Avoiding "Too Little"
Maintenance, Part 2
Motor System Repair Mistakes,
NEC in the Facility
Answer to Electrical
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MRO Insider addresses topics such
Working with management and supervision
National Electrical Code® on the production floor
Safety procedures and programs
Equipment maintenance and testing tips
Managing motors and generators
Trends in training and education
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The designations "National Electrical Code” and “NEC” refer to the
National Electrical Code®, which is a registered
trademark of the National Fire Protection Association.
Do you manage assets, or do they manage you? To control
assets and events rather than simply reacting to them, plan your work
on information that is detailed and accurate.
Use your computerized maintenance management system (CMMS) as more
than just a work order system (you are on a CMMS, rather than paper,
aren't you?). A fully and properly utilized CMMS provides you with the
knowledge you need to properly manage every asset. For example, you
should be able to run a report on any piece of equipment and know:
With this information, you can correctly determine priorities and
allocate resources to meet them. Think about how you can use this
information to improve your maintenance process.
- History (downtime, modifications, PM, PdM, repair).
- Financial data (repair costs, annual revenue, daily minimum
- Parts and assemblies information (lead times, sources, costs,
- Drawings, manuals, software revision level, and MSDS
- Procedures for testing, troubleshooting, PM, PdM, and repair.
- Test equipment and PPE.
- Training and qualifications.
Little" Maintenance, Part 2
The tendency to "save" money by cutting back on
maintenance persists, despite its staggering costs. The decisions are
usually made by spreadsheet, rather than by intelligent analysis of
conditions in the plant.
Why does this happen? Imagine three people from dissimilar cultures
trying to discuss a complex topic -- one speaks Chinese, one speaks
Russian, and one speaks French. Even their alphabets are vastly
different. This is similar to the situation that normally exists around
maintenance expenditures. Typically, maintenance people speak
managers speak "ROI," and financial people speak "net present value" or
"cash flow." These are incompatible languages.
You can learn to speak all three languages fluently by spending a
hours with a book on financial analysis. Then, you can make your case
the language each level of gatekeeper can understand. This is the only
way you can prevent mixed signals, false assumptions, and expensive
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A critical conveyer stopped three times in the past
month. It stopped again, just moments ago. The production supervisor
hands you three heater-style motor overloads and says, "I kept spares
my desk after the last shutdown. All you have to do is replace these,
and we're good to go."
What's wrong with the supervisor's assessment, and what should you do?
The answer to this question appears at the end of this
Repair Mistakes, Part 2
We know to record "as founds" before changing anything
for PM or repair. With motor systems, this is especially critical.
However, this step is often omitted when production is down and
Fortunately, most of the "as founds" won't change during a motor
system repair. It's better to have incomplete "as founds" than none at
all. If the repair doesn't require motor removal (e.g., open overload),
then before you change anything check:
If the repair requires removing the motor, then also check:
- Weatherhead. Look carefully for signs of trouble, including
three key points -- bolt tightness of the cover, gasket integrity, and
evidence of moisture ingress.
- Connections. Visually inspect, then measure resistance
them (make sure power is off).
Checking these few items is a compromise that may not reveal the
cause. Not checking them "as found" may obliterate evidence that could
have identified the cause of failure.
- Motor/load alignment. A few measurements with a straightedge
and tape rule reveals gross misalignments.
- Condition of motor feet (unless face-mounted). A common
response to vibration is to tighten the mounting bolts, which usually
causes overtightening and warped motor feet. Look carefully at those
feet before loosening the bolts to remove the motor.
- Condition of motor pedestal and base. Look for cracks,
warping, and other deficiencies while the weight of the motor and
tension of its fasteners is bearing on those structures.
Motors don't fail by pure chance. Schedule a complete PM/PdM to be
done within 48 hours. Before performing the PM/PdM, check the supply
voltage. If any two phases differ by more than 2% of the nominal
voltage, that motor will prematurely fail -- and you already know the
NEC in the
You have a work request for installing 16A of 120V task
lighting for some workbenches along one wall of a room that contains
several hot injection molding machines and a large curing oven. The
circuit originates in a lighting panel in a room adjacent to the
opposite wall. The drawing shows 1/2-inch EMT running along the
You may have a code violation. Use a "heat gun" or thermal camera to
determine the temperature in that proposed raceway path. If the
specified wire isn't rated for that temperature (per the ampacity
tables), then you have a violation of 410.24. Reroute or upgrade, as
needed. Be sure you account for the season. A February reading won't
give you the August temperatures.
Make these two safety habits part of the maintenance
of doing things:
- Be proactive. Think ahead to protect people and property.
Ask, "What could go wrong?" Then, follow the procedures that prevent
and/or minimize those hazards.
- Follow the rules. A common misperception is that safety
are more stringent than they need to be and it's OK to cheat on them.
The reality is that today's safety rules were "purchased" with the
injuries and deaths of people doing the same work you're doing. There
no reason for you to pay that bill again, so don't.
Electrical Troubleshooting Quiz
Repeated interruption of a critical system is normally
greater problem than a period of downtime long enough to prevent those
repeats. If the heaters are burning open this often, the heaters aren't
the problem. The problem is whatever anomaly they are protecting the
The fact that the motor runs for many days with new heaters is helpful.
A good start on solving this problem would be to:
- Take those quick "as found" data mentioned earlier.
- Replace the heaters.
- Take complete "as left" data.
- Use a power analyzer on the supply to check for voltage imbalance,
harmonics, and low power factor.
- Perform PdM within the next 48 hours.
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