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February 5, 2008 A Penton Media Publication Vol. IV No. 3

Down With Documentation

Motor Maintenance Tip, Part 6

Electrical Troubleshooting Quiz

Reducing Repair Variability

NEC in the Facility


Answer to Electrical Troubleshooting Quiz

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MRO Insider addresses topics such as:

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  • National Electrical Code® on the production floor
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  • Equipment maintenance and testing tips
  • Managing motors and generators
  • Trends in training and education
  • Managing energy use

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    Down With Documentation
    Mention "documentation" and many maintenance people glance nervously about for the nearest exit. After all, the thinking goes, sitting around filling out paperwork or massaging spreadsheets doesn't get equipment running or keep it from failing in the first place. That thinking ignores what documentation can really do, such as:
    • Show the ROI on maintenance. Company managers need to see a return on maintenance dollars invested. In an information vacuum, maintenance dollars are the first to be cut when budgets are set.
    • Justify future maintenance expenditures. Gatekeepers typically believe spending more on maintenance won't have a noticeable effect on operations. Show them otherwise.
    • Show how maintenance efforts, properly supported, directly increase revenue and profits. In addition, they directly improve delivery times.
    • Show areas needing improvement. Guesswork doesn't cut it. Document those failure causes that are the highest frequency and most expensive. That way, you'll know which ones to solve first.
    • Show the maintenance team where they've done well. A sense of pride and accomplishment is one of the best possible motivators.
    • Show operators how their teamwork with maintenance improves their job security. What happens when operators can clearly see the results of cooperating with, rather than fighting, maintenance? They become key allies in the maintenance effort.
    • Improve your own resumé. A good resumé succinctly shows what you accomplished and monetizes those accomplishments. If you haven't been documenting things, you can't articulate them in an interview or on a resumé.
    Document your results, and submit regular reports to all stakeholders (managers, maintenance employees, and operations people). We have just looked at why you should. In our next issue, we'll look at how you should go about doing this.

    Motor Maintenance Tip, Part 6
    A 3.5% voltage imbalance produces a 25% rise in temperature in the typical motor. This can cause a properly rated motor to fail when it otherwise would give many years of service.

    Whenever a motor trips, test for phase imbalance. You'll be taking measurements anyway, so don't leave this one out. However, don't wait until a motor trips before checking. On smaller motors, check this on a routine schedule. On larger motors and on critical systems, monitor it automatically and continually.

    Your power monitoring system should provide a way to monitor specific feeders or branch circuits -- if not, look into upgrading that system. You can also install individual phase monitors. If you have an electronic drive on a motor, see if the drive has this feature. If not, consider upgrading the drive.

    A "quick "fix" for a phase imbalance is to adjust the circuit protection to prevent a trip. This merely masks the problem. Worse, it can easily result in extended downtime while you're scrambling to find a replacement motor. Instead, track down the root cause and repair it.

    The NEW Fluke 568 IR and contact thermometer
    With a straight-forward user interface and soft-key menus, the Fluke 568 makes even complex measurements easy. Quickly navigate and adjust emissivity, start data logging, or turn on and off alarms, with just a few pushes of a button. A rugged, ergonomic design means the 568 can stand up to tough industrial, electrical, and mechanical environments.

    Electrical Troubleshooting Quiz
    A production line motor trips its temperature overloads at least once per day. After about an hour, they can be reset. The motor draws the expected current, supply voltage is correct on all three phases, power factor is good, and harmonics are minimal. What should you do? What is the likely problem?

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

    Reducing Repair Variability
    In the typical plant, operators develop preferences for who handles their repairs. Although it's true that people aren't interchangeable parts, it's also true that repair techs should provide a level of service that isn't markedly different from tech to tech. Operators should feel comfortable and confident with any tech. If they don't, then petty complaints and phantom problems will undermine your maintenance and repair efforts.

    Here are some tips to keep in mind when developing your team players:

    • Develop standardized troubleshooting procedures, based on best practices. Find out what works best on specific equipment, document that, and train everyone in those procedures.
    • Train on interpersonal skills. People's emotions definitely color their perception of reality, and how the repair tech speaks to them influences their emotions. Yet, the typical maintenance organization doesn't train its techs on how to interact in a manner that leaves operators feeling respected and confident that they are being taken care of.
    • Train on interview skills. The hardest part of the job for some techs is getting an accurate description of the problem from the operators. Some people seem gifted at this, while others beat their heads in frustration. It's a learned skill, so ensure everyone is taught it.

    NEC in the Facility
    When you size the conductors for a continuous duty motor, you select a conductor with an ampacity that is 125% of the motor's full-load current rating [403.22(A)]. But some motors operate in a different duty cycle (e.g., periodic). Do you still size the conductor at 125%? The answer is, no. The inrush current required to start a motor subjects the conductors to higher heat loading.

    Your ampacity calculations must account for the duty cycle and rating of the motor. This is where Table 430.22(E) comes in handy. It provides you with the necessary multipliers for any combination.

    Sometimes, a motor can be continuous duty but just not in all modes of operation. An example would be a batch tank impeller motor. When in mix mode, the motor runs continuously. But in batch storage mode, perhaps the motor runs intermittently. So, which way do you classify the motor? When confronted with such a question, see the Note in Table 430.22(E).

    Look carefully at your safety manual. Often, such manuals are filled with legalese and OSHA excerpts. They are often bulked out with information, such as administrative procedures, of no relevance whatsoever to the intended user. For safety manuals to be of any real value, they need to be in plain language and apply directly to the work and circumstance of their intended users.

    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    The motor isn't cooling properly. You should use a thermal imaging camera to inspect the temperature profile. If this problem is fairly recent, ask, "What has changed?" However, what hasn't been changed is sometimes the problem. On a production line, a motor is often tucked into a tight place and has cooling air supplied to it via filtered ducts. Check the air filter(s).

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