Rail Gnawing

Rail Gnawing

How to Solve the Phenomenon of Rail Gnawing in Bridge Cranes?

Crane is a kind of commonly used equipment. Not only on land, we can see various types of cranes, which are widely used in metallurgy, mining, machinery manufacturing and processing and other industries. With the increasing use frequency of enterprises, bridge cranes often gnaw on rails during normal use and maintenance.

1. Definition of track gnawing

Rail gnawing means that during the operation of the crane or car, the wheel rim of the truck or car should maintain a certain gap with the side of the track, but due to the horizontal lateral thrust generated by the contact between the wheel rim and the side of the track, causing friction and wear between the wheel rim and the track, usually called rail gnawing.

2. The hazards of rail gnawing

(1) Reduce the service life of the wheel

Because the material of the wheel of the crane is generally cast steel, after quenching and other processes, it can generally be used for more than 10 years. However, due to rail gnawing, the service life of the wheels will be greatly reduced, which will seriously affect production safety and production efficiency.

(2) Wear track

In the event of rail gnawing, the wheels and rails are in rigid contact, which will aggravate the wear of the rails to a certain extent. With the increase of wear, the stability of cranes and vehicles will decrease, which will seriously affect safety.

(3) Risk of derailment

When the wheels or tracks are severely worn, the wheels may climb to the top surface of the track, causing the cart or trolley to derail, causing safety accidents.

(4) Affect the structure of the plant

Noise and vibration will occur when the crane is used to gnaw the rails, and the horizontal lateral force will be generated when the crane is running, which will cause the crane to generate abnormal vibration, which will cause the plant structure to vibrate and be damaged to a certain extent.

3. Judgment and manifestation of rail gnawing

(1) On the side of the crane track, there are obvious rubbing and bright planes, there are sharp edges and corners on the guide rail, and there are snow-white bright spots on the top surface of the track.

(2) When the bridge crane is running, the gap between the wheel flange and the track becomes larger or smaller obviously.

(3) During the operation of the bridge crane, the car body is skewed and the wheels are deflected.

(4) There will be ear-piercing rail-gnawing sound when the cart is running. When the rail-gnawing is serious, the cart will not only produce ear-piercing noise, but also cause the cart to jump slightly. This is what we usually call the rail climbing phenomenon.

4. Analysis of the cause of rail gnawing

There are many reasons for crane rail gnawing, but the main reasons are these two aspects: one is the deformation of the rail; the other is the defects in the manufacturing technology of the crane industry and the lack of installation ability and technology of the installer.

(1) Because the crane and the car often walk back and forth on the track, the pressure on the track is intermittent externally, and the stress in the track is manifested as alternating stress, which will cause the track to deform or displace.

(2) Under the ideal design, the crane big car walking mechanism is walking in a straight line. But in the actual work, is the load walking, this will not have any impact, but different enterprises have different management methods, the operational skills of the staff are also different, which will exist outside the phenomenon of oblique lifting, this phenomenon is bound to chew the rail.

(3) Orbital foundation changes. Such as geological subsidence. Whether the crane can walk normally mainly depends on the state of the track. At present, the most common method is to constantly adjust the orbit.

The quality of the installation of the wheel and the quality of the wheel itself are also important reasons for the phenomenon of rail biting:

(1) The crane is overloaded for a long time, or the residual stress of the crane main beam causes the main beam, end beam and frame of the crane to deform, causing the skew of the wheel, resulting in rail gnawing.

(2) The diameter of the tread of the two active wheels is not equal. When the crane is running, because the wheel diameter is different, the wheels on both sides of the motor speed is the same, the running speed must be different, which will cause the phenomenon of “drawing the circle”, which makes the rim and the two sides of the track rigid contact, resulting in the phenomenon of gnawing the rail.

(3) The driver host is not synchronized. The two motor speeds of the driving truck are different or one side of the motor is damaged, resulting in different linear speeds of the wheels, resulting in the overall deviation of the car body, resulting in the phenomenon of rail gnawing; the transmission gap difference between the two ends of the coupling is too large, causing the wheel can not start at the same time, but also cause rail gnawing;

The wheel doesn’t fit the track. If the wheels don’t match the tracks. If the gap is too small, it will make the rim contact with the side of the track, resulting in rail gnawing. The same thing happens when the gap is too large. The four wheels are not in the same horizontal plane, resulting in a driving wheel suspension or slip, so that the car body skew running; at the same time, the debris on the top of the track causes the running speed of the wheel to be inconsistent. These are all causes of track-biting.

5.Gnawing solution

Correction track

After the new track is installed, it must be strictly adjusted before it can be delivered. Corresponding tools should be prepared before adjustment, such as: steel tape, level, tensioner and thin steel wire, etc. Use a steel tape to measure the gauge between the two rails, and use a spirit level to check whether the level of the two rails is the same. Use tensioners and thin steel wires to adjust the level and straightness of the track. When installing the wheels, the horizontal deviation should be controlled within △ ≤ L/1000 (L is the length of the measured diameter of the wheel on the parallel datum line), and the vertical deviation should be controlled within △ ≤ H/1000 (H is the measured height of the wheel in the vertical direction length).

The method of adjusting the old track is roughly the same as that of correcting the new track, but before adjusting the old track, it should be checked in detail. The inspection contents include:

(1) Check the track for cracks or breaks.

(2) Check whether all bolts and nuts are loose or damaged.

(3) Check whether the pressure plates and gaskets of all tracks are damaged.

(4) When correcting the track, use corresponding tools and accurate methods to measure the gauge, levelness and horizontal straightness errors of the two tracks, and record them.

Solve rail gnawing by adjusting the wheels

By replacing the worn wheels in pairs, the influence of wheel diameter difference on operation can be eliminated, and the installation accuracy of the wheel set can be adjusted. Reduce the manufacturing error existing in the wheel set itself.

Check and verify transmission mechanism

(1) Through careful inspection of the transmission mechanism, if it is found that the transmission mechanism gap is large, the coupling and transmission must be repaired or replaced.

(2) the driving wheel of the truck is adjusted and installed first, and then based on this, the horizontal axis between the integrated coupling, reducer and the motor of the truck is calibrated in turn, in order to avoid displacement, the positioning block should be used to weld the reducer.

(3) To detect and adjust the motor speed on the transmission mechanism, if the motor speed on both sides is still inconsistent, it is recommended to replace with the same manufacturer of the same model motor.

(4) Coordinate the adjustment of the brakes at both ends, that is, the brakes at both ends are completely opened without additional friction resistance during operation, which can prevent the phenomenon of unequal braking torque and rail gnawing of the crane when braking.

For the phenomenon of crane rail gnawing, the most important thing is to prevent it. The usual daily maintenance is very important, early detection and early maintenance. Using the above method for analysis and maintenance can solve the problem of rail gnawing. This can improve work efficiency and eliminate potential safety hazards.