1. What is a tower crane?
Tower crane, referred to as tower crane, is what everyone often calls tower crane. It is a kind of mobile crane. A rotating crane whose arms are mounted on the upper part of a tall tower. This kind of crane has a large working space and is mainly used for vertical and horizontal transportation of materials and installation of building components in house construction.
2. What are the safety devices of tower cranes?
Tower cranes are large construction machinery. In order to ensure the normal and safe use of tower cranes, we must enforce Safety requirements: Tower cranes must be equipped with prescribed safety devices during installation, including:
1. Lifting moment limiter
When the tower crane is hoisting objects, The product of the hoisting radius and the weight of the hoisted object is an invariable fixed number. Based on this principle, a lifting torque limiter is made, whose main function is to prevent overloading as a safety device. The moment limiter only protects the overload moment in the longitudinal vertical plane of the tower crane boom, and cannot protect against overturning accidents caused by inclined cranes, wind loads, inclination or collapse of the track, etc.
2. Lifting weight limiter
The function of the lifting weight limiter is to protect the weight of the lifted objects from exceeding the maximum allowable lifting weight of the tower crane and to prevent the tower crane from The weight of the hoisted object on the machine exceeds the maximum rated load to avoid mechanical damage accidents.
3. Lifting height limiter
The lifting height limiter is used to limit the hook from contacting the head of the boom or the load. Before the trolley, or before it descends to the lowest point (the ground or several meters below the ground), the lifting mechanism automatically cuts off power and stops working to prevent the lifting arm from being damaged due to excessive lifting of the lifting hook.
4. Amplitude limiter
A device used to limit the boom from exceeding the limit position during pitching. An alarm will sound before the lifting pitch reaches a certain limit, and the power will be automatically cut off when the limit position is reached.
5. Stroke limiter
(1) Trolley stroke limiter: located at the head and root of the trolley luffing boom , used to cut off the circuit of the car’s traction mechanism to prevent the car from going offside.
(2) Cart travel limiter: used to prevent the crane from derailing.
6. Rail clamping pliers
Used to clamp the rails to prevent cranes fromIt is a device that causes the tower crane to derail and tip over when it is blown by the wind under strong wind conditions.
7. Anemometer
Automatically records the wind speed and automatically alarms when the wind speed exceeds Level 6.
8. Wire rope anti-slip groove device
It is mainly used to prevent the wire rope from breaking away from the pulley groove during the transmission process and causing the wire rope to break.
9. Hook insurance
A device that prevents the lifting wire rope from decoupling and the hanging object falling due to excessive angle or improper hook. .
3. Tower Crane Safety Operating Procedures
In order to ensure the safety of tower crane operations, in addition to configuring necessary safety devices, operators must also pay attention to following the tower crane’s operating procedures. Safety operating procedures:
1. Pre-operation inspection
(1) Shift handover procedures must be carried out before work, and mechanical resumes and shift handover records must be checked. Fill in the information and record the information.
(2) Before operation, the rail clamp should be loosened and fixed according to the prescribed method. Clear obstacles on the running track, check that the running limit stops at both ends of the cross-rail are not less than 2~3m from the end, and check the straightness, slope and height difference of the two tracks, which should comply with the relevant safety regulations of the tower crane. Technical regulations stipulate that the roadbed must not have subsidence, landslides, cracks, etc.
(3) After the track is installed, it must comply with the following regulations: the height difference between the two tracks shall not be greater than 1/1000. The longitudinal and transverse slopes are not greater than 1/1000. The error between the track gauge and the nominal value is not greater than 1/1000, and its absolute value is not greater than 6mm. The gap between rail joints is between 2 and 4 mm. The height difference between the tops of the two rails at the joint is not greater than 2 mm. The joints of the two rails must be staggered by 1.5 m.
(4) Check the tightening condition of each main bolt and make sure that there are no cracks or open welding in the welds and main steel.
(5) Check that the oil level of the mechanical transmission gearbox, hydraulic oil tank, etc. meets the standards.
(6) Check that all brake wheels and brake belts (shoes) are not damaged and the brakes are sensitive; hooks, pulleys, snap rings, and wire ropes should comply with standards; safety devices (torque limiter, weight Limiter, travel, height amplitude limiter and hook insurance, etc.) are sensitive and reliable.
(7) The operating system and electrical system are in good contact, with no looseness or exposed wires.
(8) For tower cranes with elevators, it must be verified that all safety devices are safe and reliable.
(9) Before sending power to the distribution box, the linkage controller should be in the zero position. After closing, check that there is no leakage in the metal structure before getting on the machine.
(10) All electrical systems must have good grounding or zero protection. A set of groundings every 20m shall not be connected to the building, and the grounding resistance shall not be greater than 4Ω (ohms).
(11) There must be no obstacles within 1m of any part of the crane during operation.
(12) The tower crane should be operated without load or tested before operation, and it can be put into production only after confirmation.
2. Safe operation
(1) The driver must perform operations according to the lifting performance of the tower crane he is driving
( 2) When various safety protection devices on the machine malfunction, fail or are inaccurate during operation, the machine must be shut down immediately for repairs. It is strictly prohibited to operate while sick and perform maintenance during operation.
(3) Drivers must operate in strict accordance with command signals, flags, and gestures under the command of personnel wearing command signal armbands. A sound signal should be given before operation, and blind operation is not allowed when the command signal is unclear. The right to refuse execution or proactively take preventive or corresponding emergency measures for command errors.
(4) When safety devices such as lifting weight, lifting height, and amplitude display or approach critical alarm values, the driver must pay close attention and forced operation is strictly prohibited.
(5) During operation, drivers are not allowed to chat, smoke, read, report or do other things unrelated to operation. Do not leave the operating position without permission.
(6) When the hook pulley block is lifted close to the boom, low-speed lifting should be used.
(7) It is strictly forbidden for heavy objects to fall freely. When the lifting object descends close to the positioning point, it must be moved into position slowly. When the heavy object is in place, the brake can be used to lower it slowly.
(8) When using a non-direct impact height limiter, adjust the height limiter to: the distance between the hook pulley block and the corresponding lowest part shall not be less than 1m, and the distance between the direct impact type shall not be less than 1.5m.
(9) It is strictly forbidden to use hooks to directly hang heavy objects.
(10) When operating the controller, you must start from zero, push to the first gear, and then increase gears step by step, stopping for 1 to 2 seconds at each gear until you reach the highest gear. When the transmission device needs to change direction during motion, the controller should be pulled to the zero position first, and then operated in the reverse direction after the transmission stops. It is strictly prohibited to directly change the direction of operation. Tower cranes that have operating time limits for the slow-position gear must be used within the specified time, and the slow-position gear must not be used without restriction.
(11) When translating the lifting object during operation, the weight should be at least 100mm higher than the height of the obstacle it crosses.
(12) When the crane approaches the track limit, it should slow down and stop in advance.
(13) When lifting heavy objects, it is not allowed to lift unstable heavy objects. It is strictly forbidden to attach heavy objects to the lifted objects. When lifting loose materials or special-shaped components, they must be tied firmly with wire ropes and should be tied up first. Lift the heavy object about 50cm from the ground and stop. Make sure the brakes, material lashing and slings are correct before commanding to lift.
(14) When the crane is working at night, it must have sufficient lighting.
(15) When the crane is shut down, taking a rest or having a power outage, the heavy objects should be unloaded and no heavy objects should be suspended in the air.
(16) In the operating room,Irrelevant personnel are not allowed to enter, and it is prohibited to place flammable materials and items that hinder operation.
(17) It is strictly prohibited to transport or lift people on the crane. When lifting or lowering heavy objects, it is strictly forbidden to stand under the heavy objects.
(18) The boom and lifting objects of the crane must maintain a safe distance from high and low voltage overhead transmission lines.
(19) When two erected cranes are operating on the same track or on two parallel or mutually perpendicular tracks, a safe distance between any part of the two machines should be maintained. The minimum Less than 5m.
(20) Hoisting operations should be suspended when the following circumstances occur: severe weather such as heavy rain, heavy snow, heavy fog, and strong winds above Level 6 (inclusive) on the construction work surface affect safe construction. hour. Electricity leakage occurred in the crane. The wire rope was severely worn and reached the scrap standard. The safety protection device fails or the display is inaccurate.
(21) Drivers must go up and down the escalator. It is strictly forbidden to carry tools or items when going up or down the escalator.
(22) It is strictly prohibited to throw any objects or defecate downwards from the tower crane.
(23) When heating the tower crane operating room in winter, measures should be taken to prevent electric shock and fire.
(24) Any tower crane with an elevator must comply with the regulations in the elevator’s instruction manual. Overloading and violation of operating procedures are strictly prohibited.
(25) When operating with multiple machines, overlapping operations of two or more tower cranes within the slew radius should be avoided. In special circumstances, when overlapping operations are required, the vertical safety distance of the booms and the safety distance between each other when lifting materials must be ensured, and reliable safety technical measures must be taken before construction is approved by the competent technical leader.
(26) After the heavy object is lifted off the ground, the three movements of lifting, turning and walking of the luffing jib tower crane can be carried out at the same time, but the amplitude can only be carried out separately, and it is strictly prohibited to carry the amplitude with load. Cranes that are allowed to luff with load shall not luff when at full load or close to full load.
(27) Cranes whose hoisting winch is not installed on the rotating part are not allowed to rotate continuously in one direction during lifting operations.
(28) For a crane equipped with a mechanical torque limiter, after multiple amplitude changes, the tonnage indicator plate of the overload limiter must be adjusted according to the gyration radius and the rated load of the radius. .
(29) The curved rail roadbed must comply with regulations. When the crane turns, sand should be sprinkled on the outer rail surface, and grease should be applied on the inner rail surface and both wings. The counterweight box should be turned in the direction of the turning outer wheel. It is strictly prohibited to perform lifting operations on curves or turn with heavy objects.
3. Inspection after shutdown
(1) After the tower crane stops operating, it is necessary to select a position where there are no obstacles when the tower crane rotates and the middle of the track is suitable The position and arm should be stopped in the wind direction, and all rail clamps should be locked.
(2) For any tower crane with a normally closed or braking device in the slewing mechanism, after stopping operation, the driver must remove the handle and release the brake so that the crane can operate in strong winds.It rotates in the direction of the wind when blown.
(3) The hook should be lifted to a position where the minimum distance from the lifting wall is no more than 5m. It is strictly prohibited to hang heavy objects on the hook. No method shall be used to restrict the rotation of the boom in the wind without taking reliable measures.
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