Rental of folding boom crane In fact, there are many accidents, and the gear cannot be engaged due to hoisting. Currently available Crane rental company The equipment will be improved, but attention should also be paid to the possibility of arm dropping when changing the lifting weight. The accidents of folding boom cranes are mostly rollover and arm breakage, which are mostly caused by improper operation of drivers. So today, Huai'an Crane Rental I would like to introduce some reasons for crane accidents, and I hope it will be helpful!

1、 Crane rollover accident

① Overload

The lifting capacity of the self-propelled boom crane changes with the boom inclination. The Regulations on Safety Management of Cranes points out that "the lifting weight and boom inclination shall meet the design requirements", and stipulates that "overload operation of lifting machinery is prohibited." In actual work, the crane loses its stability due to unclear estimation of the weight of the lifted object or overload operation due to insufficient attention to safety, resulting in "rollover".

② Outriggers are not on the horizontal plane

The root cause of accidents such as rollover is that the hardness and hardness of the ground contacted by the legs are different, resulting in uneven sinking of the legs. For example, on September 18, 1973, a 16T tire truck crane lifted a receiver. Because the terrain is low-lying and there is water, the front wheel stops on a 100mm * 100mm raft, the rear wheel stops on the rail, and four legs are placed on a sleeper.

Lift a receiver with a diameter of 10m, and the boom is at the rated lifting capacity of 2.5t. The commander said that the weight is only 1t. The first and second trial lifts were normal, and the third lift caused a "rollover" accident. Later, it was found that the reason was that the legs were not in a horizontal plane and were overweight.

The main measures to prevent the outrigger from sinking are as follows:

The outrigger must be supported on a flat and solid ground, usually with a cushion.

The outriggers shall not be supported near the excavated foundation to prevent landslide.

The outriggers cannot be supported on various buried objects (underground pipelines, entrances and exits of underground works) to prevent collapse.

③ Rotating too fast

At the beginning of lifting objects, cranes generally do not roll over, often in the process of turning. For example, a factory uses a tire crane to buckle the floor, and the components are about 15-20m away from the building. The crane works between the building and the components. The terrain is high in the north and low in the south, with wind and snow. When the first block is hoisted, the working range of the boom is 10m, the inclination is 600 °, and the boom after hoisting is about 450 °. The car leans forward. Someone yells "Danger" at the construction site. The driver brakes suddenly, but finds that it is under the board.

Someone turned his arm again, brake again after avoiding people, and overturned due to turn back. This is because the rotation will produce centrifugal force. The faster the rotation is, the greater the centrifugal force will be. At the same time, it will turn to unstable positions such as downwind

The rollover accident is caused by a variety of factors, so it should be noted that the speed should not be too fast.

④ Luffing and telescopic boom operation program error

When lifting with full load, only the boom can be retracted (from large to small, from long to short), and cannot be extended or dropped, otherwise it will overturn. For example, in a construction site, there is a Q51 truck crane with a slewing radius of 305 meters, which can lift 3t. At this time, the 2.6t crane is not overloaded. However, due to the wrong signal, the commander asked the driver to start the arm. "The driver mistakenly heard that the arm fell, resulting in a car rollover accident.

Incorrect telescopic boom of hydraulic crane will also lead to rollover. For example, when a factory was put into production in a certain year, the 8T tire crane lifted 3.2T, which should have been retracted and misoperated to extend, resulting in rollover.

⑤ Danger angle

Some cranes have a dangerous angle. When the boom is very long, even if the goods are not lifted, the weight of the boom itself will cause rollover.

⑥ Turning speed too high

Since the center of gravity of automobiles and tire cranes is higher than that of ordinary automobiles, rollover may occur if the turning speed is too high.

⑦ Connecting bolt of cutting off rotary table

For example, one year at a construction site, a truck crane overturned and killed a hooker. The cause of the inspection accident was that the connecting bolts of the rotary table were cut off continuously, leading to a rollover accident. Therefore, continuous bolts must be safe and reliable to meet the strength requirements.

2、 Crane "falling boom" and "folding boom" accidents

For the luffing mechanism without mechanical test, the "arm dropping" accident is mostly caused by breaking the luffing rope. For hydraulic luffing mechanism, accidents of balance valve or oil pipe may cause arm dropping accident.

When installing and inspecting the long and thin boom, sleepers must be placed under the boom, otherwise the dead weight of the boom is enough to cause the crane to tilt forward.

"Arm dropping" has both operational and institutional reasons. For example, the brake of the luffing mechanism of the Q51 truck crane is a normally closed band brake, which is closed by the tension of the spring. If the maintenance is not enough, the arm may fall due to vibration or other reasons. It was later discovered that the cause was brake failure.

The "boom break" accidents are mostly caused by the small elevation angle of the boom, and the inertia causes the boom to break. If the lifting rope is excessively wound or the travel of the luffing mechanism is too large, the arm may fold back. The collision between the boom and the building is also one of the reasons for the folding boom accident.