A safety assessment method for metal structures of hydraulic gantry cranes and bridge cranes

Abstract

The present invention discloses a safety assessment method for the metal structure of hydraulic gantry cranes and bridge cranes, comprising: dividing assessment units according to the structure of the assessment object, preliminarily determining the welds and corrosion conditions by visual inspection and marking key locations in the assessment units; performing non-destructive testing on the welds at the key locations marked by visual inspection in the assessment units with the aid of special equipment; performing corrosion detection with the aid of the equipment; performing full-size three-dimensional solid modeling on the steel beam structure, and performing static analysis using ANSYS, wherein fixed constraints are added to the key structures according to the walking characteristics of the steel structures of gantry cranes and bridge cranes, and different loads are added according to actual working conditions, and after the static analysis is solved, the solution results are analyzed using a post-processing tool to determine the most dangerous stress point of the metal structure of the assessment object under each working condition; performing on-site static stress measurement; and determining a comprehensive conclusion. The present invention solves the problem of safety assessment of the metal structure of hydraulic gantry cranes and bridge cranes.

Description

Technical Field

[0001] The present invention relates to the technical field of safety assessment of metal structures of hydraulic gantry cranes and bridge cranes, and in particular to a method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes. Background Art

[0002] Currently, my country's economy is experiencing rapid growth, with increasing demand for electricity from both the domestic and industrial sectors. Capitalizing on my country's abundant water resources, hydropower stations of varying capacities are rapidly being constructed along the main streams and tributaries of the Yangtze and Yellow Rivers. Gantry cranes and bridge cranes play a vital role in the safe operation of hydropower stations, and damage to their metal structures is a major cause of crane accidents. Gantry and bridge cranes operate outdoors for extended periods, exposed to wind and rain. Their metal structures are inevitably susceptible to aging, corrosion, and weld cracks. Furthermore, prolonged lifting of heavy objects can lead to fatigue fractures in stress-concentrated areas. Therefore, timely identification of hidden dangers in the metal structures of gantry and bridge cranes and a comprehensive assessment of their operating conditions are crucial to support subsequent maintenance and repair. Developing a reliable method for comprehensively evaluating the metal structures of gantry and bridge cranes, integrating various risk factors, is crucial. Currently, no comprehensive multi-factor assessment method for hydraulic gantry and bridge cranes has been studied. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes to solve the safety assessment problems of metal structures of hydraulic gantry cranes and bridge cranes, and to construct a comprehensive assessment method by comprehensively considering the severity and probability levels of damage such as welds, corrosion and stress in key parts of the metal structures.

[0004] In order to solve the above technical problems, the present invention adopts a technical solution: a method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes, which comprises the following steps:

[0005] S1. Divide the assessment unit according to the structure of the assessment object, preliminarily determine the weld and corrosion conditions by visual inspection and mark the key areas in the assessment unit to provide a certain reference for special inspection of welds and corrosion;

[0006] S2. Perform non-destructive testing on the welds using specialized equipment based on visual inspection of the key areas marked in the evaluation unit.

[0007] S3. Carry out corrosion inspection on the key areas marked in the evaluation unit based on visual inspection and with the help of equipment;

[0008] S4. Based on the original design drawings and field measurements of the gantry and bridge cranes, full-scale 3D solid modeling of the steel beam structure was performed. Static analysis was then performed using ANSYS. Fixed constraints were added to key structures based on the travel characteristics of the gantry and bridge crane steel structures, and different loads were applied based on actual operating conditions. After the static analysis was completed, post-processing tools were used to analyze the solution results to determine the most critical stress points in the metal structure under each operating condition.

[0009] S5. On-site static stress measurement;

[0010] S6. Comprehensive conclusion and judgment.

[0011] Furthermore, in step S1, the key visual parts include the metal structural parts that are mainly subjected to stress and prone to corrosion, namely, the main stress-bearing parts and welds of the structure, the parts with variable cross-sections of the structure, the joints of the metal structure, and the parts where abnormal conditions frequently occur during use, the joints between the flange plates of the steel structure, the connecting bolts, the water accumulation parts on the surface of each beam, the defective parts of the welding surface of the running pattern plate, the drainage grooves and other parts with severe electrochemical corrosion.

[0012] Furthermore, the step S2 specifically includes the following steps:

[0013] (2.1) Surface defect detection adopts magnetic particle testing or penetrant testing method. If the surface finish of the material is good, eddy current testing method is adopted. For ferromagnetic material structure, magnetic particle testing method is adopted.

[0014] (2.2) Internal defect detection should use ultrasonic testing technology. Weld spot inspection should include the stress-bearing parts of the main structure. If there are unacceptable defects, additional weld inspection should be carried out on the same structural part.

[0015] (2.3) According to the test results, the severity and probability level of the weld quality of each measuring point in the evaluation unit are determined, and then the risk level and four risk categories are obtained by combining them. After determining the risk category of the weld quality of each measuring point, each risk category is assigned a value to obtain v1, where v = A, B, C, ..., representing the different evaluation units contained in the evaluation object, and 1 represents the weld risk scenario.

[0016] Furthermore, in step S3, the corrosion detection items include the designed plate thickness D, the designed coating thickness D ty , measure the plate thickness D f , measure the coating thickness D tc , average depth of erosion pits Maximum depth of erosion pit SK max , the depth of the nth etch pit Sk n, the number of pits m within a certain detection area, the time t the steel structure is exposed to the environment, and the average depth of the pits are calculated by the following formula Maximum depth of erosion pit SK max , average pit depth to plate thickness ratio Ratio of maximum pit depth to plate thickness Measure the ratio of coating thickness to design thickness P tc , corrosion rate P;

[0017] Assume that the corresponding depth of m pits is SK m ,

[0018]

[0019] SK max =max(SK n )

[0020]

[0021]

[0022]

[0023]

[0024] According to the parameter values ​​obtained above, the corrosion conditions of the evaluation unit measuring points are evaluated according to the test results, and their severity and probability level of damage are determined. Then, the risk level and four risk categories are obtained by combining them. After determining the risk category of each measuring point, each risk category is assigned a value to obtain v2, where 2 represents the corrosion risk scenario.

[0025] Furthermore, the test in step S5 includes:

[0026] (5.1) The parts of the object with the highest stress obtained from the finite element analysis results;

[0027] (5.2) Some non-stress concentration points;

[0028] This test is designed to confirm the stress level in dangerous parts of the metal structure of the assessment object, providing a basis for the subsequent reliability assessment report. The measured maximum stress value is compared with the design value and allowable value to determine its severity and the probability level of injury. The risk level and four risk categories are then combined to determine the risk category of each measuring point. After determining the risk category of each measuring point, each risk category is assigned a value to obtain v3, where 3 represents the stress risk scenario.

[0029] Furthermore, the step S6 specifically includes the following steps:

[0030] (6.1) Determination of safety level of assessment unit;

[0031] After determining the risk category assignment for each risk scenario in each assessment unit, the safety status score of the assessment unit is calculated according to the following formula:

[0032]

[0033] Where, is the safety assessment score of the assessment unit, which represents the weighted value of the risk category grouping corresponding to the i-th risk scenario, where i = 1, ..., N v , N v Represents the total number of measurement points for all risk scenarios in the safety assessment of the assessment unit; 4 means that in all assessment items of each part of the gantry and bridge crane, there are four levels of assessment: Level I, Level II, Level III, and Level IV; Nv i represents the number of measurement points corresponding to the i-th risk scenario for safety assessment of the assessment unit; v i Score the safety status of the i-th risk scenario in a certain assessment unit;

[0034] The safety assessment level of each assessment unit is obtained according to the safety status score of the assessment unit;

[0035] (6.2) Overall machine safety assessment level and risk conclusion determination;

[0036] Each assessment unit is equally important for the overall safety assessment of the metal structure of the assessment object, that is, the proportional weight is the same. In this case, the overall score is simplified to the average of the scores of each assessment unit, defined as:

[0037]

[0038] The overall score is used to determine the safety assessment level of the entire machine. Taking into account the risks involved and the costs of risk reduction measures, the safety assessment of the entire machine is divided into the following four levels:

[0039] a)Ⅰ D Level 5: The crane's safety is unacceptable and safety precautions should be taken immediately to eliminate the risk. If the risk cannot be eliminated, the crane should be scrapped.

[0040] b)Ⅱ D Level, the crane should take safety protection measures in time, and after eliminating the risks, the safety is acceptable;

[0041] c)Ⅲ D Level 5: Crane safety is acceptable and safety measures need to be taken to eliminate or reduce risks;

[0042] d) IV D Level, the crane has good safety performance.

[0043] (6.3) Recommendations on safety measures to reduce risks;

[0044] (6.3.1) Based on the safety assessment results of each crane item and in combination with the replacement conditions, technical conditions and costs of parts, make recommendations for repair, major repair, modification or replacement of the crane;

[0045] (6.3.2) The evaluation recommends considering the following factors:

[0046] a) Matching between new components and between new components and existing components;

[0047] b) Take corresponding measures to address existing security risks;

[0048] c) Comprehensive consideration of the investment costs and actual value of major repairs, renovations, and updates;

[0049] d) Other circumstances;

[0050] (6.4) If the subject of assessment has risk category II D and III D The risk can be eliminated or reduced through repair and modification. It is recommended to only carry out repairs (including major repairs) or modifications. If the risk category is I D If the risk of damage affects the safe operation of gantry cranes and bridge cranes and there is no value in repairing or renovating them, it is recommended that the cranes be dismantled or replaced.

[0051] Beneficial effects of the present invention:

[0052] 1. The assessment method of the present invention comprehensively considers the factors affecting the metal structure, which can fully grasp the operating status of the crane, identify the risks for subsequent maintenance work, and provide accurate and powerful data support.

[0053] 2. The evaluation method of the present invention adds probability levels and weighted assignments to make the safety evaluation results more scientific and reasonable.

[0054] 3. The present invention can obtain the scores of each risk scenario and the overall score of different evaluation units of the crane, and realize accurate maintenance according to the scores, thereby improving maintenance efficiency.

[0055] 4. The present invention solves the problem of safety assessment of metal structures of hydraulic gantry cranes and bridge cranes, and constructs a comprehensive assessment method based on the severity and probability level of damage such as welds, corrosion and stress in key parts of the metal structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The present invention is a flow chart of a safety assessment method for metal structures of hydraulic gantry cranes and bridge cranes. DETAILED DESCRIPTION

[0057] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0058] like Figure 1 As shown, a method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes comprises the following steps:

[0059] S1. Divide the assessment unit according to the structure of the assessment object, preliminarily determine the weld and corrosion conditions through visual inspection, and mark the key areas in the assessment unit to provide a certain reference for special inspections of welds and corrosion; the visual key areas include the main stress-bearing and corrosion-prone metal structural parts, namely the main stress-bearing parts and welds of the structure, the parts with variable cross-sections of the structure, the joints of the metal structure, and the parts where abnormal conditions frequently occur during use, the joints between the flange plates of the steel structure, the connecting bolts, the water accumulation areas on the surface of each beam, the defective areas on the welding surface of the running pattern plate, the drainage grooves and other areas with severe electrochemical corrosion.

[0060] S2. Perform non-destructive testing on the welds using specialized equipment based on visual inspection of the key areas marked in the evaluation unit. This includes the following steps:

[0061] (2.1) Surface defect detection adopts magnetic particle testing or penetrant testing method. If the surface finish of the material is good, eddy current testing method is adopted. For ferromagnetic material structure, magnetic particle testing method is adopted.

[0062] (2.2) Internal defect detection should use ultrasonic testing technology. Weld spot inspection should include the stress-bearing parts of the main structure. If there are unacceptable defects, additional weld inspection should be carried out on the same structural part.

[0063] (2.3) Based on the test results, the severity and probability of injury are determined for each weld quality point in the assessment unit according to Appendix 1.1 and Appendix 1.2. The risk level and four risk categories are then determined according to Appendix 1.3. After determining the risk category for the weld quality at each measurement point, each risk category is assigned a value according to Appendix 1.4 to obtain v1, where v = A, B, C, ..., representing the different assessment units included in the assessment object, such as A - main beam, B - end beam, etc. for a gantry crane; 1 represents the weld risk scenario.

[0064] S3. Carry out corrosion inspection on the key parts marked in the evaluation unit based on visual inspection with the help of equipment; the corrosion inspection items include the design plate thickness D, the design coating thickness D ty , measure the plate thickness D f , measure the coating thickness D tc , average depth of erosion pits Maximum depth of erosion pit SK max , the depth of the nth etch pit Sk n, the number of pits m within a certain detection area, the time t the steel structure is exposed to the environment, and the average depth of the pits are calculated by the following formula Maximum depth of erosion pit SK max , average pit depth to plate thickness ratio Ratio of maximum pit depth to plate thickness Measure the ratio of coating thickness to design thickness P tc , corrosion rate P;

[0065] Assume that the corresponding depth of m pits is SK m ,

[0066]

[0067] SK max =max(SK n )

[0068]

[0069]

[0070]

[0071]

[0072] Based on the parameter values ​​obtained above, the corrosion conditions at the assessment unit measurement points are evaluated based on the test results according to Appendix 1.1 and Appendix 1.2 to determine their severity and probability of occurrence. Then, according to Appendix 1.3, the risk level and four risk categories are determined. After determining the risk category for each measurement point, each risk category is assigned a value as shown in Appendix 1.4 to obtain v2, where 2 represents the corrosion risk scenario.

[0073] S4. Based on the original design drawings and field measurements of the gantry and bridge cranes, full-scale 3D solid modeling of the steel beam structure was performed. Static analysis was then performed using ANSYS. Fixed constraints were added to key structures based on the travel characteristics of the gantry and bridge crane steel structures, and different loads were applied based on actual operating conditions. After the static analysis was completed, post-processing tools were used to analyze the solution results to determine the most critical stress points in the metal structure under each operating condition.

[0074] S5. On-site static stress measurement; the test includes:

[0075] (5.1) The parts of the object with the highest stress obtained from the finite element analysis results;

[0076] (5.2) Some non-stress concentration points.

[0077] This test is designed to confirm the stress levels in hazardous areas of the metal structure being assessed, providing a basis for subsequent reliability assessment reports. The measured maximum stress values ​​are compared with the design and allowable values, and the severity and probability of injury are determined according to Appendix 1.1 and Appendix 1.2. The risk level and four risk categories are then combined according to Appendix 1.3. After determining the risk category for each measuring point, each risk category is assigned a value according to Appendix 1.4, resulting in v3, where 3 represents the stress risk scenario.

[0078] S6. Comprehensive conclusion determination;

[0079] (6.1) Determination of safety level of assessment unit;

[0080] After determining the risk category assignment for each risk scenario in each assessment unit, the safety status score of the assessment unit is calculated according to the following formula:

[0081]

[0082] Where, is the safety assessment score of the assessment unit, which represents the weighted value of the risk category grouping corresponding to the i-th risk scenario, where i = 1, ..., N v , N v Represents the total number of measurement points for all risk scenarios in the safety assessment of the assessment unit; 4 means that in all assessment items of each part of the gantry and bridge crane, there are four levels of assessment: Level I, Level II, Level III, and Level IV; Nv i represents the number of measurement points corresponding to the i-th risk scenario for safety assessment of the assessment unit; v i The safety status score of the ith risk scenario of a certain assessment unit, where v = A, B, C, ..., represents the different assessment units contained in the assessment object, such as A-main beam, B-end beam, etc. of a gantry crane, so v i It is the safety status score of the i-th risk scenario of a certain assessment unit, such as A1 and B2 in the following embodiment;

[0083] According to the safety status score of each assessment unit, the safety assessment level of the assessment unit is obtained according to Appendix 1.5.

[0084] (6.2) Machine safety assessment level and risk conclusion determination

[0085] Each assessment unit is equally important for the overall safety assessment of the metal structure of the assessment object, that is, the proportional weight is the same. In this case, the overall score is simplified to the average of the scores of each assessment unit, defined as:

[0086]

[0087] Based on the overall score, the safety assessment level of the entire machine is determined according to Appendix 1.5. Taking into account the existing risks and the costs of risk reduction and protection measures, the safety assessment of the entire machine is divided into the following four levels:

[0088] a)Ⅰ D Level 5: The crane's safety is unacceptable and safety precautions should be taken immediately to eliminate the risk. If the risk cannot be eliminated, the crane should be scrapped.

[0089] b)Ⅱ D Level, the crane should take safety protection measures in time, and after eliminating the risks, the safety is acceptable;

[0090] c)Ⅲ D Level 5: Crane safety is acceptable and safety measures need to be taken to eliminate or reduce risks;

[0091] d) IV D Level, the crane has good safety performance.

[0092] (6.3) Recommended safety measures to reduce risks

[0093] (6.3.1) Based on the safety assessment results of each crane item, combined with the replacement of parts, technical conditions and costs, recommendations for repair, major repair, modification or replacement of the crane shall be made.

[0094] (6.3.2) The evaluation recommendations mainly consider the following factors:

[0095] a) Matching between new components and between new components and existing components;

[0096] b) Take corresponding measures to address existing security risks;

[0097] c) Comprehensive consideration of the investment costs and actual value of major repairs, renovations, and updates;

[0098] d) Other situations, etc.

[0099] (6.4) If the subject of assessment has risk category II D and III D The risk can be eliminated or reduced through repair and modification. It is recommended to only carry out repairs (including major repairs) or modifications. If the risk category is I D If the risk of damage affects the safe operation of gantry cranes and bridge cranes and there is no value in repairing or renovating them, it is recommended that the cranes be dismantled or replaced.

[0100] Table 1.1 Severity table

[0101]

[0102] Table 1.2 Probability level table

[0103] Probability level illustrate A-Frequent During the service life, the system or components may often B - Very likely During its life cycle, a system or component may experience C-Occasionally During the service life, the system or components may have secondary D - Very rare Not necessarily, but may happen once during the use cycle E - Unlikely Not likely to occur during the use cycle F-Impossible The probability is almost zero

[0104] Table 1.3 Risk Category Table

[0105]

[0106] Table 1.4 Risk category assignment

[0107] Risk Category Grouping Ⅰ Ⅱ Ⅲ Ⅳ Weighted Assignment 0 1 2 3

[0108] Table 1.5 Correspondence between overall assessment scores and safety levels

[0109]

[0110] Example:

[0111] The evaluation units are divided according to the structure of the evaluation object (taking a gantry crane as an example), specifically into A-main beam, B-end beam, C-support leg, D-trolley frame, and E-balance beam.

[0112] 1. Appearance quality inspection

[0113] 1.1 General Provisions

[0114] 1.1.1 Appearance quality inspection shall include but not be limited to the following main load-bearing components:

[0115] a) Main beam;

[0116] b) end beams;

[0117] c) outriggers;

[0118] d) Trolley frame;

[0119] e) End beam.

[0120] 1.1.2 For other structural forms, the inspection shall be based on the principle of testing the main load-bearing structural parts, such as slewing boom and vertical arm.

[0121] 1.1.3 Mainly to gain preliminary understanding of the welds and corrosion conditions of the gantry crane.

[0122] 1.2 Visual inspection of welds

[0123] 1.2.1 The quality grade of defects in steel arc welded joints is divided into three levels, represented by the symbols B, C and D respectively. Quality grade B corresponds to the highest requirement for welding; the quality grade refers to the quality of the weld, not the capability of the entire machine.

[0124] 1.2.2 Visual inspection of welds may be used for the following welding methods:

[0125] a) Metal arc welding without gas shielding;

[0126] b) submerged arc welding;

[0127] c) Gas shielded arc welding;

[0128] d) Non-metallic electrode gas shielded arc welding.

[0129] 1.2.3 Direct visual inspection is usually used for local inspection. It is suitable for visual inspection when the distance between the eyes and the weld surface is within 600 mm and the visual angle between the eyes and the weld surface is not less than 30°. A mirror can be used to improve the viewing angle, and magnifying glasses, endoscopes, optical fibers and other equipment can also be used to assist in inspection.

[0130] 1.2.4 When direct visual inspection is not possible, a validated indirect visual inspection system may be used.

[0131] 1.2.5 The limit values ​​of defects shall be in accordance with the provisions of Table 1 of GB / T 19418-2003.

[0132] 1.2.6 When inspecting for defects, only those defects that can be detected at a magnification of 10x or less need to be considered.

[0133] 1.2.7 For a welded joint, each separate type of imperfection shall be evaluated separately.

[0134] 1.2.8 Two adjacent defects are considered to be the same defect if the distance between them is less than the major dimension of the smaller defect. The total size of the defects is the sum of the sizes of the two defects and the distance between them.

[0135] 1.3 Visual inspection of corrosion conditions

[0136] 1.3.1 Carry out an external inspection of the gantry crane’s outriggers, balance beams, end beams, main beams and trolleys, and conduct a subjective preliminary assessment of any corroded areas.

[0137] 1.3.2 Corrosion appearance: powdering; discoloration; cracks; blistering; shedding; rusting; location and distribution

[0138] 1.3.3 Coating thickness: meets the requirements; falls off

[0139] 1.3.4 Focus on marking the locations where corrosion is more serious during visual inspection to provide a reference for special corrosion inspection.

[0140] 2. Risk categories and category assignment selection

[0141] The risk category and category assignment of each assessment unit in the gantry crane metal structure safety assessment object are specified. Since the main load-bearing structure of the gantry crane is the main beam, outriggers, and trolley frame, the end beam mainly plays the role of connecting the double main beams of the gantry crane and bearing local loads; the balance beam plays the role of connecting the four legs of the gantry crane. According to Tables 1.1 and 1.2, the probability of damage to the main beam, end beam, outriggers, trolley frame, and balance beam corresponds to Class B, Class D, Class B, Class D, and Class E, respectively. The above (injury) severity is used as the input for the calculation of the metal structure safety assessment score and combined into a risk level. Then, Table 1.3 Risk Category Table and Table 1.4 Risk Category and Assignment Correspondence Table are used to obtain the risk category and category assignment of the main beam, end beam, outriggers, trolley frame, and balance beam.

[0142] 3. Overall safety score of gantry crane metal structure

[0143] 3.1 Main beam safety grade score

[0144] 3.1.1 Main beam weld inspection score: A1 = 2 + 2 + 1 + 2 + 2 + 0 + 1 + 2 + 2 + 1 = 15

[0145] 3.1.2 Main beam corrosion detection score: A2 = 1 + 2 + 1 + 2 + 2 = 8

[0146] 3.1.3 Main beam stress test score: A3 = 2 × 5 = 10

[0147]

[0148] in and The number of measuring points for the main beam weld inspection, corrosion inspection, and stress inspection are 10, 5, and 5 respectively. According to Appendix 1.5, the corresponding safety level of this main beam is II. D Level 1, safety protection measures should be taken in time, and after the risks are eliminated, the safety is acceptable.

[0149] 3.2 End beam safety level score

[0150] 3.2.1 End beam-main beam weld inspection score: B1 = 3 + 3 + 2 + 3 + 3 + 2 + 2 + 3 + 3 + 3 = 27

[0151] 3.2.2 End beam corrosion detection score: B1 = 3 + 2 + 3 + 2 + 2 = 12

[0152] 3.2.3 End beam stress test score: B3 = 3 × 5 = 15

[0153]

[0154] in and The number of end beam inspection points, corrosion inspection points, and stress inspection points are 10, 5, and 5 respectively. According to Appendix 1.5, the corresponding safety level of this end beam is II D Level 2: security is acceptable and safety measures need to be taken to eliminate or reduce risks.

[0155] 3.3 Outrigger safety rating score

[0156] 3.3.1 Leg weld inspection score: C1 = 1 + 1 + 1 + 2 + 1 + 1 + 2 + 2 + 2 = 14

[0157] 3.3.2 Leg corrosion detection score: C2 = 2 + 3 + 3 + 3 + 3 = 14

[0158] 3.3.3 Outrigger stress test score: C3 = 2 × 5 = 10

[0159]

[0160] in and The number of test points for weld inspection, corrosion inspection and stress inspection of the outriggers are 10, 5 and 5 respectively. According to Appendix 1.5, the corresponding safety level of this outrigger is II. D Level 1, safety protection measures should be taken in time, and after the risks are eliminated, the safety is acceptable.

[0161] 3.4 Safety rating score of small vehicle frame

[0162] 3.4.1 Trolley frame weld inspection score: D1 = 2 + 3 + 3 + 3 + 3 + 4 + 4 + 3 + 3 + 3 = 31

[0163] 3.4.2 Trolley frame corrosion detection score: D2 = 3 + 2 + 2 + 2 + 3 = 12

[0164] 3.4.3 Trolley frame stress test score: D3 = 3 × 4 = 12

[0165]

[0166] in and The number of test points for weld crack detection, corrosion detection, and stress detection of the trolley frame are 10, 5, and 4 respectively. According to Appendix 1.5, the corresponding safety level of this trolley frame is III. D Level 5: Security is acceptable and safety measures need to be taken to eliminate or reduce risks.

[0167] 3.5 Balance beam safety rating score

[0168] 3.5.1 Balance beam-leg frame weld inspection score: E1 = 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 = 40

[0169] 3.5.2 Balance beam corrosion test score: E2 = 4 + 4 + 4 + 4 + 4 = 20

[0170] 3.5.3 Balance beam stress test score: E3 = 4 × 5 = 20

[0171]

[0172] in and The number of measuring points for weld inspection, corrosion inspection and stress inspection of the balance beam are 10, 5 and 5 respectively. According to Appendix 1.5, the corresponding safety level of this balance beam is IV. D Level, good safety performance.

[0173] 4. Overall safety level score of the gantry crane metal structure

[0174] According to the formula in (6.2), the gantry crane is considered as a whole, without distinguishing the name of the metal structure to be tested and the weld crack, corrosion and stress tests. All the measuring points are considered as a test unit, and the overall score of the gantry crane metal structure is:

[0175]

[0176] According to the attached table 1.5, the corresponding safety level of this gantry crane is Ⅱ D Level 1, safety protection measures should be taken in time, and after the risks are eliminated, the safety is acceptable.

[0177] 5. Evaluation Recommendations

[0178] Based on the safety assessment results of each crane item, combined with the replacement of parts, technical conditions and costs, recommendations for repair, major repair, modification or replacement of the crane should be made. The following factors should be considered: a) the compatibility between new parts and between new parts and existing parts;

[0179] b) Take corresponding measures to address existing security risks;

[0180] c) Comprehensive consideration of the investment costs and actual value of major repairs, renovations, and updates;

[0181] d) Other situations, etc.

[0182] If the crane has risk category II D and III DThe risk can be eliminated or reduced through repair and modification. It is recommended to only carry out repairs (including major repairs) or modifications. If the risk category of the crane is I D If the risk is great and affects the safe operation of bridge and gantry cranes and there is no value in repairing or renovating them, it is recommended that the cranes be dismantled or replaced.

[0183] (1) If the safety function of the parts or systems of the risk items can be restored through repair, a suggestion for repair of the crane should be made.

[0184] (2) If the safety function of the parts or systems of the risk items cannot be restored through repair, suggestions for modifying the crane should be made.

[0185] (3) If the parts or systems of risky projects cannot be restored to their safety functions through repair or modification, or the value of the parts replaced by repair or modification is higher than 50% of the value of similar complete machines, it is proposed to update the crane.

[0186] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined with each other unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent alternatives to the technical features of the technical solutions described in the claims. Equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes, characterized by: It includes the following steps: S1. Divide the assessment unit according to the structure of the assessment object, preliminarily determine the weld and corrosion conditions by visual inspection and mark the key areas in the assessment unit to provide reference for special inspection of welds and corrosion; S2. Perform non-destructive testing on the welds using specialized equipment based on visual inspection of the key areas marked in the evaluation unit. S3. Carry out corrosion inspection on the key areas marked in the evaluation unit based on visual inspection and with the help of equipment; S4. Based on the original design drawings and field measurements of the gantry and bridge cranes, full-scale 3D solid modeling of the steel beam structure was performed. Static analysis was then performed using ANSYS. Fixed constraints were added to key structures based on the travel characteristics of the gantry and bridge crane steel structures, and different loads were applied based on actual operating conditions. After the static analysis was completed, post-processing tools were used to analyze the solution results to determine the most critical stress points in the metal structure under each operating condition. S5. On-site static stress measurement; S6. Comprehensive conclusion determination; In step S3, the corrosion detection items include the designed plate thickness D, the designed coating thickness D ty , measure the plate thickness D f , measure the coating thickness D tc , average depth of erosion pits Maximum depth of erosion pit SK max , the depth of the nth etch pit Sk n , the number of pits m within the detection area, the time t the steel structure is exposed to the environment, and the average depth of the pits are calculated by the following formula Maximum depth of erosion pit SK max , average pit depth to plate thickness ratio Ratio of maximum pit depth to plate thickness p SKmax , Measure the coating thickness and the ratio of the designed thickness P tc , corrosion rate P; Assume that the corresponding depth of m pits is SK m , SK max =max(SK n ) According to the parameter values ​​obtained above, the corrosion conditions of the evaluation unit measuring points are evaluated according to the test results, and their severity and probability level of damage are determined. Then, the risk level and four risk categories are obtained by combining them. After determining the risk category of each measuring point, each risk category is assigned a value to obtain v2, where 2 represents the corrosion risk scenario.

2. A method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes according to claim 1, characterized in that: In step S1, the key visual parts include the metal structural parts that are mainly subjected to stress and prone to corrosion, namely, the main stress-bearing parts and welds of the structure, the parts with variable cross-sections of the structure, the joints of the metal structure, and the parts where abnormal conditions frequently occur during use, the joints between the flange plates of the steel structure, the connecting bolts, the water accumulation parts on the surface of each beam, the defective parts of the welding surface of the running pattern plate, and the parts of the drainage trough where there is severe electrochemical corrosion.

3. A method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes according to claim 1, characterized in that: The step S2 specifically includes the following steps: (2.1) Surface defects are detected by magnetic particle testing or penetrant testing, and the structure of ferromagnetic materials is detected by magnetic particle testing; (2.2) Internal defect detection should use ultrasonic testing technology. Weld spot inspection should include the stress-bearing parts of the main structure. If there are unacceptable defects, additional weld inspection should be carried out on the same structural part. (2.3) According to the test results, the severity and probability level of the weld quality of each measuring point in the evaluation unit are determined, and then the risk level and four risk categories are obtained by combining them. After determining the risk category of the weld quality of each measuring point, each risk category is assigned a value to obtain v1, where v = A, B, C, ..., representing the different evaluation units contained in the evaluation object, and 1 represents the weld risk scenario.

4. A method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes according to claim 1, characterized in that: The test in step S5 includes: (5.1) The parts of the object with the greatest stress obtained from the finite element analysis results; (5.2) Some non-stress concentration points; This test is designed to confirm the stress level in dangerous parts of the metal structure of the assessment object, providing a basis for the subsequent reliability assessment report. The measured maximum stress value is compared with the design value and allowable value to determine its severity and the probability level of injury. The risk level and four risk categories are then combined to determine the risk category of each measuring point. After determining the risk category of each measuring point, each risk category is assigned a value to obtain v3, where 3 represents the stress risk scenario.

5. The method for safety assessment of metal structures of hydraulic gantry cranes and bridge cranes according to claim 1 is characterized in that: The step S6 specifically includes the following steps: (6.1) Determination of safety level of assessment unit; After determining the risk category assignment for each risk scenario in each assessment unit, the safety status score of the assessment unit is calculated according to the following formula: Where, is the safety evaluation score of the i-th evaluation unit, where i = 1, ..., N v , N v Represents the total number of measurement points for all risk scenarios in the safety assessment of the assessment unit; 4 means that in all assessment items of each part of the gantry and bridge crane, there are four levels of assessment: Level I, Level II, Level III, and Level IV; Nv i represents the number of measurement points corresponding to the i-th risk scenario for safety assessment of the assessment unit; v i Score the safety status of the i-th risk scenario in a certain assessment unit; The safety assessment level of each assessment unit is obtained according to the safety status score of the assessment unit; (6.2) Overall machine safety assessment level and risk conclusion determination; Each assessment unit is equally important for the overall safety assessment of the metal structure of the assessment object, that is, the proportional weight is the same. In this case, the overall score is simplified to the average of the scores of each assessment unit, defined as: The overall score is used to determine the safety assessment level of the entire machine. Taking into account the risks involved and the costs of risk reduction measures, the safety assessment of the entire machine is divided into the following four levels: a)Ⅰ D Level 5: The crane's safety is unacceptable and safety precautions should be taken immediately to eliminate the risk. If the risk cannot be eliminated, the crane should be scrapped. b)Ⅱ D Level, the crane should take safety protection measures in time, and after eliminating the risks, the safety is acceptable; c)Ⅲ D Level 5: Crane safety is acceptable and safety measures need to be taken to eliminate or reduce risks; d) IV D Level, the crane has good safety performance; (6.3) Recommendations on safety measures to reduce risks; (6.3.1) Based on the safety assessment results of each crane item and in combination with the replacement conditions, technical conditions and costs of parts, make recommendations for repair, major repair, modification or replacement of the crane; (6.3.2) The evaluation recommends considering the following factors: a) Matching between new components and between new components and existing components; b) Take corresponding measures to address existing security risks; c) Comprehensive consideration of the investment costs and actual value of major repairs, renovations, and updates; d) Other circumstances; (6.4) If the assessment object has risk category II D and III D The risk can be eliminated or reduced through repair and modification. It is recommended to only repair or modify it. If the risk category is I D If the risk of damage affects the safe operation of gantry cranes and bridge cranes and there is no value in repairing or renovating them, it is recommended that the cranes be dismantled or replaced.

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