A Brief Discussion on Common Malfunctions Analysis and Improvement Suggestions of European Steel Wire Rope Electric Hoists

Abstract

European steel wire rope electric hoists, widely used in industrial lifting operations, are prone to malfunctions such as brake failure, motor abnormalities, and control system faults during long-term use. This paper analyzes typical malfunctions, explores their root causes, and proposes targeted improvement strategies to enhance equipment reliability and operational safety.

1. Brake System Malfunctions

1.1 Excessive Brake Slip

Symptoms: Brake slip exceeds 80 mm during operation, failing to hold suspended loads.

Root Causes:

Excessive Brake Clearance: Cone-shaped rotor axial clearance exceeds 1.5–3 mm standard, reducing braking force.

Contaminated Friction Surfaces: Oil, grease, or debris on brake pads or discs degrades friction.

Worn Brake Components: Brake rings or friction pads exceed wear limits.

Improvement Strategies:

Adjust locknuts to set rotor axial clearance within 1.5–3 mm.

Clean friction surfaces with degreasers and replace contaminated components.

Replace worn brake rings or pads when wear exceeds 2 mm.

1.2 Brake Non-Engagement

Symptoms: Brake fails to engage after motor shutdown.

Root Causes:

Frozen Brake Mechanism: Rust or corrosion prevents brake disc movement.

Electrical Control Faults: Faulty rectifier modules or incorrect wiring delay brake activation.

Improvement Strategies:

Disassemble and clean brake components, applying anti-corrosion coatings.

Verify rectifier module wiring (e.g., ensure terminals 5 and 6 connect to control box terminals 153 and 151).

Replace over-励磁整流器 (over-excitation rectifiers) to reduce response time by 50%.

2. Motor System Malfunctions

2.1 Motor Startup Failure

Symptoms: Motor fails to start or hums without rotation.

Root Causes:

Voltage Deficiency: Input voltage drops below 90% of rated value (e.g., 342 V for 380 V systems).

Capacitor Degradation: Single-phase motor capacitors lose capacitance.

Phase Loss: Three-phase motor operates on two phases due to contactor faults.

Improvement Strategies:

Use voltmeters to verify input voltage and stabilize power supply.

Test capacitors with multimeters and replace those with capacitance below 80% of rated value.

Inspect contactors for burnt contacts or welded触点 (welded contacts) and replace faulty units.

2.2 Motor Overheating

Symptoms: Motor temperature exceeds 80°C during operation.

Root Causes:

Overloading: Exceeding rated lifting capacity.

Brake Drag: Insufficient brake clearance causes continuous friction.

Bearing Failure: Worn bearings increase mechanical resistance.

Improvement Strategies:

Install load sensors to prevent overloading.

Adjust brake clearance to eliminate drag.

Lubricate bearings monthly and replace those with axial play >0.1 mm.

3. Control System Malfunctions

3.1 Unresponsive Controls

Symptoms: Remote/button controls fail to activate hoist functions.

Root Causes:

Oxidized Contacts: Button or relay contacts corrode.

Loose Wiring: Control cable joints disconnect.

Faulty Limit Switches: Mechanical撞块 (limit stop blocks) misalign or switch contacts oxidize.

Improvement Strategies:

Clean contacts with contact cleaners and apply dielectric grease.

Tighten all electrical connections and replace frayed cables.

Realign limit stop blocks and replace oxidized microswitches.

3.2 Erratic Direction Control

Symptoms: Hoist moves opposite to commanded direction.

Root Causes:

Phase Reversal: Three-phase motor wiring reversed.

Control Logic Errors: PLC or relay programming mistakes.

Improvement Strategies:

Verify phase sequence with phase sequence meters and correct wiring.

Reprogram PLCs or relays per manufacturer diagrams.

4. Mechanical System Malfunctions

4.1 Chain/Wire Rope Jamming

Symptoms: Chain or wire rope binds during operation.

Root Causes:

Lubrication Failure: Rust forms on chains or ropes.

Guide Pulley Damage: Bearings in guide pulleys seize.

Misalignment: Wire rope derails from sheaves.

Improvement Strategies:

Apply specialized chain lubricants quarterly.

Replace seized guide pulley bearings.

Install rope guides to prevent derailment.

4.2 Gearbox Oil Leaks

Symptoms: Oil seeps from gearbox housing.

Root Causes:

Loose Fasteners: Bolts on gearbox cover loosen.

Degraded Gaskets: Aged seals fail to contain oil.

Improvement Strategies:

Torque all cover bolts to manufacturer specifications (e.g., 15–20 N·m).

Replace gaskets with silicone-based alternatives for better durability.

5. Environmental and Operational Factors

5.1 Cold-Weather Startup Failure

Symptoms: Motor fails to start in sub-zero temperatures.

Root Causes:

Frozen Brake Components: Moisture in brakes freezes.

Thickened Lubricants: Cold increases oil viscosity.

Improvement Strategies:

Install electric heaters in brake housings.

Use low-temperature lubricants (e.g., synthetic oils rated for -30°C).

5.2 Dust-Induced Faults

Symptoms: Limit switches or contacts fail due to dust accumulation.

Root Causes:

Contaminated Components: Dust blocks mechanical or electrical parts.

Improvement Strategies:

Enclose control boxes in IP65-rated housings.

Schedule weekly cleaning of limit switches and contacts.

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