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July 25, 2007 A Penton Media Publication Vol. III No. 14

Pay Attention to the Details

Electrical Troubleshooting Quiz

Infrared and Repairs

NEC in the Facility

Safety Rules

Mitigating Harmonics in Commercial Environments

Answer to Electrical Troubleshooting Quiz

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This twice-a-month
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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 National Electrical Code®, which is a registered trademark of the National Fire Protection Association.



    Pay Attention to the Details
    You've probably heard the saying, "The devil is in the details." This expression means that proper execution at the detail level makes all the difference in how well a project turns out. For example, a wiring job is good only when wiring is properly dressed and labeled.

    In the maintenance world, even a minor detail can mean the difference between high uptime and a lengthy loss of service. Examine 100 failures, and you'll probably find that 80 occurred because a detail or two wasn't right.

    Don't take this too far, however. Focusing on details without regard to the larger picture will bedevil your maintenance efforts. Experts on subjects ranging from time management to family relationships say to start with deciding on your mission, goal, or desired result. In his book, "The Seven Habits of Highly Successful People," Stephen R. Covey writes, "Begin with the end in mind." This philosophy also applies to maintenance.

    Unfortunately, managers at the corporate, division, and plant level often seem oblivious to this idea. Rather than understand and support the maintenance mission, some of them try to score short-term points by "saving money" -- usually at great cost.

    An example of this occurred in a plant that made parts for HVAC systems. The plant controller decided to reduce expenditures by limiting the maintenance credit card to $100/month. He didn't understand that the card was used by a second-shift hourly person to buy chemicals for treating the chilled water and to buy oil for the presses.

    When that employee was unable to use the card to buy the $120 worth of chilled water chemicals needed for that month, he felt frustrated and angry at management. So, he gave up and didn't make the necessary purchases. The untreated water was soon filled with algae, and things started shutting down. Sure, that controller saved $20. But the total cost of repair was more than $15,000. Downtime costs were considerably more. In our next issue, we'll look at how to get everyone on the same page.

    Sign Up Today for InfraMation and Save
    Register by July 31st for InfraMation, the world's largest infrared camera applications conference, and receive 3 free hotel nights and a free guest pass. Hosted by FLIR, InfraMation will happen on October 15-19, 2007 in Las Vegas. InfraMation features clinics on electrical applications as well as sessions on condition monitoring and predictive and preventive maintenance. Visit, or call 1-800-254-0632.

    Electrical Troubleshooting Quiz
    The overloads for a 75-hp conveyor motor trip several times per week. You've confirmed that the nominal voltage is correct. You've confirmed that the overloads are tripping on high current. You've performed insulation resistance tests on the motor, and see no problems. While the motor was running, you checked bearing temperatures and conducted vibration analysis -- no problems. What is the most likely cause, and how do you check for it?

    The answer to this question appears at the end of this newsletter.

    Infrared and Repairs
    Most of us are aware of how valuable infrared testing is for predictive maintenance. One use can easily justify the purchase of the test equipment. But why not gain even more ROI from that purchase? You can use IR for more effective repairs.

    Consider the following example. A 75-hp motor tripped its overloads three times in two days. The standard approach in most plants is to replace the motor and send it out for repair. This approach is quick, because no troubleshooting is involved. However, it violates a fundamental rule: Always take "as found" measurements before changing something. Using an IR gun, methodically take the temperatures of the motor and surrounding equipment (work from input to output). You may find a problem that a motor replacement won't solve or that doesn't require a motor replacement to solve. A good fix is always better than a quick fix.

    NEC in the Facility
    In some facilities, a bare copper cable runs from a panel to a ground rod driven near the panel. This supposedly complies with 408.40, which says panelboard cabinets and frames shall be grounded. But the installation does not comply with 408.40.

    This is another case in which the NEC uses "grounding" to mean "bonding." To understand what 408.40 means, read it in its entirety. It's talking about tying metallic objects together and connecting them to the equipment grounding (bonding) conductor.

    A review of Article 250, Part V, will help clarify 408.40. Two other good resources are IEEE-142 (Green Book) and IAEI (International Association of Electrical Inspectors) Soares Book on Grounding.

    Safety Rules
    This week, make a concerted effort to practice these two rules of safety:

    • Reread safety information. Out of sight, out of mind. Don't let this happen with your safety information. It's easy to fall into a rut of "I've done this before, so I know what I'm doing," but that's how people get hurt. Review small bits of your safety information frequently (for example, every Tuesday and Thursday, read your safety handbook for 10 minutes).
    • Communicate problems clearly. Too often, people lodge a safety complaint in a manner that makes followup unlikely. Remember that your goal is to get the problem fixed. Focus on that. Be specific, and ask for a specific outcome. Ask when it will be done.

    Show & Events
    Mitigating Harmonics in Commercial Environments
    This free live conference will be presented by John DeDad, EC&M magazine, on August 16th at 10 a.m. Eastern and Pacific times, in the EC&M e-Tradeshow. To gain access to the event, go to, sign in or register as an attendee, and follow the signs to the presentation room. And be sure to take a look at the On-Demand Theater, where you can view past online conferences 24 hours a day, 7 days a week, and 365 days a year.

    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    A conveyor motor nearly always has a gearbox. Conveyors require torque, and you multiply motor torque with a gearbox. So in this example, it should be no surprise to the reader that this motor has a gearbox.

    You can use an IR gun to quickly check the gearbox temperature while the motor is running. It should not be much above ambient. Here are four other gearbox tests:

    1. Listen. You might hear a whirring sound, but you should not hear a whining sound. Knowing the correct sound takes experience, so ask an old hand if you don't know.
    2. Feel. The vibration should feel "smooth" and minimal. Knowing the right feel also takes experience.
    3. Look inside. This is the easiest thing to do. If the line shuts down for shift changes or maintenance, you can check the oil level in the gearboxes on that line. In fact, someone should do this routinely.
    4. Smell the oil. A sulfur smell is normal; a burnt smell is not.
    Note that if you have gearbox lubrication and/or wear problems, replacing the motor won't accomplish anything. Any time you do replace the motor, check the gearbox. That's also a good time for a gearbox oil change, even if the box checks OK.

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