Repair and maintenance of metal structural parts

　　1. Strictly implement the scrapping standards for crane steel structures.

　　2. Check the metal fatigue strength, weld cracks, structural deformation, damage, etc. of the main stressed structural parts. The key welds of the main stressed structural parts and the base material of the welding heat affected zone should be inspected. Abnormalities should be dealt with. The inspection of structural parts should be carried out according to the following procedures.

　　(A) Daily inspection: The tower crane should be inspected every 80 hours of operation. The driver of the tower crane should check the tightening of the bolts of each connection part when handing over the shift, and if there is any looseness, it should be tightened in time.

　　(B) When the tower crane has abnormal sounds, or there is faulty operation, or the tower crane safety protection device fails, it should be checked and recorded.

　　(C) When a project is completed, after the tower crane is disassembled, the engineering technicians and professional maintenance personnel should conduct a detailed inspection and make a record.

　　3. Try to prevent deformation and collision damage of structural parts during transportation.

　　4. Spray paint every six months to a year. Before painting, all rust, oil and other dirt on the metal surface should be removed.

　　Wire rope and its maintenance

　　1. During the use of the wire rope, the wire rope should be prevented from ringing, kinking, bending or sticking to the debris, and to prevent friction with machinery or other debris.

　　2. After the tower crane is installed (before use), the steel wire rope should be lubricated. Apply graphite grease once, and then lubricate the steel wire rope according to the "Crane Lubrication Table".

　　3. The overall design of the tower crane does not allow the wire rope to have an indefinite life. One of the following circumstances should be scrapped:

　　A. Wire rope 6×19-d (d wire rope diameter) has more than 5 broken wires in 6d length and more than 10 broken wires in 30d length.

　　B. Wire rope 6×37-d (d wire rope diameter) has more than 10 broken wires in 6d length and more than 19 broken wires in 30d length.

　　C. The steel ropes are close together, even if the number of broken wires does not exceed 5 in the 6d length, they should be scrapped.

　　D. Although the wire rope is not broken, the wear of the wire rope reaches 40% of its diameter, or when the wire rope is reduced by 7% or more relative to the nominal diameter, or the wire rope bends significantly.

　　E. The wire rope loses its normal shape and produces deformities, such as waves, cage distortion, strand extrusion, wire extrusion, partial increase in the diameter of the rope, kinks, partial decrease in the diameter of the rope, and part of it is flattened or bent.

　　F. When the diameter of the wire rope is affected by special heat, and a recognizable color appears on the outside.

　　Note: When lifting molten or hot metal, acid solution, explosives, flammables, the number of scrapped wire ropes is halved. This manual does not mention the situation according to the provisions of GB5972.

　　Maintenance and repair of mechanical parts

　　1. Daily maintenance

　　(1) Maintain the cleanliness of each institution frequently, and clean up all parts of dust in time;

　　(2) Check the oil quantity of each reducer, if it is lower than the specified oil level height, it should be refueled in time;

　　(3) Check whether the vent plug of each reducer can freely exhaust, if it is blocked, it should be dredged in time;

　　(4) Check the effectiveness of each brake, if it is not sensitive and reliable, it should be adjusted in time;

　　(5) Check the bolts at each connection, if they are loose or fall off, they should be fastened and supplemented in time;

　　(6) Check all kinds of safety devices, if any malfunction is found, it should be adjusted in time;

　　(7) Check the steel wire ropes and pulleys of various parts, if excessive wear is found, it should be dealt with in time;

　　(8) Check the lubrication of each lubricating part and add grease in time.

　　2. Minor repair (to be done after the tower crane works for 1000 hours)

　　(1) Perform daily maintenance tasks;

　　(2) Remove and clean the gears of the reducer and adjust the backlash;

　　(3) Clean the gears of the open drive, apply grease after adjustment;

　　(4) Check and adjust the slewing bearing device;

　　(5) Check and adjust brakes and safety devices;

　　(6) Check the wear of hooks, pulleys and wire ropes, and make adjustments, repairs and changes if necessary.

　　3. Intermediate repair (to be carried out after 4000 hours of tower crane work)

　　(1) Perform various minor repairs;

　　(2) Repair or change the damaged parts of each coupling;

　　(3) Repair or replace the brake shoe;

　　(4) Replace steel wire rope, pulley, etc.;

　　(5) Check the connecting bolts of the slewing bearing part and replace if necessary. Note: use high-strength bolts when replacing;

　　(6) Derusting and painting.

　　4. Overhaul (Tower crane works after 8000 hours)

　　(1) Carry out minor repairs and intermediate repairs;

　　(2) Repair or replace brake wheels, brakes, etc.;

　　(3) Repair or replace the reducer assembly;

　　(4) Repair or replace the slewing bearing assembly.

　　Maintenance and maintenance of other main components

　　1. Brake parts should be scrapped if one of the following conditions:

　　(1) Crack;

　　(2) The wear of the friction pad of the brake pad reaches 50% of the thickness of the raw material;

　　(3) The surface wear of the brake wheel reaches 5mm ~ 2mm;

　　(4) Plastic deformation of the spring;

　　(5) The idle stroke of the lever system exceeds its rated stroke by about 10%.

　　2. The hook is forbidden to repair welding, and one of the following conditions shall be scrapped:

　　(1) Observe the surface for cracks and breaks with a 20x magnifying glass;

　　(2) Dangerous sections such as hook tails and threaded parts and hook bars are permanently deformed;

　　(3) The section wear at the lanyard exceeds 10% of the original height;

　　(4) The amount of mandrel wear exceeds 5% of its diameter;

　　(5) The opening degree is increased by 15% compared with the original size.

　　3. Reels and pulleys should be scrapped if one of the following conditions occurs:

　　(1) Cracks and broken rims;

　　(2) The volume of the reel wall wears up to 10% of the original wall thickness;

　　(3) The wear of the bottom of the pulley rope groove exceeds 25% of the corresponding wire rope diameter.

　　4. Wheels with one of the following conditions shall be scrapped:

　　(1) Crack;

　　(2) The wear of the wheel tread thickness reaches 15% of the original thickness;

　　(3) The wear of the wheel rim thickness reaches 50% of the original thickness.

　　5. The operating driver must always check the sensitivity and effectiveness of the safety limiter. If a malfunction is found, it should be adjusted or repaired in time, and the limiter circuit must not be removed.

　　Maintenance of slewing bearing device

　　(1) The mounting support of the slewing bearing (the seat that supports the lower bottom surface of the ring gear and the seat that is placed on the upper surface of the inner ring) must be sufficiently rigid, and the mounting surface should be flat. Before assembling the slewing bearing, the bearing should be stress-relieved to reduce the deformation of the slewing bearing. The contact surface of the bearing and the slewing bearing must be cleaned up during assembly.

　　(2) Pay attention to the change of noise and the change of rotation resistance torque during use, and disassemble and inspect if there is any abnormal phenomenon.

　　(3) The slewing bearing must be lifted or stored horizontally. Do not lift or store it vertically to avoid deformation.

　　(4) Before the bolts are fully tightened, the gear meshing inspection should be performed, and the meshing condition should meet the requirements of gear accuracy: that is, the contact spots distributed on the tooth surface of the gear pair after running under slight braking are in the height direction of the gear teeth Not less than 25%, not less than 30% in the length direction of gear teeth.

　　(5) The debris should be removed once for 10 shifts of tooth surface work, and re-applied with grease.

　　(6) In order to ensure the reliability of the bolt work and avoid the insufficient preload of the bolt, the preload torque of the bolt should be checked separately after the first 100 hours and 500 hours of the slewing bearing work. The pre-tightening torque should be checked every 1000 hours thereafter.

　　(7) High-strength bolts and nuts are used for bolts and nuts connected to the slewing bearing; double nuts are used for fastening and anti-loosening.

　　(8) When tightening the nut, the thread of the bolt and the end surface of the nut should be coated with lubricating oil, and should be tightened with a torque wrench symmetrically and evenly in the circumferential direction multiple times. During the last tightening, the pre-tightening torque on each bolt should be approximately uniform.

　　(9) Four oil cups are evenly distributed on the upper surface of the slewing ring gear aligned with the raceway, thereby adding grease to the raceway. Under normal circumstances, the slewing bearing is lubricated once every 50 hours. Each time you add oil, you must add enough oil until grease leaks from the seal.