Plant Productivity and Lighting Maintenance

A firehouse in Livermore, California, is home to the world’s longest burning light bulb. Dubbed the Centennial Bulb, this lamp burns 24 hours a day and has done so since 1901 with few interruptions except for power outages and moving to a new firehouse.

You can read more about this amazing lightbulb and view a webcam here.

Unfortunately, that’s not possible in today’s industrial lighting. Lamps do burn out, luminaire components fail, and lighting maintenance is a necessity. Although lighting technology has progressed, with newer lighting types increasing longevity, ongoing lighting maintenance is still necessary.

Lighting definitions
 To understand lighting maintenance, and the relationship to productivity, a few terms need to be explained.

Wattage— This refers to the power consumption of a lamp, not its light output. Because a 100-watt incandescent bulb is brighter than a 60-watt bulb, the term is often confused to mean brightness. Wattage has more to do with your electricity bill than workplace illumination.
 • Footcandle/lumen — This is the unit of luminance of light falling onto a measured surface. It’s based on the level of light from a standard candle falling on an area one foot away. The quantity of light falling on a 1 square foot area that is illuminated to 1 foot-candle is called a lumen.
 • Lux— This is the measurement unit of light falling on a surface. One lux is equal to one lumen per square meter. Ten lux are approximately equal to one foot-candle. Many light meters will record either lux or foot-candle.
 • Color rendering — This refers to how a lamp renders object colors, defined by an international standard called the Color Rendering Index (CRI). The higher the CRI, the richer the colors appear.
 • Color temperature — Also called the Kelvin Temperature, this is a numerical scale that is used to describe the color of light. High color temperatures will have a bluish-white to white tint. Lower temperatures render as red or orange to yellow tints.
 • Lamp/luminaire — Lamps are often called bulbs and are the actual light source. Luminaires refer to the complete fixture, including components such as bases, sockets and ballasts, that support and supply energy to lamps.

One final term to explain is lumen maintenance. This is not the physical maintaining of lamps or luminaires to maintain lighting level. Lumen maintenance refers to the percentage of initial lumens that a light source maintains over a specified time.

For example, a lamp with a rating of L70 over 60,000 hours indicates that it will retain 70% of its original lumens over that time period. This is often shown in graph form on sell sheets or packaging.

Lighting levels and productivity
Worker comfort and productivity go hand in hand. Particularly on demanding or critical inspection tasks, having an adequate amount of lighting can be vital. Additionally, research has shown that proper lighting affects worker attitude as well.

And as the workforce gets older, proper lighting becomes even more important. Reducing eyestrain and eye fatigue helps prevent “guesswork” and increases accuracy.

It’s important to understand that various types of lamps degrade at different rates. None of them lose their luminosity as a straight line in a graph. It’s more of a curve.

Incandescent sources, gas-filled globe lamps with a filament, degrade quickly at first, often to 80% of their original lumens within the first 20% of their expected life. Metal halide and high pressure sodium lamps are examples of these, often called HID or High Intensity Discharge lamps.

Fluorescent and LED (light emitting diode) lamps may drop to 90% of their initial lumens between 40–60% of their life expectancy. However, they often maintain that level, or close to it, until failure. Therefore, they maintain proper lighting levels beyond that of the less efficient, comparable incandescent lamps.

Lighting maintenance is always necessary
 LED lighting technology is still relatively new. Even so, it is promising to be a more efficient and reliable source of lighting. With its longer life — often up to 50,000 hours or more — and its high lumen maintenance, LED luminaires are being developed to replace many common forms of workplace lighting, such as low-bay HID fixtures.

It’s a misconception that when LED fixtures are installed, lighting maintenance is unnecessary. There are other factors that contribute to lighting degradation in all types of fixtures, especially in outdoor luminaires.

For example, plastic and acrylic lenses that protect the lamps from weather get brittle over time. Crazing, the appearance of small cracks caused by exposure, deflect and inhibit emitted light.

Although indoor luminaires are less subject to these conditions, build-up of dust, dirt and other airborne contaminants coat the lenses or bare bulbs, reducing lighting efficiency.

With LED fixtures, ongoing servicing such as routine lens cleaning and inspection ensure optimal performance.

Routine checks, using a light meter, ensure that proper light levels are maintained. This keeps productivity at optimal levels and reduces product failures caused by worker fatigue and mistakes.

Many industrial lighting fixtures are in elevated or hard to reach locations. Make sure the proper equipment is available to service them safely. When adding light fixtures, or upgrading to LED technology, consider improving the lighting support system. For many installations, both new and retrofitted, there are lowering systems available that eliminate hazards caused by fixture location.

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Existing non-lowering poles can easily be converted to lowering poles, allowing upgrades to the latest lighting technologies.