Common Faults and Troubleshooting of Crane Mechanical Components

1. General Overview

Cranes are mainly composed of three interactive systems: mechanical transmission mechanisms, metal structures, and electrical control systems. The mechanical part includes hoisting, traveling, luffing, and slewing mechanisms.

During long-term operation, mechanical parts are subject to wear, fatigue, overload, poor lubrication, improper installation, and environmental factors, which lead to various failures. This document specifies typical faults, root causes, potential hazards, and standardized troubleshooting measures for key crane components and mechanisms.

2. Common Faults and Treatment of Key Components

2.1 Forged Hook

Fault & Damage	Main Causes & Hazards	Treatment Measures
Fatigue cracks	Overload, material defects, long-term fatigue; may cause fracture and falling load	Replace immediately
Wear at dangerous section > 10%	Long-term friction and fatigue; reduces structural strength	Replace the hook
Plastic deformation or opening enlargement	Long-term overload or high-temperature radiation; risk of unhooking	Replace immediately
Unauthorized welding repair	Causes internal stress and brittle fracture; seriously reduces load capacity	Prohibited; replace the hook

2.2 Laminated Hook

Fault & Damage	Main Causes & Hazards	Treatment Measures
Deformation, cracks	Overload, fatigue damage; risk of sudden fracture	Replace the hook assembly
Pin shaft wear > 3%–5% of diameter	Poor lubrication, eccentric force; easy to cause pin fracture	Replace the pin shaft
Lug bushing wear > 50% thickness	Improper stress distribution; increases vibration and wear	Replace the bushing

2.3 Steel Wire Rope

Fault & Damage	Main Causes & Hazards	Treatment Measures
Broken wires, broken strands, corrosion, kinking	Improper lubrication, friction, overload, electrical arcing; may cause sudden breakage	Replace in accordance with relevant standards
Cage deformation, severe flattening	Improper winding, mechanical damage; extremely dangerous	Replace immediately

2.4 Pulley

Fault & Damage	Main Causes & Hazards	Treatment Measures
Uneven groove wear, rim cracking	Misalignment, substandard material; accelerates rope wear	Repair or replace pulley
Spindle wear exceeding limit	Poor lubrication; may cause shaft breakage	Replace spindle
Non-rotation or jamming	Contamination, bearing damage; causes severe rope wear	Clean, lubricate, or replace bearings

2.5 Drum

Fault & Damage	Main Causes & Hazards	Treatment Measures
Fatigue cracks	Long-term cyclic load; risk of rupture	Replace drum; welding repair is prohibited
Wall thickness wear 15%–20%	Long-term friction; reduces load-bearing capacity	Replace drum
Shaft or key wear	Loose connection, overload; may cause shaft shear	Inspect and replace shaft or keys

2.6 Gears

Fault & Damage	Main Causes & Hazards	Treatment Measures
Tooth breakage, pitting, wear > 15%–25%	Overload, poor lubrication, improper meshing; causes transmission failure	Replace gears; for hoisting mechanisms, replace strictly
Keyway damage	Loose fit, overload; causes power loss	Replace or repair keyway

2.7 Shafts

Fault & Damage	Main Causes & Hazards	Treatment Measures
Cracks, bending > 0.5 mm/m	Material defects, overload; causes vibration and fracture	Replace the shaft
Keyway wear or damage	Loose connection; reduces transmission stability	Replace for hoisting mechanisms; repair for traveling mechanisms

2.8 Wheels

Fault & Damage	Main Causes & Hazards	Treatment Measures
Cracks on tread or web	Improper heat treatment, fatigue; risk of derailment	Replace wheels
Tread wear > 15%, flange wear > 50%	Rail gnawing, uneven load; causes derailment	Replace in pairs

2.9 Brake Components

Fault & Damage	Main Causes & Hazards	Treatment Measures
Cracks on pull rods or springs	Fatigue, overload; causes brake failure	Replace immediately
Brake wheel or lining wear exceeding limit	Friction, high temperature; causes slipping and failure	Replace lining; regrind or replace brake wheel
Misalignment, loose connections	Improper adjustment; unstable braking torque	Adjust and fasten

2.10 Couplings

Fault & Damage	Main Causes & Hazards	Treatment Measures
Cracks, tooth wear, pin hole deformation	Vibration, impact, overload; causes power transmission failure	Replace coupling assembly
Rubber parts or pins wear	Aging, fatigue; causes backlash and vibration	Replace wearing parts

3. Faults and Troubleshooting of Mechanical Assemblies

3.1 Rolling Bearings

• Overheating, abnormal noise, grinding sound

  Causes: Contamination, insufficient or improper lubrication, bearing damage

  Measures: Clean components, replace lubricant, replace bearings

3.2 Braking System

• Failure to hold load (slipping)

  Causes: Oil contamination, worn linings, improper clearance, weak springs

  Measures: Clean friction surfaces, adjust clearance, replace worn parts

• Brake fails to release

  Causes: Stuck mechanism, burnt coil, improper spring adjustment

  Measures: Lubricate hinges, replace electrical parts, readjust braking force

• Overheating and rapid wear

  Causes: Uneven clearance, rough contact surface

  Measures: Re-adjust, resurface or replace brake wheel

3.3 Speed Reducers

• Abnormal noise, vibration, overheating

  Causes: Improper meshing, bearing damage, insufficient oil, leakage

  Measures: Re-align, replace bearings, replenish or change oil, replace seals

3.4 Crane Traveling & Trolley Mechanisms

• Rail gnawing, skewing, three-legged running

  Causes: Uneven wheel diameter, frame deformation, misaligned rails, loose fasteners

  Measures: Adjust or replace wheels, align axles, correct rail position, tighten bolts

• Trolley slipping, swinging

  Causes: Contamination on rail, uneven wheel pressure, unstable drive

  Measures: Clean surfaces, adjust wheel load, inspect motors and gears

3.5 Rope-Pulley System

• Rapid wire rope wear or breakage

  Causes: Small pulley diameter, dirty grooves, misalignment, poor lubrication

  Measures: Clean and lubricate, replace pulleys, adjust alignment

4. General Safety Principles

• Any component with cracks or dangerous deformations must be replaced immediately.

• Welding repair on key load-bearing parts is strictly prohibited.

• Wearing parts that reach scrap standards shall not be reused.

• Maintenance must follow equipment specifications and relevant safety standards.