Analysis and preventive measures of crane mechanic

Brief description of crane mechanical fault analysis and preventive measures

bridge crane brings efficiency, convenience and rapidity in the production process of enterprises. At the same time, due to mechanical unsafe factors, frequent accidents have caused economic losses to the country and the people, and pain to the parties and their families. The main reason for the accident is the mechanical failure and misoperation of the machine itself

studying mechanical faults, analyzing causes and formulating preventive measures are the main measures to reduce mechanical accidents of bridge cranes, which requires special equipment managers to pay attention to the hidden dangers of mechanical faults of cranes while standardizing the operation of operators, and formulate thorough and feasible preventive measures according to the conditions of cranes to ensure the safe operation of cranes

through production practice, the mechanical faults and preventive measures of bridge crane during operation are analyzed as follows. This paper analyzes seven aspects that can cause mechanical failure of bridge crane, such as steel wire rope, drum, steel wire rope pressing plate, hook, reducer gear, brake, wheel and track and safety accessories, and puts forward measures and suggestions to prevent mechanical failure of crane

fault analysis of steel wire rope

during the operation of steel wire rope, the stress condition of each steel wire rope is very complex. Due to the different positions of each steel wire in the rope, some are in the outer layer and some are in the inner layer. Even under the simplest tensile force, the stress distribution between each steel wire rope is also different. In addition, when the steel wire rope bypasses the winding Jane and pulley, it produces bending stress, extrusion force between steel wires, etc., so it is difficult to accurately calculate its stress, and the static calculation method is generally used

the maximum static tension in the steel wire rope shall meet the requirements of the following formula:

Pmax ≤ Pd/N

where: Pmax - the maximum static stress that the steel wire rope can bear during operation

pd -- breaking stress of steel wire rope

n - safety factor

Pmax=(Q+q)/(a η)

where: Q - rated lifting capacity of crane

q - weight of hook group

a - total number of rope branches carried by the pulley block

η—— Total efficiency of pulley block

the calculation formula of the maximum allowable working tension of the steel wire rope is:

p=pd/n

where: P - the rated maximum static stress of the steel wire rope during operation

P ≥ Pmax is safe. It can be seen from this that the main reason for the breaking of the steel wire rope is overload, and it is also related to the number of times of threading and winding on the pulley and drum. Each time the steel wire rope is threaded and wound, it will produce a process of changing from straight to curved and then from curved to straight. The more times of threading and winding, it will be easy to be damaged and broken; Secondly, the breaking of steel wire rope is related to the diameter of bypassing pulley and drum, working environment, type of work and maintenance

2 preventive measures

2.1 the lifting capacity of the crane during operation shall not exceed the rated lifting capacity

2.2 the steel wire rope of the crane should be selected according to the work 1. The type of power switch and the environment

2.3 regularly lubricate the steel wire rope (determine the lubrication cycle according to the working environment)

2.4 do not subject the steel wire rope to sudden impact during crane operation

2.5 steel wire ropes in high temperature and corrosive medium environment must have isolation devices

drum and steel wire rope pressing plate

drum is an important load-bearing part of crane. During use, there will be barrel wall thinning, holes and fracture faults. The reason for these failures is that the drum and the steel wire rope are in contact with each other, squeezing and rubbing. When the drum is thinned to a certain extent, it breaks because it cannot bear the pressure exerted by the steel wire rope. In order to prevent this kind of mechanical accident of the drum, according to the national standard, the drum wall should be replaced in time when it is worn to 20% of the original or cracks appear. At the same time, it should be noted that the modified PP bumper has the advantages of low cost, light weight, easy coating, recyclable use and so on. It is used for environmental sanitation and lubrication of the drum and steel wire rope

hook

hook is the most used pick-up device of overhead crane. It bears all the loads of hoisting. In the process of use, once the hook is damaged and broken, it is easy to cause major accidents. The reason for the damage and fracture of the hook is the crack, deformation, damage and fracture of the hook caused by friction and overload. To prevent hook 2 The test space is adjustable and can be used to test the requirements of different heights With good rigidity, small deformation, accurate measurement data, the base and beam adopt an integral casting structure, which is reasonable in structure, the workpiece is rigid, and the external decoration is beautiful, ensuring the safety and reliability of all parts In case of failure, it is strictly prohibited to overload hoisting in the process of use. During the inspection, pay attention to the opening of the hook and the wear of the dangerous section. At the same time, the hook should be annealed regularly. Once the hook is found to be cracked, it should be scrapped according to GB, and the hook should not be welded. The special equipment management personnel shall judge whether the hook can be used according to the requirements of GB when inspecting the hook

reducer gear

1 fault analysis

reducer is an important transmission component of overhead crane. It transmits torque through gear meshing, and adjusts the high-speed operation of the motor to the required speed. In the process of transmitting torque, the gear will have mechanical faults such as tooth fracture, tooth surface pitting, tooth surface glue and, tooth surface wear. The causes of gear faults are as follows:

a. short-term overload or impact load, Fatigue fracture caused by repeated bending

b. the tooth surface is not smooth, there are convex points to produce stress concentration, or the lubricant is not clean

c. lubrication failure due to high temperature

d. wear caused by hard particles entering the friction surface

2 preventive measures

a. the crane cannot be used for lifting, and the starting and braking should be slow and stable. Sudden reverse driving is prohibited under non-specific circumstances

b. replace the lubricant in time, clean the shell, and select the appropriate lubricant

c. always check whether the lubricating oil is clean; If the lubrication is not clean, replace it in time

brake

1 fault analysis

brake is an important safety component of bridge crane, which has the functions of preventing the falling of suspended objects and realizing parking. Only a good brake can guarantee the accuracy of crane operation and safe production. In crane operation, the brake will have mechanical faults such as insufficient braking force, sudden brake failure, too high temperature of brake wheel, smoking of brake gasket, and non opening of brake arm. The causes of these mechanical faults are analyzed as follows:

a. the brake belt or brake wheel is excessively worn; Local falling off of brake belt; The main spring is adjusted too loosely; There is oil dirt between the brake belt and the brake wheel; There are stuck places or excessively worn parts outside the movable hinge; The lock nut is loose, and the whole pull rod is loose; The impeller of the hydraulic push rod brake release does not rotate flexibly

b. the brake gasket is seriously or large pieces fall off, or the long stroke electromagnet is stuck, the main spring fails, or the main components of the brake are damaged

c. the clearance between brake and gasket is adjusted too large or too small

d. the hinge is stuck or the braking torque is adjusted too much, or the hydraulic push rod brake release cylinder is short of oil and mixed with air, or the grease used for hydraulic push rod brake release does not meet the requirements, or there is dirt between the brake pad and the brake wheel

2 preventive measures

check and maintain the brakes regularly. The brakes of the lifting mechanism must be checked once a shift and the brakes of the operating mechanism must be checked once a day. The main checks are as follows:

a. whether there is stagnation and wear at the hinge and whether there is slack at each fastening

b. whether the action of all moving parts is normal

c. whether the hydraulic system is normal

d. whether the wear between the brake wheel and the brake belt is normal and clean

determine whether the brake is normal according to the inspection, resolutely put an end to faulty operation, and regularly lubricate and maintain the brake. In order to ensure the safe operation of the crane, the brake must be adjusted frequently to ensure the working requirements of the corresponding mechanism

wheel and rail

common faults of wheel and rail during crane operation are wheel gnawing and unequal height and slipping of trolley. Among them, there are many reasons for road gnawing, and the forms of road gnawing are diverse. Those who bite the road lightly will affect the service life of the crane, and those who bite the road seriously will cause serious casualties. Therefore, special equipment managers should pay enough attention to biting the road. The main reasons for gnawing the track are the non-conforming error and uneven friction during installation, the excessive wear of parts in the crane transmission system and the excessive key connection clearance, resulting in the asynchronous braking. Therefore, the competent department of special equipment of each unit must find a qualified unit to install and maintain the crane, so as to ensure the safety and operating life of the equipment; At the same time, the special equipment management personnel should strengthen the usual inspection management to avoid the mechanical failure of the crane biting the track. In the inspection process, they should carefully and carefully find out the causes of biting the track and take corresponding measures. So do you know what stages the metal material tensile testing machine needs to carry out in the tensile test? Construction. The unequal height of the trolley wheels is a very unsafe factor in the operation of the crane. The unequal height of the trolley makes one wheel suspended or the wheel pressure is too small during the operation of the trolley, which may cause the vibration of the trolley body. The factors causing the unequal height of the trolley wheels are caused by many reasons, but the main reasons are that the installation error does not meet the requirements and the weight of the trolley design itself is uneven. Therefore, the fault of unequal height of the trolley should be comprehensively analyzed and the problem of unequal height of the trolley should be solved

during the operation of the crane, due to the unclean track, excessive startup, uneven trolley track, oval wheels and unequal wheel pressure between the driving wheels, the trolley has a slip ring image, which requires the special equipment management personnel to be careful in the inspection process, and solve the problems found in time to avoid the trolley slipping phenomenon

safety accessories

the safety accessories of the bridge crane are completely protective devices set from the perspective of protective equipment and operators. The management of safety accessories must be in accordance with the requirements of the regulations on safety supervision of special equipment, strengthen the management and supervision of safety accessories, make the safety accessories in good condition, and ensure the safe operation of the bridge crane