(1) Establish an accident model
The weight attached to the top item off as an accident, the crane hanging objects attached to various drop occurring phenomenon, to establish the relationship tree branch node (see figure below).
(2) qualitative analysis
1) Find fault tree minimal cut sets
T = A1 + A2 + A3 + xl
= X2 · X3 + X4 + B1 + X5 + X6 (X9 + X10) + X1
= X2 · X3 + X4 + X7 · X8 + X5 + X6 · X9 + X6 · X10 + X1
= X2 · X3 + X4 + X7 · X8 + X5 + X6 · X9 + X6 · X10 + X1
Based on the calculated 7 minimal cut sets
{X2, X3} {x4} {X7, X8} {X5} {X6, X9} {X6, X10} {X1}
2) with a minimal cut set represents the equivalent fault tree
3) The structure of each basic event sequence is not considered an important degree of probability of occurrence of basic events, fault tree and used only on minimal cut set represents the equivalent tree analysis: X1, X4, X5 and most important, followed by equal footing X6 X2 , X3, X7, X8, X9, X10 relatively the most important and in the same position so that the basic structure of an important event order: I1 = I4 = I5> I6> I2 = I3 = I7 = I8 = I9 = I10
3 Conclusions and measures
The foregoing analysis, resulting in hanging objects fall of the main factors are: safety device failure; bundled bad, after lifting heavy objects falling; illegal use of wire rope; lifting abnormal fracture in ropes, these are the most important reason. After shaking encounter obstacles hanging objects swing, and the operator can not take emergency measures: is one important reason. Summed up in one person's unsafe behavior, that person's technical quality and responsibility. Whether the operator through specialized safety training, operational compliance with safety rules, whether a strong sense of responsibility, etc. It is not possible to ensure hanging objects abnormal fall of the key. Of course, does not rule out defects in the equipment on top of the possibility of occurrence. But in people with this contradiction, the contradiction between people are the main aspects of the device defect is a human can check it out in advance and to be repaired. To do this, make the following precautions:
1) on the crane driver shall organize regular technical exercises and job training, to enhance safety and technical training and safety education, improve their skills and dedication of production safety, responsibility and accident emergency handling ability.
2) lifting the operator must be certified: strictly abide by the rules and the rules and regulations.
3) strengthen equipment maintenance, in addition to the national requirements for regular inspection of lifting equipment outside (1/2 years). Workshop lifting equipment should be used for the routine maintenance, to ensure their safety technical characteristics. In using lifting equipment and safety accessories, safety devices, safety checks should be carried out daily. Abnormality was found in time. Strengthen inspection and preventive maintenance shift, especially over hoisting limiter, hook, spreader inspection and maintenance.
4) strengthen management, especially for sling, earnestly implement the wire rope safety factor selection criteria and scrap standards. On the spreader to keep and maintain a good, not arbitrarily throw, misplacing.
