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November 18, 2008 A Penton Media Publication Vol. IV No. 22


CONTENTS
Maintaining Batteries, Part 1

Maintaining for Energy Savings, Part 2

Electrical Troubleshooting Quiz

Solving for Motor Heat

NEC in the Facility

Safety

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
    Maintaining Batteries, Part 1
    Until recently, data centers were about the only places where you’d find racks of stationary lead acid batteries. A factory might have a small point-of-use UPS in the accounting office and a few more for things such as the plant Ethernet and the emergency phone system.

    Special equipment wasn’t needed for maintaining the small VRLA batteries that backed up this handful of systems. Maintenance was basically a matter of battery replacement on a regular schedule or when the UPS began to give off a bad smell.

    Today, many facilities have racks of lead acid batteries. Unfortunately, the maintenance program in many cases is identical to that for the small systems. Realizing that calendar or failure-based replacement is insufficient, some users have added hygrometer testing in the mistaken belief it tells them the condition of the battery.

    This under-maintenance leaves the batteries unable to support the load upon power loss, defeating the purpose of having the batteries in the first place. Furthermore, calendar-based replacements invariably result in wastefully replacing good batteries. In Part 2, we’ll explain some basic strategies for keeping reliability up and costs down.


    Maintaining for Energy Savings, Part 2
    Just about every production facility has undergone extensive modifications, for reasons such as expansion, refurbishment, or production changes. The building structure modifications include:

    • Addition of wall-mounted equipment.
    • External add-ons of rooms as new buildings.
    • Relocation of windows or doors.
    • Temporary openings (e.g., when installing new equipment).
    These modifications create opportunities for leaks in the building envelope, resulting in energy loss and added load on the HVAC. If you’re smart, you already do infrared thermography on your power distribution equipment. Apply this same technology to the entire envelope of your building(s), especially at corners, seams, and joints.

    Begin with a thorough scan of each room that has an outside wall and plug all the holes. After that, routinely conduct a thermographic scan after any penetration of the building envelope. You may want to check the performance of doors and windows annually.


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    Repair
    Electrical Troubleshooting Quiz
    A critical motor has failed. Based on discoloration of the rotor and bearings, you determined that overheating killed the motor. But what caused the overheating?
    • The MCC has inputs to your central power monitor. The power logs showed no evidence of voltage imbalance.
    • The motor is properly ventilated, lubricated, and aligned.
    • The motor was balanced at the motor shop and inspected before installation.
    • The motor is the correct size, type, and heat rating for the application.
    • The motor drives a gearbox, which operates freely and shows no signs of overheating.
    Because this is the second motor failure in two months, you’re under pressure to find what caused this motor to overheat. The previous motor lasted 17 years, and there have been no configuration changes in the last four years. What is your next troubleshooting step?


    Solving for Motor Heat
    Overheating is the main cause of motor failure. Just replacing a failed motor with a new one doesn’t solve the overheating problem and thus is not a complete repair. Fortunately, a dead motor provides clues as to what killed it.

    Discolored paint is an obvious sign of overheating. Nevertheless, its absence doesn’t mean heat wasn’t the culprit. Look inside the motor for burns or scorch marks on the rotor, windings, and bearings. Also, see if the bearing grease has “coked” into a hard substance.

    The most common cause of motor overheating is voltage imbalance. The source of this could be anywhere between the service distribution panels and the motor. To complete the repair, locate and correct the underlying cause of the overheating.


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    Operation
    NEC in the Facility
    Don’t be intimidated by Hazardous Location Classes and Divisions, as covered in NEC Chapter 5. They are much simpler than they seem.

    If an area contains:

    • Flammable gases or vapors, it’s Class I.
    • Combustible dust, it’s Class II.
    • Combustible fibers, it’s Class III.
    Do you see the pattern? The larger the particle, the higher the Class.

    But what about Divisions? Just remember normal and abnormal. If the area meets a Class designation during normal operations, it’s Division 1. If it meets that designation during abnormal operations, it’s Division 2.


    Safety
    Jewelry and electrical work are mutually exclusive. The most obvious reason is that jewelry helps form a conductive path, but jewelry can be deadly even without direct contact to energized components. One reason is it increases the risk of flashover. Another reason is that dangling jewelry can get caught in rotating parts.

    Piercings and metallic implants are increasingly common among younger workers. Although they may seem like part of the body, it doesn’t make them any less dangerous. They are still jewelry and are still too dangerous to wear when doing electrical work.


    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    The fact that this motor failed so soon after installation indicates a problem with the installation.

    We know that overheating killed this motor. We also know that voltage imbalance is the No.1 cause of overheating. The power monitor doesn’t show imbalance, but the input to the power monitor is back at the MCC and not at the motor itself.

    Before you disconnect the motor leads, use an insulation resistance tester (not a 9V DMM) to measure across each wire joint at the motor. You probably have one high-resistance wire joint, and this is how you will find it.


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