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CONTENTS
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Cast Your Vote for the
EC&M Product of the Year!
You and IR, Part 2
Electrical Troubleshooting
Quiz
Troubleshooting PLC Digital
Input Modules, Part 1
NEC in the Facility
Safety
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About This Newsletter
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This twice-a-month
e-newsletter is brought to you from the
publisher of EC&M magazine. MRO Insider addresses topics such
as:
Working with management and supervision
National Electrical Code® on the production floor
Safety procedures and programs
Troubleshooting techniques
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
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Product of the Year Competition
Cast Your
Vote for the EC&M Product of the Year!
Would you like to help pick the prestigious EC&M
Product of the Year winner and qualify for a chance to win $100? If
you're an EC&M subscriber, make your vote count by visiting the
2010
EC&M Product of the Year category winners list. To review
the
products, click on the links for each of the 33 category winners to
read
a brief description and view a photo. Once you're finished with your
review, visit the
polling page, enter your contact information, choose your favorite
product from the drop-down menu, and click submit.Your selection
will
help us identify the 2010 EC&M Product of the Year Platinum,
Gold, and Silver award winners. As an added incentive, three lucky
voters will be randomly selected to receive a $100 gift check. The
voting poll will remain open through 5 p.m. on June 18, 2010. Please,
only one vote per EC&M subscriber. Any votes received from
manufacturers, PR firms, or non-EC&M readers will be
discarded.
Maintenance
You and IR, Part 2
A fundamental question to ask when analyzing anything
is, "Compared to what?" With no point of reference, facts and figures
can grossly mislead you. It’s the same with infrared thermography
(IR)
— you need benchmarks.
Most thermographic cameras provide for various benchmarks, such
as:
- Ambient. What's the temperature outside that cabinet?
- Background. What's the temperature inside that cabinet?
- Reference. What's the temperature of the side panel surface
of that cabinet?
When you later analyze images and spot temperatures, you'll be looking
for the deltas between benchmarks and readings. If this is the latest
in
a series of trended surveys (including perhaps a baseline survey), then
you can compare the deltas over time. An area or object with a rise in
delta will be easy to spot graphically.
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Repair
Electrical
Troubleshooting Quiz
You report in on the night shift to discover that a
solvent day tank overflowed three times that afternoon. However,
operators say the tank is properly supplying the process.
The notes from the responding tech include:
- Tested level switch by operating rocker. Meter shows voltage change
when switch operates.
- Simulated open signal to tank fill valve, and it functions
properly.
Simulation was done by forcing logic in PLC.
- Unable to test further, due to time constraints.
With this information on hand, what should you do next?
Visit EC&M's
website to see the answer.
Troubleshooting
PLC Digital Input Modules, Part 1
By definition, digital inputs are either on or off.
Thus, verifying the absence or presence of voltage is a critical part
of
troubleshooting digital input modules. But what voltage should you look
for? That depends on the power source for the input loop(s) in
question.
The following are some basic facts about input loop power
sources:
- The input module usually isn't a loop power source.
- Although 120V is common for digital loops, other voltages are also
used.
- There are two types of digital input, differentiated by their power
source: isolated and non-isolated.
- Non-isolated inputs are powered by a common source. For example,
the
wiring diagram shows a non-isolated input module with L1 (common power
source) feeding an array of input devices displayed in ladder fashion.
- An isolated input is on its own channel and may be powered by its
own source. If your system had four such inputs, then the wiring
diagram
would again show an array of input devices displayed in ladder fashion.
But this time, they wouldn’t share L1. Instead, each would be
supplied
by L1a, L1b, L1c, and L1d.
To read more on this story, visit EC&M's website.
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Operation
NEC in the
Facility
How do you find the ampacity requirements that apply to
your facility's power distribution wiring, and which of the many
ampacity tables in Art. 310 is the right one?
To answer the first question, we can quickly cut Art. 310 down to
size. About half of it is for 2,001V or more, and everything from
310.60
onward is for 2,001V or more. The parts that typically apply to
facilities end at Section 310.15.
The requirements in 310.1 through 310.14 are general requirements.
Then, you have 310.15 and the next section is 310.60 (2,001V and
above).
This means that, for purposes of calculating ampacity, your
requirements
are in 310.15 (unless you're working power distribution at greater than
2,000V).
To read more on this story, visit EC&M's website.
Safety
Some ladder safety rules depend on the type of ladder
you use.
Three rules for extension ladders include:
- Secure the ladder so it can't inadvertently slide out from under
you. One way to do this is to tie a lower rung to an anchor point
(e.g.,
vertical I-beam).
- Leave at least three rungs of overlap between sections, or get a
longer ladder.
- Extend the ladder so it reaches 3 ft above the top supporting
point.
Three rules for step ladders include:
- Open it completely, and lock the braces.
- Rest all four feet on level footing.
- Stand only on steps that are below the top step.
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