The hoisting mechanism of the bridge crane is the core mechanism, and its performance is the key to ensuring the safe operation of the crane. Therefore, as a crane (overhead crane) driver, he must master the operating method of the hoisting mechanism in order to operate the bridge crane more safely and reliably .
The middle position of the cam controller is the zero gear, that is, the stop gear. There are five gears before and after it. Push the handle away from the zero gear and the hoisting mechanism will start to run. When the handle is pushed forward, the lifting mechanism moves upward; when the handle is pushed backward, the lifting mechanism moves downward.
The lifting operation can be divided into three types: light-load lifting, medium-load lifting and heavy-load lifting.
The lifting weight of light load lifting G≤0.4G amount. The operation method is: from zero gear to the rear (lifting direction) step by step, until the fifth gear, each gear must stay for more than 1 second, from standstill, accelerating to the rated speed (fifth gear), generally need to go through 5 More than seconds. When the hanging object is raised to a predetermined height, the handle should be pulled back to the zero position step by step. In the same way, each gear must stay for more than 1 second to gradually decelerate the motor, and finally brake to stop.
The lifting weight of medium load is G≈0.5—0.6G. The operation method is: start, slowly accelerate, when the handle is pushed to the first gear in the lifting direction, stay for about 2 seconds, then accelerate step by step, and stay for about 1 second in each gear until the fifth gear. When braking, the handle should be pulled back to the zero position step by step, and each gear stays for about 1 second, and the motor gradually decelerates until the brake is finally stopped.
Lifting weight of heavy load G≥O. 7G amount. The method of operation is: when the handle is pushed to the first gear in the lifting direction, the motor cannot start because the load torque is greater than the lifting torque of the motor in this gear, so the handle should be quickly pushed to the second gear to gradually lift the object rise. After the object is hoisted, it accelerates step by step until the fifth gear. If the motor still does not start after the handle is pushed to the second gear, it means that the lifted object has exceeded the rated lifting capacity, and the lifting should be stopped immediately. In addition, if the object is lifted to a predetermined height, the handle should be pulled back to the zero position one by one, and the stay time in the second gear should be a little longer to reduce the impact; but it cannot stay in the first gear, and it must be quickly pulled back to zero. Otherwise, the heavy object will slide down.
The descending operation is the opposite of the step-by-step acceleration of the position speed of each gear when it is ascending, and the speed of the first, second, third, fourth, and fifth gears of the descending handle slows down step by step. Its operation can be divided into three types: light-load descent, medium-load descent and heavy-load descent.
Lifting weight G ≤ 0.4G for light load drop. The method of operation is: push the handle to the first down gear, then the suspended object will drop at about 1.5 times the rated lifting speed. This is the most reasonable operating gear for long-distance object descent, which can speed up the lifting speed and improve work efficiency.
Lifting weight G=0.5—0.6G for medium load drop. The operation method is: it is more appropriate to push the handle to the third gear, and it should not drop at a high speed at the speed of the first gear to avoid accidents. This operation can not only ensure safety, but also achieve the purpose of improving work efficiency.
Lifting weight Q>O. 7Q amount. The operation method is: when the handle is pushed to the fifth gear, it will descend at the slowest speed. When the suspended object reaches the stop position, the handle should be quickly pulled back from the fifth gear to the zero position, without stopping in the middle, to avoid acceleration of the descent speed and excessive braking.
The following points should also be paid attention to in the operation of heavy load drop:
The operation of the lifting mechanism of the crane is the key to ensuring the safety of the crane. Therefore, the crane driver must not only master the operating essentials of the hoisting mechanism, but also master its safety technology.
Every time an object is hoisted, the hook head should be aligned with the center of gravity of the object to be hoisted, or the mass and center of gravity of the object to be hoisted should be estimated correctly, and then the hook should be adjusted to an appropriate position.
Align the hook to the left and right, and move the cart to the left or right according to the left and right deviation of the hook wire rope after the hook head hangs the object, so that the hook head is aligned with the center of gravity of the object.
After the wire rope is straightened, check the hanging object, spreader and surrounding environment before lifting it. During the lifting process, the object should be lifted at a low speed. When the object to be lifted is separated from the surrounding obstacles, push the handle to the fastest gear one by one, so that the object can be lifted at the fastest speed. It is forbidden to push the gear quickly or start suddenly. Avoid hanging objects colliding with nearby people and equipment, and pulling the wire rope, causing personal or equipment accidents.
Generally, the lifting height is within the lifting range, 0.5 meters above the highest obstacle on the ground, and then moved to the lifting channel by a trolley and then lifted along the lifting channel. It is not allowed to pass over the ground personnel and equipment to prevent occurrence Accident. When the hanging object needs to pass over the place where the ground personnel are standing, a signal shall be sent out, and the ground personnel shall not pass until the ground personnel have avoided.
4. It is not allowed to use each limit switch as a stop button to cut off the power during work, and it is not allowed to pull down the knife to cut off the power when the motor is running (with load).
When the object is hoisted to the place where it should be parked, it should fall after the scheduled stop point. When descending, the appropriate descending speed should be selected according to the height of the hanging object from the drop point. And when the hanging object drops close to the ground, continue to operate the lifting mechanism to slowly descend to the ground, not too fast or too violently. When the hanging object is placed on the ground, do not drop the rope and unhook immediately. It must be confirmed that the hanging object is stable and the ground commander sends out the rope dropping signal before dropping the rope and unhooking.
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