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March 26, 2007 A Penton Media Publication Vol. III No. 6


CONTENTS
Striking a Balance

Electrical Troubleshooting Quiz

Fast vs. Good vs. Cheap

NEC at the Facility

Unsafe Assumptions

Answer to Electrical Troubleshooting Quiz


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
    Striking a Balance
    How do you know if you're doing too much or too little maintenance? How do you know if you need to do less of some tasks and more of others? These questions all center around maintenance frequency. The answer differs, depending on such factors as:
    • Which piece of equipment you're talking about. Putting all equipment on the same schedule might be the easy thing to do, initially. But it makes no sense technically, and it wastes labor and other resources.
    • The conditions under which that equipment is operating. The manufacturer's recommendations assume normal usage. But are your conditions normal? Harsh duty means accelerating those schedules, while light duty may allow you to stretch those out.
    • The age of a given piece of equipment. Maintenance schedules that were fine for new equipment are probably not adequate as that equipment ages. Small damage accumulates. For example, insulation deteriorates over time. That's a key consideration for your insulation resistance testing program and motor maintenance program.
    • The maintenance procedure itself. Due to conditions, the scheduling of one procedure may need to be accelerated while another can be relaxed.
    • Maintenance and repair history. This is a key element in both "condition-based maintenance" and "predictive maintenance," which have established good track records. Be careful you don't read too much between the lines. While you can predict failure from measured conditions or past results, you have to allow for those contributing factors you didn't measure or observe.
    • Risk tolerance. How much will one downtime incident cost your company? How does this affect your personal job security?
    These factors, and others you must consider, are interactive. Striking the right balance to optimize the maintenance investment requires good judgment and sometimes plain luck.

    In our next issue, we'll look at questions that center around doing the right maintenance, rather than how often you do maintenance.



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    Repair
    Electrical Troubleshooting Quiz
    A major production line went down, due to loss of a motor. The motor had been in service for many years. When you disconnected the motor leads, you noticed they were stiff. They also left a black residue on your hands. This motor is one of several on this line, and all of these motors get an annual inspection. Based on what you found, what further troubleshooting is called for on this line?

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


    Fast vs. Good vs. Cheap
    Most repairs happen under the pressure of unplanned downtime, where speed is of the essence. But experience teaches us that when it comes to good, fast, and cheap, you can have no more than two of these simultaneously. Since "fast" is a condition of downtime, you have to balance quality and price when doing repairs. But what if you could remove "cheap" from the equation altogether? While this may seem like wishful thinking, you can make it a reality.

    The single most potent constraint in this process is not a technical one. When things are humming along just fine, production managers are looking for ways to squeeze out more profit. That invariably means cutting costs. So the idea of spending, for example, $3,500 for a spare assembly that will cut the repair time of a critical piece of equipment by 80%, is likely to fall on deaf ears while goods are moving out the door.

    When equipment is down, production managers have only one thing in mind. They want production restored. With no production, revenue goes to zero while fixed costs still need to be paid. In this situation, production managers are very motivated to sign off on an expenditure that will prevent a recurrence. Wait until the day after production is restored, and they are once again focused on cost cutting.

    What's the first key to getting adequate funding for training, spare assemblies (rather than just spare parts), test equipment, and other items that reduce "time to repair" without sacrificing quality? It's getting a commitment when the gatekeepers are over the proverbial barrel. In our next issue, we'll look at some specific ways of doing that.


    Operation
    NEC at the Facility
    If you have a requirement to install an isolated ground (IG) receptacle, what's the right way? First, understand that an IG receptacle is just a normal receptacle with the yoke not bonded to the receptacle grounding lug. This allows you to put the equipment ground for that receptacle on a separate bonding path.

    406.2(D) requires the IG receptacle to be marked with an orange triangle, which is easy enough to comply with. But 406(D)(1) refers you to 250.146(D). That's where things get interesting. An IG does not have its own ground rod. An IG is merely an insulated bonding path that runs, eventually, to the same grounding point as the other equipment grounds in the facility.


    Unsafe Assumptions
    Never make the following assumptions when working in confined spaces:

    • "The confined entry permit addresses all possible dangers." Actually, the permit addresses the dangers related to gases. It does not necessarily address other dangers. It's just one element of a total safety protocol for that particular space.
    • "If others have been working safely in the confined space, then there's no need for me to read the permit." This assumption fails on two counts. First, conditions change. The permit that was valid this morning may not be valid now. Second, the permit often contains information that each person entering the space needs to know. Read it carefully. If there's anything you disagree with or don't understand, discuss it with the entry supervisor.

    Quiz Answers
    Answer to Electrical Troubleshooting Quiz You have discovered one of the reasons for not using time-based preventive maintenance. The stiff leads and black residue are signs of insulation breakdown, which is a natural consequence of age. Because one motor has failed due to this cause, the remaining motors are probably marginal. Get a schedule in place to conduct insulation resistance tests on each of the remaining motors -- the sooner the better.


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