Slewing bearings consist of an inner ring, an outer ring, balls or rollers, and raceway hardening (e.g., hardened to HRC 55-60) to improve wear resistance and rigidity.
Slewing bearings can simultaneously withstand large radial loads, axial loads and tilting moments, which is suitable for heavy loads and complex working conditions.
include four-point contact ball type, eight-point contact ball type, crossed roller type, three-row roller type and other structures, each type has its own advantages in terms of precision, rigidity and load capacity.
Many slewing bearing bearings are available with internal or external gear drives, allowing for easy mechanical actuation with simultaneous lubrication and sealing.
comes with mounting holes, seals and lubrication holes for routine maintenance and lubrication replenishment, thus extending service life.
Slewing bearings are core components in construction machinery. They enable the upper structure to rotate 360 degrees relative to the chassis through slewing bearing bearings, ensuring that heavy equipment such as excavators, cranes, and hoists can operate efficiently and stably. They are critical to ensuring the smooth and reliable rotation of the equipment.
When dealing with the harsh marine environment and high load requirements, port ships slewing bearings serve as key load-bearing and transmission components. Their outstanding precision, reliability, and corrosion resistance ensure the efficient and stable operation of ship machinery.
Before slewing ring bearing installation begins, inspect the slewing bearing thoroughly for physical damage, dents, or corrosion. Use lifting eyes and rigging equipment rated for the full weight, never lift manually.
Clean and verify the mounting surface is flat, level, and free from debris, burrs, weld slag, paint, or rust. If gaps exist, use shims to ensure proper seating and alignment.
Align the ring so that the hardness gap (“S” mark) and soft belt are located outside the main load zone—typically staggered 90° from load direction.
Adjust gear backlash at the radial run‑out point. Use feeler gauges or lead wire on the three highest marked teeth, rotate the slewing ring bearing to confirm smooth engagement, and re‑check clearance after bolting.
Use high-strength bolts (strength class typically 10.9 or above) with hardened flat washers only; spring washers are prohibited.
Tighten bolts symmetrically in a cross pattern or alternating 180° sequence, in progressive stages (e.g., 60%, 80%, then 100% of specified torque).
Ensure even pre‑tightening force around the circumference and mark bolts after tightening to detect loosening over time.
After all bolts are torqued, manually rotate the slewing ring to confirm smooth motion; no tight spots or binding. If binding is observed, loosen and re‑adjust alignment.
Conduct a final torque check, inspect gear backlash and bearing clearance again to confirm values remain within tolerance, especially after settling.
Slewing ring bearings typically ship with initial grease. After installation, re‑lubricate gear teeth and raceways, rotating the bearing while applying grease until fresh material appears at seals.
Apply protective coatings or grease to exposed outer surfaces and gear teeth, and consider automatic centralized lubrication systems for longevity and minimal maintenance.
Periodically inspect for wear, vibration, noise, or misalignment. Lubricate regularly, typically every ~100 operating hours (roller types may require more frequent grease).
Check bolt preload at intervals or after downtime, and re‑tighten if necessary to compensate for settling.
Proper slewing bearing lubrication is critical for reliable operation. Inadequate lubrication is the most common cause of premature bearings failures: surface damage, cracks, spalling, and seal wear all stem from poor lubrication practices. In slewing ring bearings, a heavy‑duty extreme pressure grease or correct oil lubrication must be used.Regular lubrication helps reduce friction, dissipate heat, prevent corrosion, remove wear particles, and extend service life.
Grease Lubrication
Most common method, especially for small or low‑speed slewing bearings. Grease (typically lithium-based heavy duty extreme-pressure grease NLGI 1 or 2) is injected into the raceway until fresh grease extrudes from seal lips . Grease contains base oil, thickener, and additives like anti-wear agents and rust inhibitors. It resists water washout and performs under high load and temperature .
Oil Lubrication
Used in medium to high-speed or high-temperature slewing bearings. Oil lubrication methods include:
Oil bath lubrication: partial immersion picks up oil via rotation, ideal for moderate speeds.
Drip or splash lubrication: delivers controlled drip to the raceway (~1 drop every 3–8 s), or utilizes splash action at sufficient rotational speed.
Circulating oil lubrication: pumped, filtered, cooled oil circulated continuously to remove heat—suitable for heavy-duty and continuous operation.
Spray or oil mist lubrication: oil mist or fine spray delivered via compressed air; offers efficient cooling and contamination control in high-speed environments.
Jet lubrication: high-pressure oil injected precisely into the bearing via nozzles, effective for high-load, high-speed slewing bearings .
Grease Regreasing Guidelines
After installation, grease immediately until fresh grease extrudes uniformly around the lip seals and forms a closed grease collar (~1 cm thick).
Regrease protocols typically recommend intervals every 50–100 operating hours, or more frequently in continuous or harsh conditions (as short as every 8 hours).
Unscheduled regreasing is mandatory if the machine is idle for more than 2 months, or in damp or dusty environments.
Oil-Based Lubrication Maintenance
Ensure seals are intact and leak‑free before applying oil lubrication systems.
Oil bath and splash systems require regular monitoring of oil level and replacement of filtered oil.
Circulating or oil mist systems must include filters, coolers, pumps, and control systems; they offer more consistent lubrication but demand careful operation.
Seal & Raceway Integrity
Always inspect seals every six months and maintain lip or labyrinth seals to retain grease or oil, and to exclude contaminants.
For bearing raceways and gear teeth (if present), re‑lubricate before and after long downtimes and clean sealing zones carefully to avoid damage.
Slewing Bearing Lubrication
Slewing Bearing Inspection
Test the Bearing for Smoothness
Bearing Mounting Drilling
Packaging Video
Introduction to PRS Bearing
