256HC Mast Section Operation technology and inspection precautions of standard bolt connection of tower crane
First, after the initial installation of the tower crane, the fastening of all connecting bolts shall be inspected once after two shifts, and then once about half a month later. After the tower is lifted, the key inspection of bolts at the above parts shall be carried out. During the inspection, the position of tower arm shall also be rotated. The bolts to be inspected are directly below the position of balance arm, so it is reliable and effective to check whether the bolts are tightened.
Second, in the work of tower crane, when the preload of a group of connection pairs at the same connection is too large, the axial force borne by the bolts of each connection pair is very different. The bolts with large preload are under heavy load for a long time, which is easy to produce fatigue fracture. In the actual inspection, one of the eight foundation bolts has been found to be broken, which belongs to this phenomenon. Attention shall be paid to the consistency of the pre tightening torque during installation. During field operation, due to the different strength of workers, it is likely that the pre tightening torque of the four column bolts is different. The torque wrench can be used for better control. In a word, the experienced foreman shall check, adjust and fasten the same.
Third, when the tower crane is transferred to the site, all the connecting bolts of the tower body shall be inspected, derusted and lubricated in detail, and any abnormality such as crack, wear, serious corrosion, overall or local plastic deformation must be replaced. It is recommended not to use it more than twice to avoid fatigue damage. Most of the existing tower cranes may not meet this requirement. If the shortage is found, it is not suitable to process and manufacture by itself. Because the construction unit is not easy to control the processing quality and material of high-strength bolts, it is better to purchase from the original tower crane manufacturer. The high-strength bolts shall be marked by the manufacturer and grade.
