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Tech Notes, Volume 1, Issue 8

December, 2010


Grease Compatibility

Often, for one reason or another, it becomes necessary to change the brand of grease used to lubricate a particular machine. If the grease in use may become mixed with a new brand, the question of grease compatibility must be addressed to insure trouble-free changeover.

The NLGI Lubricating Grease Guide, Fourth Edition, 1996 defines grease Incompatibility as follows: “When greases made from different thickeners are mixed the mixture may be poorer in service performance or physical properties than either of the component products. This lessening in performance capability is called incompatibility. It may show up in any of several areas, such as (1) lower heat resistance; (2) change in consistency, usually softening; or (3) decrease in shear stability. Mixtures which show none of these changes are considered compatible.”

Incompatibility is not always caused by the thickener, since each of the greases in the mixture is a complete package – thickener, fluid and additives. Sometimes the thickener of one grease is incompatible with the fluid or the additives present in the second formulation. If the mixture proves to be significantly softer; less shear stable, or less heat resistant than the original grease, the mixture must be deemed incompatible.

“Incompatibility is best determined in service or in service-related tests; it is not predictable. Certain thickener combinations often have been found unsatisfactory and are generally so recognized. These would include lithium and sodium grease and organo-clay and most soap grease. Tests should be run on the specific grease of interest.”

Grease compatibility is a complex subject because of the many variables and changing conditions involved. At one end of the scale, mixing a fresh lubricant with a severely oxidized portion of the same lubricant may produce immediate or progressive changes in the mixture. At the other end of the scale, greases with different thickeners may be mixed resulting in hardening or very soft or low melting mixtures which may not provide adequate lubrication and may lead to early failures. Add to this the diverse operating conditions of time, temperature, and contaminants — and the uncertainties of predicting or measuring compatibility of greases are apparent. There is no practical rule one can apply to all mixtures of different greases to determine compatibility properties.

Grease compatibility is, nevertheless, of more than academic interest, especially when a current or potential customer questions a grease recommendation on the basis of compatibility. Incompatibility alone should not prevent a change in lubricating grease; product performance and overall economics determine lubricant selection. Once the proper lubricant type is thus selected, unwarranted and arbitrary changes should be discouraged.

Ideally, the best procedure to follow when changing grease brands is to completely remove all old grease before new grease is added. This is usually done, for example, when automotive wheel bearings are repacked with grease.  In some pieces of equipment such as electric motors, the grease-lubricated bearings are not designed to be relubricated, as the grease lubrication life and the bearing life are about the same. In these cases, the bearing is replaced with a new pregreased bearing and the old one discarded.

In the majority of cases, however, grease lubrication is performed periodically by adding grease to the existing grease in a piece of equipment.  During a change from one grease brand to another, when complete removal of the old grease is impractical, much of the old grease may be removed by purging with new grease. This can be done initially and/or progressively by temporarily increasing both the application intervals and the quantity of grease applied. Purging old, hard, contaminated grease with new grease is advisable even if grease brands are not changed to ensure that all parts of the equipment are actually receiving new grease. Sometimes, small openings in the grease-lubricated area become clogged with contaminated or old grease and normal relubrication is not sufficient to distribute fresh lubricant to all parts of the equipment. After thorough purging with the new grease, the equipment should be monitored for signs of possible incompatibility such as grease leakage, abnormally high operating temperatures (if equipment is not overpacked with grease), or noise.


Bel-Ray Protection Superior in Cement Industry

Bel-Ray manufactures high performance lubricants that fulfill the lubrication requirements of the complete cement process from raw material mining at the quarry to transport of the finished cement. However, because Bel-Ray is best known for high performance industrial and mining lubricants, this series focuses on the actual cement manufacturing section of the process where the superior performance of the Bel-Ray high performance lubricants is easily demonstrated and their cost benefits easily proven.

The manufacturing section of the cement process begins with raw material grinding and includes cooking, clinker cooling and cement grinding. In this series of articles the equipment used in the cement manufacturing process will be discussed beginning with the grinding step.

The cement manufacturing process is not complex and it offers several opportunities to sell Bel-Ray high performance lubricants. Stepwise, after the primary raw material, limestone, is mined at the quarry, it is crushed into more manageable size pieces. This is most often done by gyratory or cone crushers and less often with jaw crushers. Vibrating screens control the size of the pieces that move on to the actual cement manufacturing process. Large pieces are re-crushed.

Although crushers and vibrating screens are generally considered to be part of the quarry, they can benefit from the use of Bel-Ray high performance lubricants. Theproduct list for crushers and vibrating screens is limited. Although Bel-Ray 100 Gear Oil and Molylube 126 EP Grease or Termalene EP Grease are consistently topperformers for gearboxes and bearings, a good rule of thumb is to follow the machine manufacturer’s basic recommendations regarding viscosity, penetration and base oil viscosity for these applications. If this information is not available consult with your Bel-Ray Representative or Bel-Ray Technical Service Query at

Grinding is performed at two points in the cement manufacturing process. As limestone, the primary raw material in cement, enters the process and in the final step of the process where the clinker is ground to its final, talc-like consistency. This powder is the basis of cement. Fuel grinding for the kiln may also present opportunities to sell Bel-Ray high performance lubricants

Grinding is done with grinding mills. There are two types of grinding mills, horizontal mills and vertical roller mills.

Horizontal mills consist of a rotating horizontal tube. Limestone from the quarry, clinker from the kiln or fuel are added to the tube along with the grinding media which is typically steel balls, rods or bars. As the tube rotates, the process material is impinged upon by the grinding media grinding it into a fine powder.

This type of mill offers opportunities to sell several types of Bel-Ray high performance lubricants including an open gear lubricant, a bearing oil, a gearbox oil and an electric motor bearing grease. See the table below.

Some horizontal mills are designed using a direct drive system eliminating the girth gear and pinions. In the direct drive system all speed reductions are made through enclosed gearboxes. Often gear oil volumes are higher. At times a gear oil reservoir is used in a circulation loop including the reservoir, filters and the gearboxes.

The following table provides Bel-Ray recommendations for various mill applications:

The second type of grinding mill often used in the cement process is a vertical roller mill. The vertical roller mill consists of a rotating table with heavily loaded crushing discs. Process material is placed onto the rotating table where is it crushed under the discs. Vertical roller mill lubrication opportunities are limited to a drive system gear oil, bearing grease, hydraulic oil and a compressor lubricant.  In this picture the drive system turns the rotating table. Process material to be ground is deposited on the rotating table where the crushing discs pulverize it. A steady air flow carries ground process material out of the mill. When a particle is too large to be carried out of the mill on the air stream it falls back onto the rotating table to be reground.  Often the crushing discs are hydraulically loaded through a rocker arm assembly.



Friction Modified Thumper Racing 4T Engine Oil & Thumper Gear Saver Transmission Oil

Introducing, the New Friction Modified Thumper engine oil, specifically formulated for motorcycles with separate engine and transmission oils. This exciting new product contains friction reducing additives that lower the drag on all moving components of the engine, reducing the heat generated by friction and increasing horsepower output.

Bel-Ray Friction Modified Thumper Racing 4T Engine Oil is JASO MB rated and should only be used in engine applications, never in a wet clutch application. By using friction reducing additives, lower SAE viscosities reduce horsepower-robbing fluid friction to increase horsepower output. Friction Modified 4T is available in both 10W-30 and 10W-40 viscosities.

The best applications for this product are the Honda CRF 250R and 450R.

For use in the wet clutch found on the Hondas, we recommend another new Bel-Ray product.  The Thumper Gear Saver Transmission Oil 80W-85 is multi-viscosity transmission oil that will provide the lubrication needed as the transmission and wet clutch heat up during a race.

Bel-Ray Thumper Gear Saver Transmission Oil 80W-85 can also be used in all 2 stroke racing applications.

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