How to Solve the Problem of Rail Gnawing in Bridge Cranes
rail gnawing in bridge cranes
How to solve the problem of rail gnawing in bridge cranes
Crane is a commonly used equipment. We can see various types of cranes not only on land, but also widely used in metallurgy, mining, machinery manufacturing and processing and other industries. As the frequency of use of enterprises becomes higher and higher, bridge cranes often have rail gnawing 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 dangers of chewing rails
(1) Reduce the service life of wheels
Since the material of crane wheels 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 life of the wheels will be greatly reduced, which will seriously affect production safety and production efficiency.
(2) Worn track
The occurrence of rail gnawing, due to the rigid contact between the wheels and the track, will aggravate the wear of the track to a certain extent. As the amount of wear increases, the stability of the crane’s large and small trucks decreases, seriously affecting safety.
(3) Danger of derailment
When the wheels or rails are severely worn, the wheels may climb to the top of the rails, causing the cart or trolley to derail, causing a safety accident.
(4) Affects the structure of the factory building
When used by a crane to gnaw the rails, it will make noise and cause vibrations. Moreover, when the crane is running, it will generate horizontal lateral forces, causing the crane to produce abnormal vibrations. As a result, the factory building structure will vibrate and suffer a certain degree of damage.
3. Judgment and expression of rail chewing
(1) On the side of the crane rail, there is an obvious friction and shiny flat surface, there are very sharp edges on the guide rail, and there are snow-white bright spots on the top surface of the rail.
(2) When the bridge crane is traveling, the gap between the wheel rim and the track will obviously become larger or smaller.
(3) When the bridge crane is in operation, the body of the bridge crane is skewed and the wheels are deflected.
(4) When the cart is running, it will produce a harsh rail gnawing sound. When the rail gnawing is severe, the cart will not only produce a harsh noise, but also cause the cart to beat slightly. This is what we usually call rail climbing.
4. Analysis of causes of rail chewing
There are many reasons for cranes to gnaw rails, but the main reasons include these two aspects: first, rail deformation; second, defects in crane industrial manufacturing technology and the installer’s insufficient installation ability and technology.
The causes of orbital deformation are as follows:
(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 driving 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 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;
(4) The wheel does not match 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. 4 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. Solution to rail chewing
(1) Correction track
After the new track is installed, it must be strictly adjusted before it can be put into use. Corresponding tools should be prepared before adjustment, such as steel tape measure, level, tensioner and thin steel wire. Use a steel tape measure to measure the gauge between the two rails, and use a spirit level to check whether the level of the wheel rails is consistent. Use tensioners and thin steel wires to adjust track level and straightness. When installing the wheel, the horizontal deviation should be controlled at △≤L/1000 (L is the length of the measured diameter of the wheel on the parallel reference line), and the vertical deviation should be controlled at △≤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 check contents include: whether the track has cracks or breaks; Whether all bolts and nuts are loose or damaged; Whether the pressure plate and gasket of all tracks are damaged; When correcting the track, use the appropriate tools and accurate methods to measure the gauge, levelness and horizontal straightness errors of the two tracks and record them.
(2) Solve rail gnawing by adjusting the wheel
By replacing the worn wheels in pairs, the influence of the wheel diameter difference on the operation can be eliminated, and the installation accuracy of the wheel group can be adjusted. Reduce the manufacturing error of the wheel set itself.
(3) Check and verify the 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 First the driving wheel of the truck is adjusted and installed, and then based on this, the horizontal axis between the integrated coupling, reducer and the truck walking motor is calibrated in turn, in order to avoid displacement, positioning block welding reducer should be used.
③ The motor speed on the transmission mechanism is detected and adjusted, if the motor speed on both sides is still inconsistent, it is recommended to replace the motor of the same manufacturer.
④ Coordinate the adjustment of the brakes at both ends, that is, the brakes at both ends are fully opened without additional friction resistance during operation, which can prevent unequal braking torque and the phenomenon of the crane gnawing the rail when braking.
Regarding the rail-gnawing phenomenon of cranes, the most important thing is to prevent it. Daily maintenance is very important. Early detection and early repair. By using the above methods for analysis and maintenance, you can solve the problem of rail chewing. This can improve work efficiency and eliminate safety hazards.