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January 8, 2008 A Penton Media Publication Vol. IV No. 1


CONTENTS
Motor Maintenance Tip, Part 4

Working Your Work Order System

Electrical Troubleshooting Quiz

Recovering Repair Costs

NEC in the Facility

Safety

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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    Maintenance
    Motor Maintenance Tip, Part 4
    If an angry elephant charged into your home, the amount of damage would be catastrophic. Yet, if you asked homeowners in your neighborhood, you'd find that nobody carries insurance against rampaging elephants.

    Are these people crazy? Of course not. Elephants don't rampage through homes in our country. We forego elephant protection and spend our prevention and insurance dollars on events that are more likely.

    Apply this same philosophy to your motor maintenance program. There are more than 70 different tests you can do on a motor, most of which you don't need to perform. However, if you neglect the few tests you should be doing, the consequences can be expensive.

    Which do you need? Identify the most likely failure causes for each motor. Determine which tests are appropriate for each cause, and what resources you need to adequately perform those tests. Finally, weigh the cost of testing and prevention against the cost of failure.


    Working Your Work Order System
    Does your work order system sometimes get in the way of maintenance and repairs? One key to preventing this issue is to make sure you don't use the same process for urgent work as you do for non-urgent work. Your work order system should schedule non-urgent work, such as PdM, PM, and project work. But it should follow a direct method of initiating urgent work, such as a supervisor's issuing verbal instructions.

    When an equipment failure is affecting production, you have a high-priority situation. In non-urgent work, your work order system leads the action. But in a high-priority situation, the work order helps move work that's already in progress. By removing the need to wait for the work order, you remove an unnecessary barrier to reducing downtime.

    How well do your work orders support those doing the work? Good work orders include information such as:

    • What. Identify the specific equipment, permits, procedures, materials, tools, and test equipment needed to do the job. When this information is in a standard work order (e.g., a PM), you eliminate duplication of labor and sources of error.
    • Where. Provide the location of the equipment and its power supply.
    • Who. Note the specific skills and certifications required for this work so it doesn't get assigned to unqualified personnel. Also note which job titles (e.g., control room supervisor) must provide permissions and sign-offs.
    For non-urgent work orders, add:
    • Why. Explain the purpose. For example, "IR measurements to identify loose connections."
    • When. Show the intended start date.



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    Repair
    Electrical Troubleshooting Quiz
    Line Four has been blowing circuit boards for several months. Current and voltage measurements by the DMM look normal. An electrician accidentally discovered the cause during a Line Four installation project while adding up the loads. It turned out that the 75kVA transformer was already supporting 91kVA of load.

    What piece of test equipment could you have used to eliminate repeated and fruitless DMM measurements months ago?

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


    Recovering Repair Costs
    Your company's executives think of repairs expenditures as losses, not investments. "We spent $30,000 on repairs." To them, the money is gone forever.

    In reality, the money is recoverable. How can this be? Think of repair expenditures as tuition. Now that you've spent this money on this repair, what can you learn from it? Places to look for "lessons learned" include:

    • Root cause analysis. Prevent occurrences in this and related equipment by identifying the cause of the cause (e.g., a bonding error rather than "a voltage spike").
    • Training deficiencies. Determine what mistakes people made, what false paths they followed, and what rework occurred during the repair. You have now identified specific training needs.
    • Test equipment deficiencies. If troubleshooting took a lot of time or involved critical equipment, closely examine the troubleshooting steps taken. How much downtime did you "spend" due to lack of a TDR, power analyzer, thermal camera, digital megohmeter, ultrasonic detector, or wire tracer?

    Operation
    NEC in the Facility
    Excess heat is the number one enemy of motors. We usually look to electrical causes, focusing on such things as harmonics and bonding errors. One pervasive cause isn't even electrical. Motors need adequate ventilation, and the NEC requires you provide it [430.14]. The NEC doesn't provide specifics to define "adequate."

    However, your thermal camera will. If you're getting heat transfer from the motor to the surrounding air, you'll see a thermal gradient as evidence of this. The presence of this gradient doesn't necessarily mean there's enough space around the motor. You also must allow sufficient room for maintenance [110.26]. Maintenance space may be greater than the minimum working clearance required by Table 110.26(A)(1).


    Safety
    When you operate energized disconnects and circuit breakers, do you do so in a safe manner? If you enter an equipment room with no personal protective equipment and stand directly in front of energized devices when operating them, you need to rethink your work practices. It's critical to always consider the potential arc flash blast path and where you are in relation to it.


    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    When electronics are burning up, even though a DMM shows correct voltage and current, a likely cause is waveform distortion.

    Using a power analyzer, you can identify waveform distortion in seconds. In this case, the overloaded transformer would have produced a flat-topped waveform due to core saturation. This "expensive" instrument pays for itself in replacement parts alone, not to mention downtime and reduced exposure to personnel (think NFPA 70E).


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