L68A1 Mast Section What is tower crane overload? What are the causes of overload?
What is tower crane overload? Overload of tower crane generally means that the working load exceeds the rated load of crane itself. Due to different types of tower cranes, different height of tower body, different length of boom and different elevation angle, the lifting capacity is also different. All of the above conditions can be found from the instructions of different tower cranes. In addition to the above variable conditions, the overload is also caused by the operation conditions not specified in the instructions. Here is an example.
L68A1 Mast Section：
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1. The height difference of the track is too large
For example, tq3-8t tower crane specifies that the longitudinal and transverse deviation of the track is 11000. The deviation of rail top is often too large due to the failure of ground endurance to meet the requirements and the irregularity of road and wood laying. In the technical requirements of tower crane, the deviation value between the center of tower tip and the center of ground is not more than 35mm and 35m in height. For this reason, the top adjustment of two tracks is 4mm11000. When the slope is more than 1 / 1000, the balance moment of tower crane moves closer to the tipping point, that is, the balance moment decreases while the overturning moment is far away from the tipping point, that is, the overturning moment increases, and the stability coefficient decreases. The greater the slope deviation, the greater the inclination. Although the surface of the tower crane is still operated according to the lifting capacity in use, the inclination of the crane is changed due to the excessive deviation of the slope, and the turning radius is increased, resulting in overload.
2. Construction not in accordance with the specification
Although there is a certain safety factor in the design of tower crane, because the construction conditions of assembly conditions can not meet the design requirements, such as the influence of subgrade conditions, component location and the serious inertia force during the operation and lifting descending, and the weather factors, especially when the windward side of the crane is large, also produce adverse effects, etc., which are difficult to accurately consider in the design.
L68A1 Mast Section：
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For this reason, the safety factor in the design is not allowed to be used in the actual construction except for the overload test during the test run of the whole machine. Because the bearing capacity of the tower crane is determined by the stability, its stability will be significantly reduced when the rated bearing capacity is exceeded in use. Although there is no collapse accident sometimes, the overturning moment caused by gust increases or when the boom rotates from the parallel track direction to the vertical track direction, the stability moment decreases due to the reduction of the gantry support spacing and the uneven track when the crane moves The increase of load inertia force will make the tower crane suddenly lose stability and cause collapse accident.
3. The problem of cable-stayed heavy objects in construction
Inclined pulling is often used to lift components in place due to improper positioning. The inclined crane not only increases the vertical lifting load, but also increases the lateral deformation of the boom due to the generation of a horizontal component force. At the same time, it also produces a overturning moment on the tower body, which is easy to cause instability and collapse. In addition, due to poor construction conditions and overload use, there may be no collapse accident. If the crane operates in violation of regulations for a long time, the deformation and early damage of the parts will lead to the decline of lifting capacity, which will bring potential accidents to the future use of the tower crane.
L68A1 Mast Section：
http://www.towercranesupply.com/product/l68a1-mast-section-for-tower-crane-masts
