The bolt looseness of standard section of tower crane is aimed at the tower body connected by bolts and sleeves between standard sections. Most small and medium-sized tower cranes (60t m and below) made by tower crane manufacturers adopt this connection form, and the bolts are all high-strength bolts.
The bolt pre-tightening force of the actually installed tower crane is difficult to reach the required pre-tightening force, which is an important reason for the bolt looseness. In addition, when lifting the ceiling of the tower, the standard joint connection contact surface on the boom side is pulled, and the standard joint connection contact surface on the balance arm side is compressed. Under the same tightening torque, the pre-tightening force in the bolts on both sides is equal at this time.
When the tower crane rotates and the direction of the boom changes, the compression and tension of the contact surface of the standard section of the tower body change, and the force in the bolt changes greatly. Especially when the boom turns to the direction opposite to the lifting joint, the connection contact surface of the original standard joint on the boom side changes from tension to compression, and the tension on the bolt is greatly reduced. Especially when the original pre-tightening force is less than the correct value, there may be no pre-tightening force, which is another important reason for bolt looseness.
Operating procedures of tower crane
1 Before use, check that the metal structural components and appearance are in good condition, the no-load running sound is normal, the heavy-load test braking is reliable, and the safety limit and protection devices are complete and intact.
2. When operating each controller, it should be operated step by step, and it is forbidden to operate beyond the block. When changing the running direction, the operating handle should be reset to zero, and the motor should stop running and then run in the opposite direction, so as to be stable. It is forbidden to start and stop suddenly.
3, equipment in operation, such as the discovery of mechanical anomalies, should immediately stop check, wait for troubleshooting rear can run.
4, strictly hold relevant certificates, it is forbidden to work after drinking, it is forbidden to use travel switch instead of parking operation, it is forbidden to work illegally and leave the post or give the machine to others to drive.
5, when loading heavy objects, should leave the ground for a certain distance, check the braking reliable rear can continue.
6, adhere to ten. After the operation, the box should be locked, without electricity, and the mechanical crossover operation should be done well.