Viscosity - D445-97
Significance and Use
Many petroleum products, and some non-petroleum materials, are used as
lubricants, and the correct operation of the equipment depends upon the
appropriate viscosity of the liquid being used. In addition, the
viscosity of many petroleum fuels is important for the estimation of
optimum storage, handling an operational conditions. Thus, the accurate
determination of viscosity is essential to many product specifications.
Summary of Test Method
The time is measured for a fixed volume of liquid to flow under gravity
through the capillary of a calibrated viscometer under a reproducible
driving head and a closely controlled and known temperature. The
Kinematic viscosity is the product of the measured flow time and the
calibration constant of the viscometer.
Very closely allied to this test method is: ASTM D446-97: Standard
Specifications and Operating Instructions for Glass Capillary Kinematic
Viscometers. In actual practice, the first does not exist without the
When we are told the kind of oil we are testing, we can use this test to
determine whether it is on specification, whether it is thickening and
whether it is thinning out; there are limits to how much thinning or
thickening can be tolerated.
Notwithstanding the fact that we are bound to signal an
“off-specification” viscosity result, there are times when, whether the
viscosity is off or not, we are required to do some “extra” testing so
that we may better interpret (analyze) the test result obtained. In the
case of oil thickening this may be Infra-red Spectrometry or “Fuel Soot
Actual Determination” In the case of oil thinning we would do a Flash
Point Test or a Simulated Distillation. NOTE: These tests are covered
One way or another, other routine tests or extra tests or both are often
needed to interpret the test result obtained.
For more information about viscosity units click here.