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June 10, 2008 A Penton Media Publication Vol. IV No. 11

The Power of Information -- Take 3

Motor Maintenance Tip, Part 14

Electrical Troubleshooting Quiz

Circuit Breaker Repair Tips -- Take 3

Fuse, Interrupted

NEC in the Facility

Identify Critical Equipment

Safety: Spreading the Word

Learn About the Changes in the 2008 National Electrical Code

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.




    The Power of Information — Take 3
    These three information sources are vital to cost-efficient maintenance:
    1. Equipment service manuals. Avoid guesswork and costly mistakes in application, setup, programming, and spare parts. Review each maintenance procedure against the manual to eliminate unnecessary maintenance and add what’s missing.
    2. Troubleshooting guides. If the manufacturer doesn’t provide a troubleshooting flowchart, create your own with input from technicians familiar with the equipment. The better you can document the process of resolving downtime issues, the shorter downtime will be.
    3. Operational instructions. Are operators using the equipment correctly? Can maintenance people run it through its paces after a repair?

    Motor Maintenance Tip, Part 14
    Moisture can cause a motor to run hot if it penetrates the insulation and creates parallel leakage current paths. Sometimes, the motor is so wet it can’t even start — the insulating material fails, and you have shorted winding conductors.

    A motor may be wet due to condensation. You can prevent condensation by installing a motor heater. Or, a motor may be wet because an operator hosed water into the motor vents. You may need to use a totally enclosed motor to prevent recurrence.

    Don’t run a wet motor to dry it out, or you may permanently damage the insulation. If you suspect a motor is wet, dry the motor without running it. A common approach is to use an insulation resistance tester, but consult your motor service manual (or the manufacturer) for specific recommendations.

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    Electrical Troubleshooting Quiz
    Motor starting problems and outright failures began to occur frequently not long after a new VP of operations came onboard and started an aggressive cleanliness campaign.

    You’ve always had weekly washdowns in the production area, and these haven’t caused a problem before. You suspect the operators are now washing more vigorously and getting water into the motor vents. Yet, the failed motors are dry when you replace them. How can you tell for certain if water is the problem?

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

    Circuit Breaker Repair Tips — Take 3
    A visual inspection of a breaker that has been in service for a long time is likely to reveal contacts that don't look quite right. Naturally, you want to fix this. That’s a repair, and you want to do it correctly.

    Before cleaning the contacts or tightening the connection points:

    1. Take “as-found” contact resistance readings.
    2. Review the “as-found” readings against the manufacturer's specifications.
    3. Check alignment. Contacts should be centered on each other.
    4. Clean the contacts. If it takes more than a light sanding to clean up the contacts, replace them.
    After cleaning and alignment:
    1. Take “as-left” contact resistance readings.
    2. Lubricate per the manufacturer's recommended procedure.
    3. Manually operate the breaker again.
    If the above steps aren't enough to place the readings within specifications, contact the manufacturer's support department. If you put the breaker back in service, you won't be any worse off than you were before the maintenance work. However, you don't have assurance that the breaker is serviceable. If you can replace this breaker at this time, do so.

    Fuse, Interrupted
    Know the fault level (for the nominal circuit voltage) and the current that is available at the line terminals of the equipment before selecting a fuse. Per 110.9, a fuse must have an interrupting rating sufficient for these two factors, if you intend for it to interrupt at fault levels.

    NEC in the Facility
    You need to be able to disconnect motors and controllers [430.101]. Provide a disconnecting means for each controller, in sight from the controller location [430.102]. Article 100 defines “in sight.”

    Identify Critical Equipment
    This is the equipment that, if it fails to operate normally, causes one of two conditions:
    1. It fails to protect people, property, or your key processes from serious threats.
    2. The misoperation itself presents a serious threat to people, property, or your key processes.
    Any system that falls under NEC Art. 700 or 701 (emergency systems and legally required standby systems) obviously is critical. So is any system that has to do with fire alarms, fire suppression, and emergency communications.

    Parts of systems can be critical, even if the system itself is not. For example, a pressure relief valve keeps a non-critical vessel from rupturing and leaking acid.

    Safety: Spreading the Word
    You may have heard the expression, “Safety is no accident.” Part of the message being conveyed is you must take an active role in safety meetings, discussions, and training.

    Simply being quiet but inattentive won’t make you safer. People learn a little by osmosis, but real learning comes from participation. Think of how you learned how to perform electrical work. You didn’t just show up and hope something sank in — you asked questions and solved problems. Those problems may have been assigned by your teacher or may have been actual problems, but they were problems you dealt with.

    Learn safety the same way. When you are at a safety meeting or in a safety training session, ask questions and seek advice.

    Also, managers can’t be everywhere. Use these meetings and training sessions as a chance to mention concerns, unsafe acts, and unsafe conditions.

    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:
    PORTLAND, OR: September 4-5.
    SAN ANTONIO, TX: September 8-9.
    For more information and to register online, go to

    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    A wet motor can start and run if it’s not too wet. But this doesn’t mean all is well. Most likely, enough water is splashing through the vents to wet the insulation without soaking it. You don’t have a direct short, but you do have leakage around and through the insulation.

    This leakage causes permanent damage to the insulation. Although the wet motor runs, dries itself, and appears not to have a moisture problem, moisture is, in fact, destroying the motor.

    Start by taking baseline insulation resistance (IR) readings on the suspect motors. Then, take IR readings daily and trend the readings. If you don’t have power anomalies degrading your insulation, the trend will slope so little that it will appear to be a straight line. If the trend dips on the day following the washdown, you have identified the problem.

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