Knagen aan bovenloopkranen: oorzaken, diagnose en preventieve maatregelen

During the operation of an overhead crane, if there is any issue that causes the wheels to slide laterally against the track, it results in the wheel being pressed against the rail, increasing running resistance and causing wear between the wheel flange and the rail. This phenomenon is called flange rubbing or “wheel flange gnawing” (also known as “crane wheel gnawing”). Flange rubbing significantly reduces the lifespan of both the wheels and the tracks, and in severe cases, can cause the crane to derail, leading to equipment damage and personal injury. It can also cause varying degrees of damage to the track fixings and beams (or foundations). Based on practical experience, this article summarizes the causes of crane wheel flange rubbing and safety measures for prevention.

Causes of Wheel Flange Gnawing and Rubbing

(1) Wheel Issues

1. Wheel Installation Misalignment

• Excessive Horizontal Deviation
  This is one of the common causes of wheel flange rubbing in bridge cranes. When the horizontal deviation is too large, the centerline of the wheel tread forms an angle with the centerline of the track. When the crane moves in one direction, the wheel flange rubs against one side of the track. When moving in the opposite direction, the same wheel flange rubs against the other side, and the rubbing position is not fixed. During installation, the horizontal deviation should not exceed L/1000 (where L is the measurement length of the wheel). Additionally, the tilt direction of a pair of wheels on the same axis should be opposite; otherwise, the wheels will rub the track.

• Excessive Vertical Deviation
  This refers to the angle formed between the wheel’s end face centerline and the vertical line, resulting in an inclined wheel position. In this case, the contact area between the wheel tread and the rail is reduced, and pressure on the unit area increases. This leads to uneven wear on the wheel tread. In severe cases, annular wear grooves form on the wheel tread. In this case, the feature of flange rubbing is that the wheel flange always rubs against the same side of the track (the side of the tilted wheel), and the wear marks are slightly lower than usual. The crane often emits a hissing sound during operation. During installation, the vertical deviation of the wheel should not exceed L/400, and the top of the wheel should face outward. This issue of flange rubbing caused by vertical deviation concerns the driving wheel, not the idle wheel.

• Unequal Wheel Gauge or Diagonal Alignment
  If the wheel gauge or diagonal alignment of the wheels on the same track is improper, it can cause flange rubbing. In these cases, flange wear can be seen on both sides of the wheel flange along the track.

2. Wheel Processing Errors
   When manufacturing the wheels, errors may cause the wheel diameters to differ. If the diameters of the two driving wheels differ, the left and right wheels will operate at different speeds. After running a certain distance, the crane may skew laterally, resulting in flange rubbing, which is especially noticeable in centrally-driven mechanisms.

(2) Track Issues

Poor track installation quality may cause excessive deviation between the two rails, leading to flange rubbing during crane operation. This typically occurs in specific sections of the track.

1. Excessive Relative Elevation Deviation of Rails
   If there is a height difference between the two rails, one end beam of the crane will be higher than the other. During operation, the crane will shift toward the lower side, causing flange rubbing. The side with a higher rail elevation will result in the wheel flange pressing against the outer side of the rail, while the side with a lower elevation will cause the flange to press against the inner side of the rail.

2. Excessive Horizontal Straightness Deviation of Rails
   If the rail straightness is not up to standard during installation, causing excessive bending of the rail, it will result in wheel flange rubbing when the deviation exceeds the span tolerance.

3. Adjacent Rails at Different Elevations
   When the crane reaches the rail joint, lateral movement may occur, leading to flange rubbing. The characteristic of this type of flange rubbing is that the wheels make a metallic collision sound at the joint.

4. Oil, Water, or Frost on the Track Surface
   If the rail top surface is covered with oil, water, or frost, it may cause the wheels to slip, leading to lateral movement of the crane and subsequent flange rubbing.

(3) Bridge Frame Issues

If the bridge frame deforms, it will cause the wheels to become misaligned and change the crane’s span. This results in horizontal bending of the end beam, causing horizontal and vertical deviations of the wheels, leading to flange rubbing.

(4) Drive System Issues

Excessive manufacturing errors in the drive system or significant wear during use can cause the two main driving wheels to operate at different speeds, resulting in lateral skew and flange rubbing.

1. Unequal Gear Clearance or Loose Shaft Keys
   In cranes with separately driven mechanisms, if the gear clearance of one drive system is larger than the other, or if the shaft keys in one system are loose, the two main wheels will run at different speeds, leading to lateral movement and flange rubbing.

2. Uneven Brake Adjustments
   If the brake adjustments of the two drive systems are not synchronized or differ in tightness, it can also cause skewing and flange rubbing during startup or braking.

3. Excessive Speed Differences Between Motors
   For independently driven systems, if the two drive motors run at significantly different speeds, it can cause one side of the crane to run faster than the other, resulting in skewing and flange rubbing.

Diagnosis of Crane Wheel Gnawing and Rubbing

The occurrence of flange rubbing during crane operation can be diagnosed through the following signs:

1. Bright marks on the side of the rail, with serious marks showing burrs; shiny spots on the inner side of the wheel flange.

2. Bright spots on the top surface of the rail.

3. Noticeable changes in the gap between the wheel flange and the rail side within a short distance during operation.

4. Skewing or twisting of the crane body during startup or braking.

Measures to Prevent Wheel Gnawing and Rubbing

For both centrally driven and separately driven cranes, the methods to prevent or improve wheel flange rubbing may vary. Careful inspection and adjustment of wheel and track alignment are essential. Special attention should be paid to synchronization issues between the motors, brakes, and reducers of the separately driven systems.

1. Limit the Ratio of Bridge Span (L) to Wheel Gauge (K)
   During normal crane operation, a certain degree of lateral tilt between the wheel flange and the rail is allowed, i.e., the wheel flange is allowed to move laterally a certain distance (usually 20-30mm). The larger this distance, the less likely flange rubbing will occur. Additionally, the ratio of L/K affects whether flange rubbing will occur: the smaller the ratio, the less lateral tilt is allowed, making flange rubbing more likely. Therefore, a lower L/K ratio (preferably less than 5-6) is beneficial.

2. Wheel Tapered Tread
   If the crane has 4 wheels, with 2 main driving wheels, the wheel tread can adopt a conical shape (with a cone angle of 1:10), and the large end of the cone should face inward. The use of a convex rail ensures that the crane will automatically adjust its running direction after a few oscillations, reducing friction between the wheel and the track.

3. For Centrally-Driven Systems
   If the diameters of the two main driving wheels differ, they should be machined or replaced.

4. Lubricate the Wheel Flange and Track Side
   Lubricating the wheel flange and track surface reduces friction and minimizes wear on both components.

5. Regularly Check for Deformation in the Bridge Frame
   Ensure the bridge frame is not deformed, and correct it promptly if necessary. Any deviations in the wheel’s diagonal, verticality, or horizontal alignment should be adjusted.

6. For Separately-Driven Systems
   If the two motors operate at different speeds, replace them with motors of the same model from the same manufacturer. Adjust the brakes if their operation is not synchronized or if their tightness is uneven.

7. Excessive Clearance in the Transmission System
   Inspect and repair or replace parts like couplings or gearboxes if there is excessive clearance.

8. Track Problems
   Track issues should be addressed according to the technical requirements for track installation. Debris on the track should be removed promptly.

Repair Methods for Wheel Gnawing and Rubbing

1. Wheel Repair Methods:

• Check the condition of wheel wear. If the wear is severe, replace the wheel.
• For lighter wear, the wheel tread can be ground to restore the original shape and dimensions.
• If the flange rubbing issue is due to poor wheel-rail matching, the wheel can be widened, thickened, or replaced with a larger-capacity wheel.

2. Track Repair Methods:

• Check the track installation to ensure it is level and secure.
• If the track is misaligned, adjust its position or install shims.
• Replace old or severely damaged tracks.

3. Adjusting the Drive System

• During the installation of separately driven systems, ensure the tension is properly adjusted. The speed differences between the two motors should be carefully checked and corrected.
• Check for wear in the reducer and couplings and replace them as necessary.
• Ensure that the conical tread wheels are installed with the large end facing inward.

4. Repairing Small Crane Flange Rubbing
   After the main beam sags, the gauge between the two small tracks may decrease. If the gauge becomes too small, the crane may derail or experience track jamming. Flame correction can be used to restore the sag and reinforce the beam, ensuring the track gauge is within tolerance.

5. Repairing Large Crane Flange Rubbing Caused by Bridge Frame Deformation
   For the deformation of the bridge frame, targeted repairs should be made, such as using flame correction for structural deformation when vertical diagonal deviations are out of tolerance.

6. Repairing Flange Rubbing Caused by Wheel Skew
   Identify which wheel has a smaller workload for better adjustment. For horizontal skew, aim to balance the skew effects. Before adjustments, lift the end beam or balance beam using a jack to relieve the wheels and then adjust by loosening the fasteners.

Conclusie

Wheel flange rubbing in bridge cranes can severely affect crane mobility and may lead to safety risks. It is essential to promptly analyze and apply appropriate repairs. Regular inspections and maintenance can help prevent flange rubbing and ensure the safe and reliable operation of the crane.

kristal

Kraan OEM-expert

Met 8 jaar ervaring in het aanpassen van hijsapparatuur, heb ik meer dan 10.000 klanten geholpen met hun pre-sales vragen en zorgen. Als u gerelateerde behoeften heeft, neem dan gerust contact met mij op!

Whatsappen: +86 199 1373 9708

E-mail: krystalli@kscranegroup.com