On the basis of the absolute value of the shear viscosity as well as the percentage viscosity loss, the tribologist assessing your grease sample at OELCHECK can derive whether the thickener can still transfer sufficient lubricating oil to the friction point under load. The changes allow conclusions to be drawn as to how strongly the grease can still resist the effect of shear forces in comparison with fresh grease. The percentage change is calculated as a “relative viscosity change” of the shear viscosity with known fresh grease. The velocity gradient between the plates is given as the shear rate in 1/s. s (Pascal seconds) and specified as shear viscosity for lubricating greases.The resistance between the upper and lower plates can be measured as dynamic viscosity in Pa This simulates the behaviour of the grease in the lubrication gap in a practically-oriented manner. An upper plate of equal size is lowered to 1 mm from the lower plate and then rotated. This allows information about the change in penetration to be obtained indirectly.ĭuring the analysis, a grease blob is applied to a lower plate with a diameter of approx. It measures the change in “dynamic viscosity” or shear viscosity based on 1.5 ml of grease. In these cases, a rheometer (rotational viscometer) is used. Especially in bearings with low grease filling, the amount required for penetration measurement is sometimes not available because the grease has already been consumed for the other analyses. An OELCHECK grease sampling hose holds 9 ml, a sufficient amount of grease for all tests.

Relative viscosity test