Crane Reducer, Drum & Pulley: Common Faults, Causes & Solutions
The crane reducer is a mechanical device specially used in crane equipment, mainly used to reduce the speed of the motor and increase the torque to meet the needs of hoisting operations. The crane drum is one of the main components of the hoisting mechanism drum set, and it is a part that directly winds the steel wire rope.
The main material of the drum body is HT20-40 cast iron, ZG270-250 cast steel or Q235B/Q355B steel plate welding, among which the steel plate drum set is suitable for large-tonnage cranes. (JB/T 9006-2013 Crane Drum)
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Drum Set
The drum set is mainly composed of a drum, drum shaft, gear disc coupling (or large gear), drum hub, bearing housing and bearings, and realizes the lifting of heavy objects by winding the steel wire rope.
The role of the crane pulley is mainly reflected in two aspects: labor saving and changing the direction of force, which depends on the type of pulley (fixed pulley, movable pulley or pulley block) and its arrangement in the system. Through reasonable combination, it can save labor, change the direction of force application, and ensure the stable and safe operation of the crane. As the main load-bearing components of the motion mechanism, the reducer, drum and pulley may have some faults during daily use, inspection and maintenance, which affect the safety of crane operation.
The following are some faults of the reducer, drum and pulley, analyze the possible causes for the faults, and put forward certain solutions.
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Fracture of the high-speed gear shaft of the lifting reducer
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Reducer Faults
High-speed Gear Shaft Breakage of Hoisting Reducer
1) There is periodic gear flutter, which is particularly obvious on the driven wheel.
Fault Cause: Excessive pitch error and excessive backlash.
Solution: Repair and reinstall.
2) Severe metal friction sound, reducer vibration, and clinking sound of the casing.
Fault Cause: Too small backlash of the transmission gear, non-parallelism of the two gear shafts, sharp edges on the tooth top; uneven working surface of the gear teeth.
Solution: Repair and reinstall, including replacing parts such as gears and gear shafts.
3) Uneven knocking sound during gear meshing and casing vibration.
Fault Cause: Defects on the tooth surface, the gear is not in contact along the entire tooth surface, but only at one corner.
Solution: Replace the gear.
4) The casing, especially the bearing installation position, is overheated.
Fault Cause: Bearing damage; journal jamming; gear tooth wear; lack of lubricating oil.
Solution: Replace the bearing; trim the gear; replace the lubricating oil.
5) Oil leakage at the split surface.
Fault Cause: Seal failure; box deformation; uneven split surface; loose connecting bolts.
Solution: Replace the seal; inspect the split surface of the box, replace it if the deformation is severe; level the split surface; clean the oil return groove and tighten the bolts.
6) The reducer vibrates on the base.
Fault Cause: Loose fixing bolts; misalignment of the connecting axes with various parts; poor rigidity of the base.
Solution: Adjust and tighten the fixing bolts; align the axes to reduce circular runout; reinforce the base to increase rigidity.
7) Overall overheating of the reducer.
Fault Cause: Excessive lubricating oil.
Solution: Adjust the oil quantity according to the manufacturer’s recommendation.
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Drum Faults
Drum Inspection
1) Drum cracks.
Fault Cause: Drum fatigue or overloading operation.
Solution: Replace the drum.
2) Wear of drum shaft and key.
Fault Cause: Lack of daily maintenance.
Solution: Stop using it and immediately inspect and replace the shaft and key.
3) Steel wire rope skipping on the drum.
Fault Cause: Improper operation.
Solution: Operate correctly.
4) Severe wear of the drum wall.
Fault Cause: Lack of daily lubrication of the steel wire rope or long service life.
Solution: Strengthen daily maintenance, and replace it in time when the wear amount reaches 15%~20% of the original wall thickness.
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Pulley rim fracture
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Pulley Faults
Pulley Flange Breakage
1) Uneven wear of the pulley groove.
Fault Cause: Uneven material, improper installation, and poor contact between the rope and the pulley.
Solution: Replace when the wear amount of the groove wall reaches 1/10 of the original thickness and the radial wear reaches 1/5 of the rope diameter.
2) The wear amount of the pulley spindle reaches 3%~5% of the nominal diameter of the shaft.
Fault Cause: Spindle damage.
Solution: Replace.
3) The pulley cannot rotate.
Fault Cause: Lack of oil.
Solution: Inspect and apply lubricating oil.
4) Pulley tilt and looseness.
Fault Cause: Improper operation, loose positioning of parts on the shaft, or steel wire rope jumping out of the groove.
Solution: Inspect and strengthen correct operation.
5) Pulley cracks or flange breakage.
Fault Cause: Pulley damage.
Solution: Replace.
