Causes and treatment of instability and tower coll

2022-08-10
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Reasons and treatment of tower crane instability and tower toppling

instability is the main reason for tower crane toppling. According to the analysis of the stability conditions of torque balance, the algebra and m-Positive of the positive torque of the tower crane to maintain stability must be greater than the algebra and m-negative of the counter torque of the unstable inverted tower, and the ratio of m-Positive/m-negative is preferably 1.4~1.5. The stability of the tower crane is mainly considered in three states: operation, non operation, installation or disassembly

1. Cause analysis of unstable operation state

(1) overload. Overload is generally caused by the inaccurate estimation of the actual weight of the lifted object. The lighter the new energy vehicle, the greater the weight of the lifted object, the greater the dumping torque generated by the heavy object. Secondly, as the wind-proof area of the heavy object increases, the dumping torque generated by the wind also increases, and the stability becomes worse

(2) inclined lifting. The force on the tower crane during inclined hoisting is much larger than that during vertical hoisting. The greater the angle of inclination, the longer the force arm, the greater the dumping torque and the smaller the stability coefficient

(3) sudden unloading. There are two main situations. First, the tower crane is broken. Overwinding is caused by overload hoisting, pulling and lifting underground objects, unskilled startup of non operators, failure of brakes or safety devices, etc; The wire rope is not arranged neatly, jumping out of the drum and squeezing into the gear, etc. will cause the wire rope to break. The second is the broken arm of the tower crane. Because of overload, the connecting bolts and pins of the tower arm are cut off due to excessive shear. In addition, when installing the tower crane, the connecting pieces are not installed firmly and in place, and the tower crane will also break its arm after being used for a period of time

(4) the track installation does not meet the standard. For example, the track datum, ballast thickness, track straightness, etc. are unqualified, and the tower crane is shaking or skewed during operation; There are civil air defense works or cavities under the track, and the subgrade treatment is not in place. In the rainy season, water and soil loss and subgrade subsidence. The loose connecting bolts of the track will cause the displacement of the track and also cause the tower to fall. The requirement of no cracking or warping on the track slope is based on the stability of the tower crane. If the slope is large, the gravity center of the tower crane's self weight and balance will move to the low side. If the hook is on the low side, the stability torque will be reduced and the dumping torque will be increased

2. Cause analysis of instability in non operating state

in order to increase the stability torque of tower crane during operation, a certain weight of counterweight is often added at the rear and each mechanism is placed as far back as possible. However, if the counterweight is added too much or the position is too biased, the tower crane may also dump backward when it is not working, so it is necessary to consider not only the problem of dumping forward during operation, but also the problem of dumping backward when there is no load

3. Cause analysis of instability during installation or disassembly

tower crane disassembly and assembly is a difficult and highly technical operation. If the disassembly and assembly procedure is not changed without authorization according to the instructions, it is very easy to cause a dumping accident

for the unstable factors in the above state, the following treatment measures are proposed

1. Governance measures for unstable operation state

(1) tower crane overload and over wind operation are not allowed. If overload is required under special circumstances, it shall not exceed 10% of the rated load and must be reported to the supervisor for approval. Before operation, check the hook, sling and this standard is applicable to the hanging of plastic film and sheet weight with thickness less than 1mm, and take other safety measures; Experienced tower crane drivers and commanders shall be selected for operation, and records shall be kept

(2) the tower crane shall not pull or lift the heavy objects obliquely, and shall not lift and pull the heavy objects buried underground or bonded to the equipment

(3) tower crane operators should work with certificates and abide by operating procedures; In the process of installing the tower crane, the connectors of all installed parts must be installed completely and firmly according to the instructions

(4) if the tower crane track is laid on the top of underground buildings (such as underground ditches, air raid shelters, etc.), reinforcement measures must be taken. Before laying stones, the pavement must be compacted according to the design requirements, the gravel foundation must be leveled and tamped, and gravel should be filled between sleepers. Drainage ditches are set on both sides of the subgrade to ensure no ponding. The track shall be reliably connected with the sleeper through the sizing block, and a gauge tie rod shall be set every 6m. The track shall not move during use. The rail joint must be supported by sleepers in the first 10 years of his prime minister's term of office and shall not be suspended. The inclination of the track top in the longitudinal and transverse directions shall not be greater than 1 ‰; The gauge error shall not be greater than 1 ‰, and the absolute value shall not be greater than 6mm; The gap between the rail joints shall not be greater than 4mm, staggered with the rail joints on the other side, and the distance shall not be less than 1.5m. The height difference between the two rail tops at the joint shall not be greater than 2mm

2. Treatment measures for unstable non operating state

after stopping the operation, the jib is absolutely not allowed to rotate with the wind; The boom type tower crane shall place the jib at the maximum amplitude position, and the trolley luffing crane shall drive the trolley to the position specified in the manual and lift the hook to the specified height. It is strictly forbidden to hang heavy objects on the hook, and the rail clamp shall be locked to prevent the tower crane from blowing out of the track and falling down due to strong wind

3. Treatment measures for instability in the state of installation or disassembly

operators should receive professional training and work with certificates. During operation, they should not exceed the specified wind level (less than level 5). All inspections and preparations should be done before operation. The installation and disassembly procedures specified in the instructions must be understood in detail and strictly followed. It is strictly prohibited to make any changes to the installation and disassembly procedures specified in the product manual; When installing 205C or disassembling the tower crane with boom, it is strictly forbidden to interrupt the operation after disassembling only one boom. When lifting the tower body and attaching and anchoring, it must also be operated according to the instructions

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