KRL Tapered Roller Bearing Shear Stability Tester

 

KRL is a method to test the Shear Stability of polymer-containing fluids (Usually refers to lubricant oil containing Viscosity Index Improver). The test method measures the percent viscosity loss of lubricant fluid at 100°C.

The KRL Shear Stability Test method has been recognized in the lubricant industry as an accurate shear test method for predicting the viscosity loss of lubricating oil under actual operating conditions and has become an important evaluation tool in the development of modern lubricating oil products.

 

Compared to other shear test methods in Lubricants, KRL is considered one of the most severe shear tests. It has a more obvious shear effect， so it is an ideal test method for evaluating the shear stability of heavy-duty oils, such as gear oils.  When the lubricant blender purchases the Viscosity Index Improvers, If you are going to blend a type of gear oil, so please make sure to the lubricant additives suppliers that you are buying a Viscosity Index Improver (VII), which should meet the KRL 20h testing. e.g. Polymethacrylate Viscosity Improver (PMA VI)

 

The viscosity loss is measured by KV@ 100°C before shear and after shear, it is the Permanent Shear Stability Index (PSSI).

 

Permanent shear stability is more commonly defined by the Permanent Shear Stability Index (PSSI) or simply SSI, according to ASTM D6022 as follows:

 

PSSI=SSI=（V₀-V_S）/ (V₀-V_b)*100

 

V_o = viscosity of unsheared oil
V_s = viscosity of sheared oil
V_b = viscosity of the base fluid (without polymer)

Some types of Four-Ball Testers have a KRL shear stability Attachment to determine the viscosity loss of lubricants.

 

In the China National Standard, the technical requirements for heavy-duty vehicle gear oils have added a mandatory requirement—KRL shear stability (20 h), which uses the "Determination of viscosity shear stability of transmission lubricants using the tapered roller bearing" for determination.  

 

Standards:

NB/SH/T 0845-2010

Determination of viscosity shear stability of transmission lubricants using the tapered roller bearing.

 

CEC L-45-A-99

Viscosity Shear Stability of Transmission Lubricants

 

DIN 51350-6

Testing of lubricants –Testing in the Shell four-ball tester - Part 6: Determination of shear stability of lubricating oils containing polymers