L48A1 Mast Section Tower hanging security check key items, tower hanging security check what issues
Tower hoist is a large construction machinery, playing a huge role and there are also risks, it is very necessary to do a good job of security inspection. Tower hanging security check key items, tower hanging security check what issues? Tower crane manufacturers with you to discuss.
1, basic inspection
The foundation of tower crane is an important link in relation to the security of tower crane. In the inspection, we should first pay attention to whether the base ground endurance of the tower crane meets the manufacturer's design requirements. At present, most tower lifting bases generally require 200 to 300 KPA, corresponding to the Geological Survey report to see if it meets the requirements. If the actual endurance does not meet the design requirements, check whether the tower hanging foundation has been piling and the foundation has been enlarged.
For the following forms of Tower lifting basic treatment, special attention should be paid to the following checkpoints in the inspection:
(1) Foundation sinking form
The foundation sinking form refers to the form where the base surface of the tower is below ± 0.00 elevation and is placed at the bottom elevation of the basement pit. For this kind of Tower hanging foundation treatment, attention should be paid to the drainage of the tower hanging foundation to avoid water accumulation. Last year, there was a tower fall accident in Xiamen due to the water in the foundation section of the tower, which affected the driver and inspectors and failed to find the weld cracks in the base section in time. In addition, the steel fatigue damage in the weld area occurred.
(2) The foundation is placed on the slope
In addition to the above requirements, the side pressure generated by the slope should also be fully considered. When testing, construction units should be required to take measures to resist the side pressure when excavating the slope. If we take measures such as soil nail protection or bolt treatment, there will be too many cases where the construction unit did not consider the side pressure of the slope during the inspection visit, and when the soil excavation caused a serious deviation of the tower hanging foundation. The construction unit brings about a lot of economic losses.
(3) Problems with pre-buried pieces
The author believes that the use of pre-buried base or fixed legs should be advocated. For the use of pre-buried high-strength bolts, the material should be provided by the original factory. The manufacturer should provide a test report, and the construction unit should report to the supervision unit for examination and approval before pre-burial. And make relevant hidden acceptance records. The collapse of a tower crane in Xiamen city earlier this year was caused by the pre-buried high-strength bolts of the rental unit, the nut and bolt metric Heying system confusion, the tower crane installed in the first section of the weight of the crane dump occurred a major accident.
(4) No soil layer shall be covered at the base of the tower
The base of the tower crane must no longer cover the soil layer. One increases the bearing capacity of the foundation, and the other is not conducive to observing the welds of the base. Last year, Xiamen had a tower crane with basic cover soil. Fortunately, the driver was more sophisticated and felt that the tower crane had a different sound. Immediately check all the standard section bolts, did not find problems, and then cleared the soil, the results found that the weld of the base steel structure has cracking phenomenon, after timely treatment, did not cause major consequences.
2, metal structural connections
(1) Tower bolt connection
Regarding the connection of metal structures, the General Administration of Quality Supervision, Inspection and Quarantine's "Regulations on Supervision and Inspection of Lifting Machinery" clearly requires: "Bolt connections must not be loosened, defects such as missing parts and damage should not be allowed, and high-strength bolts should have sufficient pre-tightening torque." The inspection method is stipulated as "check the state of high-strength bolts with a torque wrench". It is very important to pre-tighten the torque in the high strength bolt connection of the tower body. Since the torque is generated when the tower body rotates, if the pre-tightening torque of the high-strength bolt pair of the tower body does not meet the design requirements, the bolt will be shear force, resulting in the bolt being cut, pulled and uneven, making the bolt force more complicated and dangerous. The inspection of the pre-tightening moment of the standard bolt of the tower body can be preceded by a direct inspection method, that is, the inspectors observe the standard section connection at the main strut of the tower in the middle of the standard section of the tower body. If you can see a small gap at the standard joint, it indicates that the bolt pre-tightening force is not enough; At the same time, let the tower crane rotate around. If you can hear the squeaky sound of the metal, it also shows that the bolt connection is not tight; Then use the torque wrench or other methods to carefully check to improve the inspection efficiency. The author has encountered a case where the bolt loosening resulted in the reinforcement of the bolt on the upper part of the crane base. Due to the discovery and timely treatment, no major accident occurred.
(2) Heavy arm shaft connection
When checking the connection status of lifting arm pin, we should pay attention to the fixed condition of shaft end baffle and pin opening pin. Particular attention should be paid to the form of axle connection of the loader shaft, as shown in figure 2, which is an equal-diameter shaft, where the inner displacement of the shaft is stopped by the axle baffle. When the tower is used for many years, the axle baffle is easy to wear or fall off, so that the shaft may be removed. Caused a folding arm accident. Last year, there was a folding arm accident caused by the inline fall of the axle of this heavy arm. Special attention should be paid to the condition of the axle baffle during the inspection.
