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Steel Mill Great Lakes Steel Mill

Steel mill gains maintenance advantages,
visibilty with prismatic lighting

Maintenance was a major concern when Great Lakes Division, National Steel retrofit the lighting in its hot rolling mill area. Located near Detroit, Great Lakes is an integrated mill, making steel from "scratch."

The lighting was retrofit in the roll shop and mechanical and electrical maintenance areas within the mill's quarter-mile long building.

Originally, these areas were illuminated by 1,000 watt high pressure sodium fixtures with aluminum reflectors. Some 1,000 watt mercury vapor fixtures were also used.

According to Robert Douglas, day-turn foreman, Great Lakes Division, remote ballast failures were a continuing problem. Three bays of luminaires were controlled from a centralized station, referred to as the "crow's nest." Because the ballasts were remotely located, reliable starting was a problem. Over a period of time this caused premature lamp and ballast failures. Ballast maintenance was costly since the units had to be serviced from an overhead crane borrowed from production.

Light levels were also insufficient, with illumination at five to eight footcandles.

Based on the performance of test luminaires evaluated earlier, Prismalume® prismatic glass luminaires from Holophane Lighting, Inc. were installed. The units are integrally ballasted to be used with 1,000 watt high pressure sodium lamps. All lamps are dual-arc tube type, providing instant backup in case of momentary voltage dips. Since the burning time can now be switched between the two arc tubes, lamp life can be extended to as much as 40,000 hours.

The Prismalume fixtures have an optional quick disconnect feature that facilitates maintenance. When maintenance is required, an individual luminaire can be disconnected and removed, and a new fixture installed on the disconnect hanger in minutes. This feature also made installation easier, since the hanger can be threaded onto the conduit and fixtures installed and energized at the same time.

A total of 300 to 400 luminaires are installed, mounted at 35 to 40 feet. Spacing is 20 feet on center. The Prismalume fixtures provide 20 percent uplight, which illuminates the light green corrugated steel ceiling, giving the environment a "totally lighted" appearance. Light levels are 55 to 60 footcandles.

"Before the retrofit, the ceiling was very dark. Since the new system was installed, the illumination is very uniform. The difference is amazing," Douglas said.

The Holophane fixtures also include a "protective" starter. If a lamp has failed, the starter will continue to send starting pulses to the lamp for approximately 3 minutes. When the lamp does not start the "protective" starter essentially turns off the fixture preventing stress on the electrical components. Normally, a starter will continue sending starting pulses to a failed lamp, which over a period of time damages the electrical components.

Presently, plant personnel are developing a maintenance schedule for inspecting and cleaning the luminaires, although Douglas expects maintenance to be minimal.

"The glass reflectors stay cleaner," Douglas said. "This is a real benefit because the less time we have to be up there maintaining fixtures, the better."


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