Scope & Purpose
This maintenance manual covers preventive maintenance on electric hoisting installations with a lifting capacity of 0.5 to 10 tons, in accordance with EN 14492-1 and ISO 4301. The procedure includes gearbox inspection, brake disc wear measurement and chain stretch verification.
Perform this maintenance:
- Every 250 operating hours (or quarterly for heavy use)
- After every 10,000 lift cycles
- With reduced lifting performance
- In case of abnormal noises during operation
- For annual inspection in accordance with NEN 2644
Safety procedures
CRITICAL SAFETY WARNINGS:
• LOTO PROCEDURE MANDATORY: Switch off main power, lock and label in accordance with NEN-EN-IEC 60204-32
• FALLING WEIGHT HAZARD: Never leave a certain load hanging from a crane during maintenance
• TENSIONED PARTS: Brake spring is under preload - gradual adjustment required
• PROTECT WORK AREA: 3m safety zone around hoisting installation
• PERSONAL PROTECTIVE EQUIPMENT MANDATORY: Safety helmet, safety glasses, non-slip work gloves, safety shoes S3
Tools & Materials
| Tools | Specification | Quantity | Explanation |
|---|---|---|---|
| Torque wrench | 10-100 Nm, ±3% accuracy | 1 | For gearbox mounting |
| Digital caliper | 0-200mm, 0.01mm resolution | 1 | Brake disc thickness measurement |
| Chain stretch measuring instrument | For 1m chain length | 1 | DIN 5686 compliant |
| Endoscopy camera | Ø8mm, 1m cable, LED lighting | 1 | Internal gearbox inspection |
| Digital torque meter | 0.1-10 Nm range | 1 | Bearing clearance check |
| Magnetic base dial indicator | 0-10mm, 0.01mm scale | 1 | Axial clearance measurement |
| Alignment strap | Precision 0.02mm/m | 1 | Engine-gearbox alignment |
| Vibration analyzer | 10Hz-10kHz, RMS measurement | 1 | Bearing condition assessment |
Pre-Maintenance Inspection Checklist
| Inspection Item | Control | Accept/Reject Criteria | Notes |
|---|---|---|---|
| Power supply status | LOTO performed | Locked + tagged | □ Agreed |
| Load on hook | Complete impeachment | No hanging weight | □ Agreed |
| Workspace | 3m safety zone | No obstacles/personnel | □ Agreed |
| Visual gearbox | External damage | No cracks/deformations | □ Agreed |
| Oil level indication | Dipstick/window | Between MIN-MAX marking | □ Agreed |
| Chain running | Visual inspection | No visible damage | □ Agreed |
| Brake disc access | Accessibility | Free access for measurement | □ Agreed |
| Documentation | Last maintenance | Max. 3 months ago | □ Agreed |
Step-by-Step Maintenance Procedure
PHASE 1: Gearbox Inspection
Step 1: External gearbox control
- Measure vibration levels on bearing housings: maximum 4.5 mm/s RMS according to ISO 10816-1
- Check motor flange mounting: torque 45±5 Nm for M10 bolts
- Verify engine-gearbox alignment: maximum 0.05mm eccentric/0.02° angular deviation
- Inspect oil drain plug: no leak visible
Common mistake: Vibration measurement without thermal stabilization - wait 30 minutes after standstill.
Step 2: Internal Gear Inspection
- Remove inspection cover (M8 bolts, 25 Nm torque)
- Perform endoscopic inspection of gears:
- Tooth flank wear: maximum 5% of tooth thickness
- Pitting: no zones >10mm²
- Tooth fracture: not acceptable
- Manually rotate output shaft 360° - check for snags
- Measure gear backlash: 0.2-0.4mm backslash for modules 2-4
Step 3: Bearing clearance verification
- Measure axial play main shaft: 0.05-0.15mm allowed
- Check radial clearance: maximum 0.02mm for precision bearings
- Bearing running torque test: <2 Nm for unloaded axle
- Assess grease color: bright yellow/brown acceptable, black = replace
PHASE 2: Brake Disc Wear Measurement
Step 4: Make the brake disc accessible
- Remove brake hood (6x M6 bolts, 12 Nm)
- Adjust brake pressure gradually to 0 bar
- Carefully remove brake lining
Warning: Brake spring remains tensioned - use suitable clamps.
Step 5: Disc thickness measurement
- Measure brake disc thickness at 8 positions (45° intervals)
- Minimum thickness according to manufacturer: usually 80% of original thickness
- Maximum difference between measuring points: 0.05mm
- Check surface roughness: Ra <3.2μm required
| Measuring position | Standard Thickness (mm) | Wear limit (mm) | Replace at (mm) |
|---|---|---|---|
| 0° | 12.0 | 9.6 | ≤9.5 |
| 45° | 12.0 | 9.6 | ≤9.5 |
| 90° | 12.0 | 9.6 | ≤9.5 |
| 135° | 12.0 | 9.6 | ≤9.5 | >
Step 6: Brake lining inspection
- Measure lining thickness: minimum 3mm of material over rivets
- Check for cracks/crumbling
- Verify mounting rivets: no loose or damaged ones
- Assess wear pattern: evenly over entire surface
PHASE 3: Chain Stretch Control
Step 7: Chain elongation measurement
- Measure 1 meter chain length under 1% working load
- Acceptable stretch: maximum 2% for Class M(4) chain according to DIN 5686
- Replace if >3% stretch or if in doubt
- Check chain tension: 0.5-1.5% sag when unloaded
| Chain Pitch | Standard Length 1m | Wear limit | Replace at |
|---|---|---|---|
| 8mm | 1000mm | 1020mm | ≥1025mm |
| 10mm | 1000mm | 1020mm | ≥1025mm |
| 13mm | 1000mm | 1020mm | ≥1025mm |
Step 8: Sprocket Teeth Check
- Inspect tooth profile for wear: maximum 10% tooth reduction
- Check tooth clearance with chain: 0.1-0.3mm normal
- Verify sprocket mounting: 180±10 Nm for M16 bolt
- Chain running test: smooth without hitches through full lift stroke
PHASE 4: Reassembly
Step 9: Installing brake parts
- Install brake lining with specified torque: 15±2 Nm
- Adjust braking force: 1.2x safety coefficient in accordance with NEN 2644
- Check braking performance: complete standstill within 0.5m at rated load
- Replace brake hood: 12±1 Nm for M6 bolts
Step 10: Close gearbox
- Replace inspection cover gasket if damaged
- Mount cover: 25±3 Nm for M8 bolts (tighten crosswise)
- Check oil level after 15 minutes of stabilization
- Check tightness: no leakage after 24 hours
Post-Maintenance Verification Checklist
| Test | Expected Result | Actual Result | Pass/Fail |
|---|---|---|---|
| Test run without load | Smooth running, <70dB | ____ | □ Pass □ Fail |
| Brake test 25% load | Stop within 0.3m | ____ | □ Pass □ Fail |
| Brake test 100% load | Stop within 0.5m | ____ | □ Pass □ Fail |
| Vibration level | <4.5mm/s RMS | ____ | □ Pass □ Fail |
| Temperature rise | <40°C above ambient | ____ | □ Pass □ Fail |
| Full lift stroke | Without hitches | ____ | □ Pass □ Fail |
| Emergency stop function | Immediate stop | ____ | □ Pass □ Fail |
| Limit switches | Correct functioning | ____ | □ Pass □ Fail |
Troubleshooting Guide
| Symptom | Probable Cause | Corrective Action |
|---|---|---|
| Excessive vibration (>6 mm/s) | Gearbox bearing stroke | Replace bearings, check alignment |
| Abnormal noises during lifting | Gear wear/damage | Inspect gears, replace if necessary |
| Brakes do not fully engage | Brake disc below minimum thickness | Replace brake disc and lining |
| Jerky movement under load | Chain stretch >3% | Replace entire chain |
| Gearbox overheating | Insufficient/contaminated lubricant | Replace transmission oil, check level |
| Reduced lifting speed | Slipping engine clutch | Adjust or replace coupling |
| Irregular chain running | Worn sprocket | Replace sprocket |
| Frequent brake lining wear | Incorrect brake force adjustment | Calibrate braking system according to specification |
Recommended Maintenance Schedule
| Maintenance activity | Frequency | Estimated Duration | Required Skill Level |
|---|---|---|---|
| Visual inspection general | Weekly | 15 minutes | Operator |
| Sprocket lubrication | Monthly | 30 minutes | Maintenance technician |
| Full Inspection (this procedure) | Quarterly | 4-6 hours | Experienced technician | >
| Change transmission oil | Annually | 2 hours | Maintenance technician |
| Complete overhaul of gearbox | 5 years/10,000 hours | 4-24 hours | Specialist |
| Replace chain | As required/at 3% stretch | 3 hours | Experienced technician |
| Legal inspection | Annually | 8 hours | Certified inspector |
Spare Parts Reference
| Part description | Typical Specification | UNITEC Category |
|---|---|---|
| Transmission oil | ISO VG 320, DIN 51517 Part 3 | Lubricants & Oils |
| Ball bearings gearbox | 6308-2RS, ABEC-3 quality | Bearings & Bearing Technology |
| Brake disc | GG-20, hardness 180-220 HB | Braking systems |
| Brake lining | Asbestos-free, μ=0.35-0.45 | Braking systems |
| Lifting chain | DIN 5686 Class M(4), galvanized | Lifting materials |
| Sprocket | C45 hardened, HRC 45-55 | Lifting materials |
| Gearbox seals | NBR 70 Shore A, -30/+100°C | Seals |
| Gearbox bolts | DIN 912 M8x25, 8.8 quality | Fastening materials |
For specific part numbers and technical drawings, consult the UNITEC-D e-catalog at www.unitecd.com/e-catalog/. Our technical team is available to advise on compatibility and alternative specifications.
References
- NEN 2644: Periodic inspection of hoisting equipment
- EN 14492-1: Crane parts - Wire barrels and sprockets for steel cable or chain - Safety aspects
- ISO 4301-1: Cranes - Classification
- DIN 5686: Endless round bar steel chain, closed welded links
- ISO 10816-1: Mechanical vibration - Evaluation of machine vibrations by measurements on non-rotating parts
- NEN-EN-IEC 60204-32: Safety of machines - Electrical equipment of machines - Part 32: Requirements for lifting equipment
