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Engines, most gearboxes, rolling-element
bearings and most hydraulics are among the
types of equipment that are most likely to
produce magnetic wear particles.
A ferrogram is easy to heat-treat for
identification purposes and has excellent
transmission of bottom light. Unfortunately,
the particles tend to pile up, and the prepara-
tion equipment is generally more expensive.
On the other hand, a filtergram has no
bias toward ferrous particles and is easy to
prepare. e necessary hardware is also less
expensive. However, it is more difficult to
distinguish metal types and to prepare two
membranes (one ferrous and one non-fer-
rous). Special patches are also required
for heat-treating, and the transmission of
bottom light is not as effective. Equipment
with critical non-ferrous frictional surfaces
include worm gears, stainless-steel machinery
and turbomachiner y with bronze or
Babbitt bearings.
A patch test, also called patch ferrog-
raphy, can be used to collect all types of
solid particles in oil, since the fluid is simply
filtered through a patch or paper. With this
method, there is no bias toward a ferromag-
netic element or metallic debris.
After particle samples are taken and
analyzed with a microscope, it is possible to
ML
heat the sample to observe color changes in the
particles. is helps to identify the metal type.
is procedure is typically run in ferrograms.
For reference, be sure to consult the
corresponding ASTM methods (D7684-11
and D7690-11). Noria's oil analysis training
courses can also provide more information
about these techniques and the value of
oil analysis. ML
If you have a question for one
of Noria's experts, email it to
editor@noria.com.
CALL 203.288.3509
W W W . D E X S I L . C O M
One Hamden Park Drive, Hamden, CT
ON-SITE Condition Monitoring
of Industrial Oils
Titra-Lube
®
TBN
ASTM Method D-5984-96
Quantitatively determines total
base number in lubricating oils
Titra-Lube
®
TAN
Correlates with ASTM Method D-664-04
Quantitatively determines total
acid number in lubricating oils
HydroSCOUT
®
Quantification
of Water in
Lubricating and
Industrial Oils
ON-SITE OR
LABORATORY SETTING
● Range: 50-10,000 ppm
total water
● Results in less than
4 minutes
