L68B1 Mast Section problems in safety inspection of tower crane and corresponding solutions
1. Safety inspection of tower crane foundation
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Foundation sinking form: refers to the form that the bottom surface of tower crane foundation is lower than ± 0.00 elevation and placed at the bottom elevation of basement foundation pit.
L68B1 Mast Section For this type of tower crane foundation treatment, attention should be paid to the drainage of the tower crane foundation to avoid water accumulation.
The foundation is placed on the side slope: the foundation must be pile driven. In addition to the above requirements, the side pressure generated by the side slope shall be fully considered. During the inspection, the construction company shall be required to take anti side pressure measures when excavating the side slope, such as soil nail protection or anchor bolt treatment. During the inspection and return visit of our door, too many reasons have occurred that the construction company did not consider the side of the slope The case of serious deviation of tower crane foundation caused by pressure and earth excavation will bring considerable economic loss to the construction unit; (the method of tower crane foundation, the treatment of tower crane foundation in special cases)
The foundation of the tower crane shall not be covered with soil layer, one is to increase the bearing capacity of the foundation, the other is not conducive to the observation of the welds on the base. Last year, there was a tower crane with the foundation covered with soil. Fortunately, the operator of the tower crane was more experienced and felt that the tower crane had abnormal noise, he immediately checked all the bolts of the standard section, found no problem, and then removed the soil. As a result, it was found that the welds on the steel structure of the base were cracked After timely handling, no major consequences have been caused.
2. Safety inspection for embedded parts
For the embedded parts, it is recommended to use the embedded base or fixed leg. For the embedded high-strength bolt, the material shall be provided by the original factory, the manufacturer shall provide the test report, and the construction unit shall report to the supervision unit for approval before embedding, and make the relevant concealed acceptance records. At the beginning of this year, a tower crane collapse occurred because the high-strength bolts embedded in the leasing unit did not meet the requirements, the nuts and bolts were confused with metric system and English system, and the tower crane toppled when
L68B1 Mast Sectionwas installed to the first section of the crane counterweight;
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3. Connection of tower crane metal structure
For the connection of metal structure, it is clearly required in the supervision and inspection regulations for cranes that the bolt connection shall not be loose, and there shall be no defects such as missing parts and damage. The high-strength bolt shall have enough pre tightening torque. The inspection method is to check the connection condition of high-strength bolt with torque wrench. The pre tightening moment is very important in height strength bolt connection of tower. Due to the torque generated during the rotation of the tower body, if the pre tightening torque of the height strength bolt pair of the tower fails to meet the design requirements, the bolt will be subject to shear force, resulting in the bolt being sheared, tensioned at the same time and uneven stress, making the stress condition of the bolt more complex and dangerous.
In the inspection, the pre tightening torque of the standard section bolt of tower crane can be inspected by the visual method first, that is, the inspector is located in the middle of the standard section of the tower body to observe the connection of the standard section at the tension main chord of the tower body. If there is a small gap at the connection of the standard section, it indicates that the pre tightening force of the bolt is not enough; at the same time, let the tower crane rotate left and right, if you can hear the metal squeaking, it also indicates that the bolt connection Do not tighten; then use torque wrench or other methods to check carefully to improve the inspection efficiency.
4. Inspection of boom pin shaft connection
When the pin shaft of the boom is connected, attention shall be paid to the fixation of the end stop and the pin shaft cotter pin. When the tower crane has been used for many years, the pin block is easy to wear or fall off, which may cause the pin to move and fall off, resulting in the accident of arm folding. Special attention shall be paid to the condition of pin shaft blank during inspection.
5. Safe distance between tower crane and transmission line
There are many construction sites where tower cranes and overhead transmission lines negotiate in urban construction. There have been many accidents in other areas due to short circuit of transmission lines and falling of steel wire rope due to collision between tower cranes and steel wire ropes entering the dangerous area of overhead transmission lines and transmission lines. The national standards and inspection regulations have the requirements that the safety distance between any part of the crane and the transmission line must meet a certain safety distance. During the inspection, it is found that tower crane and steel wire rope may enter the dangerous area of the transmission line. It is required to put forward protection requirements, require the construction party to set up protective barriers, and establish safety protection measures and systems. During the normal operation of the tower crane, the protective barrier shall ensure that the crane and steel wire rope cannot enter the dangerous area of the transmission line. When the wind force is greater than 20 m / s, the crane shall stop working, and the hook shall be placed at the root end of the boom to avoid the hook and steel wire rope entering the dangerous area of the transmission line when rotating with the wind;
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