Greases / 4 min
Where and How to Apply High-Temperature and Heavy-Duty Greases
In industrial processes (iron & steel, cement, ceramic furnaces) that exceed the temperature and load limits of conventional lithium or calcium greases, high-temperature and heavy-load greases are needed to protect equipment. The wrong grease application causes bearing seizures, downtime and fire risks.
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
- - Dropping Point and Melting
- - Thickener Types (Complex, Polyurea, PTFE)
- - Heavy-Load (EP) and Solid Lubricant Additives (MoS2)
- - Application Frequency and Grease Bleeding
Dropping Point and Melting
The temperature at which grease liquefies and starts to flow under heat is called the dropping point. However, a grease's operating temperature should always stay roughly 30-40°C below its dropping point. Standard greases fall short for bearings operating above 150°C.
Thickener Types (Complex, Polyurea, PTFE)
The thickeners that form a grease's skeletal structure are specially selected to resist heat. Lithium complex and calcium sulfonate complex greases operate around 160-180°C, while polyurea greases offer long life at even higher temperatures. At extreme temperatures (250°C and above), specialty synthetic pastes based on Teflon (PTFE) are used.
Heavy-Load (EP) and Solid Lubricant Additives (MoS2)
At points carrying low-speed but massive loads, such as mining or excavator pins, the liquid oil film tears. In these cases, heavy-duty greases containing solid lubricants such as Molybdenum Disulfide (MoS2) or Graphite should be used, forming a lasting shield against shock loads.
Application Frequency and Grease Bleeding
In greases exposed to extreme heat, the internal oil evaporates, leaving behind only the charred residue of the thickener. This is why high-temperature greases should be applied in smaller amounts but at much more frequent intervals than standard greases.
Frequently Asked Questions
If a bearing is overheating, should I apply thicker grease?
Usually not. Overheating in a bearing is generally caused by over-greasing (churning friction) or by using a grease with the wrong speed factor. The correct fix is to use a grease with a consistency suited to the speed, formulated for the high temperature.
Can polyurea grease be mixed with lithium grease?
Polyurea greases are chemically incompatible with conventional lithium or calcium-based greases. When mixed, they turn to sludge or completely liquefy and run. Do not switch until the bearing is fully cleaned.
Where should MoS2 (Molybdenum Disulfide) grease not be used?
MoS2 greases containing solid particles are not used in tight-tolerance electric motor bearings or fan bearings spinning at very high speeds, as they cause vibration and imbalance.
What is non-melting (bentonite) grease?
Bentonite (clay) based greases have no dropping (melting) point — they don't flow even at very high temperatures. However, once the oil inside evaporates, a hard, abrasive clay layer can remain, so the lubrication interval must be watched closely.