Mississippi is home to more than 650 operational industrial plants. Industrial-scale construction projects got off to a strong start this year with site work at SeverCorr's $700 million steel mini-mill. The plant is scheduled to come online in 2008. Construction kickoff on a $140 million engineered wood manufacturing plant will push spending in the pulp, paper and wood industry to $205 million. And IIR projects expenditures of $577 million in capital and maintenance from 41 projects in the industrial manufacturing industry.

Maintenance
Power Monitoring
A power monitor is more than just a great forensics tool. You get a huge return on investment if you use a power monitoring system as a predictive maintenance tool. A well-thought-out monitoring system, as opposed to a single-point-only monitor, looks at all of the important power points in your facility.

The monitoring system can show trends, such as growing voltage imbalances or increasing levels of harmonics. It's particularly useful to set the monitor to alert you for specific events. Doing so can help prevent unscheduled downtime. For example, have the system alert you when there's been a voltage spike of X magnitude (X being determined via engineering review). A single such spike may not cause problems.

But suppose you get an X magnitude or larger spike every time certain equipment starts. Over time, the cumulative conductor insulation damage will cause failure. It's a fundamental law of electricity that the failure will happen either the day before your vacation or just before your performance review.

The monitor can make you aware of the spike and can track recurrences. Armed with that information, you can determine the source. Your next step is preventive repair.

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Electrical Troubleshooting Quiz
Reviewing your power monitoring logs for the past six months, you notice an odd trend that coincided with an uptick in equipment troubles. Voltage levels in some production areas are significantly lower in the morning than in the afternoon. But operations are identical during the two times, and there is no equipment start-up -- nor is this a facility-wide issue. Even more interesting, the problem seemed to clear up all on its own last month, after -- along with the equipment trouble rate -- steadily improving over the preceding two months. Yet, you've had no configuration changes.

How can you determine what this was, so you can stop it from coming back?

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

Tracing Power Events to Their Source
Nothing is more frustrating than seeing a problem but being unable to do anything about it. For example, your power monitor reveals a consistent pattern of high-energy power spikes. You are looking forward to the Fourth of July, but you don't want to see fireworks in June -- and you certainly don't want to generate them via a cable fault. How can you find the power event source so you can repair it?

Power quality experts use a methodical approach and standardized techniques that, while logical and effective, are fairly elaborate. For a thorough analysis and solution, you should apply those techniques. However, event correlation (one technique from their repertoire) may allow you to troubleshoot quickly.

With event correlation, you note when each power anomaly occurred. Then, you compare the times to operations. You may find, for example, there's a shift change coincidental with each anomaly.

But what if the anomalies occur seemingly at random? Things may not be random, after all. Talk to individual operators, reviewing when each anomaly occurred. Each anomaly may have coincided with some operational procedure such as a batch change or random operation of a large scrap grinder.

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Operation
NEC at the Facility
Art. 250 is (arguably) the most commonly misapplied Article of the NEC. A major reason for misapplication is the NEC's confusing use of "grounding" to mean "bonding." In Art. 100, we see that "grounding" means "connected to the earth". But "bonding" involves establishing a conductive path back to the source. NEC Figure 250.4 shows bonding (Part V) tied to six of the nine Parts of Article 250. This has serious implications for any facility.

For example, suppose you are experiencing motor failure, and post-mortem examination shows severe pitting in the bearings. This is almost surely due to "grounding" used in place of bonding. If you drive a ground rod next to the motor instead of bonding the "ground" connection to the main bonding jumper, you have provided a high-impedance path back to the source.

Electricity follows all paths before it. Current flows in inverse proportion to the resistances of those paths. Without the correct bonding, you create a preferred return path right through the motor bearings. Consequently, your "grounding" results in pitted bearings and premature motor failure. Providing a low-impedance path via bonding will dramatically reduce current flow through the bearings. To prove this, draw out the circuit (with possible return paths) and apply Kirchoff's Law.

The Practical Implications
of OSHA 1926.406
This addresses safety issues for cranes, elevators, escalators, welders, and x-ray machines. The goals are basically to prevent personal contact with energized conductors and to prevent accidental operation of the equipment.

At the core of achieving these goals is the disconnecting means. Look closely at each disconnect in your facility. Is it readily accessible? During the original installation, the definition of "readily" might have been stretched. For example, a disconnect mounted such that a person cannot stand to the right of it and operate it with the left hand is not readily accessible. Other requirements also apply to disconnects -- be sure your installation complies.

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Quiz Answers
Answer to Electrical Troubleshooting Quiz
Notice the timing. This is now June. Six months ago, you were in the dead of winter. Things began to improve as the weather began warming. The problem "cleared up on its own" in May. So, this is probably temperature-related. However, the low voltage is isolated to specific areas in the facility.

Your next troubleshooting step is to ask individual production people if their work area was too cold in winter. If so, they probably were using personal space heaters. A clue here is the morning versus afternoon voltage levels. Personal space heater use tends to be heavier in the mornings. If company policy forbids personal heaters, that doesn't mean people weren't using them. Previous complaints about a comfort problem may have fallen on deaf ears.

Try to solve the root problem by adjusting the make-up air. You may need to repair or upgrade your existing HVAC controls to do this. Also, examine your power distribution to ensure convenience receptacles don't (eventually) share the production equipment feeder.