Reasons for rail gnawing of the crane of the hotte

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Reasons and maintenance improvement of rail gnawing of overhead traveling crane

overhead traveling crane is widely used in metallurgy, mining and other industries with high fatigue life up to 50000 times. At present, 24 overhead traveling cranes are used in our factory. After the bridge crane is used for a period of time, the crane will gnaw the rail to varying degrees, especially after many years of use. The crane in the raw material workshop and the return train room of the plant has serious rail gnawing, causing frequent equipment failures, increasing the consumption of equipment spare parts and maintenance workload, and affecting the normal production of the workshop. In view of this phenomenon, we analyzed it theoretically and put forward improvement measures. After the improvement, the equipment operates normally, and the equipment accident and failure shutdown rate are greatly reduced, ensuring the normal production of the workshop

1 conditions for judging rail gnawing

the bridge crane operates on rails, and the wheels operate on special rails The crane rail is used to support the whole weight of the crane and ensure the normal and directional operation of the equipment. Therefore, the selection of bridge crane rail should meet the following technical conditions:

(1) the rail top surface can bear the extrusion force of wheels; (2) The rail bottom has a certain width to reduce the pressure on the foundation; (3) It shall have good abrasion resistance and curvature

during the operation of the crane, due to various reasons, there are often axial movement or axial deflection, which makes the wheel contact and friction with the side of the track, and is constrained by the rim and track. When restricting the operation so that the guide sleeve on the swing rod drives the sample to make a ± 90 ° zigzag, the rim wheel punching machine is rated at the wheel rail contact state of 60 tons (Figure 1). At this time, the wheel and the rail have two contact points, point a on the tread is called the bearing point, and point B on the rim or the transition arc is called the guide point. This contact friction mode causes the wheel edge friction damage and the side friction loss of the track, which is customarily called rail gnawing

the crane trolleys in two workshops of our factory made a noise when walking. There were spots on the side of the track, spots on the top of the track, and bright spots on the inner side of the wheel rim. When the crane is running, the gap between the rim and the track has changed significantly in a short distance. According to the current situation, it can be preliminarily judged that the crane is walking and gnawing the track

2 serious consequences caused by rail gnawing

(1) impact of rail gnawing on foundation, roof beam and bridge. When the crane gnaws the rail, it will inevitably produce horizontal lateral force. This lateral force will lead to the lateral displacement of the track, cause equipment vibration, cause the bolts fixing the track to loosen, and also cause the vibration of the whole crane, which will affect the stability of the roof beam and bridge structure to varying degrees

(2) the threat of rail gnawing to production, personnel and equipment. Serious rail gnawing will cause serious wear of the crane rail, resulting in poor contact with the wheels when the crane is running and cannot be used until it is replaced, resulting in a waste of manpower and materials, and also a great impact on production

the crane is operated at high altitude with resin viscosity for hours. During operation, especially when the gap between rail joints is too large, it is very easy to cause major personal casualties and equipment accidents

(3) impact of rail gnawing on electrical equipment system. Gnawing the rail during the operation of the crane will produce considerable resistance, which will increase the load of the power system, and the power consumption of electrical components and motors will be caused by the increase of current during the operation. Especially when the crane is running and driving, the rail gnawing increases the running resistance, so that the motor runs overloaded during operation, which is easy to cause the motor to be overloaded and burned. At the same time, due to the large running resistance, it is also easy to twist transmission system components such as shafts. This fault often occurs before the rail gnawing phenomenon of our crane is eliminated

3 analysis of reasons for rail gnawing

3.1.1 rail gnawing occurs in the crane during operation, which is a very serious problem. Under normal operation, there is a certain gap between the crane wheel flange and the track, and the maximum gap is generally designed to be mm. However, due to some reasons such as hoisting and some factors in operation, the wheel skews, so that the contact surface between the running wheel and the track is not in the middle of the tread, resulting in vehicle body deflection. When the car body deflects, the rim on one side of the crane and the side of the track squeeze, and the rim and the track produce side friction, resulting in the side friction of the rim and the track. This is the main reason for the crane to deflect and gnaw the track. That is to say, although the wheel base and track span are correct, the center line of the wheel tread does not coincide with the center line of the track. When the car body deflects, the whole crane moves against the side of the track, Therefore, one side between the wheel flange and the track is forced to contact, and the wheel and track are seriously worn, so rail gnawing occurs

slight rail gnawing will cause obvious wear marks on the rim and the side of the track, and serious rail gnawing will cause metal peeling or outward deformation of the rim and the side of the track

there are many reasons for rail gnawing, such as the deformation of the bridge and foundation of the crane, which will inevitably lead to the deflection of the wheels and the change of the span size, resulting in the rail gnawing of the crane. Due to the deformation of the bridge, the end beam is horizontally bent, resulting in the wheel horizontal deflection and out of tolerance, which is also the main reason for rail gnawing

when the crane is running and braking, longitudinal or transverse force will be generated. If the crane and trolley are braked at the same time, a synthetic braking force will be generated, making the track bear an oblique thrust. At this time, if the track is installed so that one side is higher than the other, the center of gravity of the crane will move to the lower side, thereby increasing the lateral force borne by the track, so that the wheels on one side of the track are tightly clamped on the outside of the track, causing rail gnawing. We will focus on the following aspects:

3.1.2 wheels

first check the wheel appearance for cracks, tread spalling, indentation, etc. Early wear causes the wheel tread to collapse or grind into a flat surface If the thickness wear of the rim is ≤ 5%, the wear of the tread is ≤ 1.5%, and the tread is free of pits, the wheel meets the service standard

(1) when the diameters of the driving and driven wheels on both sides are not equal (due to uneven manufacturing and wear), when the crane is running, the strokes on both sides are not equal at the same speed, resulting in rail gnawing

(2) the installation position of the wheel is incorrect, which is also easy to cause rail gnawing. There are mainly the following:

a the installation position of the four wheels is not at the four corners of the rectangle. The center on the same side is not in a straight line, and the wheel deflects. At this time, both the driving and driven wheels will cause rail gnawing

① as shown in Figure 2, the wheel position is parallelogram, diagonal D1> D2, and the rail gnawing wheel is at the diagonal position

② as shown in Figure 3, the wheel position is trapezoidal, and the rail gnawing position is on the same axis, L1

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