EXPLANATION
Apparent viscosity versus shear rate information is useful in predicting pressure drops in grease distribution systems under steady-state flow conditions at constant temperature. This test covers measurements in the temperature range from -53 to 37.8° C(-65 to 100° F). The measurements are limited to the range from 25 to 100 000 poises at 0.1 s(-1) and 1 to 100 at poises at 15 000 s(-1). At very low temperatures the shear rate may be reduced because of the great force required to force grease through the smaller capillaries. Precision has not been determined below 10 s(-1).
TEST SUMMARY
The sample is forced through a capillary by means of a floating piston actuated by the hydraulic system. From the predetermined flow rate and the force developed in the system, the apparent viscosity is calculated by means of Poiseuille's equation. A series of eight capillaries and two pump speeds are used to determine the apparent viscosity at 16 shear rates. The results are expressed as a log-log plot of apparent viscosity versus shear rate.
TEST PRECISION
The repeatability and reproducibility values are as percent of mean.
The bias of this test method has not been determined.