Slewing bearings (also known as slewing rings) typically operate under low speed, heavy load and frequent shock conditions. In industrial applications, improper lubrication is one of the most common causes of slewing bearing failure. Correct grease selection, reasonable lubrication period and proper greasing methods play a decisive role in service life, running smoothness and long-term reliability.
Slewing bearings must be lubricated with grease rather than liquid oil. ZZ Slewing Bearing normally use lithium-based grease with NLGI grade 2 and extreme pressure (EP) additives is recommended, as it provides good load-carrying capacity, water resistance and overall versatility.
For low-speed and heavy-duty applications with frequent start-stop or impact loads, EP grease or grease containing molybdenum disulfide (MoS2) can be used, although high MoS2 content is not recommended for high-speed or precision slewing systems.
In humid, dusty or marine environments, water-resistant grease such as calcium-based or composite grease is preferred. For operating temperatures above 120℃, high-temperature grease such as complex lithium or polyurea grease should be selected.
Lubrication Period
Under normal operating conditions, slewing bearings should be lubricated every 100–150 operating hours or at least once per week for continuously running equipment. For heavy-duty or shock-loaded applications, the lubrication period should be shortened to 50–100 hours.
In dusty, muddy or wet environments, daily or per-shift lubrication is recommended. If the equipment has been out of service over three months, the slewing bearing must be fully relubricated before restarting.
Correct Greasing Method
Correct greasing method is as important as grease selection. Grease should always be injected while the slewing bearing is rotating slowly, allowing the grease to distribute evenly inside the raceway. Greasing should continue until old grease is uniformly expelled from the seals, ensuring that fresh grease has fully replaced the old lubricant. After greasing, excess grease should be removed from the seals and surrounding surfaces.
Greasing bearing, lubricating from only one grease nipple, or adding grease after long idle periods without rotation can lead to uneven lubrication, local dry contact and increased risk of pitting or cracking.
Gear ring lubrication
In addition to raceway lubrication, the gear teeth of slewing bearings require separate lubrication. High-adhesion open gear grease or spray-type gear lubricant should be applied directly to the gear teeth. Under normal conditions, gear lubrication is recommended every one to two weeks, and more frequently in dusty or wet environments.
Why Lubrication Matters?
Improper lubrication can result in increased friction torque, abnormal noise, raceway pitting, gear wear and even premature cracking of the bearing rings. Field experience shows that lubrication-related issues account for a significant proportion of slewing bearing failures, often exceeding material or manufacturing-related causes.
Need Technical Support for Slewing Bearing Lubrication?
If you are unsure about grease selection, lubrication Periods or proper greasing procedures for your specific application, our engineering team is ready to support you with professional recommendations.
