Down With Documentation
Motor Maintenance Tip, Part
NEC in the Facility
Answer to Electrical
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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.
Mention "documentation" and many maintenance people
glance nervously about for the nearest exit. After all, the thinking
goes, sitting around filling out paperwork or massaging spreadsheets
doesn't get equipment running or keep it from failing in the first
place. That thinking ignores what documentation can really do, such
Document your results, and submit regular reports to all stakeholders
(managers, maintenance employees, and operations people). We have just
looked at why you should. In our next issue, we'll look at how you
should go about doing this.
- Show the ROI on maintenance. Company managers need to see a
return on maintenance dollars invested. In an information vacuum,
maintenance dollars are the first to be cut when budgets are set.
- Justify future maintenance expenditures. Gatekeepers
typically believe spending more on maintenance won't have a noticeable
effect on operations. Show them otherwise.
- Show how maintenance efforts, properly supported, directly
increase revenue and profits. In addition, they directly improve
- Show areas needing improvement. Guesswork doesn't cut it.
Document those failure causes that are the highest frequency and most
expensive. That way, you'll know which ones to solve first.
- Show the maintenance team where they've done well. A sense
pride and accomplishment is one of the best possible motivators.
- Show operators how their teamwork with maintenance improves
job security. What happens when operators can clearly see the
results of cooperating with, rather than fighting, maintenance? They
become key allies in the maintenance effort.
- Improve your own resumé. A good resumé succinctly
shows what you accomplished and monetizes those accomplishments. If you
haven't been documenting things, you can't articulate them in an
interview or on a resumé.
Tip, Part 6
A 3.5% voltage imbalance produces a 25% rise in
temperature in the typical motor. This can cause a properly rated motor
to fail when it otherwise would give many years of service.
Whenever a motor trips, test for phase imbalance. You'll be taking
measurements anyway, so don't leave this one out. However, don't wait
until a motor trips before checking. On smaller motors, check this on a
routine schedule. On larger motors and on critical systems, monitor it
automatically and continually.
Your power monitoring system should provide a way to monitor
feeders or branch circuits -- if not, look into upgrading that
You can also install individual phase monitors. If you have an
electronic drive on a motor, see if the drive has this feature. If not,
consider upgrading the drive.
A "quick "fix" for a phase imbalance is to adjust the circuit
protection to prevent a trip. This merely masks the problem. Worse, it
can easily result in extended downtime while you're scrambling to find
replacement motor. Instead, track down the root cause and repair
NEW Fluke 568 IR and contact thermometer
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stand up to tough industrial, electrical, and mechanical
A production line motor trips its temperature overloads
at least once per day. After about an hour, they can be reset. The
draws the expected current, supply voltage is correct on all three
phases, power factor is good, and harmonics are minimal. What should
do? What is the likely problem?
The answer to this question appears at the end of this
In the typical plant, operators develop preferences for
who handles their repairs. Although it's true that people aren't
interchangeable parts, it's also true that repair techs should provide
level of service that isn't markedly different from tech to tech.
Operators should feel comfortable and confident with any tech. If they
don't, then petty complaints and phantom problems will undermine your
maintenance and repair efforts.
Here are some tips to keep in mind when developing your team
- Develop standardized troubleshooting procedures, based on best
practices. Find out what works best on specific equipment, document
that, and train everyone in those procedures.
- Train on interpersonal skills. People's emotions definitely
color their perception of reality, and how the repair tech speaks to
them influences their emotions. Yet, the typical maintenance
organization doesn't train its techs on how to interact in a manner
leaves operators feeling respected and confident that they are being
taken care of.
- Train on interview skills. The hardest part of the job for
some techs is getting an accurate description of the problem from the
operators. Some people seem gifted at this, while others beat their
heads in frustration. It's a learned skill, so ensure everyone is
NEC in the Facility
When you size the conductors for a continuous duty
motor, you select a conductor with an ampacity that is 125% of the
motor's full-load current rating [403.22(A)]. But some motors operate
a different duty cycle (e.g., periodic). Do you still size the
at 125%? The answer is, no. The inrush current required to start a
subjects the conductors to higher heat loading.
Your ampacity calculations must account for the duty cycle and
of the motor. This is where Table 430.22(E) comes in handy. It provides
you with the necessary multipliers for any combination.
Sometimes, a motor can be continuous duty but just not in all modes
of operation. An example would be a batch tank impeller motor. When in
mix mode, the motor runs continuously. But in batch storage mode,
perhaps the motor runs intermittently. So, which way do you classify
motor? When confronted with such a question, see the Note in Table
Look carefully at your safety manual. Often, such
manuals are filled with legalese and OSHA excerpts. They are often
bulked out with information, such as administrative procedures, of no
relevance whatsoever to the intended user. For safety manuals to be of
any real value, they need to be in plain language and apply directly to
the work and circumstance of their intended users.
Electrical Troubleshooting Quiz
The motor isn't cooling properly. You should use a
thermal imaging camera to inspect the temperature profile. If this
problem is fairly recent, ask, "What has changed?" However, what
hasn't been changed is sometimes the problem. On a production
line, a motor is often tucked into a tight place and has cooling air
supplied to it via filtered ducts. Check the air filter(s).
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