The Power of Information -- Take
Motor Maintenance Tip, Part
OCPDs and Short-Circuit Current
NEC in the Facility
Answer to Electrical
About This Newsletter
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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
Managing energy use
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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.
The Power of
Information -- Take 4
Three types of information can take maintenance to the
next level of performance:
- Replacement parts information. Hunting around for spare
is inefficient. Installing the wrong part can cause massive failure.
critical spare parts, identify part numbers, acceptable substitutes,
sources, and lead times.
- Software documentation. Today, software documentation is
seldom in print form. Typically, you access it via the Help menu, which
may be online or resident in the software. Producing a paper archive of
documentation can create an “information silo” that does more harm
than good. Instead of printouts, keep a record in your system of the
following: default settings, your settings, revision history (with
and exactly what was changed), license codes or keys, and vendor
information (URL and e-mail).
- Supplemental information. This includes technical bulletins,
upgrade information, user group information, and training materials.
Many training materials today are online and in video form.
Tip, Part 15
Excess vibration destroys motor bearings, windings, and
even cases. Vibration causes are usually mechanical: excessive belt
tension, defective ball or sleeve bearings, misalignment, imbalance, a
weak motor base, or a weak motor pad.
The most common cause of vibration is an unbalanced rotating part,
such as the rotor, a drive train component, or the rotating load. The
motor rotor is the least likely culprit. If you uncouple the
motor from the load and run it, you usually find the vibration is gone.
This means you have isolated the problem to the load.
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After a system crash and restore, the control system
Line 3 isn’t working. The operators can see their controls, but they
can’t get the system to respond to control commands. Is it time to
make a panic call to the equipment vendor, or is there something you
do to restore operation?
The answer to this question appears at the end of this
Repair on some equipment requires special tools,
fixtures, or test equipment. Make sure these special items are there
serviceable before the need for them arises.
One technique for making this happen is to create equipment-specific
repair kits, and keep them at the equipment or in a cabinet nearby.
way, you never spend precious downtime walking around looking for
things. If these kits contain any consumables (e.g., special greases),
put them on a PM schedule so they’re ready when you need
Short-Circuit Current Ratings
The NEC requires overcurrent protection devices (OCPDs)
to clear a fault without extensive damage to the electrical components
of the circuit [110.10]. The short-circuit current rating of each
component in the circuit is one of the factors 110.10 requires you
consider when selecting OCPDs.
NEC in the Facility
Most facilities contract out the installation, repair,
and maintenance of chillers and HVAC systems. This makes sense for many
reasons, including licensing requirements pertaining to the coolant.
However, it has a downside. The techs of the typical HVAC firm are
mechanical, not electrical. Violations of Art. 440 (and several other
Code requirements) naturally result from such a situation. Violations
typically get caught after job completion, when resolution costs more
than doing the job right the first time.
The obvious solution is to review plans and drawings prior to
commencement of the work. Review the work in progress to ensure those
plans and drawings are being followed. The most common errors
Misapplication of raceways is another common error, occurring in both
- Design stage: Circuit protection.
- Installation stage: Location of disconnects.
Work neatly. To many people, this idea belongs in the
category of good workmanship, not safety. Yes, working neatly is a
proven way to do work that looks good. But it’s also a proven way to
prevent lethal errors.
Good housekeeping doesn’t mean cleaning up after the job is done.
It means making neatness part of how you do your work. A messy
is a dangerous workplace. Think about the number of tripping hazards
presented by a few scattered tools or boxes. Keep work areas free of
debris, scrap, and loose parts.
But this goes well beyond tripping hazards. As you work, make sure
you aren’t leaving yourself exposed to the additional hazards of
slipping, and cutting. Examples:
- Fire. Small spills of solvent. Clean these up immediately.
- Slipping. Small spills of cable lube. Clean these up before
you start the next pull.
- Cutting. So, you’ve made a nice hole in a cabinet for that
control switch. Remove any burrs from that hole and clean up the metal
Electrical Troubleshooting Quiz
Today, a system may consist of several subsystems
provided by multiple vendors, each with their own software licenses.
systems tend to be modular, and each module (subsystem) must work for
the system to work. For example, a production control system might have
a Crystal Reports license for sending managers statistical process
control (SPC) reports, along with an interlock that prevents operation
if this subsystem isn’t running.
In the case of a system crash and restore, you may need to reinstall
licenses so you can run the full version instead of the demo. You will
probably have to replace factory default settings with those you were
using prior to the crash. To get the system running, start by resolving
any error messages and network access issues.
If you set up your maintenance system correctly, you should have a
listing of the licenses (typically a text string, but possibly a token
or XML file) and a record of the required settings for each of
the various subsystems. It’s now just a matter of checking to see
every subsystem has its license and the settings are correct. That
process is fairly quick and painless.
But if you don’t have your maintenance system set up correctly,
will have to locate the license keys — possibly by digging through
archived e-mails. The next challenge is determining the correct
settings. If the necessary settings aren’t on record, you will
essentially need to re-engineer the system.
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