Practices for Preventive Maintenance
Example best practices and the
questions you need to ask to determine if your plant
is using them.
Partner, IDCON, Inc.,
a maintenance management consulting and training
Further information is
available by contacting
plants in different corners of the world, we often are
asked: “What are the current best practices for
preventive maintenance (PM)?” We usually answer that we
define preventive maintenance using 95 key elements. We
also point out, to some people’s dismay, that there is
no single silver bullet for improving PM, but rather
many combined efforts will be required to eventually
a few key elements that have been extracted from our
program of Current Best Practices (CBP) along with test
questions and best practice (BP) examples to help you
gauge how well your plant practices measure up.
Do you have a definition for preventive maintenance?
Interview test: Ask people in
maintenance and operations to define what is included in
Best Practice example: We have
a definition of preventive maintenance that is
documented, understood, and well communicated across our
definition of preventive maintenance is important for
good communication in meetings, improvement efforts, and
training seminars. For example, are detailed cleaning,
balancing, and alignment part of preventive maintenance?
Is operator inspection part of PM? Are operating
practices part of PM?
often attended meetings or interviews where we are told
a plant is continuously working on improving preventive
maintenance. When we ask for the plant’s definition of
PM, we notice that there are as many definitions of PM
as there are people. How can we expect to improve PM if
we are not clear on what PM really is? We define PM as
essential care and condition monitoring (PM/ECCM) as
shown in Fig. 1. Perhaps you can use the definition in
Do you know how satisfactory PM is done today?
Test: Ask the plant manager,
maintenance manager, and operations manager for the PM
improvement plan. If there is one, is it specific with
timelines? For example: “Lubrication storage improvement
complete by September 2003.”
Best Practice : Plant
management is aware of strengths and weaknesses of the
PM program. The plant therefore has specific plans and
timelines in place for improvement actions.
experience of Ian Farrell, maintenance manager at
UPM-Kymmene in Scotland, illustrates the awareness
factor. Farrell, whose company has deployed the CBP
education and training assessment in several plants in
the United Kingdom, expressed the experience of
interviewing people in the plants in a presentation at a
recent maintenance conference.
interviewed people in the plants to get a good idea of
how well PM is done. When initially asking a person how
well PM is done in the plant, the first answer is ‘Yes,
we do this all the time.’ After some more discussion and
specific questions around PM, the interviewee changes
the statement to ‘Well, we probably do this most of the
time.’ After more small talk and several cups of coffee
and more explanations around PM the interviewee states,
‘I know we definitely, sometimes do it.’
questions become more specific and the interviewee
downgrades the statement to ‘I think we do it.’ Time
passes and questions around, for example, alignment
standards, condition monitoring routes, and operator
involvement make the interviewee think of what good PM
really is, and the statement is changed to ‘Somebody
told me we did it.’ When we finally have defined what
best practices in preventive maintenance are and there
is a stack of coffee mugs, the person muses, ‘We used to
do it all the time.’”
defining what PM is, and then educating and training
people in the current state of their actual PM
performance, the groundwork for improvement is laid.
Do you have an alignment standard, and is it followed?
Test: Ask for an alignment
standard and check quality of standard. Go look at
equipment for signs of good or poor alignment.
Best Practice : There is a
well-documented alignment standard. More importantly,
the standard is followed.
world-class reliability and maintenance organization,
all alignments are done to 0.002 in. (0.05 mm) for
equipment running below 3600 rpm and 0.001 in. (0.025
mm) for equipment running above 3600 rpm. There is a
well-defined alignment standard explaining how to set
up, clean, check for pipe strain, check for soft foot,
tour of your plant. If alignment is done well there are
jacking bolts (push bolts) installed on all motors,
gears, and other equipment of significance. Bases and
foundations are in good condition and no more than four
shims are used under the motor feet (Fig. 2). Overall
vibration level is low in the plant (0.1 in./sec
unfiltered average). As a tracking indicator, see if
alignment records are kept for each alignment job.
Do you have a lubrication standard, and it is followed?
Test: The standard should
include storage, handling, filtering, and cleanliness of
lubricants. Visually check cleanliness of storage areas
Best Practice : There is a
well-documented lubrication standard. More importantly,
the standard is followed.
cleanliness standard for each piece of equipment should
match the clearances in the equipment’s lubricated
surfaces. For example, a hydraulic unit may need to be
filtered down to 3 microns (200 beta) and a gearbox to
12 microns (75 beta).
to reach the right cleanliness levels of lubricants, oil
and grease have to be stored, handled, and filtered
correctly. Few people know that new oil usually is
delivered at around 40 microns cleanliness level, which
means that oil going into equipment with fine clearances
should be filtered.
Are inspections (condition monitoring) done where it is
cost effective to do so?
Test: Go through inspection
lists, check for level of detail, and make sure the
route is actually completed.
Best Practice : There are
inspection routes for all mechanical, electrical, and
instrumentation equipment (where it is cost effective to
top-notch plant, inspections are documented and
completed according to schedule. The plant is using an
inspection list or, even better, a handheld computer.
The list or handheld computer describes exactly what to
do for each inspection. The inspections are a
combination of measuring condition and subjective (look,
listen, feel, smell) inspections.
inspections are completed while equipment is operating
because we do not want to waste valuable
shutdown/offline time on inspections that could be done
on the run. Inspections can usually be done better when
equipment is operating. For example, a pump cannot
really be inspected well when it is down since there are
no vibration, no operating pressures, and no seal water
To see if
your plant is performing according to world-class
reliability and maintenance standards, take an
inspection list, or handheld computer (if you do not
have inspection lists, it is time to develop them), and
walk the route. For example, check the following:
- Do we
have condition monitoring routes covering all
- Do we
use simple inspection tools such as a stroboscope,
infrared thermometer, vibration pen, industrial
stethoscope, bright flashlights (500,000 candela), and
- Can we
inspect couplings, belts, and chains on the run, or do
guards make it impossible (Fig. 3)?
inspections being done? Are oil glasses clean enough
to see oil levels, are base bolts clean enough to
people educated and trained in basic inspection
Is detailed cleaning of equipment done well?
Test: Take a walk in your
plant and visually check the cleanliness and condition
of the equipment.
Best Practice : Detailed
cleaning of equipment is done consistently. Dirty areas
are redesigned in order to protect equipment from
cleaning can be checked easily. For example, a clean
hydraulic unit can be inspected for leaks in about 10
sec by taking a quick look at the pan underneath the
unit (Fig. 4). A dirty hydraulic unit would take 20-30
min to check for leaks.
Is an ultrasonic or vibration monitor used when greasing
Test: Check lubricator’s
Best Practice : Vibration or
ultrasonic levels (or other method) are checked while
greasing in order to apply the correct amount of grease.
is done by measuring ultrasonic or vibration levels
while applying grease to the bearing. It is almost
impossible to know how much grease is applied to a
bearing without a measurement. The measurement tools
indicate to us when the grease hits the bearings and
monitor the vibration or ultrasonic levels as grease is
squeezed into the bearing. Over and under greasing can
be avoided by using the right tools. An alternate method
is to use a volume meter, assuming the required grease
volume for the bearing is known.
just a sample of the 95 points we use to evaluate plant
performance, these example tests and best practices
demonstrate the methodology by which one can build a
system for discussing performance levels.
Idhammar is partner and vice president of IDCON, Inc.,
reliability and maintenance consultants, 7200 Falls of
Neuse Rd., Suite 200, Raleigh, NC 27615-5384; telephone
Care and Condition Monitoring
Fig. 1. Essential Care (EC) includes preventing
failure from occurring, with tasks such as detailed
cleaning, lubrication, alignment, balancing, operating
procedures, adjustments, and installation procedures.
Fixed Time Maintenance (FTM) is all replacements that
are done on a fixed schedule regardless of condition,
e.g., programmed replacements and overhauls. Condition
monitoring (CM) is all inspections from simple
subjective look, listen, feel, smell inspections done by
operators or crafts people to objective vibration
analysis, oil sampling, ultrasonic leak detection,
pressure checks, current readings, etc.
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Fig. 2. Left: A motor has not been aligned properly. We
can clearly see the beat marks from the sledgehammer,
the motor is missing push bolts, and there are too many
shims under the feet. Right: A motor with the correct
set up to enable good alignment.
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Fig. 3. This equipment guard allows for on-the-run
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Fig. 4. The hydraulic unit on the left would take
20-30 min to inspect and identify leaks, while the
hydraulic unit on the right can be inspected for leaks
in about 10 sec by looking for oil in the pan underneath
Further information is available