Cement & Mining Lubricants / 6 min
Open Gear and Bearing Lubrication in Cement and Mining Facilities
The cement and mining industry pushes lubrication technology to its extremes with massive rotary kilns, ball mills and outdoor crushers. Matching products for open gears and bearings that operate under extreme dust, mud, constant vibration and immense loads without a suitable equivalent carries major risk to facility safety.
Published by: Rotek Technical Content Team
Content is published based on manufacturer technical documentation and equipment requirements as the basis for final selection. This is general guidance and does not replace equipment-specific manufacturer approval.
Review our editorial guidelinesTable of Contents
- - The Demanding Operating Environment of Cement and Mining Facilities
- - Lubrication Challenges and Adhesion on Open Gears
- - Special Grease Needs for Kiln Bearings
- - Compatibility with Central Lubrication Systems
- - Technical Evaluation and Approvals in Product Selection
The Demanding Operating Environment of Cement and Mining Facilities
Mining equipment (excavators, draglines) and cement mills operate outdoors, continuously exposed to dust and moisture. These contaminants act like an abrasive stone, wearing gears down quickly. Lubricants chosen must form a barrier against contaminants and have the ability to repel water (water resistance).
Lubrication Challenges and Adhesion on Open Gears
Large open gears (girth gears) driving a rotary kiln or mill don't operate inside an enclosed casing, so it's very hard for oil to stay on the surface. This is why highly viscous adherent greases, thick asphaltic-based oils, or high-molecular-weight transparent/synthetic specialty open-gear sprays (pastes) are used. Preventing the product from being flung off by centrifugal force is the most critical factor.
Special Grease Needs for Kiln Bearings
The support bearings of cement kilns are under the influence of immense heat from outside. Ordinary greases evaporate or char (leaving carbon deposits) at these temperatures. Only synthetic greases with a high-quality base oil, in polyurea or calcium sulfonate complex thickeners, can operate safely at these points.
Compatibility with Central Lubrication Systems
Manual lubrication is impossible at massive facilities, so automatic central lubrication systems (spray systems, injector lines) are always used. When switching products, whether the new grease or open-gear oil's NLGI number and pumpability suit the system's pressure settings must be carefully calculated.
Technical Evaluation and Approvals in Product Selection
For high-technology products used at cement and mining facilities, exact brand equivalence (X=Y) between different manufacturers cannot be assumed. An open-gear grease's spray formulation can differ radically between manufacturers, and final suitability requires OEM approval. Share your facility's current product, with brand, code and label information, and our technical team will evaluate its suitability for your mining and kiln conditions.
Frequently Asked Questions
Why are special spray greases or pastes used on open gears instead of liquid oil?
Because open gears don't have an enclosed casing, and liquid oils quickly run off the surface due to gravity or centrifugal force. Specialty pastes adhere to the surface, leaving a thick anti-wear film.
Why isn't lithium complex grease used in kiln bearings?
Kiln bearings reach very high temperatures, and lithium complex grease's dropping point and thermal stability are generally insufficient for these extreme conditions, causing it to char and clog the bearing.
Is NLGI 2 grease used in central lubrication systems?
Usually not — to prevent clogging in the piping and ensure easy pumping, more fluid (softer) NLGI 0, 00 or 1 grades are preferred for central systems.
Are open-gear oils harmful to the environment?
Older asphaltic-type products and those containing heavy metals carried environmental risk, but new-generation synthetic and transparent open-gear oils are far more environmentally compliant and easier to dispose of.