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June 8, 2010 A Penton Media Publication Vol. VI No. 11



CONTENTS
Cast Your Vote for the EC&M Product of the Year!

You and IR, Part 3

Electrical Troubleshooting Quiz

Troubleshooting PLC Digital Input Modules, Part 2

NEC in the Facility

Safety



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About This Newsletter
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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    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 3
    When you do thermographic surveys, do you look for problems, or do you expect things to be OK? You can fix problems, but you can't fix what’s OK. Experts advise performing surveys under normal running conditions, because equipment that isn't running won't generate a very useful thermal signature (although some defects will still show up).

    Problem: If you don't find defects under normal operating conditions, this doesn't mean they don't exist. Normal running conditions aren't the conditions under which the next failure is likely to happen.

    Solution: Follow up with a stress mode survey. To the extent possible, run key equipment under maximum load, and repeat the thermographic survey. Look at the delta between the two surveys. Caution: Plan this out with operations first.


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    Repair
    Electrical Troubleshooting Quiz
    You reported in on the nightshift to discover that a solvent day tank sometimes overflows and sometimes runs dry. The consequences alternate between solvent spills and ruined product batches. You found extensive notes from the dayshift, showing methodical testing in the entire process loop, including point to point continuity tests. The I/O modules work properly, and simulated signals to the control valve provide the correct response.

    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 2
    In our previous issue, we noted that the first step in troubleshooting digital input modules is to verify the power source of each loop. If input power is missing, the causes can be such things as blown fuses, broken wiring, or broken connections.

    Once you've fixed any power problems, you're ready to simulate input changes. Connect a DMM across the input (at the module). Then, actuate the field device and watch for the voltage to change. If it doesn't, you have a problem in the loop between the input module and the field device. It's probably a wiring issue. If the voltage changes, you've just verified the integrity of the loop between the input module and the field device. So where is the problem?

    To read more on this story, visit EC&M's website.


    Operation
    NEC in the Facility
    Although Annex B is not part of the NEC requirements, it does provide information that can help you with NEC compliance. The Chapter 3 ampacity tables don't address every type of installation. If yours isn't covered by a table, how can you get the correct minimum ampacity?

    If the problem is simply that you have more than three conductors, the answer is to use those Chapter 3 tables and just derate the ampacities per Table 310.15(B)(2)(a). For other applications not covered by these tables, you'll need to determine ampacity under "engineering supervision." The NEC helps clarify what that entails in Annex B.

    The bulk of Annex B consists of tables that provide "typical ampacities for conductors rated 0V through 2000V"…duct bank tables, and…"conductors rated up to 0V to 5,000V."

    To read more on this story, visit EC&M's website.


    Safety
    Stairways and ramps aren't moved around the way ladders are, but they still aren't inherently safe. OSHA requires inspection and maintenance. Check for:

    • Illumination. A change in grade or elevation requires some depth perception to safely navigate. Poor lighting interferes with this, making falls likely.
    • Structural and mechanical integrity. Ramps may fail at mechanical/structural stress points during high load conditions. A qualified person needs to inspect these points at established intervals.
    • Cleanliness. Ensure everyone understands that grease, oil, or trash on a ramp or stairway must be removed immediately or the route must be closed off until it can be.


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