Brookfield KU-2 Viscometer - Manual (Page 8)

Brookfield Engineering Labs., Inc. Page 8 Manual No. M04-242-D0612
I.8 Viscosity Units
The Krebs Unit is a special measure of viscosity that is not based on the Newtonian model of
flow. The ASTM test method D562 was originally developed around the special conditions of an
instrument that used gravity to drive a paddle spindle at 200 rpm. The weight required to achieve
200 rpm varied depending upon the viscosity of the fluid under test. The Krebs unit was devel-
oped through the correlation of the weights used and the time required for 100 revolutions of the
paddle. The ASTM standard also provided a correlation from Krebs Units to the scientific measure
of viscosity in centipoise.
The Grams scale represents the weight required to drive the paddle through the test fluid at a rate
of 200 rpm. The gravity drive system specified in ASTM D562 required that the weight be varied
until 100 revolutions were achieved in 30 seconds (200 rpm). The KU-2 drives the unit at 200 rpm
automatically and provides the grams value that would be required on the gravity drive system.
The grams scale is not a viscosity unit.
The Centipoise scale is available through a correlation originally defined in the ASTM test method.
Since this value is based on the Krebs Unit, it is not equivalent to centipoise values determined using
other types of viscometers, such as the Brookfield RVDV-I+. The centipoise values displayed on
the KU-2 are for reference only. Comparisons to measured values from other instruments should
not be made.
I.9 Cleaning
Make sure the instrument is in a decent working environment (dust-free, moderate
temperature, low humidity, etc.).
Make sure the instrument is on a level surface.
Hands/fingers must be clean and free of residue sample. Not doing so may result in
deposit build up on the upper part of the shaft and cause interference between the shaft
and the pivot cup.
Be sure to remove the spindle from the instrument prior to cleaning. Note left-handed
thread. Severe instrument damage may result if the spindle is cleaned in place.
Instrument and Keypad: Clean with a dry, non-abrasive cloth. Do not use solvents
or cleaners.
Immersed Components (spindles): Spindles are made of stainless steel. Clean with a non-
abrasive cloth and solvent appropriate for sample material.
When cleaning, do not apply excessive force, which may result in bending spindles.