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July 7, 2009 A Penton Media Publication Vol. V No. 13

Diagnostic Tools

Electrical Troubleshooting Quiz

Failure Mode Analysis

NEC in the Facility


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MRO Insider addresses topics such as:

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    Diagnostic Tools
    When you use a wrench, your brain sees it as an extension of your hand and you can actually feel the bolt through the wrench instead of directly with your fingers. If not for this, your wrench would constantly slip off the bolt.

    When you drive a car, the brake pedal is like that wrench. You can feel how much bite the brakes have, even though your only contact is through that pedal. You really don’t want to be "feeling" other cars on the road, which is why you look through your windows. As you do this, you constantly compare what you see with what you expect. If there’s a difference, you adjust speed or direction.

    Using diagnostic tools is much like looking through your windows. Instead of reading road signs and traffic, you look at such things as voltages, waveforms, and temperature profiles. As with driving, you can’t usefully interpret what you see unless you know what to expect.

    To read more on this story, visit EC&M's Web site.


    Stainless Steel Liquid Tight Connectors
    ElecDirect’s line of Stainless Steel Liquid-Tight Conduit Connectors are made of corrosion resistant 304 stainless steel and designed specifically for flexible liquid tight conduit. Ideal for highly corrosive environments, these connectors are extremely durable and UV resistant. They also include an insulated throat for further cable protection.

    Starting from only $17.43—it’s time to stop replacing broken plastic and rusted steel connectors. — or call toll free 800-701-0975 for more information.

    Electrical Troubleshooting Quiz
    Since the end of winter, there's been an epidemic of PC workstation failures. The failed components are mostly power supplies and motherboards.

    The power monitor doesn't show any anomalies that could account for this. However, from the repair records, you find:

    • It's not affecting any particular brand or model.
    • It's affecting only PCs in the administrative offices, not any PCs on the factory floor.
    Fortunately, the company keeps data on servers and not on individual workstations. Therefore, there hasn't been a catastrophic data loss. Nevertheless, the work interruptions and repair costs now have upper management's attention, and they want this fixed. What should you do?

    Visit EC&M's Web site to see the answer.

    Failure Mode Analysis
    Simple failure mode analysis consists of looking up the description of a failure (that's the "mode" we're talking about) in a chart and seeing the corresponding cause. For example, the chart might show "burnt winding" and list "overheating" as one of the possible causes.

    However, this approach is often too simplistic. What caused the overheating? Did unbalanced voltage do the deed? Perhaps misalignment and vibration were the villains — the motor is drawing more current to do the same amount of useful work.

    To read more on this story, visit EC&M's Web site.

    NEC in the Facility
    One potential solution to equipment failures and operational anomalies attributable to electrical noise is the use of an isolated ground. Don't reach for this as your first solution. Instead, review the installation for conformance to NEC Article 250, Parts V and VI.

    A note of caution: Part VI talks about equipment "grounding" when it should say "bonding." Article 100 defines "grounding" as connecting to the earth and bonding as establishing electrical continuity. These are entirely different methods with entirely different objectives. They are not interchangeable. If you apply Part VI without recognizing the Article 100 conflict, you'll ensure that your equipment has noise problems. An isolated ground won't solve problems that arise from that particular cause.

    One way personal protective equipment (PPE) differs from other kinds of protective equipment is that it's personally for you. Contrast a railing (for everyone) with a harness (for you).

    Many people think another way PPE differs from general protection is that you are responsible for inspecting your PPE and someone else is responsible for inspecting general protective equipment. This kind of thinking can result in the "someone will take care of it" danger zone.

    To read more on this story, visit EC&M's Web site.

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