20 Ton Workshop Overhead Crane - Rail Gnawing

20 ton Workshop Overhead Crane - Rail Gnawing

 

The rail gnawing of the 20 ton workshop bridge crane is generally caused by the skew of the wheel and the lateral sliding of the wheel.

Rail gnawing will reduce the service life of wheels and rails and increase running resistance. In severe cases, it may cause motor burnout or twisting of drive shaft accidents; rail gnawing can also cause derailment and affect the service life of the plant.
 

According to Dejun's experience, the cause and repair method of the wheel rail gnawing are discussed.

 

 

Reason for rail gnawing
 

1. Left and right wheel drive out of sync
 

Because the two sets of transmission mechanisms driven separately are not synchronized, the car body is inclined and the rails are gnawed. The characteristic of this kind of rail gnawing is that when the crane starts and brakes, the car body twists and gnaws the rail.
 

2. Excessive track deviation
 

The characteristic of rail gnawing due to excessive track deviation is that the crane gnaws the rail in some sections.
 

If the span of the track and the horizontal linearity of the track are poor, under the premise that the span of the crane remains unchanged, the gap between the wheel rim and the side of the track will be reduced. If the top surface of the track is not in the same plane, it may cause rail gnawing.
 

3. structural deformation
 

The wheels of the large and small vehicles are respectively fixed on the end beams of the bridge frame and the side beams of the small vehicle frame. Therefore, when the bridge or small frame is deformed, it will inevitably cause the skew of the wheel and the change of the span. The rail gnawing caused by this mostly occurs in the bridge frame of the cart, which will be explained separately.
 

(1) The span of the two wheels changes or the diagonal length of the four wheels is out of tolerance due to structural deformation, resulting in rail gnawing.
 

(2) Rail gnawing caused by excessive vertical deflection of the wheel due to structural deformation. Rail gnawing may occur when the wheel is installed outside the vertical deflection tolerance.
 

(3) Due to the deformation of the bridge structure, the horizontal bending of the end beam is caused, which causes the horizontal deflection of the wheel to be out of tolerance. The rail gnawing caused by the horizontal deflection of the wheel will have the same effect whether it is the driving wheel or the driven wheel.
 

However, if the two wheels at the same end or the two wheels on the same side have opposite horizontal deflection directions, there will be an obvious mutual neutralization and cancellation effect, which should be utilized in the repair and adjustment of the wheels.
 

4. Tapered tread wheel assembly error
 

The bridge crane with centralized drive is adopted. In order to adjust the mutual advance or lag at both ends of the cart and avoid running rails, the active wheel treads of the traveling mechanism of the cart adopt a taper of 1:10.
 

The installation of this tapered wheel has a certain direction, and the taper directions of the two wheels should be opposite. If the assembly direction is wrong, the leading wheel will be more advanced, and the lagging wheel will be more lagging, and the rail gnawing will become more and more serious, so the tapered wheel must be installed carefully not to be wrong.

 

 

Checking method for rail gnawing
 

1. During the operation of the crane, if the gap between the wheel rim and the rail changes significantly within a short distance, the crane will bite the rail.
 

2. Through observation, it is found that there are bright marks on the side of the rail, and in severe cases, there are burrs, or there are bright spots on the inner side of the wheel rim, and it can be concluded that the crane has gnawed on the rail.
 

3. When the crane is running, especially when starting and braking, the car body will deviate and twist.
 

4. When the rail gnawing is particularly severe, a louder rail gnawing sound will be issued.

 

Repair method of wheel gnawing rail
 

1. Adjust the transmission mechanism of the cart
 

The tightness of the two sets of driving mechanisms of the cranes driven separately should be carefully adjusted when assembling; the speed difference between the motors of the two carts should be carefully checked and repaired; the tightness of the two sets of brakes should be adjusted properly; Both sides should be updated at the same time; the installation of tapered tread wheels should pay attention to the big end facing inward.
 

2. Repairs to trolley rail gnawing
 

After the main girder of the crane is deflected, the distance between the two tracks of the trolley will become smaller. When the gauge is small to a certain extent, for the trolley with the outer single rim, it may derail during operation; for the trolley with double rim, the rail clamping phenomenon will occur during operation.
 

At this time, flame correction should be used to repair the upper camber of the main beam of the bridge frame and strengthen it so that the track gauge of the trolley is within the tolerance range. When using flame to correct the deflection of the main beam or replace the track, pay attention to jacking up the middle of the main beam.
 

3. For the repair of the rail gnawing caused by the deformation of the bridge frame mechanism, there are many reasons for the rail gnawing of the cart, and the repair should be targeted. If the deviation of the vertical diagonal line of the bridge frame is out of tolerance, the flame should be used to correct the structural deformation.
 

4. Repair of rail gnawing caused by wheel deflection
 

At this time, it should be analyzed to determine which wheel to adjust has a small workload and good effect, and at the same time, try to adjust the passive wheel.
 

For the adjustment of the horizontal deflection of the wheel, the effect of mutual neutralization and offset should be considered. Before adjusting the wheel, first use a jack to lift the end beam (or balance beam) to make the wheel hang in the air, and then loosen the fastening bolts for adjustment. For a small amount of adjustment, the fastening bolts can be loosened, and a backing plate can be added in the keyway of the angular bearing box. Adjustment.
 

For vertical deflection adjustments, it should be adjusted so that both wheels are deflected to the outside. In this way, after the bridge structure is loaded, it is beneficial to increase the contact area between the wheel and the track.
 

5. Adjustments to the cart track
 

The elevation, span and straightness of the track should be adjusted in strict accordance with the technical requirements; the tightening of the bolts should be checked.
 

For heavy-duty cranes and large-capacity cranes, they should be inspected every six months, and other inspections and adjustments should be made every six months to one year. Only in this way can the cart be well prevented from gnawing on the rail.