Reasons for rail gnawing of the hottest bridge cra

2022-09-23
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Reasons and technical transformation scheme of bridge crane gnawing rail

bridge crane is a crane supported on the elevated rail through the wheels at both ends of the bridge, also known as "traveling crane" or "crown block". In the process of operation, the wheel flange of the crane or trolley of the operating mechanism contacts the side of the track, generating horizontal lateral thrust, causing friction and wear between the wheel flange and the track. This phenomenon is called "rail gnawing"

this paper mainly studies and analyzes the phenomenon of "rail gnawing" of bridge crane equipped with various attachments, and puts forward improvement methods

manifestations

first, there are spots on the side of the track or the inner side of the wheel rim, and in serious cases, there are burrs or iron chips at the traces. The second is that the car body is skewed during operation, and the wheels deviate and sway, and the reaction is more obvious when starting or braking. Third, metal gnawing "hissing" or "uttering" sound during operation. Fourth, there is rail climbing or derailment in serious cases

cause analysis

1. Causes of wheels. First, due to processing errors during manufacturing, uneven wear during use, single-sided replacement during maintenance, etc., the diameters of wheels on both sides are different. When running at the same speed, the strokes on both sides are not equal, and the side with large diameter will gradually lead, forming another asynchrony, causing the car body to skew and gnaw the rail. Second, the installation position of the four wheels is not in the four corners of the rectangle, and the center of the wheel on the same side is not in a straight line, forming the deviation of the wheel center line, resulting in rail gnawing

2. Cause of orbit. First, due to the irregular laying of the track, the horizontal bending is too large, and the straightness error is greater than 2mm, causing the fixed section to gnaw the track. Second, the track gauge is too large, and the outer rim gnaws the rail; On the contrary, the inner rim gnaws the rail. Third, the vertical height difference of the tread on the same section of the two tracks is greater than 15mm, causing the crane to move sideways and cause rail gnawing. Fourth, the parallelism of the two tracks is out of tolerance, forming a "splay" or horn shape, causing rail gnawing. Fifth, the track foundation is not solid, and subsidence occurs when loading, resulting in rail gnawing

The stronger the system is

3. The cause of bridge deformation. First, the bridge deformation causes the end beam to bend horizontally. When the diagonal length out of tolerance is greater than 5mm or more, it causes the span out of tolerance. If it is positive, it gnaws the inner rim of the wheel; On the contrary, bite the outer rim of the wheel. Second, the horizontal bending of the end beam causes the wheel to deflect horizontally, so that the center line of the wheel and the center line of the track are not in a straight line, forming the same direction deflection, resulting in rail gnawing. The third is the vertical deformation of the bridge, which causes the vertical deflection of the wheel, making the included angle between the center line of the tread and the plumb line, and changing the rolling radius of the wheel. After the load, the vertical deflection of one side of the wheel gradually increases, and the vertical deflection of the other side decreases, forming different rolling radii, resulting in rail gnawing

4. The speed of two motors of the crane cart running mechanism driven separately is inconsistent, or the clearance adjustment of the two brakes is different, resulting in unequal braking torque and inconsistent pace, resulting in rail gnawing

5. The gap between the couplings at both ends of the transmission mechanism is too large, causing the wheels to not focus on key materials and drive at the same time, resulting in rail gnawing

6. there is oil or debris on the track tread, which causes the running speed of the wheels on both sides to be different, and also leads to rail gnawing

improvement method

as mentioned above, the reasons for crane rail gnawing are complex and diverse. We should sort out one by one according to the specific situation, comprehensively analyze, find out the reasons, and formulate reasonable improvement methods

1. wheel repair. First, reduce the wheel diameter difference: if the diameter difference between the two driving wheels exceeds 0.2mm of its diameter, and the driven wheel exceeds 0.5mm, it shall be reprocessed to the same basic size, and the diameter difference between the driving wheel and the driven wheel shall not exceed 3mm. Second, the adjustment of wheel span, diagonal and wheel alignment difference: the deviation of crane wheel span and diagonal is not more than ± 7mm, the deviation of trolley wheel span and diagonal is not more than ± 3mm, and the wheel alignment difference is not more than 2mm. Specific adjustment method: increase the wheel bearing spacer ring on both sides and reduce it on the other side to move the wheel. You can also expand the bolt hole of the bearing box on the end beam and move the positioning key for adjustment

2. Track renovation. First, check the levelness, straightness, tread perpendicularity and track width of the track, analyze the causes of rail gnawing, and adjust it to meet the standard tolerance requirements. Second, during butt welding of rail joints, welding rods and welds shall meet the requirements of rail material and welding quality. The deviation of the left, right and upper sides of the joint shall not be greater than 1mm, and the joint clearance shall not be greater than 2mm

3. for rail gnawing caused by the change of wheel span and verticality caused by the downward deflection of the bridge, the deviation should be adjusted by moving the wheel position as far as possible, and it is generally not advocated to repair the main beam

4. the rail gnawing caused by the problem of the driving mechanism or transmission mechanism should be checked and adjusted to make the speed of the two motors and the braking torque of the brake the same, so as to achieve synchronous starting or braking

in addition, managers and operators at all levels of the crane should establish a strong heart and a high degree of safety awareness, and develop standardized working habits to ensure the safe production of lifting operations

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