I. General Provisions1. Scope of ApplicationThis regulation applies to the maintenance of electric single-girder and double-girder overhead cranes.2. Structure BriefAn overhead crane mainly consists of three parts: mechanical part, metal structure part and electrical part.Mechanical part: Main hoisting mechanism, auxiliary hoisting mechanism, trolley travelling mechanism and bridge travelling mechanism.Metal structure part: Crane bridge and trolley frame.Electrical part: Electrical equipment and electrical circuits.3. Main Technical ParametersRated lifting capacity: 3～50 tLifting height: Main hook 12～16 m; Auxiliary hook 14～18 mCrane span: 7.5～31.5 mII. Acceptance Standard for Good Condition1. Parts and ComponentsAll parts, components and accessories shall be complete and conform to quality standards.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.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 ConditionThe unit shall reach the rated capacity or verified capacity.All operating parameters shall meet technical requirements.The lubrication system shall be unobstructed and well lubricated; oil quality, oil level and oil temperature shall comply with regulations.The unit shall operate in good condition with all indicators up to standard.3. Technical DocumentsComplete records of acceptance, maintenance, inspection and operation.Complete equipment drawings and operation manuals.Complete equipment archives.Qualification certificate for pressure vessel inspection.Complete operating regulations and maintenance specifications.Complete drawings of vulnerable spare parts.4. Equipment and EnvironmentThe working environment shall be spacious, well-lit and safe for operation.The equipment and surrounding area shall be clean and tidy; no sundries on the track; no leakage at all sealing points.III. Maintenance CycleMinor maintenance: Every 3 monthsIntermediate maintenance: Every 12 monthsOverhaul: Every 24～36 monthsIV. Maintenance Contents1. Minor MaintenanceFasten or replace connecting bolts of all parts.Inspect and repair brakes; replace wearing parts.Inspect and repair couplings; replace wearing parts.Check and replace lubricating oil of all transmission devices.Overhaul reducers, replace vulnerable parts and eliminate oil leakage.Inspect motors and other safety protection devices.Inspect steel wire ropes and hooks.Check lighting facilities and clean dirt on sliding contact lines.2. Intermediate MaintenanceInclude all contents of minor maintenance.Inspect and replace pulleys, hooks and steel wire ropes.Inspect all transmission devices, clean and replace lubricant, renew wearing parts.Inspect main electrical components and electrical protection devices.Check the running condition of bridge and trolley wheels, and eliminate rail gnawing.3. OverhaulInclude all contents of intermediate maintenance.Repair or replace brake drums, rope drums, transmission shafts and other components.Rectify bridge deformation; adjust or replace rails.Fully overhaul and restore hoisting mechanisms and travelling mechanisms.Comprehensive repair and renovation of electrical equipment and safety protection devices.Derusting and full anti-corrosion coating.V. Maintenance Quality Standard3. Steel Wire RopeThe quality of steel wire ropes shall comply with GB 1102 Round Strand Steel Wire Rope.The length of new steel wire rope shall be the sum of lifting height plus 3.5 reserved coils on the drum.The rope shall be scrapped when surface corrosion or wear exceeds 40%; broken wires are not allowed.4. DrumReplace the drum when groove wear cannot restrain the steel wire rope normally.Scrap the drum if cracks appear or the wall wear reaches 20% of the original thickness.5. HookThe hook shall be equipped with a safety device to prevent accidental unhooking.The hook surface shall be smooth and clean without peeling, sharp corners, burrs or cracks. Welding repair of hook defects is prohibited.The hook must undergo load inspection as required.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. PulleyThe 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.The pulley groove shall be smooth and free from defects that may damage the steel wire rope.7. Gear CouplingReplace the coupling if one fatigue crack exists at the tooth root or any tooth is broken.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. WheelThe wheel shall be scrapped if any of the following occurs:Wheel cracks;Flange wear exceeds 50% of original thickness;Uniform end wear exceeds 30% of original thickness after machining;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. BrakeAll brake parts shall meet the following requirements: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.No cracks on the brake drum; surface dents and scars shall not exceed 2 mm².Brakes of travelling mechanism shall stop the bridge and trolley within 200 mm.The braking torque shall reliably support 1.25 times the rated lifting load.10. Safety Protection DevicesThe 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.The comprehensive error of moment limiter shall not exceed

Within the warranty period, on the premise that the crane is properly kept, correctly installed and used by the user, our company guarantees to provide the following services:Respond to user inquiriesAfter contract execution and product delivery, we shall promptly and responsibly reply to users’ inquiries concerning product technology and quality issues.Provide personnel training for operators, maintenance staff and management personnel.Fulfill product quality liabilitiesIf the product fails to meet quality standards or obviously affects normal use, we implement the policy of Three Guarantees and One Compensation: warranty repair, replacement, return, and compensation for economic losses.Provide free on-site guidance for equipment installation, commissioning and maintenance as required by the user.User visit: Collect opinions, improve products and optimize design to meet user demands.After the equipment operates normally, to better satisfy the user’s production needs and continuously improve our product quality and manufacturing level, users are kindly requested to fill in the Equipment Quality Feedback Form enclosed in the packing documents and send it back to our company, so that we can provide dedicated service for you.Undertake all product liabilities specified in the technical specifications of the contract to fully meet user requirements.Upon your request and through mutual negotiation, our company may undertake the whole process of installation and commissioning of the contracted equipment, or send professional technicians to the site to provide installation guidance.The warranty period is 12 months. Within the warranty period, any quality problems caused by our manufacturing defects shall be repaired or replaced free of charge.For equipment damage not caused by our liability, we shall give priority to supplying spare parts and providing maintenance services.We will supply wearing parts at preferential prices on a long-term basis.If the equipment breaks down within the warranty period, our on-site service personnel will arrive at the site within 24 hours after receiving your notice, with all services free of charge.

A dedicated construction team shall be organized for the construction. All construction personnel must hold Crane Installation and Maintenance Qualification Certificates.Prior to construction, constructors shall carefully inspect the original technical state of the equipment, including span, diagonal dimension, camber, etc., and check the completeness of spare parts and accessories, with all results properly recorded.Adopt suitable lifting equipment to move the crane into position and hoist it to the predetermined mounting location.Arrange electrical circuits including layout, wiring, cable laying and conduit threading; connect and position all electrical components in accordance with relevant specifications.Inspect and adjust electrical installations to ensure correct and in-place mounting, and conduct necessary performance tests.Inspect and adjust all mechanical components such as the lifting mechanism, crab travelling mechanism and trolley travelling mechanism, to ensure accurate installation and flexible operation so as to meet technical requirements.Inspect all safety protection devices and limit devices to ensure correct installation and compliance with relevant standards.Perform trial operation, and further inspect and adjust electrical systems, mechanical mechanisms and safety devices during operation.Carry out static load test, dynamic load test and related commissioning tests in accordance with GB 5905-86, and conduct overall inspection and adjustment of the complete crane.After all above works are completed and adjusted, proceed with formal handover and acceptance. The final acceptance shall be conducted jointly by Party A, safety supervision authority and relevant personnel.

PrefaceThis paper analyzes seven major mechanical fault sources of overhead cranes, including steel wire ropes, drums and rope pressure plates, hooks, reducer gears, brakes, wheels and rails, as well as safety accessories. Corresponding preventive measures and suggestions are put forward.While overhead cranes bring high efficiency, convenience and speed to enterprise production, frequent accidents occur due to inherent mechanical hidden dangers and improper operation, causing economic losses to the country and society and bringing suffering to the personnel involved and their families.The main causes of accidents are inherent mechanical failures and human operational errors. Studying mechanical faults, analyzing root causes and formulating preventive measures are key means to reduce crane mechanical accidents.Special equipment managers shall standardize operator behaviors, attach importance to potential mechanical faults, and formulate thorough and feasible prevention plans according to actual equipment conditions, so as to ensure safe crane operation. Based on practical production experience, the mechanical faults and preventive measures of overhead cranes are analyzed as follows.2. Steel Wire Rope2.1 Fault AnalysisDuring operation, the stress state of steel wire ropes is extremely complex. Steel wires are distributed in outer and inner layers, bearing uneven force even under simple tension. When the rope bends around drums and pulleys, it generates bending stress and mutual extrusion pressure between steel wires, making accurate stress calculation difficult. The static calculation method is generally adopted.The maximum static tension of the steel wire rope shall satisfy the formula:Pmax≤Pd/nWhere:Pmax — Maximum allowable static tension of the rope in operation;Pd — Breaking tension of the steel wire rope;