More Than Meets the Light

Maintain a more productive and safer construction work site with advanced light-tower technology.

Light is something we all take for granted. All we have to do is flip a switch to turn on the lights. But when a power failure occurs, we immediately appreciate the importance of light—not only for convenience, but also for everyone’s safety and well-being.

Light is especially necessary on construction work sites. Your construction workers often have to work at night to complete a project on schedule. And light towers play an important role in keeping jobsites safe and productive after dark. But not all light towers are the same. Light-tower technology continues to evolve, and the latest generation of light towers can produce higher levels of illumination, better quality light and a more productive and safer work site than ever before.

Understanding Light Output

A watt is not a measure of light output. Watts only measure the lamp’s power consumption. The industry standard measurement of light output is the lumen, and the standard measurement of illumination level is the foot-candle (fc). In each case, higher lumen and higher foot-candle numbers are desirable and indicate greater light output. The most efficient light source will be the one that produces the most lumens per watt.

The Illuminating Engineering Society of North America (IES) recommends of the following minimum foot-candle levels: 10 fc for general construction and 2 fc for excavation work.

Choosing Lights

The quantity of light produced is critical to consider when choosing a light tower. Light towers with a higher lumen output can adequately light a larger area. In many applications, light towers with a higher output can actually reduce the number of light towers required on the site while still maintaining the recommended levels for a safe work environment.

Before choosing a light tower, ask an independent testing facility to provide the manufacturer’s photometric data. This data should show the illumination area in square feet and the level of illumination in foot-candles. This helps accurately determine the number of light towers required and their placement on the work site.

Recent advances in light tower technology now use 1,250-watt metal halide lamps producing 150,000 lumens each. Not only is the higher quantity of light important, but also the quality is also crucial to worker safety and productivity. High-quality light with a greater Color Rendering Index (CRI) reproduces the colors of objects more accurately as they would appear in sunlight. Lights designed with a higher color temperature provide a whiter light that closely resembles natural light.

These advances provide superior performance compared with the older technology that uses 1,000-watt metal halide lamps. The higher illumination levels, improved CRI and color temperatures allow workers to work more comfortably, ultimately improving safety.

Lamp fixture design and efficiency is another important factor to consider. Most light produced by lamps comes from the side. But parallel light fixtures have lamps that mount parallel to the lens. This design allows half the light produced to pass directly through the lens and the other half to be reflected.

Conical fixtures, on the other hand, direct mostly reflected light to the work site. The reflector’s efficiency is never as good as direct light, making this style very inefficient. Most light towers today use parallel lamp fixtures, but some older models still use conical reflectors, resulting in less light.

Setting Up Light Towers

To properly set up single or multiple light towers, the area that needs to be illuminated should be evaluated, and the required illumination level should be determined. The jobsite layout will dictate the towers’ position, and the type of work will dictate how the fixtures should be positioned and how many light towers are required.

Once the position is established, the trailer should be positioned in a way that allows the outriggers to fully extend, and it should firmly support the jacks on solid ground. The jacks should be used to level the trailer, and the trailer should be stable before raising the lights. The tower should only be raised when there are no overhead power lines or other obstructions that can cause operator injury or death.

It is often beneficial to use at least two light towers positioned across from each other to provide the most uniform lighting and minimize shadows that can hide various safety hazards.

Properly setting up light towers to take advantage of the modern lighting capability is not difficult. For a typical application with the light tower off to the side, setting the light fixtures at 10-degrees to 20-degrees below horizontal and aiming them 45-degrees apart will provide a fairly even light distribution over a large area.

Adjusting the lights can sometimes be tricky with a standard fold-down tower because it requires you to visualize how the lights should be positioned while the tower is lying down. The new vertical-only light tower designs simplify setup and allow the lights to be aimed while the tower is in the lowered vertical position. Since the lights do not change their orientation as the tower is raised, it is easy to see beforehand exactly how the lights should be positioned for the most effective coverage

Highway projects present a different set of problems. The lights should not blind oncoming traffic. In this case, choose a light tower that aims all of the lights straight down—like a streetlight—to illuminate the work area without creating a blinding glare for drivers travelling through the construction zone.

Light tower design is continually evolving, and today’s models are brighter, more efficient and easier to operate than ever before. A little homework before choosing light towers for your next job can result in a safer, more productive workplace, ultimately saving valuable time and money in the process.

Construction Business Owner, September 2011