Discussion on safety performance of crane brake
1 crane brake out of control causing casualties
2003-03-09 large hydropower plant in the construction of the project to contract the left river power plant construction work, according to the work plan to carry out the wheel back. To hold the class meeting, before the operation of work arrangements and safety technical disclosure, the relevant staff ready and began to work. Erected a runner cone, the overall test hanging wheel amounts, 1028 began to pit lifting, 1030 when the wheel is lifted to the machine pit and decentralization is about 3M, bridge machine suddenly out of control wheel acceleration whereabouts. In this process, the bridge machine brake burst, gear crack, wire breakage, runner down to the pit. Accidents caused by the bridge on the bridge is responsible for the monitoring of the staff 1 people were killed and 2 people were injured.
A preliminary analysis of the cause of the accident was the bridge hanging out in the machine when decentralization, causing the bridge machine out of control.
2 crane brake mode is not reasonable
It is understood, the vast majority of crane brake, wheel hub type brake, when the gate is opened to or brake, through the electromagnet, or pump start, stop, brake spring elastic pressing or releasing, the brake shoe away from the brake wheel and fit clamps on the brake wheel, reach the gate or braking. And now heavy work, especially when lifting heavy weights, often on a crane equipped with several staff responsible for monitoring, disengaging the purpose of lifting, hook gliding accident shall be with crowbars and other tools to increase brake shoe pressure of brake wheel, so as to achieve the emergency braking to reduce the accident damage. 3.9 accident, bridge machine responsible for care staff have taken such measures, but we have made no corresponding effect, but because the brake is cracking, brake debris fly out care casualties caused major accident. Why pay a painful price of personnel casualties but failed to reduce the level of damage to the accident?
First, mechanical staff responsible for monitoring use crowbars and other tools increase the brake shoe pressure of brake wheel, so as to achieve the objective method in the emergency brake is questionable. When the crane in lifting heavy weights and occurrence of disengagement, hook gliding accident, start the motor and the transmission shaft will with weights to accelerate the decline in the runaway speed, the brake wheel on the transmission shaft is changed with the strong radial vibration. At this point, the crane brake brake, brake shoe will have huge radial impact force, if to artificially increase the brake shoe pressure on the brake wheel, brake shoe itself by the tremendous impact will be greater, brake shoe occurred cracking risk of increased, the front brake pressure on the staff of danger can be imagined. Therefore, the author thinks staff use crowbars etc. increase brake shoe pressure of brake wheel, so as to achieve the objective method in the emergency brake is not desirable. Secondly, the brake is only set on the drive shaft is not enough to improve. Because if disengagement and brake and mechanical damage when, there is no any method can reduce the accident loss of the it should be how to reduce crane due to the unsymmetry of the accident loss it? The author thinks that the braking mode of ship lift can be used for reference.
Discussion on improving the safety performance of crane brake 3
In Yantan vertical entering water shiplift braking mode as an example, the bearing of ship chamber 1430t concrete counterweight heavy 1100-t main hoisting machine brake hydraulic disc brakes, including working brake and safety brake system. Ship lift each need action, safe brake first gate gate in place after the main hoist motor output torque is reached after working brake gate, ship lift running; need to stop, the brakes to work with the main lifting electric closing brake first, delay 6S after peace closing brake, complete the operation process. Failure and accident, but also in accordance with the preparation of the braking action sequence, safe and emergency braking. The whole process safety, reliable verification debugging device of ship lift and several years of operation. Therefore, if the crane adopts the following braking mode, can achieve safe and reliable effect.
3.1 hydraulic disc brake
Compared with wheel brake, hydraulic disc brake with brake principle is simple and reliable, making rapid response etc.. Closing brake, the brake pads on the brake disc of the force is the axial and radial is not to make the brake disc to withstand the impact of the very small, let brake failure probability is reduced to the minimum.
3.2 increase the safety brake
Here to increase the safety brake, with reference to the vertical ship lift the braking settings, reel to increase local brake disc and in the appropriate position placed array disc brake, make it become completely independent of a safety brake system. The advantages of doing so are obvious
1 to liberate the human operator, to reduce the risk of injury;
2 to enhance the safety and reliability of crane operation, when the crane accident can effectively prevent the expansion of the accident. The popular saying is if crane disengagement, hook gliding accident, even starting motor, drive shaft, brake, gear box failure situation, the safe brake drum can effectively closing brake to stop hook continued to decline, to prevent the accident further;
3 some mechanical switch between low and high speed special bridge crane is composed of a gear box, just peace will brake closing brake, ensure the drum is safe brake hold, do a good job in the corresponding prevent safe brake misoperation measures, can according to need, loosen the brake for high speed and low profile of the swap work.
3.3 control system requirements