In recent years, there are many risks in the installation, disassembly and use of tower cranes, resulting in frequent tower crane accidents, which has a great negative impact on the development of the entire construction industry. Therefore, it is particularly important to take timely and targeted risk prevention measures to reduce the risk of tower crane installation and use.

1 Tower crane installation and use risk analysis

1.1 Risk of installation and disassembly operations

1. The technical quality of installation personnel is uneven. Small-scale installation units may temporarily form installation teams with installation personnel. The stability of the team is poor, and the degree of coordination between personnel is not high. Installation and demolition workers have weak safety awareness and lack of professional knowledge.

2. The special construction plan for tower crane installation and disassembly has not been prepared or the special construction plan for tower crane installation and dismantling has not been prepared before the construction work, or although there is a special construction plan, the operator ignores the content of the special plan and conducts construction based on experience , leading to deviations in work and breeding safety accidents.

3. Organizations or individuals that do not clearly assign personnel and installation supervisors to carry out hoisting operations have not assigned a plenipotentiary representative (designated personnel) during the installation and dismantling operations.

Conscientiously perform the duty of reviewing matters related to tower crane installation, and the installation supervisor does not strictly exercise the management responsibilities of all installers and auxiliary lifting equipment operators.

4. The installation of safety facilities is not perfect. When the tower crane is installed and removed, a warning area is not set up on the ground as required; the work platform for installation and removal personnel is not equipped with safety guardrails, and the installation and removal personnel working at heights do not wear seat belts correctly as required. , Not carrying a tool bag for properly storing personal tools and small components.

5. Before construction, the operators did not fully disclose the key control links to the operators. The construction and safety technical disclosures were not made to the assembly and dismantling operators, resulting in the assembly and disassembly personnel's work items, content, requirements, as well as major hazards and safety technical measures, etc. Lack of clear understanding.

6. Before the installation and dismantling of the tower crane, the obligation to notify the competent authority was not fulfilled, resulting in a lack of supervision.

1.2 Risk of using the job

1. The user's mastery of the facilities is not enough, and the illegal operations are repeatedly prohibited. The tower crane driver has no common operation data, and has no knowledge of the corresponding maximum lifting capacity at a certain working range position, and blindly carries out hoisting operations, which has potential safety hazards. The ground signal workers illegally commanded the oblique hoisting and pulling the heavy objects, the rope workers did not bundle the bulk objects firmly, and did not take protective measures when the ropes were tied and hoisted heavy objects with sharp edges.

2. The daily inspection work before use is missing or the inspection work is not comprehensive enough. The tower crane driver, signal worker and slinger did not do a good job of daily inspection, such as the broken wire of the hoisting wire rope or the sling wire rope exceeding the standard requirements, the loosening of the connecting bolts of the structural parts or the failure of the cotter pin at the end of the connecting pin.

3. Problems existing in the tower crane itself: The tower crane hoisting drum has no anti-dropping device or the drum has no rope arranging device, and the number of safety switch contacts of the tower crane torque limiter is lower than the standard requirements. For the factory defect problem, the tower crane manufacturer should be contacted in time, and corresponding measures should be taken to rectify and pass the inspection.

4. There is a lack of communication between team members. The equipment shift system for multi-shift operation is not perfect. The off-duty driver does not carefully fill in the shift record for potential safety hazards. The driver who takes over starts the operation without checking and confirming the status of the equipment, resulting in hidden dangers of safety accidents. .

1.3 Risks of maintenance operations

1. The technical quality of maintenance personnel is uneven. There is a certain gap in the basic knowledge and professional skills of different maintenance personnel. The knowledge and skills of a few maintenance personnel are difficult to perform the maintenance work they are engaged in.

2. The maintenance work is not carried out in accordance with the maintenance regulations. For example, the maintenance personnel fail to check the anti-loosening condition of the tower body bolts as required, fail to measure the verticality of the standard section of the tower body as required, and fail to check the lubrication of the pulley and the pulley anti-dropping device as required. working condition.

3. The main structural components and safety devices are not regularly maintained. Due to maintenance reasons, the connecting bolts between the adjacent standard sections of the tower body, between the standard sections of the tower body and the turntable are loosened, the wheels of the luffing trolley are excessively worn, and the torque limiter is slightly The action accuracy of the moving switch is out of tolerance, etc.

4. Problems found in the maintenance process were not rectified or reported in time, which led to the continuation and expansion of hidden dangers, which eventually led to safety accidents. Precautions

2.1 Installation and disassembly work

2.1.1 The installation and dismantling of tower cranes should be prepared according to the regulations of "Safety Management Measures for Sub-item Projects with Greater Risk" (Jianzhi [2009] No. 87), the installation and dismantling of tower cranes are dangerous For larger sub-projects, special construction plans need to be prepared. The special construction plan needs to cover the selected tower crane model and performance technical parameters, the setting of foundation and attachment devices, the weight of main installation components and the location of lifting points, installation, disassembly sequence and safety quality requirements, climbing overview and details of attachment nodes, etc. technical content.

2.1.2 Designation of plenipotentiary representatives and installation supervisors According to the provisions of GB/T 5031-2008 "Tower Cranes", a plenipotentiary representative (designated personnel) and installation supervisors should be designated for tower crane installation and dismantling operations. Should be a tower crane driver. The designated personnel should conscientiously perform the duties of reviewing the tower crane installation-related matters, and comprehensively manage the tower crane installation, dismantling, and climbing work. The installation supervisor shall exercise supervision over the entire process of all installation personnel and auxiliary equipment operators.

2.1.3 Requirements for tower crane installation and dismantling personnel

1. All personnel involved in the work have solid operational knowledge.

2. There should be installation, maintenance and operating instructions for the tower crane.

3. The installation personnel cannot carry out the installation work without fully understanding the instructions and related operating procedures.

4. The entire installation and dismantling operations should be carried out in accordance with the special construction plan and installation instructions, and the installation supervisor should be responsible.

5. The replaced parts and components should be qualified products.

6. The status of the tower crane should meet the various restrictions specified by the manufacturer. Changes to any predetermined procedures or technical parameters should be approved by the tower crane designer or engineer.

2.1.4 Safety technical disclosure work should be done well before installation and dismantling operations

1. All parts should be inspected to confirm that they are in good condition before installation.

2. The lower support of the tower crane before jacking and the jacking frame should be connected reliably.

3. Before jacking, make sure that the jacking beam is placed correctly.

4. The tower crane should be trimmed before jacking. During the jacking process, the balance of the tower crane should be ensured.

5. The sequence of jacking and sectioning shall comply with the provisions of the installation and operation manual.

6. During the jacking process, operations such as lifting, turning and luffing should not be carried out.

7. After the jacking is completed, the standard section and the lower slewing bearing should be connected reliably.

8. During the installation and disassembly of the tower crane, it is absolutely not allowed to interrupt the operation by installing or retaining only one arm. In view of the cross-operation of multiple subcontracting teams on the construction site, the tower crane installation supervisor should notify each subcontracting team that it is strictly forbidden to use the tower cranes before the tower cranes are installed and qualified.

2.1.5 Improve the protective facilities for installation and demolition work. The operating platform for installation and demolition personnel should be firm and reliable, and protective railings should be set around; operators should wear safety helmets, safety belts, gloves, non-slip shoes and work clothes. The safety belt is fastened on the support structure; the operator should carry a tool bag for holding high-altitude work tools and small components, and it is strictly forbidden for the operator to throw up and down. When the tower crane is installed and dismantled, a warning area should be set up on the ground as required.

2.1.6 Consciously fulfill the obligation of notification and accept the supervision of the competent department. According to relevant regulations, the installation and disassembly of tower cranes and other special equipment should be notified to the corresponding construction department in advance, and consciously accept the supervision of the competent department.

2.2 Using homework

The following management and inspection systems should be implemented in the operation of tower cranes to reduce the occurrence of risks.

1. Tower crane users and personnel shall establish and strictly implement the following lifting machinery rules and regulations: safety technical operation regulations; equipment management system; regular inspection report management system; personnel training management system; shift management system; accident reporting and emergency rescue management system; technical file management system.

2. Establish a safety management agency and assign safety management personnel. The user unit shall, according to the situation, set up an agency responsible for the safety management of tower cranes or assign full-time and part-time safety management personnel.

3. Timely use registration procedures Before the tower crane is put into use or within 30 days after it is put into use, the user should go to the local construction safety management department to go through the tower crane use registration procedures with the inspection report that has passed the inspection of the corresponding qualification inspection unit.

4. Establish a daily inspection system

The daily inspection of the tower crane should be carried out before each shift. The daily inspection includes the operation of lifting, luffing, the operation of the slewing mechanism (especially the operation of the brake), the operation of the indicating and limiting devices, and the obvious visible to the user's eyes. Defects, including wire rope and steel structure defects, etc. Any abnormal situation found in daily inspection should be eliminated in time before use, and corresponding records should be made.

2.3 Maintenance work

The following preventive measures should be taken in tower crane maintenance operations to ensure the quality of maintenance operations.

2.3.1 Requirements of maintenance personnel skills and sense of responsibility Responsibility for work.

2.3.2 Improve the monthly inspection and quarterly inspection system for maintenance operations

In addition to the daily maintenance of tower cranes, the maintenance unit should improve the monthly inspection and maintenance and quarterly inspection and maintenance systems.

The contents of monthly inspection and maintenance include: oil level, oil leakage and oil leakage of hydraulic and lubricating devices; whether there is visible deformation, cracks and wear on hooks and anti-dropping devices; whether the wire rope meets GB/T5972—

2 0 1 6 Requirements of "Maintenance, Maintenance, Inspection and Scrap of Crane Wire Rope"; visually inspect the rust of the joints and joints of the structural parts; use a special wrench to check whether the connecting bolts are loose, and pay special attention to whether the joints are loose when the standard section connecting bolts are loose. There are cracks; pin positioning, especially the working reliability of the boom connection pin.

The quarterly inspection and maintenance content of tower crane maintenance operations adds the following items to the monthly inspection and maintenance content.

1. Grounding device Check whether the grounding device is fixed reliably, and the grounding resistance should meet the requirements of relevant standards.

2. Whether the change in the accuracy of the limiter of the lifting moment and the lifting weight is within the scope of the standard requirements

3. Brake wear conditions: Thinning of brake pads, adjustment devices, noise, etc.

4. The aging of hydraulic hoses, especially whether the hoses bent during work show signs of aging and leakage.

5. Check the electrical installation status and observe whether there are signs of aging and condensation.

6. Check the setting status of the tower crane foundation and attachment devices, and measure whether the verticality of the tower body meets the standard requirements. Perfect periodic maintenance work is an important link to ensure the safe operation of tower cranes.

2.3.3 Strengthen the maintenance of the main components and safety devices of the tower crane. The main components and safety devices of the tower crane should be checked regularly. The standard section of the tower body, as the main structural component of the tower crane, bears all the upper weight and working load. The integrity of the standard section and its connections is a necessary condition to ensure the normal operation of the tower crane. Maintenance operations should always check the integrity of the tower body standard section and its connections, and take measures in time if the connection is found to be loose to ensure that the tower body standard section connection is firm and reliable.

2.3.4 Problems found in the maintenance process should be rectified in time. The maintenance personnel should rectify and pass the inspection in time. Problems that cannot be rectified on site should be reported to the responsible entity in a timely manner so that further rectification measures can be taken.

3: For the problems existing in the installation, disassembly and use of tower cranes, practitioners should improve their own safety awareness, actively discover the shortcomings in the work, and take targeted preventive measures to ensure the safe operation of tower cranes at the construction site.