4
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July - August 2014
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www.machinerylubrication.com
As I see It
due to limitations in alarming to weak
failure signals.
As shown in Figure 2, the detectability of
faults gets easier as failure advances.
However, even silent alarms associated with
incipient, early stage faults and failures can
be heard when oil analysis and vibration
analysis are performed with considerable
skill. For instance, sampling machine return
lines and keeping oil clean (to reduce data
clutter) can sharply improve the signal-to-
noise ratio to enable early detection of
even the weakest signals. The earlier the
detection methods are deployed, the less
costly and disruptive the machine failure is
to the organization.
What the P-F interval Can
Tell You
The smart money in machine reliability
invests not only in frequent detection of
faults and abnormal wear but also in
frequent detection of root causes. Using the
Pareto principle, you can concentrate
HIGH
LOW
HIGH
LOW
ROOT CAUSE
ZONE (A)
INCIPIENT
FAILURE ZONE (B)
IMPENDING
FAILURE ZONE (C)
ROOT CAUSE
ZONE (A)
PRECIPITOUS
FAILURE ZONE (D)
POST-MORTEM
RCA ZONE (E)
TIME
TIME
Failure
Inception
Failure
Detection
Functional
Failure
P
F
Root Cause
Adjustments
(No machine
damage)
Root Cause
Adjustments
(Minor machine
damage)
Scheduled,
Moderate Cost
Repairs
Expensive
High
Downtime
Repairs
Protective Domain
(Damage control)
Predictive Domain
(Symptom detection)
Proactive Domain
(Root cause
detection)
Catastrophic
Failure
Cumulative
Harm/Cost
to
Organization
Machine
Health/Condition
FiGURE 3. How the P-F interval relates to the cumulative harm/cost to the organization
