1. Requirements for tower crane selection

Requirements for tower crane selection: the lifting weight, lifting speed, independent height of the tower crane, maximum lifting height and other technical parameters of the tower crane within the coverage area (that is, the boom length, the minimum boom and the maximum amplitude), all need to be based on the actual construction site Circumstances and safety needs are determined. If the selected capacity is too large, it will cause a waste of resources; on the contrary, it will all bring about the problems of use and safety.

2. Requirements for tower crane operators

Requirements for operators: strong sense of responsibility and good technology. Because in the process of using the tower crane, it is inevitable that various failures will occur, but the first line of operations should generally be the first-line operators on the site. If the operators can find and deal with the failures in time, this can guarantee both Safe construction can save maintenance time and facilitate management. On the contrary, it is difficult to infer.

3. Requirements for the safe use of tower cranes

The safety issues of tower cranes are directly related to the construction progress and quality of the project, as well as the image, reputation and social impact of the enterprise, which are of vital importance. According to the author’s experience, the main points for the safe use of tower cranes are as follows, for reference only.

The use of tower cranes should abide by the regulations and regulations issued by the national competent authority, as well as the relevant regulations in the instruction manual: the working environment temperature of the tower crane is -20~40 degrees Celsius, and the maximum working air pressure is 205N/m2. Stop using when the wind speed exceeds level 6. When installing two or more tower cranes on the same construction site, pay attention to the mutual position of the tower cranes and adopt different elevation operations to avoid collisions between the tower crane boom and balance arm; safety on the tower crane Devices, namely height, luffing, rotation, lifting weight and moment limiter, etc., the last two of which are more important. If these two items fail in the test, it will be regarded as a failure of the whole machine, because it can ensure the safety of the whole machine And prevent the tower crane from tipping over. For example, in a construction site, the torque limiter of the tower crane is not replaced if it fails, and the operator mistakenly believes that it will only lift 800-1000kg of materials daily, and there will be no danger. As a result, during the process of lifting materials, due to the construction site The ground is relatively narrow, and the operator’s sight is blocked when the object is being lifted, causing the hanging object to hang on the steel reinforcement of the building, causing the tower crane frame to shake violently, and almost a major safety accident. Fortunately, the cable operator who worked on the ground notified the operator in time and immediately Stopping processing to avoid the tower crane tipping accident. It can be seen that all safety devices on the tower crane are indispensable and must be checked frequently to ensure that all safety devices are intact, sensitive and reliable.

4. Key points of using tower crane

Hoisting mechanism: The hoisting motor is generally a double-beam or three-speed motor. Overstepping operation is not allowed during use. The hoisting motor can only be used for light load or empty hook lifting at high speed. Long-term operation is not allowed at low speed. Generally, the continuous running time at low speed is not allowed to exceed 5 minutes to avoid damage to the motor due to overheating. The operating principle is light load high speed or heavy load low speed.

Slewing mechanism and hydraulic coupling: The principle of correct operation of the slewing mechanism is: low gear or jog start, stop and stop before driving in reverse, and do not use reverse driving to brake. Otherwise, the reducer of the hydraulic coupling will be damaged due to excessive impact, and even the shell will be broken. At the same time, the inertial torque of the tower will be increased. Although the fluid coupling has an automatic overload protection function, it must be operated correctly to extend its life. If it is found that the rotation speed of the tower crane has slowed down significantly, it is generally because the coupling is short of oil. First, check the liquid level. If it is not enough, add oil in time. If the amount of oil is too large, it will increase the inertia force at startup and lose the safety protection effect of buffering. , It will also cause the shell to break. The normal working temperature of the fluid coupling housing should not exceed 80 degrees Celsius. The brake of the slewing mechanism is only used under the influence of wind and the parking is unstable. Under normal circumstances, emergency braking should not be used easily, otherwise it will increase the extra torque of the tower body, or even make the tower body twisted and deformed.

Slewing ring: It is one of the most critical parts of the tower crane, which mainly bears the tipping moment and vertical load. After a failure occurs, it is extremely difficult to disassemble and replace, and the loss is large. Therefore, maintenance and inspection must be done carefully and high-grade grease must be injected every 200 hours of work until the lubrication leaks from the slewing bearing surface. The slewing bearing is connected by high-strength bolts. If the pre-tightening force is insufficient, or if it is not checked or tightened for a long time, it will loosen. If individual bolts are loosened, the remaining bolts will be overloaded, with disastrous consequences.

5. Daily maintenance

Maintenance of mechanical parts: check the brakes of each mechanism, the operation of each mechanism, the fastening of the connecting bolts of each component, the wire ropes of each part, etc., and the failure should be eliminated in time, and the connecting bolts and welding of each mechanism must be checked. Working conditions of seams and components, tighten and paint regularly.

Maintenance of the hydraulic system: add or replace hydraulic oil on time, and check the oil pipe and its joints, safety valves, hydraulic pumps, and hydraulic cylinders. If problems are found, they should be dealt with in time.

Maintenance of the electrical system: wires and cables should be free from damage, the travel switch of the safety device must be reliable, and the grounding protection resistance must meet the requirements. Lubrication work: Check the lubrication of various parts of the tower crane frequently, do a good job of periodic lubrication, and add or replace lubricants on time.

In order to ensure the normal operation of the tower crane and ensure the safety of man and machine, it is necessary to do a good job of daily maintenance centered on the six major contents of inspection, adjustment, cleaning, tightening, lubrication and replenishment.