Maintenance and Reliability
AS I SEE IT
JIM FITCH NORIA CORPORATION
Using 'UNSCHEDULED'
Oil Analysis for EARLY
PREDICTIVE Maintenance
Most oil samples are taken based
on a fixed schedule. For large,
stationary rotating equipment, monthly or
bi-monthly samples are common. Proactive maintenance programs depend on
regular checks for oil cleanliness, dryness
and lubricant quality. However, machines
can and do fail for a variety of reasons,
and there is a certain randomness to the
onset of these failures. Furthermore, the
failure development period is equally
unpredictable, with some failures taking
months to develop, while others are
sudden and abrupt.
In the March-April 2013 issue of
Machinery Lubrication, I addressed machine
criticality analysis as an essential tool to
define the Optimum Reference State
(ORS) for numerous lubrication and oil
analysis activities. The Overall Criticality
Matrix (OCM) is constructed from two
assessments: the Machine Criticality
Factor (MCF) and the Failure Occurrence
Factor (FOF). The MCF relates to the
consequences of machine failure while the
FOF relates to the probability of machine
failure. Both the MCF and the FOF are
highly influenced by the effectiveness of
"early fault detection." In other words, the
effectiveness of early fault detection
sharply reduces machine criticality (for
details on this, read the article at www.
machinerylubrication.com/Read/29346/
machinery-criticality-analysis).
This is the critical link to the "unscheduled" oil analysis strategy. Its theme is not
Figure 1. Early Predictive Maintenance P-F Interval Scheme
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May - June 2013
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