake clearances.

Lubrication and Sealing

Regularly apply specialized lubricating grease (such as lithium based grease) and avoid using corrosive lubricants;

Replace aging seals (such as oil seals, O-rings) to prevent dust and moisture from entering the gearbox.

4、 Preventive measures and maintenance recommendations

Standard operation

Overloading is strictly prohibited to avoid diagonal pulling and impact loads;

Before operation, check the status of the chain, hook, and brake to confirm that there are no abnormalities;

Keep dry and rust proof during storage, and avoid long-term exposure to humid/corrosive environments.

regular maintenance

Daily inspection: Check the lubrication of the gearbox, chain wear, and brake function before each use;

Periodic maintenance:

Light load use: lubricate gears and check gear wear every month;

Heavy duty use: Check gear meshing and bearing status every 250 hours or quarterly;

Long term disuse: Conduct a comprehensive inspection, lubrication, and no-load test before reusing.

Professional Intervention

Complex faults (such as abnormal gearbox noise and brake failure) need to be handled by qualified professionals;

Perform no-load and heavy load tests after maintenance to verify the reliability and transmission efficiency of the brake.

5、 Industry standards and compliance requirements

Standard basis: Adhere to ASME B30.16, OSHA, JB/T 7334-2016 and other standards to ensure that gear materials, heat treatment, lubrication, and safety devices (such as brakes and limiters) comply with specifications;

Recording and tracing: Maintenance and repair records need to be kept intact for auditing and fault tracing purposes;

Training and Qualification: Operation/maintenance personnel need to receive professional training and hold certificates to ensure standardized and safe operation.

The main equipment produced by Hebei Makita: stage electric hoist, electric chian hoist, wire rope electric hoist，Hand chain hoist, lever hoist, pneumatic hoist and other lifting equipment