Page 35 - Energize May 2021

TECHNICAL

Measuring viscosity made easy

by Steven Lumley, WearCheck

ondition monitoring specialists, To measure viscosity:
WearCheck, recently launched a • Once you have taken your sample of used oil, allow sufficient time for the oil sample to
Cquick, cost-effective viscosity test cool down to approximate room temperature. It is essential that both the used oil sample
kit known as the WearCheck Rheo-stick. and the unused oil sample are at the same temperature.
It is important to know the viscosity • When at room temperature, add 5ml of used oil to the used oil reservoir on the Rheo-stick
(thickness) of a lubricant because this by means of a clean 5ml syringe. Using new oil of the same brand/grade as the used oil,
determines its film strength and its add 5ml to the fresh oil reservoir by means of a clean 5ml syringe. The reservoirs must be
efficiency in preventing friction between filled with exactly 5 ml of oil. Therefore, the use of syringes is highly recommended.
moving parts. Thick oil has a high viscosity, • Tilt the viscosity comparator until it rests on the angled base at the opposite end from the
and thin oil has a low viscosity. Rheo-stick reservoirs and allow the oil to run down the channels. When the new oil reaches the mid-
got its name from the word “rheology”, point on the scale, return the Rheo-stick to the horizontal.
which is a branch of physics that deals • Observe the point reached by the used oil.
with the study of the deformation - and • If the used oil has not reached the scale, then the viscosity is higher than the new oil.
specifically the flow - of matter, such as • A high viscosity could be attributed to oxidation or degradation due to extended oil drain
lubricating oils. intervals, high operating temperatures, presence of water, presence of other oxidation
The most important rheological catalysts or the addition of an incorrect lubricant.
property of a lubricant is its viscosity, or • If the used oil has over-run the scale, then the viscosity is lower than the new oil.
a fluid’s resistance to flow. Viscosity is • A low viscosity could be attributed to degradation of the viscosity index improver (VII)
a property of significance as it affects additive in the oil as a result of shear or due to the use of an incorrect lubricant during
tribological qualities such as friction and refilling and topping-up procedures or fuel dilution.
wear between interacting metal surfaces. • After termination of the test, clean the equipment with a suitable degreasing solvent
If oil is too thick for the operating and dry thoroughly with WearCheck laboratory tissues. Dispose of the waste tissues in
conditions, the machine is forced to accordance with regulatory disposal legislation practices. n
work harder, thereby generating extra
heat and using more energy. This results To order a Rheo-stick kit, please contact your local WearCheck representative.
in unnecessary wear and tear on the To view a video on how to use this tool, please click here
components.
The opposite is also true - if a Contact WearCheck, Tel 031 700-5460, support@wearcheck.co.za
lubricant is too thin, the film may not be
thick enough to prevent friction. This also
creates unnecessary wear and tear.
The Rheo-stick is a user-friendly
visual viscosity comparator intended
to monitor changes in the viscosity of
lubricating oils. The Rheo-stick is suitable
for oils with a viscosity range from 32cSt
to 680 cSt @40°C.
While the Rheo-stick is an effective
on-site viscosity comparator, it does not
measure the physical viscosity of the oil in
centistokes and cannot give an indication
of the chemical composition of the oil
nor identify specific contaminants nor
degradation by-products.
To perform the viscosity comparator
test you require two clean 5ml syringes,
the Rheo-stick, a sample of the used oil
in question, a reference sample of new oil
of the same brand/grade and finally a flat
surface on which to work.

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