Motor Maintenance Tip, Part
Stop Helping Us, Please
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
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 typical maintenance report isn't very helpful in
securing resources for the department. A lack of resources can keep you
from reaching your goals or even fulfilling your mission. Think of some
resources you needed but weren't able to obtain. Does your list
include downtime windows, special test equipment, additional working
space, and specialized training?
A persuasive report can change everything. If you were a production
manager, what benefits would cause you to give up some floor space or
agree to additional downtime? The following reasons are good ones:
Those first four reasons will motivate primarily when the benefit of
implementation exceeds the cost. Find out how much revenue each machine
or line produces per hour (and therefore loses when down). If your
reports clearly show that an increase in revenue is less than the cost
of achieving it, then they will help you acquire important resources.
bar charts work well.
- Increased reliability for critical orders.
- Increased overall output.
- Increased product quality.
- Reduced need for manpower.
- Increased safety.
Tip, Part 9
Motor overloads may open due to mechanical causes, such
as bearing seizure, misalignment, or a broken drive gear. Or, they may
open due to electrical causes, such as low system voltage, harmonics,
single phasing, or winding insulation failure. Human errors, such as
mis-operation and incorrect settings, are also possibilities.
To discover the cause, where do you begin? First, check your
supply for any anomalies. Then, examine the driven load, including how
it's coupled to the motor. If you find no problems, you have
significantly isolated the cause. At this point, you can probably use a
motor troubleshooting checklist to determine that cause.
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stand up to tough industrial, electrical, and mechanical
A good motor shop provides many valuable services, such
as motor rewinding. One service that can save you money on large motors
is motor forensics. The shop can tell you what is wrong with a failed
motor and probably what caused that problem. At what motor size (and
below) does the investment in this service not make sense?
The answer to this question appears at the end of this
Stop Helping Us,
Nonessential personnel may not only slow down a repair
operation, but they can also introduce repair errors and complicate
safety. For example, a corporation with 12 plants had its headquarters
at the site of one plant. Any time production stopped, vast clouds of
managers would swarm out of the offices and descend like flies onto the
production floor, where they buzzed around the repair techs. The wall
bodies made it difficult for the techs to work, as did the constant
chatter, questions, and "advice." This extended downtime
You may not have interference to this degree -- maybe you just have
"tolerable" interference from well-intended but unnecessary
personnel who pretty much stay out of the way. Nevertheless, this still
slows you down, and it still complicates safety.
The solution is to rope off the area and enforce the restricted
access. In addition to making it easier for repair techs to work, this
prevents exposure of unneeded personnel to the dangers inherent in a
Nobody likes waiting for an out-of-stock fuse while
critical equipment is down. An obvious solution is to have all critical
fuses in stock. However, that leaves you with the problem of having to
spend downtime finding each fuse in the stockroom. The solution to this
problem is to maintain a complete set of clearly marked replacement
fuses at the protected equipment.
For example, inside the control cabinet for Line 4 is a box that
contains all of the power and control fuses for Line 4. However, this
solution also presents a potential problem: The risk of, "I'll just
stick this in and see what happens."
The solution is twofold. First, ensure the operations group has a
"no-operator-touches-a-fuse" policy. Second, write procedures for
replacing fuses in specific equipment. Include a listing of the
drawings, NFPA 70E information, pre-replacement tests, and how to
perform shutdown/startup. The procedures should be in your CMMS and
available on demand.
May 5 - 7, 2008
Battcon International Stationary Battery Conference,
Marco Island, Florida
This user-oriented conference on the applications and issues of storage
battery power systems draws users, battery and equipment manufacturers,
installers, R&D, and safety experts from power and telephone companies
and UPS manufacturers. Includes technical presentations, panels, and
Jennifer Stryker, Albércorp/Battcon, 3103 No. Andrews Ave. Ext.,
Pompano Beach, FL 33064. (954) 623-6660. www.battcon.com.
NEC in the Facility
Are you updating a motor overload protection or a motor
controller? You can use a motor controller as overload protection
[430.39]. It might make sense in this application to combine the two
functions in one device.
If a safety concern poses an immediate threat (e.g., a
gas leak), stop working. Alert others in the area, and then leave the
space. But what if you're unsure that there really is a threat? What
if you don't have enough information to know it's not safe to work
there? All you need is a reasonable doubt. If in doubt, get out.
As with a known danger, immediately alert others so they know to
leave the area. Then, report the danger to the area supervisor. Next,
report to your supervisor and ask what you should do while the problem
is being investigated.
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VISIT THE EC&M e-TRADESHOW
Look for these FREE live conferences, scheduled for THIS MONTH:
Wednesday, March 19, Noon EST, 9 a.m. PST "Poor
Working Drawings: The Construction Industry's Prevailing Problem,"
presented by John DeDad
EC&M's senior director of editorial will tap into his 40
construction experience and detail his interviews with owners,
architects, professional engineers, and contractors about the poor
working drawing problem. He'll also cite specific examples of the
shifting of responsibilities and propose recommendations to help
ease the severity of the problem.
Monday, March 24, 10 a.m. EST and PST: "Harmonic
Solutions: Side-by-Side Comparisons," presented by Dan Carnovale,
P.E., Eaton Corp.
Learn about side-by-side comparisons of various harmonic mitigation
technologies, based on testing conducted in a test lab specially
constructed to evaluate all of the major categories of harmonic
solutions for industrial and commercial power systems. See the results
of this testing, including considerations for generator applications,
harmonic resonance, and the application of phase shifting. Energy
savings observations will also be discussed. Video recordings of the
testing will be included.
Visit the many exhibitors in this virtual tradeshow and take a look
at the On-Demand Theater, where you can view past online conferences
Go to http://www.ecmweb.com/etradeshow/index.html
for information on accessing the EC&M e-Tradeshow and visiting
the On-Demand Library.
- "Understanding Electrical Safety and PPE Selection"
- "Implementing an Arc Flash Safety Compliance
- "Preparing an Arc Flash Hazard Study"
Electrical Troubleshooting Quiz
For one motor, you can do a simple cost analysis.
Sending out that 5-hp sump pump motor that failed after 20 years
cost-effective, but getting a forensic report on a failed 750-hp motor
is. The question implies there's a point in between, perhaps at 75 hp
and below, where the investment isn't worthwhile. However, it isn't
Suppose you have a large, multistage conveyor system and one of the
five dozen non-critical 10-hp conveyor motors fails every few weeks?
plant still runs, but you have a sort of rolling production outage, and
Here, the cost of a single 10-hp motor doesn't justify the expense
of a forensic exam. The real issue is the persistence of motor failure
in the system, which isn't acceptable. You must determine the root
cause. Persistent failure may also be the proverbial canary in the mine
(e.g., power anomalies due to transformer overload are killing the
A forensic exam will identify a cause or quickly eliminate several
possibilities. Consider how quickly a forensic exam can reveal, for
example, motor lubrication errors. Without that exam, you'd be
phantom causes for months rather than fixing the problem.
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