I. General Provisions

1. Scope of Application

This regulation applies to the maintenance of electric single-girder and double-girder overhead cranes.

2. Structure Brief

An overhead crane mainly consists of three parts: mechanical part, metal structure part and electrical part.

1. Mechanical part: Main hoisting mechanism, auxiliary hoisting mechanism, trolley travelling mechanism and bridge travelling mechanism.

2. Metal structure part: Crane bridge and trolley frame.

3. Electrical part: Electrical equipment and electrical circuits.

3. Main Technical Parameters

Rated lifting capacity: 3～50 tLifting height: Main hook 12～16 m; Auxiliary hook 14～18 mCrane span: 7.5～31.5 m

II. Acceptance Standard for Good Condition

1. Parts and Components

1. All parts, components and accessories shall be complete and conform to quality standards.

2. Interlocking devices and safety protection devices of main and auxiliary equipment shall be complete, accurate and sensitive, and calibrated regularly. All connecting bolts shall be fully fastened and comply with technical requirements.

3. A clear nameplate shall be fixed at an obvious position of the crane, marked with equipment name, model, rated lifting capacity, manufacturer, manufacturing date, etc. Safety marks shall be provided on the main and auxiliary hooks.

2. Operating Condition

1. The unit shall reach the rated capacity or verified capacity.

2. All operating parameters shall meet technical requirements.

3. The lubrication system shall be unobstructed and well lubricated; oil quality, oil level and oil temperature shall comply with regulations.

4. The unit shall operate in good condition with all indicators up to standard.

3. Technical Documents

1. Complete records of acceptance, maintenance, inspection and operation.

2. Complete equipment drawings and operation manuals.

3. Complete equipment archives.

4. Qualification certificate for pressure vessel inspection.

5. Complete operating regulations and maintenance specifications.

6. Complete drawings of vulnerable spare parts.

4. Equipment and Environment

1. The working environment shall be spacious, well-lit and safe for operation.

2. The equipment and surrounding area shall be clean and tidy; no sundries on the track; no leakage at all sealing points.

III. Maintenance Cycle

1. Minor maintenance: Every 3 months

2. Intermediate maintenance: Every 12 months

3. Overhaul: Every 24～36 months

IV. Maintenance Contents

1. Minor Maintenance

1. Fasten or replace connecting bolts of all parts.

2. Inspect and repair brakes; replace wearing parts.

3. Inspect and repair couplings; replace wearing parts.

4. Check and replace lubricating oil of all transmission devices.

5. Overhaul reducers, replace vulnerable parts and eliminate oil leakage.

6. Inspect motors and other safety protection devices.

7. Inspect steel wire ropes and hooks.

8. Check lighting facilities and clean dirt on sliding contact lines.

2. Intermediate Maintenance

1. Include all contents of minor maintenance.

2. Inspect and replace pulleys, hooks and steel wire ropes.

3. Inspect all transmission devices, clean and replace lubricant, renew wearing parts.

4. Inspect main electrical components and electrical protection devices.

5. Check the running condition of bridge and trolley wheels, and eliminate rail gnawing.

3. Overhaul

1. Include all contents of intermediate maintenance.

2. Repair or replace brake drums, rope drums, transmission shafts and other components.

3. Rectify bridge deformation; adjust or replace rails.

4. Fully overhaul and restore hoisting mechanisms and travelling mechanisms.

5. Comprehensive repair and renovation of electrical equipment and safety protection devices.

6. Derusting and full anti-corrosion coating.

V. Maintenance Quality Standard

3. Steel Wire Rope

1. The quality of steel wire ropes shall comply with GB 1102 Round Strand Steel Wire Rope.

2. The length of new steel wire rope shall be the sum of lifting height plus 3.5 reserved coils on the drum.

3. The rope shall be scrapped when surface corrosion or wear exceeds 40%; broken wires are not allowed.

4. Drum

1. Replace the drum when groove wear cannot restrain the steel wire rope normally.

2. Scrap the drum if cracks appear or the wall wear reaches 20% of the original thickness.

5. Hook

1. The hook shall be equipped with a safety device to prevent accidental unhooking.

2. The hook surface shall be smooth and clean without peeling, sharp corners, burrs or cracks. Welding repair of hook defects is prohibited.

3. The hook must undergo load inspection as required.

4. The hook shall be scrapped if any of the following occurs:a. Cracks;b. Wear of dangerous section reaches 10% of original size;c. Opening degree increases by 15% compared with original size;d. Torsional deformation exceeds 10°;e. Plastic deformation occurs at dangerous section or hook neck.

6. Pulley

1. The pulley shall be scrapped under any of the following conditions:a. Cracks or uneven groove wear up to 3 mm;b. Groove wall wear reaches 20% of original thickness;c. The reduction of groove bottom diameter due to wear reaches 50% of steel wire rope diameter.

2. The pulley groove shall be smooth and free from defects that may damage the steel wire rope.

7. Gear Coupling

1. Replace the coupling if one fatigue crack exists at the tooth root or any tooth is broken.

2. Replace when tooth thickness wear reaches 20% for travelling mechanism and 15% for hoisting mechanism (15% for lifting dangerous goods). The shaft alignment deviation and end clearance of outer gear sleeve shall comply with specifications.

8. Wheel

The wheel shall be scrapped if any of the following occurs:

1. Wheel cracks;

2. Flange wear exceeds 50% of original thickness;

3. Uniform end wear exceeds 30% of original thickness after machining;

4. When driving wheel wear exceeds 0.005D (D = wheel diameter), machining repair is required, and the diameter difference between two wheels shall be less than 0.005D; scrap when the diameter is reduced by 10 mm compared with the original.

9. Brake

All brake parts shall meet the following requirements:

1. The brake shoe shall fit closely to the brake drum during braking; the lining shall be in good condition. When the brake is released, the gaps on both sides of the drum shall be equal.

2. No cracks on the brake drum; surface dents and scars shall not exceed 2 mm².

3. Brakes of travelling mechanism shall stop the bridge and trolley within 200 mm.

4. The braking torque shall reliably support 1.25 times the rated lifting load.

10. Safety Protection Devices

1. The comprehensive error of overload limiter shall not exceed 8%. It shall send a prompt alarm when the load reaches 90% of rated capacity; automatically cut off the hoisting power and send a prohibition alarm when overloaded to prevent accidents.

2. The comprehensive error of moment limiter shall not exceed

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