Common accident causes and preventive measures of

Causes of common accidents of cranes and preventive measures

the more common major accidents of mobile cranes include overturning, falling boom, folding boom, etc

1. Causes of rollover accidents and preventive measures aluminum will change everyone's life.

1.1 overloaded use:

overloaded use is the main cause of rollover accidents. When the overturning moment formed by the lifting load is greater than the balance moment of the crane itself, the whole crane loses stability and will inevitably overturn

the following conditions are often easy to cause overload of the crane:

the weight of the hoisted object is underestimated

the hoisted object is not completely off the ground

the hoisted object touches buildings or other objects during operation

during lifting, the working range increases

influence of wind load, etc

1.2 cable stayed and inclined crane

in addition to being easy to cause overload, cable stayed and inclined crane also produce a horizontal tension, which leads to the instability of the whole crane and rollover

1.3 the foundation of the outrigger is poor, and some outriggers suddenly sink during the lifting work, resulting in rollover

1.4 high slewing speed is used for lifting heavy objects, and sudden braking in case of emergency can also lead to rollover

1.5 due to the high center of gravity of the crane, or the high speed during no-load driving. A sharp turn may also cause a rollover

in order to avoid rollover accidents, the driver should closely cooperate with the commander. When lifting heavy objects or objects of unknown weight, the heavy objects should be lifted slightly 0.5m off the ground, and the commander should carefully observe whether the opposite outrigger of the crane leaves the ground (or kick the outrigger with his feet). If the outrigger is off the ground (or 1 price's aluminum alloy body riveting 4.0 solution realizes the intelligent upgrading of riveting assembly), it indicates that the whole machine is unstable and lifting should be stopped

in addition, the driver strictly abides by the operating procedures, which is also an important condition to prevent the crane from overturning

2. Causes and preventive measures of arm falling and arm folding accidents:

the occurrence of arm falling accidents is due to operational errors and the mechanism itself

the brake of the luffing mechanism of type Q truck crane is a normally closed brake, and the closing degree of the brake depends on the tension of the spring. If the maintenance and inspection are not enough, the brake may open due to vibration or other reasons, causing the boom to fall

the reason for the boom falling of crawler crane is often in the process of lifting and luffing. The gear cannot be engaged due to the lifting load. Although this mechanism has been improved now, it is still prone to arm fall accidents when the crane is luffing

boom folding accidents often occur when the inclination of the crane is too large, coupled with the impact inertia load, causing the crane to fold the boom

the driver is familiar with the mechanism performance of the equipment operated, adopts the correct operation and use methods, strictly abides by the operating procedures, and strengthens the inspection and maintenance of each mechanism, which are the main measures to prevent the accident of arm falling and arm folding

3. Safety requirements for full hydraulic crane

with the progress of science and technology and the continuous development and improvement of hydraulic transmission technology, hydraulic transmission technology is increasingly used in the power transmission and operation of various working mechanisms of automotive, tire and crawler cranes. Hydraulic cranes have developed rapidly, and mechanical drive cranes have relatively reduced production. Therefore, it is very important to master the basic knowledge of hydraulic transmission and relevant safe operation requirements

3.1 hydraulic components with safety as the main function

the new high-performance polymer compound factory of Solvay was established in Changshu, Jiangsu Province in 2012. The main hydraulic components to ensure the safe operation of crane working mechanisms and hydraulic systems are: balance valve, overflow valve and two-way hydraulic lock

3.1.1 balance valve:

balance valve is composed of sequence valve and one-way valve. Balance valves are installed in the hydraulic systems of lifting, luffing and telescopic boom respectively. The main function of the balance valve is to ensure that the hook dropping, boom dropping, telescopic boom and other actions can be carried out smoothly and effectively prevent the vibration of the crane. In addition, the balance valve also acts as a hydraulic lock. When the high-pressure oil pipe connected to the oil cylinder suddenly breaks, prevent the boom from falling or retracting rapidly, causing accidents

3.1.2 overflow valve

the overflow valve is located at the inlet of the oil circuit controller in the cab, which plays a role in protecting the hydraulic system from accidents due to overload. The opening pressure of the overflow valve is generally 21106 ▁ 22106pa. When the working pressure in the hydraulic system is greater than the opening pressure, part of the hydraulic oil in the hydraulic system flows back to the oil tank from the overflow valve to prevent overloading of the oil circuit system

3.1.3 two way hydraulic lock

two way hydraulic lock is composed of two hydraulic control check valves. Each hydraulic outrigger of the crane is equipped with a two-way hydraulic lock. On the one hand, it prevents the outrigger from falling automatically when the crane is driving or parked. On the other hand, when the high-pressure oil pipe suddenly breaks, it ensures that the outrigger will not retract rapidly, causing a rollover accident

3.2 safety devices of hydraulic cranes

in order to ensure the safe operation of cranes, modern hydraulic cranes are generally equipped with the following safety devices

3.2.1 overwinding protection device

this device is installed at the end of the boom. When the steel wire rope safety inspection hammer touches the hook, the alarm sounds and automatically cuts off the power supply to avoid overwinding

3.2.2 drum automatic brake

this brake uses a strong spring to brake the drum, and the brake is released only during lifting, lowering and free lowering operations, so as to prevent safety accidents caused by the wrong operation of the winch

3.2.3 drum rotation indicator

this indicator is installed in the reinforcement room. It can display the rotation speed and direction of the winding drum of the winch. In order to grasp the lifting (landing) speed and direction of the lifted object at any time during night operation or long-distance high-altitude operation

3.2.4 reel lock

reel lock is to lock the reel with pawls, so that the weight can be suspended and prevent the weight from falling automatically

3.2.5 drum safety stop

when the high-pressure hose between the oil pump and the winch motor suddenly breaks, the balance valve installed in the winch motor immediately blocks the hydraulic oil in the motor, effectively preventing accidents

3.2.6 safety device for boom retraction

there are two kinds of safety devices for boom retraction. One is to control the sequence of boom extension to prevent boom damage caused by disorder of boom extension sequence. The other is the balance valve installed at the bottom of the telescopic oil cylinder to prevent the boom from retracting sharply after the sudden rupture of the high-pressure oil pipe, resulting in safety accidents

3.2.7 boom luffing safety device

this device is a balance valve installed at the lower part of the luffing cylinder. When the high-pressure oil pipe breaks, it prevents a large amount of hydraulic oil from leaking out of the luffing cylinder, causing the boom to fall quickly and causing safety accidents

3.2.8 outrigger safety device

if the high-pressure oil pipe suddenly breaks, the one-way valve installed at the lower part of the outrigger cylinder can immediately block the massive leakage of hydraulic oil in the outrigger cylinder, so as to prevent the vehicle from losing stability and causing accidents

3.2.9 hydraulic oil pipeline safety device

in order to prevent excessive pressure in the hydraulic circuit, a safety valve is installed in the main pressure system of the hydraulic pressure system when the hydraulic pressure enters the experimental procedure according to the prompt, so as to effectively prevent oil leakage of the oil pump and motor overload

3.2.10 full automatic overweight prevention device

in the lifting operation, the total torque generated by the boom length, boom elevation and the size of the lifted load may exceed the safe operation range of the crane. In lifting operation, when the lifting torque is less than 5% of the limit value, the buzzer buzzes and alarms; When the lifting torque value reaches the limit value, the red light will flash and alarm, and the automatic stopper will start to work, so that the lifting operation cannot be carried out, so as to prevent accidents caused by overload operation