How to Maintain a Slewing Bearing for Long Life

Slewing bearings are critical components in many heavy machinery and equipment, such as excavators, cranes, wind turbines, and industrial robots. They withstand enormous loads and moments and operate in harsh working environments. Therefore, proper maintenance of slewing bearings is crucial to ensuring equipment reliability, safety, and extending its service life.

Core Maintenance Concept: Prevention First, Frequent Inspection and Maintenance

How to Maintain a Slewing Bearing for Long Life

Slewing bearing failures are rarely sudden; they are often the result of cumulative damage from long-term lack of maintenance or improper use.

Daily Operation Prevention (Reducing Damage at the Source)

Many damages are caused during operation, and good operating habits are the first step to extending the lifespan.

Smooth Operation: Avoid abrupt starting and braking to reduce impact loads on the slewing bearing.

No Overloading: Strictly adhere to the equipment's rated load. Overloading is a major cause of raceway crushing, deformation, and bolt breakage.

Keep the Platform Level: For mobile equipment (such as excavators), operate on flat, solid ground whenever possible to avoid tilting the equipment, which could cause the slewing bearing to experience excessive overturning moments.

Watch for abnormalities: If you hear unusual noises (clicking, clicking) or feel any sticking or jumping during operation, stop the machine immediately and inspect it.

The following are some key points for maintaining slewing bearings to extend their service life:

1. Regular Lubrication

Poor lubrication is the most common cause of premature failure of slewing bearings. Lubricants have three primary functions: reducing friction and wear, preventing rust and corrosion, and removing wear debris.

1) Grease Selection

Raceway lubrication: Use extreme-pressure lithium-based grease (such as No. 2 EP Lithium-based Grease) or a specialized grease specified by the equipment manufacturer. EP additives form a protective film under high loads, preventing direct metal-to-metal contact.

Ring Gear Lubrication:

Open gears: Use open gear grease, which has strong adhesion and can withstand centrifugal forces and rainwater erosion.

Enclosed gears: Use gear oil of the same grade as the gearbox.

2) Lubrication Interval

Initial Lubrication: New equipment or newly replaced slewing bearings should be lubricated and bolts re-tightened after 100 hours of operation.

Regular Lubrication:

General equipment: Lubricate every 500 hours of operation or every other month.

Harsh operating conditions (such as dusty conditions, high temperatures, high humidity, and continuous operation): The lubrication interval should be shortened. It is recommended to check and lubricate every 100-250 hours of operation or weekly.

Equipment that has been idle for a long time: Thoroughly lubricate before idle and before re-activation.

3) Lubrication Method

Raceway Lubrication:

Slowly rotate the slewing bearing so that the grease nipple is at the top.

Use a high-pressure grease gun to apply grease through the grease nipple on the raceway until the new and old grease are squeezed out from the edge of the sealing strip. This ensures that the new grease has expelled the old grease along with internal wear debris and moisture.

Clean up any squeezed-out old grease to keep the equipment clean.

Ring Gear Lubrication:

Apply the lubricant/grease evenly to the meshing surfaces of the ring gear.

2. Regularly Check and Tighten Bolts

The mounting bolts of a slewing bearing bear significant preload and operating load. Loose bolts can lead to slewing bearing failure and even serious safety accidents.

Regularly Check Bolts: Check the preload of all mounting bolts at least every 100 hours of operation or monthly.

Using a Torque Wrench: Always use a calibrated torque wrench and tighten bolts to the manufacturer's specified torque value.

Inspect Bolts for Deformation or Damage: If deformed, cracked, or corroded, replace them immediately.

Record Inspection Results: Record the date of each inspection, the bolt torque value, and any issues found for tracking and analysis.

3. Regularly Check Gear Mesh and Backlash

For slewing bearings with gears, proper gear mesh and backlash are crucial.

Check Gear Wear: Regularly inspect the gear tooth surfaces for wear, pitting, or cracks.

Adjust Gear Backlash: Check and adjust gear backlash according to the manufacturer's recommendations to ensure smooth transmission and reduce noise and shock.

Lubricate the gears: Keep the gear surfaces clean and apply an appropriate amount of gear grease.

4. Maintain good seals

The seals in the slewing bearing prevent dust, moisture, and other contaminants from entering and prevent lubricant leakage.

Inspect the seals regularly: Inspect the seals for signs of deterioration, cracking, or damage.

Replace damaged seals promptly: If any seal damage is detected, replace it immediately to prevent contaminants from entering.

5. Avoid overloading and shock

Overloading and shock are the main causes of premature failure of slewing bearings.

Operate within the equipment's designed load: Never exceed the maximum load capacity of the slewing bearing.

Avoid sudden starts and stops: Operate the equipment as smoothly as possible to minimize shock loads.

Avoid uneven loading: Maintain an even load distribution and avoid prolonged operation with uneven loading.

6. Clean regularly

Maintaining a clean slewing bearing and its surrounding area prevents contaminants from entering and affecting its performance.

Remove dust and debris: Regularly remove dust, dirt, and other debris from the outside of the slewing bearing.

Avoid high-pressure water washing: When cleaning, avoid using a high-pressure water jet to directly wash the seals to avoid damaging them.

7. Regularly perform condition monitoring

Using advanced condition monitoring technology, early failures of slewing bearings can be detected, thus preventing further losses.

Vibration analysis: By monitoring the vibration signals of the slewing bearing, early damage to the rolling elements, raceways, or gears can be detected.

Oil analysis: Regularly analyzing the lubricating oil can monitor changes in wear particles, moisture content, and lubricant properties.

Temperature monitoring: Abnormally high slewing bearing temperature may be a sign of failure.

Create an inspection log to regularly monitor the condition of the slewing bearing.

Summary: Maintenance Schedule

For ease of implementation, you can create a simple maintenance schedule:

Daily: Visually inspect seals and bolts before starting the machine, and monitor for unusual noise and vibration during operation.

Weekly/Every 100 hours: Lubricate the raceways and ring gears (under severe operating conditions).

Monthly/Every 500 hours: Perform a comprehensive lubrication and bolt torque check.

Semi-annually/Annually/Every 2000 hours: Perform a comprehensive inspection, including clearance measurement and detailed inspection of the tooth flanks and raceway condition (if applicable).

Finally, always refer to the Operation and Maintenance Manual provided by your equipment manufacturer, as different models and equipment may have specific requirements for slewing bearings.

Conclusion

Regular and proper maintenance of slewing bearings is critical to ensuring their long-term reliable operation. By following these maintenance guidelines, companies can significantly extend the life of their slewing bearings, reduce equipment downtime, lower maintenance costs, and improve overall operational efficiency and safety. Investing in an effective maintenance program will provide long-term returns for your heavy equipment.