CN106815421A - A kind of bridge crane safety evaluation method - Google Patents

Abstract

The invention discloses a method for evaluating the safety of a bridge crane. At present, there is no set of safety assessment methods suitable for the whole system of the crane. The present invention decomposes the crane into four evaluation modules according to its structural components and key detection items, and evaluates each module or the complete crane. According to the evaluation results obtained, the safety status level of each module can be known and the safety evaluation conclusions are given accordingly. The crane user can maintain and repair the crane based on the safety evaluation conclusions. The invention not only plays a technical guiding role for the crane supervisory unit, but also provides favorable and reliable safety guarantee measures for the crane user unit.

Description

A Safety Assessment Method for Bridge Cranes

technical field

The invention belongs to the field of safety evaluation methods for special crane equipment, and in particular relates to a safety evaluation method for bridge cranes.

Background technique

Hoisting machinery is one of the eight categories of special equipment stipulated in my country's "Special Equipment Safety Law". It is widely used in logistics transportation, manufacturing, construction and other industries. From the handling of ordinary objects to the hoisting of large equipment, hoisting machinery has Become a key factor restricting the progress and safety of the entire project. Although hoisting machinery is not as dangerous as other special equipment, due to various reasons, the accident rate caused by hoisting machinery has been high in recent years, and the absolute number of casualties caused by safety accidents has always been among the top eight. The safe operation of hoisting machinery plays an important role in ensuring the safety of people's lives and property.

With the development in recent decades, my country's crane industry has formed a certain scale. Currently, there are nearly 2 million cranes in use. With the impact of the use environment and the increase in frequency of use, the number of cranes that are old or even over-age is increasing year by year. The growing trend can easily lead to the crane being in an unsafe state during work and forming a great safety hazard. At the same time, cases of major accidents caused by human factors, failure of crane electrical equipment, failure of safety protection devices and other reasons are not uncommon. Safety assessment is to achieve system safety, according to certain scientific procedures and methods, research and analyze the risk factors in the system, the possibility of accidents, and the degree of loss and casualty, so as to evaluate the overall safety of the system, for the formulation of Prevention and protective measures provide scientific basis. However, some existing evaluation methods mainly evaluate the life of the wire rope of the hoisting mechanism or the stressed structure of the crane, and there is no set of safety evaluation methods suitable for the entire system of the crane. Therefore, establishing a set of effective safety assessment methods for overhead cranes provides technical support for the safety of the entire crane system. Through the safety assessment of cranes, the Special Equipment Inspection Institute and other national management departments can know the results of the crane safety assessment, understand the safety status of the cranes, and have a comprehensive understanding of the hidden dangers of the regional cranes. The level of security used.

Contents of the invention

The purpose of the present invention is to establish a set of safety evaluation methods for the overall system of the bridge crane body in view of the lack of existing crane evaluation methods.

The present invention comprises the following steps:

Step 1: The overhead crane system is divided into modules.

Decompose the whole bridge crane into electrical and control system risk sources, main component risk sources, safety protection device risk sources and metal structure risk sources. Electrical and control system risk sources include power cutoff, main circuit breaker, power supply contactor, emergency stop switch, motor protection, line protection, phase error and phase loss protection, zero position protection, voltage loss protection, abnormal power loss of motor stator protection, overspeed protection, grounding and lightning protection, insulation resistance, lighting and signal and safety voltage. Risk sources for major components include hooks, wire ropes, drums, pulleys, wheels, reducers, open gears and couplings. Risk sources of safety protection devices include brakes, lifting height limiters, running stroke limiters, anti-collision devices, buffers and end stops, lifting weight limiters, wind resistance and anti-skid devices, anti-tipping safety hooks, interlocking Protection, safety protection, alarm and protective cover for conductive trolley lines. Risk sources for metal structures include deflection deformation, I-beam deformation, camber deformation, cracks, wear and corrosion.

Step 2: Classify the severity levels, and assign a value g _i to each risk source, where i=1, 2, ... are the serial numbers corresponding to each risk source.

The severity is divided into 5 levels: Level 1 means that the casualties, economic losses, environmental hazards, and social impacts are particularly serious; Level 2 means that the casualties, economic losses, environmental hazards, and social impacts are serious; Level 3 means Casualties, economic losses, environmental hazards, and social impacts are serious; level 4 means casualties, economic losses, environmental hazards, and social impacts are average; level 5 means casualties, economic losses, and environmental hazards , The social impact is very small.

Among the risk sources of the electrical and control system, the power cut-off level is level 3, the main circuit breaker level is level 3, the power supply contactor level is level 3, the emergency stop switch level is level 1, the motor protection level is level 5, and the circuit protection level is level 3. Level 4, wrong phase and phase loss protection level 4, zero protection level 3, voltage loss protection level 4, motor stator abnormal power loss protection level 3, overspeed protection level 4, grounding and anti- The lightning level is 4, the insulation resistance level is 4, the lighting and signal, and the safety voltage level are 5. Among the risk sources of main components, the level of the hook is level 2, the level of the wire rope is level 2, the level of the reel is level 4, the level of the pulley is level 4, the level of the wheel is level 4, the level of the reducer is level 4, and the level of the open gear is Level 4, the coupling level is level 4. Among the risk sources of safety protection devices, the level of the brake is level 2, the level of the lifting height limiter is level 1, the level of the travel limiter is level 4, the level of the anti-collision device is level 4, the level of the buffer and the end stop The level of crane limiter is level 3, the level of wind resistance and anti-skid device is level 4, the level of anti-tipping safety hook is level 4, the level of interlock protection is level 4, and the safety protection level of conductive sliding contact line is level 5 , The level of the alarm device is level 5, and the level of the protective cover is level 4. Among the risk sources of metal structures, the level of downward deflection is level 2, the level of I-beam deformation is level 3, the level of upward camber deformation is level 2, the level of cracks is level 2, the level of wear is level 3, and the level of corrosion is level 3.

The higher the severity level, the greater the score assigned, indicating that the consequences of the accident are more serious. Each severity level corresponds to a point value. Level 1 gives a score of 1, level 2 gives a score of 0.875, level 3 gives a score of 0.625, level 4 gives a score of 0.375, and level 5 gives a score of 0.125.

Step 3: According to the possibility of failure events occurring in each risk source of the crane, the probability of occurrence is divided into 5 levels: Level 1 corresponds to a very high possibility; Level 2 corresponds to a high possibility; Level 3 corresponds to a general possibility; Level 4 corresponds to a general possibility. Level 5 is less likely to correspond; level 5 is less likely to correspond. Each level corresponds to a score interval: level 1, score interval (0.875, 1]; level 2, score interval (0.625, 0.875];

Level 3, score interval (0.375, 0.625]; level 4, score interval (0.125, 0.375]; level 5, score interval (0, 0.125]. Occurrence probability value.

Step 4: When the environment in the rule base intervenes, when one or more environmental factors act on a certain risk source, and the probability r _i ≤ 0.75 of the risk source, the probability r _i of the crane failure will be re- The value r _i ' is assigned, that is, the occurrence probability of this risk source is increased by 0.25 on the basis of the initially determined occurrence probability.

The rule base includes four types of environmental impact factors, and each risk source is affected by the four types of environmental impact factors as follows:

(1) Risk sources affected by high temperature: motor protection, line protection, insulation resistance, buffers and end stops; (2) Risk sources affected by moisture: insulation resistance, wire ropes, buffers and end stops , Metal structure corrosion; (3) Risk sources affected by high corrosion: line protection, grounding and lightning protection, insulation resistance, steel wire rope, brake, buffer and end stop, metal structure corrosion; (4) Affected by dust Risk source: power supply contactor.

Step 5: Mutual coupling between risk sources

The risk sources of bridge cranes are divided according to the functional mechanism of each part of the crane, but in fact, the internal factors of the bridge crane system are interrelated and affect each other, and each risk source cannot be analyzed separately, but should be analyzed from the perspective of the bridge crane system. Starting from the overall function of the system, we study the coupling situation between various risk sources.

1) Coupling between different risk sources: When the probability R of risk source A1 reaches 0.875, the probability of risk source A2 is affected due to the increased risk of A1, then the probability will be automatically transformed and assigned as:

R _A22 = R _A21 e ^(R-0.875) (1)

_RA21 is the initial probability, and _RA22 is the new probability after the coupling effect.

2) Coupling factors: When the risk source drum is damaged, the wire rope is prone to burrs; when the risk source pulley is damaged, the wire rope is prone to burrs; when the risk source wheel ellipticity increases, the load coefficient will increase, making the wire rope easier to scrap , the main beam is more easily deformed.

Step 6: Use y to represent the risk degree of system accidents, and use formula (2) to calculate as follows:

Among them, g _i represents the serious consequences of risk source _i , and ri represents the probability of risk source i occurring.

Step 7: According to (1-y)*100, get a value between 0 and 100, which represents the system comprehensive security status score d:

d=(1-y)·100 (3)

Step 8: According to the score d of the comprehensive safety situation, judge the grade of the comprehensive safety situation.

The safety status is divided into 5 levels: Level 1, score interval (80≤D≤100), safety assessment conclusion: the risks pointed out by the assessment need to be strengthened for monitoring and use; level 2, score interval (60≤D<80), Safety assessment conclusion: safety measures need to be taken to eliminate or reduce risks; level 3, score range (40≤D<60), safety assessment conclusion: safety measures should be taken to eliminate risks; level 4, score range (20≤D<40 ), it is recommended to stop using it immediately, and take safety measures to eliminate the risk before using it; Level 5, score range (0≤D<20), it should be stopped immediately to eliminate the risk, and if necessary, carry out major repairs or renovations, and repair it if necessary If it is running but cannot be repaired, it is recommended to be discarded or downgraded for use.

Compared with existing assessment methods, the beneficial effects of the present invention are:

The present invention decomposes the crane into four evaluation modules according to its structural components and key detection items, and evaluates each module or the complete crane. According to the evaluation results obtained, the safety status level of each module can be known and the safety evaluation conclusions are given accordingly. The crane user can maintain and repair the crane based on the safety evaluation conclusions. The invention not only plays a technical guiding role for the crane supervisory unit, but also provides favorable and reliable safety guarantee measures for the crane user unit.

Description of drawings

Figure 1 is a structural diagram of the bridge crane module division.

detailed description

The present invention will be further described below in conjunction with accompanying drawing.

A safety assessment method for bridge cranes, specifically as follows:

Step 1: As shown in Figure 1, the bridge crane system is divided into modules.

Decompose the bridge crane machine A into four risk source modules: electrical and control system risk source B1, main parts risk source B2, safety protection device risk source B3, and metal structure risk source B4. Electrical and control system risk sources B1 include: power cut-off B1-1, main circuit breaker B1-2, power supply contactor B1-3, emergency stop switch B1-4, motor protection B1-5, line protection B1-6, Wrong phase and lack of phase protection B1-7, zero protection B1-8, voltage loss protection B1-9, motor stator abnormal power loss protection B1-10, overspeed protection B1-11, grounding and lightning protection B1-12, insulation resistance B1-13, lighting and signal B1-14 and safety voltage B1-15. Risk source B2 of main components includes: hook B2-1, wire rope B2-2, reel B2-3, pulley B2-4, wheel B2-5, reducer B2-6, open gear B2-7 and coupling Device B2-8. Safety protection device risk source B3 includes: brake B3-1, lifting height limiter B3-2, running stroke limiter B3-3, anti-collision device B3-4, buffer and end stopper B3-5, Lifting weight limiter B3-6, anti-wind and anti-skid device B3-7, anti-tipping safety hook B3-8, chain protection B3-9, safety protection of conductive trolley line B3-10, alarm B3-11 and protective cover B3 -12. Metal structure risk sources B4 include: downward deflection deformation B4-1, I-beam deformation B4-2, upward camber deformation B4-3, cracks B4-4, wear B4-5 and corrosion B4-6.

Step 2: Severity classification and assignment of g _i .

The severity of the consequences refers to the severity of the consequences of the accident if the crane fails. The degree of severity is divided into 5 levels: level 1 corresponds to particularly serious, which means that the seriousness of the consequences such as casualties, economic losses, environmental hazards, and social impacts is particularly serious; level 2 corresponds to serious, indicating that the resulting casualties and economic losses , environmental hazards, social impacts and other consequences are serious; Level 3 corresponds to heavy, which means that the consequences of casualties, economic losses, environmental hazards, and social impacts are serious; Level 4 corresponds to general, indicating that the personnel brought Casualties, economic losses, environmental hazards, social impacts and other consequences are of average severity; Level 5 corresponds to very small, indicating that the severity of casualties, economic losses, environmental hazards, social impacts and other consequences is very small.

The severity level is obtained by experts after a long period of collation and analysis of crane inspection data. In electrical and control system risk source B1, power cut-off B1-1 is grade 3, main circuit breaker B1-2 is grade 3, power supply contactor B1-3 is grade 3, emergency stop switch B1-4 is grade 1 Level, motor protection B1-5 level is level 5, line protection level B1-6 level 4, wrong phase and phase loss protection level B1-7 level 4, zero protection level B1-8 is level 3, voltage loss protection B1 -9 level is level 4, motor stator abnormal power loss protection level B1-10 is level 3, overspeed protection level B1-11 is level 4, grounding and lightning protection level B1-12 is level 4, insulation resistance level B1-13 is level 4 Level 4, lighting and signal B1-14, and safety voltage B1-15 are level 5. In the main component risk source B2, the hook B2-1 is grade 2, the wire rope B2-2 is grade 2, the reel B2-3 is grade 4, the pulley B2-4 is grade 4, and the wheel B2-5 Grade 4, reducer B2-6 grade 4, open gear B2-7 grade 4, coupling B2-8 grade 4. In the safety protection device risk source B3, the brake B3-1 is grade 2, the lifting height limiter B3-2 is grade 1, the running stroke limiter B3-3 is grade 4, and the anti-collision device B3-4 Grade 4, buffer and end stop B3-5 grade 4, crane limiter B3-6 grade 3, wind resistance and anti-skid device B3-7 grade 4, anti-tipping safety hook B3- 8 is level 4, interlock protection B3-9 is level 4, conductive trolley line safety protection B3-10 is level 5, alarm device B3-11 is level 5, protective cover B3-12 is level 4 class. In the metal structure risk source B4, the downward deflection deformation B4-1 is grade 2, the I-beam deformation B4-2 is grade 3, the camber deformation B4-3 is grade 2, and the crack B4-4 is grade 2 , The wear B4-5 grade is 3 grades, and the corrosion B4-6 grade is 3 grades.

The higher the severity level, the greater the score assigned, indicating that the consequences of the accident are more serious. Each severity level corresponds to a point value. Level 1 gives a score of 1, level 2 gives a score of 0.875, level 3 gives a score of 0.625, level 4 gives a score of 0.375, and level 5 gives a score of 0.125.

Step 3: Detect data, judge on site, give probability level, and assign value r _i , where i=1, 2, ... are the serial numbers corresponding to each risk source.

According to the probability of failure events occurring in each risk source of the crane, the probability of occurrence is divided into five levels: Level 1 corresponds to a very high possibility; Level 2 corresponds to a high possibility; Level 3 corresponds to a general possibility; Level 4 corresponds to a possibility The probability is small; the possibility of level 5 correspondence is very small. Each level corresponds to a score interval: level 1, score interval (0.875, 1]; level 2, score interval (0.625, 0.875]; level 3, score interval (0.375, 0.625]; level 4, score Interval (0.125, 0.375]; level 5, score interval (0, 0.125]. Inspectors determine the probability level and occurrence probability value based on the on-site detection data of risk sources and the probability of failure occurrence.

Step 4: The rule base is involved, and the risk probability is reassigned to r _i ' by the rule base.

The rule base is the impact of certain environmental factors when the crane is operating. When the rule base is involved, the environmental factors may affect the probability of some structural or component failures of the crane, and the probability r _i of the crane failure will be reassigned to _ri '.

The rule base includes four types of environmental impact factors, and each risk source is affected by the four types of environmental impact factors as follows:

(1) Risk sources affected by high temperature: motor protection, line protection, insulation resistance, buffers and end stops; (2) Risk sources affected by moisture: insulation resistance, wire ropes, buffers and end stops , Metal structure corrosion; (3) Risk sources affected by high corrosion: line protection, grounding and lightning protection, insulation resistance, steel wire rope, brake, buffer and end stop, metal structure corrosion; (4) Affected by dust Risk source: power supply contactor.

When the environment in the rule base intervenes, when one or more environmental factors act on a certain risk source, and the probability r _i ≤ 0.75 of the risk source, the occurrence probability of the risk source is determined at the beginning Add 0.25 to the base.

Step 5: Mutual coupling between risk sources

The risk sources of bridge cranes are divided according to the functional mechanism of each part of the crane, but in fact, the internal factors of the bridge crane system are interrelated and affect each other, and each risk source cannot be analyzed separately, but should be analyzed from the perspective of the bridge crane system. Starting from the overall function of the system, we study the coupling situation between various risk sources.

1) Coupling between different risk sources: When the probability R of risk source A1 reaches 0.875, the probability of risk source A2 is affected due to the increased risk of A1, then the probability will be automatically transformed and assigned as:

R _A22 = R _A21 e ^(R-0.875) (1)

_RA21 is the initial probability, and _RA22 is the new probability after the coupling effect.

2) Coupling factors: When the risk source drum is damaged, the wire rope is prone to burrs; when the risk source pulley is damaged, the wire rope is prone to burrs; when the risk source wheel ellipticity increases, the load coefficient will increase, making the wire rope easier to scrap , the main beam is more easily deformed.

Step 6: According to the formula Get a risk y.

Crane safety assessment is an assessment of the crane system, in which the risk of the crane is determined by the severity of the consequences and the probability of occurrence of the crane failure event. The severity of consequences refers to the severity of casualties, economic losses, environmental hazards, and social impacts caused by crane accidents. The probability of occurrence is the probability that the crane will be dangerous and cause an accident.

The opposite of safety is risk, we use y to represent the risk degree of system accidents, and use formula (2) to calculate as follows:

Among them, g _i represents the serious consequences of risk source _i , and ri represents the probability of risk source i occurring. For the safety assessment of bridge cranes, if the risk degree y is greater, it means that the crane has a higher risk level, lower safety, and a shorter safe use period, and accidents caused by the crane itself may bring Serious consequences such as greater casualties, economic losses, and environmental hazards; on the contrary, if the risk degree y is smaller, it means that the risk level of the crane is lower, the safety is higher, and the safe use period is longer.

Step 7: According to (1-y)*100, get a value between 0 and 100, which represents the system comprehensive security status score d:

d=(1-y)·100 (3)

Step 8: According to the score d of the comprehensive safety situation, judge the grade of the comprehensive safety situation. Corresponding this value to a certain interval score range, the comprehensive safety status level is judged, and the corresponding safety evaluation conclusion is given. This evaluation conclusion will play a certain guiding role in whether the crane needs to be maintained or repaired.

The safety status is divided into 5 levels: Level 1, score interval (80≤D≤100), safety assessment conclusion: the risks pointed out by the assessment need to be strengthened for monitoring and use; level 2, score interval (60≤D<80), Safety assessment conclusion: safety measures need to be taken to eliminate or reduce risks; level 3, score range (40≤D<60), safety assessment conclusion: safety measures should be taken as soon as possible to eliminate risks; level 4, score range (20≤D<60) 40), it is recommended to stop using it immediately, and take safety measures to eliminate the risk before using it; level 5, score interval (0≤D<20), stop using it immediately, eliminate the risk, and carry out overhaul or transformation if necessary, and use it after repairing Those that are operable but cannot be repaired are recommended to be discarded or downgraded for use.

The detection tools for risk sources are special detection instruments for cranes, including: crane comprehensive performance detector, tape measure, feeler gauge, digital multimeter, laser rangefinder, total station, thickness gauge, megger, sound level meter and Flaw detector etc.

This evaluation method can not only conduct a comprehensive evaluation of the whole machine composed of all modules of the above crane, but also evaluate a single module. The evaluation of a certain module of a bridge crane is as follows:

Conduct on-site inspection of one of the four modules of the crane, and count the probability level and numerical value of each risk source. According to the environment where the crane is located, combined with the influence of environmental factors in the rule base on some risk sources and the relationship between risk sources The coupling between them, determine the final probability, and then substitute the severity and corresponding probability value of each risk source into formula (2) to calculate the risk degree, and then substitute it into formula (3) to get the module Based on the comprehensive safety status score and the evaluation conclusion given by the corresponding grade interval, corresponding safety maintenance measures are taken for the crane according to the evaluation results. For example: select metal structure risk source B4: the total station can measure the amount of deformation, and the steel ruler and vernier caliper can measure the size of cracks, wear and corrosion. The severity level of down deflection deformation B4-1 is level 1 and assigned a score of 1, the occurrence probability level is level 5 and the probability of occurrence is 0.120; The probability level is 5 and the probability of occurrence is 0.095; the severity level of the upper camber deformation B4-3 is level 1 and the assigned score is 1, the occurrence probability level is 5 and the occurrence probability value is 0.105; the crack B4-4 severity level It is level 1 and the assigned score is 1, the occurrence probability level is 5 and the occurrence probability value is 0.075; the wear and tear B4-5 severity level is 2 level and the assigned score is 0.875, the occurrence probability level is 5 and the occurrence probability value is 0.030 ; Corrosion B4-6 has a severity level of 2 and a score of 0.875, an occurrence probability level of 5 and an occurrence probability value of 0.080. Substituting the severity value and occurrence probability value of each risk source in the metal structure into the formula (2) to obtain the risk value y=0.085, indicating that the metal structure has high safety. Substituting this y value into the formula (3 ) obtained d = 91.5, indicating that the metal structure is normal, the safety status level is level 1, and it is only necessary to strengthen the monitoring of the metal structure.

Claims (1)

1. A bridge crane safety assessment method, characterized in that: the method is as follows: Step 1: The bridge crane system is divided into modules; Decompose the whole bridge crane into electrical and control system risk sources, main component risk sources, safety protection device risk sources and metal structure risk sources; electrical and control system risk sources include power cutoff, main circuit breaker, and power supply contactor , emergency stop switch, motor protection, line protection, wrong phase and phase loss protection, zero protection, voltage loss protection, motor stator abnormal power loss protection, overspeed protection, grounding and lightning protection, insulation resistance, lighting and signal and safety Voltage; risk sources for main components include hooks, wire ropes, drums, pulleys, wheels, reducers, open gears and couplings; risk sources for safety protection devices include brakes, lifting height limiters, and operating stroke limits Devices, anti-collision devices, buffers and end stops, lifting weight limiters, wind-resistant anti-skid devices, anti-overturning safety hooks, interlock protection, safety protection for conductive trolley lines, alarms and protective covers; risk sources for metal structures Including deflection deformation, I-beam deformation, camber deformation, cracks, wear and corrosion; Step 2: Classify the severity level, and assign a value g _i to each risk source, where i=1, 2, ... are the serial numbers corresponding to each risk source; The severity is divided into 5 levels: Level 1 means that the casualties, economic losses, environmental hazards, and social impacts are particularly serious; Level 2 means that the casualties, economic losses, environmental hazards, and social impacts are serious; Level 3 means Casualties, economic losses, environmental hazards, and social impacts are serious; level 4 means casualties, economic losses, environmental hazards, and social impacts are average; level 5 means casualties, economic losses, and environmental hazards , The social impact is very small; Among the risk sources of the electrical and control system, the power cut-off level is level 3, the main circuit breaker level is level 3, the power supply contactor level is level 3, the emergency stop switch level is level 1, the motor protection level is level 5, and the circuit protection level is level 3. Level 4, wrong phase and phase loss protection level 4, zero protection level 3, voltage loss protection level 4, motor stator abnormal power loss protection level 3, overspeed protection level 4, grounding and anti- The lightning level is 4, the insulation resistance level is 4, the lighting and signal, and the safety voltage level are 5; among the main component risk sources, the hook level is 2, the wire rope level is 2, and the reel level is 4 , the pulley level is 4, the wheel level is 4, the reducer level is 4, the open gear level is 4, and the coupling level is 4; in the safety protection device risk source, the brake level is 2, the lifting The level of height limiter is level 1, the level of travel limiter is level 4, the level of anti-collision device is level 4, the level of buffer and end stop is level 4, the level of crane limiter is level 3, wind resistance and anti-skid The level of the device is level 4, the level of the anti-tipping safety hook is level 4, the level of interlock protection is level 4, the level of safety protection of the conductive trolley line is level 5, the level of the alarm device is level 5, and the level of the protective cover is level 4; Among the risk sources of metal structures, the level of downward deflection is level 2, the level of I-beam deformation is level 3, the level of upward camber deformation is level 2, the level of cracks is level 2, the level of wear is level 3, and the level of corrosion is level 3; The higher the severity level, the greater the assigned score, indicating that the consequences of the accident are more serious; each severity level corresponds to a score; level 1 is assigned a score of 1, level 2 is assigned a score of 0.875, and level 3 is assigned a score of 0.875. A score of 0.625 is given, a score of 0.375 is given for level 4, and a score of 0.125 is given for level 5; Step 3: According to the possibility of failure events occurring in each risk source of the crane, the probability of occurrence is divided into 5 levels: Level 1 corresponds to a very high possibility; Level 2 corresponds to a high possibility; Level 3 corresponds to a general possibility; Level 4 corresponds to a general possibility. The possibility of corresponding to level 5 is small; the possibility of corresponding to level 5 is very small; each level corresponds to a score interval: level 1, score interval (0.875, 1]; level 2, score interval (0.625, 0.875]; level 3 , score interval (0.375, 0.625]; level 4, score interval (0.125, 0.375]; level 5, score interval (0, 0.125]; according to the data of the risk source detection on site, determine its probability level and occurrence probability value; Step 4: When the environment in the rule base intervenes, when one or more environmental factors act on a certain risk source, and the probability r _i ≤ 0.75 of the risk source, the probability r _i of the crane failure will be re- Assign r' _i , that is, the occurrence probability of this risk source is increased by 0.25 on the basis of the initial determined occurrence probability; The rule base includes four types of environmental impact factors, and each risk source is affected by the four types of environmental impact factors as follows: (1) Risk sources affected by high temperature: motor protection, line protection, insulation resistance, buffers and end stops; (2) Risk sources affected by moisture: insulation resistance, wire ropes, buffers and end stops , Metal structure corrosion; (3) Risk sources affected by high corrosion: line protection, grounding and lightning protection, insulation resistance, steel wire rope, brake, buffer and end stop, metal structure corrosion; (4) Affected by dust Source of risk: power contactor; Step 5: Mutual coupling between risk sources The risk sources of bridge cranes are divided according to the functional mechanism of each part of the crane, but in fact, the internal factors of the bridge crane system are interrelated and affect each other, and each risk source cannot be analyzed separately, but should be analyzed from the perspective of the bridge crane system. Starting from the overall function of the system, study the coupling situation between various risk sources; 1) Coupling between different risk sources: When the probability R of risk source A1 reaches 0.875, the probability of risk source A2 is affected due to the increased risk of A1, then the probability will be automatically transformed and assigned as: R _A22 = R _A21 e ^(R-0.875) (1) R _A21 is the initial probability, and R _A22 is the new probability after the coupling effect; 2) Coupling factors: When the risk source drum is damaged, the wire rope is prone to burrs; when the risk source pulley is damaged, the wire rope is prone to burrs; when the risk source wheel ellipticity increases, the load coefficient will increase, making the wire rope easier to scrap , the main beam is more easily deformed; Step 6: Use y to represent the risk degree of system accidents, and use formula (2) to calculate as follows: $\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; \&Sigma;</span>}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; *</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span>}{{<span\; class="notranslate">\; \&Sigma;</span>}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ Among them, g _i represents the serious consequences of risk source i, and r _i represents the probability of risk source i occurring; Step 7: According to (1-y)*100, get a value between 0 and 100, which represents the system comprehensive security status score d: d=(1-y)·100 (3) Step 8: According to the score d of the comprehensive safety situation, judge the grade of the comprehensive safety situation; the safety situation is divided into 5 levels: Level 1, the score range (80≤D≤100), the conclusion of the safety assessment: the risks pointed out in the assessment need to be strengthened Monitoring use; level 2, score range (60≤D<80), safety assessment conclusion: safety measures need to be taken to eliminate or reduce risks; level 3, score range (40≤D<60), safety assessment conclusion: should be taken Safety measures to eliminate risks; level 4, score range (20≤D<40), it is recommended to stop using it immediately, and take safety measures to eliminate risks before use; level 5, score range (0≤D<20), should stop immediately Use, eliminate risks, overhaul or remodel if necessary, for those that need to be repaired before they can be operated but cannot be repaired, it is recommended to be scrapped or downgraded for use.