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September 25, 2007 A Penton Media Publication Vol. III No. 18



CONTENTS
Managing Assets

Avoiding "Too Little" Maintenance, Part 2

Electrical Troubleshooting Quiz

Motor System Repair Mistakes, Part 2

NEC in the Facility

Safety Habits

Answer to Electrical Troubleshooting Quiz



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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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    Maintenance
    Managing Assets
    Do you manage assets, or do they manage you? To control assets and events rather than simply reacting to them, plan your work based on information that is detailed and accurate.

    Use your computerized maintenance management system (CMMS) as more than just a work order system (you are on a CMMS, rather than paper, aren't you?). A fully and properly utilized CMMS provides you with the knowledge you need to properly manage every asset. For example, you should be able to run a report on any piece of equipment and know:

    • History (downtime, modifications, PM, PdM, repair).
    • Financial data (repair costs, annual revenue, daily minimum output).
    • Parts and assemblies information (lead times, sources, costs, equivalents, min/max).
    • Drawings, manuals, software revision level, and MSDS
    • Procedures for testing, troubleshooting, PM, PdM, and repair.
    • Test equipment and PPE.
    • Training and qualifications.
    With this information, you can correctly determine priorities and allocate resources to meet them. Think about how you can use this information to improve your maintenance process.


    Avoiding "Too Little" Maintenance, Part 2
    The tendency to "save" money by cutting back on maintenance persists, despite its staggering costs. The decisions are usually made by spreadsheet, rather than by intelligent analysis of conditions in the plant.

    Why does this happen? Imagine three people from dissimilar cultures trying to discuss a complex topic -- one speaks Chinese, one speaks Russian, and one speaks French. Even their alphabets are vastly different. This is similar to the situation that normally exists around maintenance expenditures. Typically, maintenance people speak "payback,' managers speak "ROI," and financial people speak "net present value" or "cash flow." These are incompatible languages.

    You can learn to speak all three languages fluently by spending a few hours with a book on financial analysis. Then, you can make your case in the language each level of gatekeeper can understand. This is the only way you can prevent mixed signals, false assumptions, and expensive "cost-saving" decisions.


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    Repair
    Electrical Troubleshooting Quiz
    A critical conveyer stopped three times in the past month. It stopped again, just moments ago. The production supervisor hands you three heater-style motor overloads and says, "I kept spares in my desk after the last shutdown. All you have to do is replace these, and we're good to go." What's wrong with the supervisor's assessment, and what should you do?

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


    Motor System Repair Mistakes, Part 2
    We know to record "as founds" before changing anything for PM or repair. With motor systems, this is especially critical. However, this step is often omitted when production is down and pressure is up.

    Fortunately, most of the "as founds" won't change during a motor system repair. It's better to have incomplete "as founds" than none at all. If the repair doesn't require motor removal (e.g., open overload), then before you change anything check:

    • Weatherhead. Look carefully for signs of trouble, including three key points -- bolt tightness of the cover, gasket integrity, and evidence of moisture ingress.
    • Connections. Visually inspect, then measure resistance across them (make sure power is off).
    If the repair requires removing the motor, then also check:
    • Motor/load alignment. A few measurements with a straightedge and tape rule reveals gross misalignments.
    • Condition of motor feet (unless face-mounted). A common response to vibration is to tighten the mounting bolts, which usually causes overtightening and warped motor feet. Look carefully at those feet before loosening the bolts to remove the motor.
    • Condition of motor pedestal and base. Look for cracks, warping, and other deficiencies while the weight of the motor and tension of its fasteners is bearing on those structures.
    Checking these few items is a compromise that may not reveal the failure cause. Not checking them "as found" may obliterate evidence that could have identified the cause of failure.

    Motors don't fail by pure chance. Schedule a complete PM/PdM to be done within 48 hours. Before performing the PM/PdM, check the supply voltage. If any two phases differ by more than 2% of the nominal voltage, that motor will prematurely fail -- and you already know the cause.


    Operation
    NEC in the Facility
    You have a work request for installing 16A of 120V task lighting for some workbenches along one wall of a room that contains several hot injection molding machines and a large curing oven. The circuit originates in a lighting panel in a room adjacent to the opposite wall. The drawing shows 1/2-inch EMT running along the ceiling. You may have a code violation. Use a "heat gun" or thermal camera to determine the temperature in that proposed raceway path. If the specified wire isn't rated for that temperature (per the ampacity tables), then you have a violation of 410.24. Reroute or upgrade, as needed. Be sure you account for the season. A February reading won't give you the August temperatures.


    Safety Habits
    Make these two safety habits part of the maintenance way of doing things:

    • Be proactive. Think ahead to protect people and property. Ask, "What could go wrong?" Then, follow the procedures that prevent and/or minimize those hazards.
    • Follow the rules. A common misperception is that safety rules are more stringent than they need to be and it's OK to cheat on them. The reality is that today's safety rules were "purchased" with the injuries and deaths of people doing the same work you're doing. There is no reason for you to pay that bill again, so don't.

    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    Repeated interruption of a critical system is normally a greater problem than a period of downtime long enough to prevent those repeats. If the heaters are burning open this often, the heaters aren't the problem. The problem is whatever anomaly they are protecting the motor from. The fact that the motor runs for many days with new heaters is helpful. A good start on solving this problem would be to:
    1. Take those quick "as found" data mentioned earlier.
    2. Replace the heaters.
    3. Take complete "as left" data.
    4. Use a power analyzer on the supply to check for voltage imbalance, harmonics, and low power factor.
    5. Perform PdM within the next 48 hours.


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