January 24, 2006 A Prism Business Media Publication Vol. II No. 2



CONTENTS
Spare Parts: Take 1

The Power of Feedback

Electrical Troubleshooting Quiz

Spare Parts: Take 2

Practical Implications of OSHA 1926.200

NEC on the Production Floor

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
    Spare Parts: Take 1
    Suppose routine maintenance reveals an impending problem. You know you need to schedule a shutdown to fix it. Production tells you the next available slot is seven weeks out. So, you schedule a shutdown for that time, and production schedules shipments around it. The day comes, and you are still waiting for the replacement parts you needed. What happened?

    Some parts require long lead times -- this is especially true when you are ordering transformers, breakers, explosion-proof motors, or stationary batteries. There is no way to shorten the production time for some items, so if the manufacturer tells you nine weeks then be prepared to wait at least that long.

    How can you avoid having to schedule a second shutdown? If your impending failure isn't too far in the danger zone -- and a shutdown doesn't require much advance notice -- you could just wait until you have all the requisite parts. But as you wait, you risk an unplanned shutdown due to a foreseeable failure.

    To balance the risk of missing parts for a planned shutdown against the risk of an unplanned shutdown, find out from each parts manufacturer what the minimum lead time is and then allow a little extra. Consider also:

    • Primary and alternate shutdown dates -- with the actual shutdown date confirmed based on the progress of the needed parts, which you will need to monitor.
    • Pooling the costs of very expensive items (e.g., service transformers or special motors) within your division or even among facilities outside your company, so it's affordable to store spares of long lead time components that are vital to operations.

    The Power of Feedback
    As part of a preventive maintenance program, Gary uses a handheld thermal scanner to spot bad contactors and connections. He fills out a form that allows him to simply mark off the items that need attention. But the form doesn't have space for Gary to note that the panels need a good cleaning, the lighting doesn't work in one of the panels, and there's an odd hum coming from a transformer that sits near the panel.

    So you get shutdown set up, and your team duly replaces the bad contactors and fixes the bad connections. But they didn't know to bring a vacuum cleaner (or to provide a way to power it), so they leave the panel dirty. They don't inspect the transformer either, because doing so wasn't on the list. When they power the panel back up, flames shoot out of the vent on that transformer.

    The problem and the solution are obvious here. Don't use your preventive maintenance forms as a means of just getting through pre-determined activities. Use them as a means of providing information that will allow you to identify problems as early as possible. Look at your forms, today -- any room for improvement?



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    Repair
    Electrical Troubleshooting Quiz
    A large, multi-tenant office building is experiencing an excessive rate of replacement for electronic ballasts and lamps on the third floor. What initial steps you should take to fix this problem?

    The answers to this question appear at the end of this newsletter.

    Spare Parts: Take 2
    If equipment goes down unexpectedly, part of your job is to repair that equipment to prevent a recurrence from the same cause. Another part of your job is to prevent downtime from another cause you could have prevented during the unrelated repair.

    For example, say a motor drive fails. You isolate the cause to the failure of one IGBT and replace it. But a week later, a second IGBT fails. This isn't coincidence. Whatever stressed that first IGBT to failure also stressed the other IGBT to near failure. You could have prevented the second downtime incident by replacing all of the IGBTs in that drive at the same time. Ensure your spare parts system allows for this approach, rather than straight jacketing you into onesies and twosies.


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    Operation
    Practical Implications of OSHA 1926.200
    This part of OSHA addresses six types of signs to use on a temporary basis: caution, exit, safety instruction, directional, traffic, and accident prevention. Using the sign appropriate for the work you are doing and the hazard presented is an easy way to alert others to potential dangers. Consider modifying your work orders such that you can include a sign checklist.

    Handy tip: Design a checklist with thumbnail examples of each type of sign.

    NEC on the Production Floor
    Production areas may have hundreds of branch circuits. Article 210 is of vital interest to anyone involved in keeping those areas safe and production equipment running. Taking care of these circuits involves far more than just being able to replace a 20A breaker in a panel. Table 210.2 lists more than two-dozen specific types of branch circuits.

    Three of the key requirements of Part I of this Article state:

    • [210.5] Identify the grounded conductor, equipment grounding conductor, and ungrounded conductors.
    • [210.6] A branch circuit can supply only certain kinds of loads, depending on its nominal voltage, and certain limitations apply.
    • [210.8(B)] Provide GFCI protection in bathrooms, on rooftops, and outdoors (adding GFCI protection beyond NEC minimums is often prudent).

    Quiz Answers
    Answer to Electrical Troubleshooting Quiz Look for the causes that are common to that floor but not to the rest of the building. This rules out low-voltage issues, except on the load side of the transformer supplying power to the third floor lighting panels. You also want to rule out power quality issues arising from heavy harmonic loads on that floor. This is where a power analyzer can be enormously helpful.

    One of the most likely causes is improper bonding -- which results in ground loops and/or a missing return path for undesired current. Eliminate any load side bonds between neutral and ground -- check every possible connection point. Visual inspection can often reveal the need for missing bonding jumpers, but you should also measure the resistance between each light fixture and the main bonding jumper to ensure a thorough job.

    Once you've completed this step, walk through the requirements of Article 250, Part V. Just be careful you don't confuse bonding with grounding.


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