How to prevent h336b tower crane hook from slippin

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How to prevent the hook of h3/36b tower crane from slipping

h3/36b tower hoists the steel bar. When the steel bar is just hoisted at a height of about 1m, the wire rope of the hook suddenly slips and the steel bar falls. Fortunately, there is no personal injury accident due to the low lifting height

after the inspection on the extended service life of the lifting mechanism motor and the reducer by all parties of the company, it was found that the 99 tooth disc and the lock nut meshed with the high-speed gear (38 teeth) and low-speed gear (19 teeth) of the spoiler outside the car, such as the motor, exited the helical gear shaft, there were obvious sliding lines on the 38 tooth and 19 tooth tooth tooth tooth surfaces, and the spline connection between the 99 tooth disc and the gear shaft was all broken, causing the accident. The reason can be attributed to the following three points:

1. The retaining function of the original design locknut is not reliable. The original design is to turn one more at the rear of M38 locknut φ 39. Insert the locking ring sleeve into the shaft end groove after tightening the nut. This structure does not use a lock washer and has a novel structure. However, practice has proved that the locking ring will crack and fracture after long-term use, so this structure is unreliable. Due to the axial force generated during the transmission of the gear shaft, the locknut will loosen and withdraw in actual use, resulting in the loose fit of the 99 tooth gear plate and the spline of the gear shaft, resulting in the loose fit of the spline teeth, uneven stress, and thus the phenomenon of gear beating

2. The spline teeth matched between the 99 tooth disc and the gear shaft in the original design are too small and not strong enough. Once loosened, it is very easy to wear and break the spline teeth, making the fit invalid, the transmission failure, and the sliding accident caused by the weight of heavy objects

3. The maintenance is not in place. During the pre installation maintenance of h3/36b tower crane in December 2001, this part was opened for maintenance and some high and low speed gears were replaced. After inspection, this part was intact. In addition, the maintenance of this part according to the original design requirements is only required when the tower crane is removed for overhaul. However, according to the on-site situation, the mechanical installation and maintenance personnel did not understand the installation of this part, especially the retaining function of the locking ring of the locking nut, and the inspection of the locking nut was not enough; In addition, the damage of this part is caused by the gradual loosening and wear accumulation, and one of the reasons is that the usual inspection and maintenance are not in place

preventive measures

after discussion between relevant personnel of the company and the project department, the following preventive measures and maintenance system are formulated for this problem and related situations

1. Before the first installation of the machinery, it must be thoroughly overhauled, including the motors, reducers, brakes, hydraulic cylinders, limiters, limiters, etc. of hoisting, luffing, slewing, hydraulic jacking machinery, which should be disassembled for maintenance, replaced with accessories, cleaned, refuelled, etc. If damaged or unreliable accessories are found before installation and during normal maintenance, they should be resolutely replaced without hidden dangers

2. Strengthen the shift management of machinery. During the shift handover, the two drivers must be on the machine at the same time. When the driver on duty carries out the test run of the machine, the driver on the previous shift must check the operation of the machine due to other parts, listen to the sound of the transmission parts of the machine, especially the parts of the hoisting winch. If abnormal conditions are found, they should be reported immediately, and the shift handover records should be made at the same time

3. Make records of the operation and maintenance of the machinery. Each large machine must have a separate operation and maintenance record. Operators and maintenance personnel must carefully record the operation, shift handover, maintenance, inspection and maintenance of the machine. After repair, inspection and maintenance, they should also register in the machine operation record for filing and inspection

4. Strengthen the usual maintenance. The mechanical maintenance personnel at the construction site shall carry out routine maintenance and repair of the tower crane once a week according to the operation manual and the company's regulations. The maintenance and repair parts are steel wire rope, pulley, roller, electrical device, frame structure, attachment arm, oil lubrication, etc., which are arranged in the interval of mechanical work

5. Arrange a half day every 15 days to carry out key maintenance of the tower crane. The key parts are hoisting, luffing and slewing machinery, including motors, reducers, brakes, electromagnetic clutches, etc., which are organized by the head of the mechanical maintenance team

6. Arrange a full day every three months to carry out special and detailed inspection on the lifting motor, reducer and brake of the tower crane, that is, the parts where the accident occurred. The safety director, institutional engineer and full-time safety officer at the site shall participate at the same time, and the relevant personnel shall sign for approval after the inspection

technical transformation measures

in view of the hidden danger of the unreliable locking function of the lock nut in the original design, we can improve its design and adopt a new locking measure according to relevant data

re mill the upper and lower retaining grooves of the original gear shaft (when the material is hard and milling cannot move, use an angular grinder to grind the groove or an EDM groove), the width is 7mm, the depth is 4mm, the upper and lower parts are aligned, and then use a 2mm thick steel plate with good material and high toughness to make a "meter" shaped retaining plate, and the width of each side of the "meter" shaped retaining plate is 7mm. Before installation, turn the puncture device of the electronic universal testing machine to the retaining lip of the locking screw nut, keep its original sharpness intact, closely fit the 99 tooth tooth disc with the spline of the gear shaft, lock and tighten it, smash the two edges of the "meter" shaped retaining plate into the two newly processed retaining grooves of the gear shaft, and then weld the four edges of the retaining plate on the locking nut. See Figure 1 for details In Figure 2 and figure 3, a stopper can only be used once

in addition, apply modified acrylate adhesive on the gear shaft and the internal and external threads of the lock nut. When the lock nut gear shaft is tightened, the lock nut must be completely tightened with a pipe wrench (1m long, or lengthened with a steel pipe), and the gear shaft and lock nut must be tightened with the high-performance adhesion of the adhesive. During installation, the subsequent installation can be carried out only after the adhesive is completely dry, and then add gear oil, etc

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