Analysis of the hottest falling accident of single

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Analysis of a high-altitude falling accident of a single beam suspension crane

I. the process of the accident

on the morning of November 6, 1998, the production workers in the north warehouse of a professional factory of a company used the LX electric single and humid environment across the North East platform, which will accelerate the destruction of the electronic components of the instrument box. The beam suspension crane (hereinafter referred to as "the car") lifted the parts rack and worked for about 20 minutes. When they just turned around after taking off the lifting appliance, The main beam of the car suddenly fell, only 20 cm away from the production workers, causing the car to be scrapped, which almost caused a major accident of personal injury

II. Results of on-site technical investigation

according to the on-site investigation, the car is a technical transformation project of a professional factory and is manufactured by a professional crane factory in another place. The vehicle has a lifting weight of 2 tons, a span of 5 meters and a lifting height of 6 meters. It was manufactured and installed in 1998. Without acceptance, it was put into use in August 1998

after on-site inspection, it was found that the pin shaft connecting the main beam and the end beam of the vehicle was separated, causing the main beam to lose its support and fall. The pin shaft disengages because the upper bolt of the pin shaft key plate falls off, the lower bolt is loose, and the key plate disengages. It can be seen that the accident was caused by the disconnection of pin uranium and the separation of main beam and end beam

III. accident cause analysis

a. direct cause of the accident

1. The supplier did not provide qualified parts according to the requirements of the design drawings. The main beam of the car is movably connected with the end beam through the connecting plate with a pin shaft. In addition, the selected materials, fasteners, accessories and welding process requirements are very strict. However, GB and M16 are not selected as per the requirements of the drawing when the vehicle is equipped with pin uranium key plate bolts × 30 bolt, while M16 is used × 35. This bolt has exceeded the effective connection range and interfered with the connecting plate of the main beam

2. The spring washer of the pin shaft key plate bolt is not selected according to the drawing requirements, Φ 16 spring washer; The spring washer used is of poor quality, and has been seriously plastic deformation and failure

3. The inner diameter of the screw hole of the fixing bolt is out of tolerance. Standard screw holes shall be Φ 13.8 mm, small diameter of solid side screw hole Φ 14.5mm, larger than the standard 0.7mm, close to the standard pitch diameter of the screw hole Φ 14.7 mm, resulting in reduced bolt preload

4. The running device of the vehicle adopts the "three in one" mechanism, which drives the edges unilaterally. The four wheels on each side are prone to "three legs". The crane is easy to produce asynchrony, skew, end beam torsion, and pin uranium key plate bolts interfere with the connecting plate of the main beam, limiting the axial and radial movement of the connection. The bolts vibrate under the long-term alternating force of the main beam connecting plate and the pin shaft key plate and during the operation of the vehicle

through investigation, the above four reasons made the bolts loose and fall off, which led to the separation of the connecting pin shaft between the main beam and the end beam, and the main beam fell

b, indirect causes of the accident

1. According to relevant national documents, the installation unit of lifting machinery must undergo professional training and obtain the qualification certificate for installation, transformation, maintenance and maintenance of special equipment issued by the provincial quality and technical supervision department. The personnel engaged in installation must have the safety qualification certificate for installation and maintenance of cranes, including passenger cars, commercial vehicles, and special vehicles The installation of hoisting machinery can be carried out only after the certificate for installation and maintenance of hoisting machinery is issued. However, the actual installation unit of the vehicle did not have the qualification in this regard. After the installation of the four cranes in a professional factory, there was no "self inspection report", and the important parts of the crane were not carefully inspected and tested according to the drawings, so that the installed cranes left major potential accidents

2. Four LX type electric single beam suspension cranes were newly installed in Kebei warehouse of a professional factory. The technical data were incomplete, and there were no drawings of vulnerable parts and crane safety technical supervision and inspection certificate. The car has not been inspected by the local municipal quality and Technical Supervision Department of the crane factory, and the crane safety card of its safety device has fatigue scars and cracks of varying degrees, which is used to stop the cotter pin Φ 4 iron wire replacement, most of the key plates of the drive system are loose, etc

IV. preventive measures

1. For the purchase, introduction, installation and technical transformation of special equipment, many friends must not know what the 4-ball experimental machine does, which conforms to the relevant national quality and technical supervision, safety and health regulations and standards, especially for the selection and purchase of dangerous lifting machinery, it is necessary to obtain the approval of the safety and equipment departments in advance

2. When the purchased crane leaves the factory, it must pass the safety technical inspection of the local municipal quality and technical supervision department, and be issued randomly after obtaining the crane safety technical supervision and inspection certificate

3. The installation unit of lifting machinery should obtain qualification certificates, and the installation personnel should have operation certificates and work licenses before they can engage in the installation of lifting machinery, and submit them to the superior safety and equipment departments for review and filing

will greatly promote the development of new polyurethane materials

4. Before the crane is delivered for trial operation, the installation unit must first conduct self inspection, fill in the self inspection report, and hand over to the receiving unit for pre acceptance. After passing the pre acceptance (with complete records), the crane can be put into trial operation after being inspected and accepted by the superior safety and equipment department

5. The formal acceptance must be carried out in accordance with the regulations of the superior department in charge of technology, safety and equipment and the requirements of the "three Simultaneities" management standard of labor protection

6. Strengthen the management of cranes. Carefully implement the crane management system and safety inspection system, do a good job in the regular inspection, maintenance and repair of the crane, and timely eliminate hidden dangers, so that the crane is always in good working condition

7. Strengthen the education and training of crane operators, strictly implement the safety operation procedures, and improve the operation technical ability and the ability to deal with emergencies

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