Motor Maintenance Tip, Part
Repair Your Procedures, Too
Fuses and Motors
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.
Planning, scheduling, and assigning are core functions
of maintenance management. How well do you perform these tasks?
When you plan maintenance work, you do such things as
the scope of work, identify the tasks within that scope, and properly
sequence the tasks. You also identify the needed resources, such as
parts and test equipment. A good PM program contains plans for all
When you schedule maintenance work, you prioritize work and
determine which jobs will be done on what days. Part of the scheduling
function is to coordinate with other groups for shutdown, entry,
operation, and testing. Also, remember that parts and supplies must
arrive on schedule.
Assigning means deciding who will do the scheduled work. At a
minimum, you assign work to qualified personnel only. Factoring in the
career development of individuals is essential to a first-class
maintenance operation. Do you formally track experience and training to
Tip, Part 16
If you have “mysterious” corrosion, evidence of
current destruction in bearings, excessive harmonics, or odd voltage
readings, it’s time to visit your grounding system -- or would that
your bonding system?
It’s unlikely your grounding system has anything to do with these
problems. If you’ve been chasing “grounding issues,” then you
to turn your attention to Article 250, Part V — which is all about
bonding. If you’ve been grounding where you should have been
bonding, the problems just mentioned are inevitable.
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An office worker received a nasty shock when hooking up
a printer. You found no obvious cause, such as a damaged power cord.
measured between the receptacle ground and a metal screw on the back of
the printer and read zero volts. What else might you measure?
The answer to this question appears at the end of this
Over the past couple of decades, various initiatives,
such as ISO9000 and TQM, have influenced maintenance practices. One of
the positive developments was the documentation of repair processes.
People performing repairs without written procedures were said to be
“repairing per trade craft.” That’s another way of referring to
the “wing-it” method.
Documentation allows you to standardize each repair process to what
is presumably the best procedure. But in many facilities, the
documentation has become so unwieldy over time that people ignore it
revert back to the wing-it method.
Review your documentation for bloat, and ruthlessly cut it.
Otherwise, its existence is pointless.
Fuses and Motors
If you use fuses for motor overload protection in a
3-wire grounded system, you must insert a fuse in each ungrounded
conductor and also in the grounded conductor [430.36].
NEC in the
You’re supposed to make appropriate provisions to
minimize the possibility of damage to transformers from external causes
where the transformers are exposed to physical damage [450.8(A)].
Noticing that the only protection for a 75kVA transformer was a
caution sign, a facility manager had a bollard installed in front of
Later that same week, a lift truck driver drove around the bollard and
hit the transformer. Lesson: Sometimes, an obvious improvement may
not be enough.
You’re not required to prevent mechanical damage, but failing to
minimize the likelihood can leave you open to personal liability for
damages. You don’t want to be the person blamed when a lift truck
driver takes out a critical transformer, and you certainly don’t want
people injured or killed in your facility.
To comply with 450.8(A):
- Examine the transformer environment for potential sources of
- Analyze mitigation steps, such as relocating the transformer or
reconfiguring specific aisle ways.
- Evaluate physical barriers for adequacy. For example, two bollards
spaced at less than the width of a lift truck will prevent lift truck
- Erect physical barriers per standard practices. For example, anchor
bollards at sufficient depth.
- Add barrier inspection to your PM schedule. Where there is evidence
of repeated strikes on a barrier, something is wrong, and it’s only a
matter of time before that barrier is breached or somebody is injured.
Fix the underlying problem.
Most safety training programs are generic in nature,
with companies using safety program materials they bought from a third
party. Although these programs do a tremendous amount of good, they
don’t tell you everything you need to know.
Some safety facts pertain specifically to your facility. Make sure
- Who the emergency responders are and how to contact them.
OSHA requires employers to post the phone numbers of ambulance
fire departments, police, and other emergency responders. Program
emergency numbers into your cell phone. Know the location of the
- What to do. Learn the emergency procedures as they apply to
- Where things are situated. Know the location of emergency
equipment, such as E-stops, first-aid kits, fire alarm pulls, fire
extinguishers (look for red bands on columns), emergency showers, and
- How to get to safety. Memorize the emergency exits and
evacuation routes for every room you pass through or work in.
Electrical Troubleshooting Quiz
Measure between the network cable connector and that
receptacle ground, and you will likely read a voltage. But why is it
If installed correctly, the branch circuit ground conductor runs
to the panel. If installed correctly, the ground conductor on the
network cabling is bonded to that same point. However, network cabling
is often installed incorrectly.
The network installer, in this case, probably drove a ground rod and
bonded to that instead of to the grounding point used by the power
supply. This means the branch circuit and the network have a difference
of potential — which you can subsequently read on your DMM at the
Usually, the easiest way to fix this problem is to bond from that
driven rod of the network to the grounding point of the power system.
the location of the driven rod makes this impractical, you will
need to remove the rod and run a bonding jumper “farther upstream.”
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