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Product of the Year Competition
Cast Your
Vote Now!
Do you want the opportunity to win a $100 gift check?
If
you’re an EC&M subscriber, we invite you to help us select
this
year’s Product of the Year winner. The deadline for voting is June
22,
2008. To make your voice heard, visit the EC&M Home page anytime before now and
then. Click on “vote now and become eligible for a $100 gift
check,”
located in the center of the page. You can click on a link for each of
the 24 category winners to read a brief description of the product
features and view a photo. Once you’re finished with your review, you
can click on the "vote here for your favorite" link, which allows you
to
enter in your contact information, choose your favorite product, and
click submit. As an added incentive to capture your vote, five lucky
voters will be randomly selected to receive one of five $100 gift
checks
― so don’t delay. Vote today!
The competition has honored innovation and excellence in product
development in the electrical industry for the past seven
years.
Maintenance
The Power of
Information -- Take 2
The previous issue of MRO Insider looked at some types
of information you can use to make your maintenance system truly
effective. Your system should also have the following information for
each piece of equipment:
- Maintenance procedures and schedules. Base these on the
manufacturer's recommended practices. Also see the relevant industry
standards, such as NFPA 70B, Recommended Practice for Electrical
Equipment Maintenance and NETA's Maintenance Testing
Specifications.
- Maintenance history information. This includes dates of
installation, inspection, repair, modifications, and upgrades. Be sure
it provides details as to what was done, who did it, and what test
equipment was used.
- Maintenance test and inspection records. This should include
the following data: as found, as left, trending, and
analysis.
In the next issue, we’ll examine three information sources that help
make maintenance cost-efficient: better maintenance, same budget.
Motor Maintenance
Tip, Part 13
When a motor is restarted too frequently, you have
overcycling. This is a problem because the resultant excess heat
dramatically shortens motor life. Good maintenance focuses on
preventing
root causes of failures, such as overcycling.
But if you have a temperature monitoring system, can’t you just
let
it tell you if there’s a problem? Wouldn’t that simultaneously
increase output and eliminate the hassle of enforcing cycle times
administratively? No. The fly in that particular ointment is this:
Temperature is an inherently slow process variable to monitor. By the
time the instrumentation can reveal an overcycling condition, the
damage
is already done.
Temperature monitoring, while highly beneficial, isn’t an
overcycling protection system. The purpose of temperature monitoring is
to reveal abnormal spot temperatures during normal operating
conditions.
With that information, you can schedule preventive repairs.
For maximum uptime, supplement the temperature monitoring system by
periodically performing thermal imaging on critical motors. Today’s
thermal cameras make accurate temperature reading easy and inexpensive.
If there’s a discrepancy, you can schedule a calibration of the
monitoring system. Or, if the thermal image shows a hotspot you’re
not
monitoring, you may add more data points to the system.
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Repair
Electrical
Troubleshooting Quiz
Your facility has three similarly constructed conveyor
systems that carry similar loads. Occasionally, they jam and stop. The
operators are supposed to clear the jam, wait for 5 minutes after
the
motor stopped, and then restart the conveyor.
In reviewing the maintenance logs, you notice the drive motor for
Line Two has been replaced four times as often as the drive motors on
the other two lines. It always fails during the second shift or shortly
after the third shift begins. You suspect the second shift operator is
overcycling the drive motor. However, the temperature monitoring system
shows only slightly high temperatures. How can you determine what’s
going on?
The answer to this question appears at the end of this
newsletter.
Circuit Breaker
Repair Tips
Circuit breaker repair or replacement usually involves
a
tight window of time. Running into problems during that window can
force
you into an incomplete or delayed repair. Address those problems ahead
of time.
For example:
- Do you have the cranking and racking tools for each model of
breaker, and are they in good condition?
- Do you have the proper lifting brackets and equipment?
- Do you have power and lighting you can use when shut down?
- Do you have the recommended spare parts?
If the answer to any of the above questions is "no" for any critical
breaker, then you have some cost-saving, outage-shortening work to do.
But it won’t save you money or shorten an outage if you wait until
you’re in an outage to do it.
Sizing Fuses
Generally, but not always, you should size a fuse at
125% of
the noncontinuous load. See the following NEC Articles:
- Services: 230
- Feeders: 215
- Branch Circuits: 210
- Motors: 430
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Operation
NEC in the Facility
If you have a multi-section motor control center, the
sections must be bonded together. You’ll see the word “grounding”
in the subtitle of 436.96 where this requirement is found. But here the
NEC means “bonding.” Don’t drive a ground rod at each section to
achieve an equipotential plane, because driving rods won’t produce
that result. Use an equipment grounding (bonding) conductor or
equivalent grounding (bonding) bus sized per Table 250.122. See the
Art.
100 definitions of bonding and grounding.
Safety
You’ve undoubtedly heard “knowledge is power.”
When
it comes to your personal safety, this is especially true. You give
yourself the power to prevent injuries to yourself or others when you
learn and follow the safety policies and procedures applicable to your
work and your location.
Sometimes, the policies and procedures are updated to be more
stringent. Some people, confronted with new rules, think, “I was
perfectly safe with the old rules, so these new ones don’t apply to
me.” What they fail to realize is that management is applying
“lessons learned” from someone else. Often, those lessons result
from actual injury or death at another location. Updating the existing
policies can help you apply those lessons and avoid a similar fate, but
only if you follow the updated policies.
Show & Events
Learn About the Changes in the 2008 National Electrical
Code
In two informative and interest-filled days with Mike Holt,
you'll learn about major NEC changes that will impact your work,
whether you're an electrician, contractor, engineer, designer, or
plant/facility maintenance person. You'll also earn continuing
education
hours and professional development hours.
Two conferences are scheduled for 2008:
--September 4-5 in Portland, Ore.
--September 8-9 in San Antonio
For more information and to register online, go to http://CodeChangeConferences.com
Quiz Answer
Answer to
Electrical Troubleshooting Quiz
The temperature monitoring system could easily be
averaging out the temperature readings, due to where the temperature
sensors are placed and the fact that temperature is a slow-responding
process variable. You can overcome part of this issue by using a
thermal
camera to get a more detailed view of the motor. A hotspot that would
“average out” at the sensor will show up in the thermal image.
To determine if the motor is being overcycled, watch the operator.
If
it’s not being overcycled, then you need to send the next failed
motor
to a motor shop for forensic analysis so you can determine what problem
you are really facing.
If it is being overcycled, you have an application mismatch. Five
minutes is a long time for operators to wait. Examine the application
for the practicality of ducting in air to cool the motor. Is the motor
of the right insulation rating? Contact the manufacturer to discuss how
you can shorten that waiting time to something the operators can live
with.
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