Efficient Plant March 2022 - 14

feature | asset troubleshooting
tooling, and related parts will turn
freely and true-again, allowing
the troubleshooter to check other
places.
A predictive-maintenance
program aims to decrease
or potentially even stop
unexpected breakdowns.
Although not every single
component of a complex
machine can be analyzed
and studied for possible signs
of failure, you can expect that
the process of elimination will
greatly contribute to quickly
fi nding the culprit.
Some of the best clues to a problem's
source can be obtained from operators.
Suppose the machine ran fi ne for years with
When troubleshooting an
issue, start with the operator.
They likely noticed when
the problem fi rst appeared
and what changes indicated
something was amiss.
product A but introducing product B led to headaches.
In that case, you
may conclude that the
original machine design
was limited in scope and
not meant to operate on
anything but the initial
parameters. Or perhaps
the production department
recently decided
to increase output by
simply speeding up
the machine. Instead of trying to determine why
the VFDs are suddenly giving over-current trips,
maybe it just requires slowing the machine back
down to standard operation.
Start by asking the operators when this issue
fi rst appeared and if the machine operated
smoothly before then. An operator may have
noticed a specifi c sound or vibration that wasn't
present before.
Keep in mind that each person will diagnose
the problem based on their background and
existing knowledge of the process. Was the
maintenance department notifi ed about a broken
part? Has an electrician been resetting continual
VFD trips?
14 | EFFICIENTPLANTMAG.COM
Early in the fact-fi nding mission, there will be
various inputs about the importance of the corrective
action and how to expedite it. Downtime
is not productive for anyone, from production
supervisors to the management. However, it's
vital to understand that a temporary fi x may lead
to more problems down the road, not to mention
that safety should never be compromised. If
the PLC or VFD program must be modifi ed or
tweaked, make sure that you have hard copies of
all the original parameters. Th is will help return
the machine to normal operation if some other
component impairs performance.
Before making changes for testing, turn off the
Before making
changes . . . take
notes and pictures
of the existing
wiring and related
parts.
machine (for safety) and take notes and pictures
of the existing wiring and related parts. Th e
wiring may have been replaced or modifi ed over
the years and not refl ect the original prints. See if
the machine will run at any speed or on any type
of product. Th is may give you a baseline to test for
stability and proper operation.
Th ese steps will make it
possible to return to a known
starting point.
Instead of focusing on
the most likely suspect, ask
yourself what other factors
may be contributing to the
problem. Collect and study
drawings and wiring diagrams
to see what fi eld component
types are connected. A bad encoder on a vector
motor could cause a current overload trip on a
VFD instead of high amps. Dirty or misaligned
sensors may aff ect light-curtain operation or show
false detections. Almost every device that triggers
an alarm or experiences random issues may be
pointing you in a diff erent direction. Mechanics
will want to blame motors and electricians will
point at gearboxes, primarily because they're not
as familiar with the devices.
IMPLEMENTING SOLUTIONS
Once enough data has been collected to point
toward a specifi c component, replacement is only
the fi rst step. If a bad bearing in a gearbox has led
MARCH 2022
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Efficient Plant March 2022

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