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April 11, 2007 A Penton Media Publication Vol. III No. 7

The Right Stuff

Electrical Troubleshooting Quiz

More Downtime is Better?

NEC at the Facility

Unsafe Assumptions

Tomorrow's FREE Conferences

Answer to Electrical Troubleshooting Quiz

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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 Right Stuff
    How do you know if you're doing the right maintenance? The answer begins with understanding why your maintenance department exists. See if you can correctly answer this multiple-choice question:

    The maintenance department exists to:

    1. Keep equipment in perfect working order.
    2. Do preventive maintenance.
    3. Repair things that break.
    4. Keep product flowing out the door.
    Which answer did you pick? Were you thinking, "All of the above?" If so, that is incorrect. You can see why by examining each of the choices provided.

    A. Keep equipment in perfect working order. Equipment needs to be in good working order. Perfect isn't realistic. Equipment that is within specifications doesn't need adjustment or repair. This assumes, of course, you have the correct specifications.

    B. Do preventive maintenance. Preventive maintenance is a means, not an end. By definition, it involves doing things to equipment. Anytime you do things to equipment, you risk causing premature failure. For example, you don't pay a garage to run your car up and down a lift, or do endless inspections and adjustments. You pay them to keep your car running smoothly. The less preventive maintenance needed to keep equipment running smoothly, the longer your equipment may last.

    C. Repair things that break. Although the maintenance department typically performs repairs, repairing isn't its reason for existing. Otherwise, it might make sense for every maintenance manager to go around breaking things so that the maintenance department has more to repair. The job isn't to repair -- it is to maintain. Maintenance performance is graded by the absence of breakdowns rather than how many get fixed.

    D. Keep product flowing out the door. This is the reason the production department exists. The maintenance department exists to support that effort.

    To determine what the right maintenance is, you need to be keenly aware of which equipment is vital to product flow (making it "critical equipment") and what maintenance actions prevent breakdowns. Complicating matters is the fact that some product flow is more important than other product flow.

    Electrical Troubleshooting Quiz
    A 400A breaker has tripped four times this week. Your "secret weapon," the power monitor, has finally let you down. For some reason, it failed to capture any triggering events. What's going on?

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

    More Downtime is Better?
    The traditional view of maintenance is that less downtime is better, but this isn't always true. Sometimes, you should choose to allow more total downtime of production equipment. However, the company pays its bills by selling products. How can increasing overall downtime be anything but counterproductive?

    The answer lies in the fact that resources are limited and not all downtime is of equal value. Let's use an example to illustrate how this works. The company makes Widget-A, Widget-B, and Widget-C.

    • The profit on each Widget line is $120, $180, and $14, respectively.
    • The average daily unit sales are 95, 70, and 8, respectively.
    • The company can barely keep up with demand on Widget-A orders. It has a three-day supply of Widget-B units and a 10-day supply of Widget-C units.
    From this, you can see that not all downtime is of equal value. On those occasions when you don't have enough resources to go around, you need to know which product(s) the company most needs to move out the door. Ask the production people regularly, not just when an emergency arises.

    In the example, suppose you can fix the Widget-B line 15 minutes faster if you have two people handing tools to the repair crew. But this leaves the Widget-C line down without maintenance support for 3 hours. Is that extra 15 minutes of Widget-B uptime worth 3 hours of Widget-C downtime? You bet! Will the Widget-C supervisor agree? Probably not.

    Don't try to placate the Widget-C supervisor by spreading out your resources. This practice leads to plant closings.

    On the other hand, don't lower yourself into the stew kettle. To stay out of hot water, ask the other production supervisors to meet with the Widget-C supervisor and review the numbers. Unless that Widget-C supervisor loves job hunting, you'll get the agreement you need. Nobody with common sense tells the plant manager, "I held down our total revenue to make my own numbers look better."

    NEC at the Facility
    Suppose you're adding a convenience receptacle at the operator station for a process control system. Per the installation manual, this system has its own ground rod. The drawing provided for the receptacle shows the receptacle grounding terminal wired to a bus that connects to that rod. Should you install per the drawing, or should you run a separate ground wire back to the panel where you connect the neutral and hot?

    The receptacle needs an equipment ground, not an earth ground. An earth ground is for lightning protection. You can't use it for the receptacle ground. Run the separate ground wire. While you're at it, make sure that ground rod is bonded back to the power source. This will fix the many Article 250 violations that exist if it is not.

    Unsafe Assumptions
    Assume any of the following during an electrical test, and you may not live to conduct another:

    1. "I don't need to check my test equipment unless there's a problem." It's a little late to inspect test equipment, especially test leads, after you've already been electrocuted. Check before you connect.
    2. "All grounds are the same." An equipment ground is part of the bonding system, not the earthing system. Connect to the wrong ground, and you may be shocked at what you find -- literally.
    3. "Nobody else is at risk if I inject a high voltage now." Verify that everyone is clear and that cables and equipment are properly isolated.

    Show & Events
    Tomorrow's FREE Conferences
    Make plans now to take part in the next round of FREE live conferences in the EC&M E-Tradeshow. These events will take place tomorrow, April 12th!
    • "Electrical Power Engineering: Industry Shortcomings and Solutions," presented by John DeDad, Senior Director, Editorial and EC&M Development [9:00 a.m. Eastern and Pacific time]
    • "The Mighty Hand-Held Power Meter!" presented by Michael Daish, Summit Technology [10:00 a.m. Eastern and Pacific time]
    • "Understanding Generator Reliability," presented by Mike Kirchner, Sales Training Manager, Generac [11:00 a.m. Eastern and Pacific time]
    Visit the exhibitors in this virtual tradeshow before and after the conferences and check out the On-Demand Theater, where you can view past online conferences any day and time of the year.

    Click here for information on accessing the EC&M e-Tradeshow and attending these FREE live conferences.

    Quiz Answers
    Answer to Electrical Troubleshooting Quiz
    Rest easy. Your trusty friend hasn't let you down. The power monitor has shown you that the failure isn't due to a triggering event. This narrows down your troubleshooting considerably. The cause is probably a worn mechanism inside the breaker. Because the frame alone is probably more than $1,000, consider the economics of having an authorized shop rebuild the breaker.

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