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March - April 2014
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www.machinerylubrication.com
As I see It
influence this probability are shown below. Collectively, the DOF
is scaled 1 to 10.
Lubricant Robustness — Synthetics and other chemically and
thermally robust lubricants lower the DOF.
Operating Temperature — Lubricants exposed to high oper-
ating temperatures, including hot spots, can experience accelerated
oxidation and degradation. The presence of such conditions will
raise the DOF.
Contaminants — Contaminants such as water, dirt, metal parti-
cles, glycol, fuel, refrigerants, process gases, etc., can sharply
shorten lubricant service life. The presence of such exposures will
raise the DOF.
Lubricant Volume and Makeup Rate — Lubricant volume
relates to the amount of additives available to fight oil degrada-
tion, the estimated runtime to complete additive depletion and the
density of contaminants. In normal service, it can take years to
burn through the additives in systems containing thousands of
gallons of lubricant. The makeup rate refers to the introduction of
new additives and base oil. New additives replenish depleted addi-
tives, and new base oil dilutes pre-existing contaminants. High oil
volume and a high makeup rate will reduce the DOF.
Armed with both the OMC and OLC, lubrication and reliability
professionals have the foundational elements needed to better
design lubrication and oil analysis condition monitoring programs.
While some guesswork may be required, using this method will
prevent wild guesses. In turn, extreme waste and poor reliability
can be avoided.
The goal is to optimize maintenance and reliability decisions.
Understandably, best practice varies considerably from machine to
machine. Precision lubrication is another way of saying one size
does not fit all. It's time to get it right. In the next issue of Machinery
Lubrication, this topic will be explored further in the context of oil
analysis and inspection.
About the Author
Jim Fitch has a wealth of "in the trenches" experience in lubrication,
oil analysis, tribology and machinery failure investigations. Over the past
two decades, he has presented hundreds of courses on these subjects.
Jim has published more than 200 technical articles, papers and publica
-
tions. He ser ves as a U.S. delegate to the ISO tribology and oil analysis
working
group. Since 2002, he has been director and board member of
the International Council for Machinery Lubrication. He is the CEO and
a co-founder of Noria Corporation. Contact Jim at jfitch@noria.com.
Figure 3. The Overall Machine Criticality (OMC) matrix includes the Machine Criticality Factor on the X-axis, the
Failure Occurrence Factor on the Y-axis and five risk zones, each represented by a different color.
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