Things to Note When Inspecting and Repairing Crane Accessories
As an important part of lifting machinery and equipment, daily maintenance and upkeep are extremely important. Don’t ignore it just because it is a small fault. In the end, the problem will break out in a large area, and the gain will outweigh the loss.
1. Inspection of crane accessories
(1) Disassemble check hook, shaft, beam, sheave, bearing and clean and lubricated, hook, beam, sheave shaft, no crack, thread part should not be loosened, bearing intact, turn sheave, thread in the groove of the knife mark or crack should be replaced;
(2) Check the dangerous section wear condition, dangerous section wear more than 10% of the original height should be replaced;
(3) The test of the hook, after overhaul, the hook should be tested and checked, suspended for 10 minutes at 1.25 times the rated load, the elastic opening of the hook mouth should not exceed 0.25% of the size of the hook mouth, and there should be no permanent deformation and cracks after unloading;
(4) Plate hook repair, plate riveting, plate and plate gap, should not be greater than 0.3mm.
2. Maintenance of steel wire rope for crane accessories
(1) Broken wire inspection: If the number of broken wires in a twist exceeds 10% of the total number of wires, it should be scrapped according to the standard;
(2) Radial wear: If the radial wear of the steel wire exceeds 40% of the original diameter, the whole steel wire rope should be scrapped;
(3) Deformation inspection: the diameter of the wire rope is reduced to 70% of the rope diameter, the core of the rope is exposed, and the broken strand should be scrapped and replaced with a new wire;
(4) Wire rope lubrication: before lubrication, clean with wire brush, kerosene, etc., and saturate with wire rope hemp grease (Q/SY1152-65) or synthetic graphite calcium based lubrication (SYA1405-65).
3. Pulley block maintenance of crane accessories
(1) Disassemble and repair the sheave set, check the crack, the sheave shaft shall not have cracks, the journal shall not wear the original diameter of 30%, the conicity is not greater than 5%, more than this value should be replaced;
(2) The overhaul of the sheave groove, check the shape of the sheave groove with a template, and the radial wear should not exceed 30% of the wall thickness, otherwise it should be scrapped. Shall not exceed the standard can be repaired, check with the template after overhaul, the bottom and side clearance should not be greater than 0.5mm, the deviation between the center line of the wheel groove and the center line of the sheave should not be greater than 0.2mm, the deviation between the center of the rope groove and the contour end face should not be greater than 1mm;
(3) The inspection of the shaft hole, after overhaul, the shaft hole is allowed to have a defect of not more than 0.25CM2, and the depth should not exceed 4mm;
(4) Assembly, after assembly, it should be able to rotate flexibly by hand, and the lateral swing should not exceed D/1000. “D”- Nominal diameter of sheave.
4. Crane accessories drum repair
(1) The drum rope groove should be re-machined if the rope groove is worn more than 2mm. After overhaul, the rope groove should meet the requirements of the drawing, but the wall thickness of the drum should not be less than 81% of the original thickness;
(2) There should be no cracks on the drum surface, no obvious loss of roundness, and the pressure plate screws should not be loose;
(3) Drum spindle, there should be no cracks on the reel shaft, and it should meet the drawing requirements after major repairs. When the wear exceeds 5% of the nominal diameter, new parts should be replaced;
(4) Assembling and installing, the centerline of the drum spindle should be parallel to the supporting surface of the trolley frame, and the deviation should not be greater than 1mm/m. After the reel is installed, the centerline deviation of the two shaft ends should not be greater than 0.15mm.
5. Wheel maintenance of crane accessories
(1) Wheel tread wear, wheel tread wear more than 15% of the original thickness should be replaced with new parts, do not exceed this value, can be re-turned, heat treatment repair. The diameter of the wheel should be within the tolerance range, the surface quenching hardness HB300~500, the thickness of the quenching layer for the wheel diameter greater than Φ400mm should be greater than 20mm; When it is less than Φ400mm, the thickness of the quenching layer should not be less than 15mm;
(2) The diameter deviation of the two matching wheels, the diameter deviation of the active wheel should not exceed 0.1% of the nominal diameter, the driven wheel should not exceed 0.2%, the diameter deviation of the electric hoist wheel should not exceed 1% of the nominal diameter, and the driven wheel should not exceed 0.2%; Wheel diameter deviation of electric hoist should not exceed 1% of nominal diameter;
(3) Rim wear and break, deformation: rim wear up to 50% of the original thickness or broken area more than 30mm2 should be scrapped, rim thickness bending deformation up to 20% of the original thickness should be scrapped;
(4) Wheel cracks: wheel cracks should be scrapped;
(5) Tread ellipticity: wheel tread ellipticity of 1mm should be scrapped;
(6) Wheel group assembly: The installed wheel assembly should be able to rotate flexibly, and several wheels installed on the same balance frame are in the same vertical plane, and the allowable deviation is 1mm.
6. Axle and bearing maintenance
(1) Maintenance of the journal: the ovality and conicity of the journal after overhaul should not be greater than 0.03mm;
(2) Repair of cracks: Use a magnetic or ultrasonic flaw detector to inspect the shaft. There must be no cracks on the shaft and the scratch depth must not exceed 0.03mm;
(3) Maintenance of rolling bearings: An axial clearance in the range of 0.03~0.18mm is allowed between the inner and outer rings of tapered roller bearings. The adjustment clearance of the bearing gland should be within the range of 0.5~1.5mm.
Maintenance and replacement of accessories are key to the normal operation of the crane. Regular inspection and improvement of the crane’s condition are key measures to ensure its normal operation. At the same time, using the crane correctly and paying attention to safe operation are also important measures to ensure its normal operation and service life.
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