Increasing the Intensity of Night
As night work promises to become more common, changes may be coming to generally standardized lighting equipment.
For contractors who often work on grading or excavation projects that take place at night, light towers are not only necessary for illuminating large areas; they’re also essential pieces of equipment for ensuring a safe nighttime work site. With the federal government having committed to subsidizing rehabilitation of many major roads via the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users and several states mandating highway and airport runway construction exclusively at night, many contractors can expect to do more work under artificial light in the next several years.
The Federal Highway Administration’s Manual on Uniform Traffic Control Devices dictates that “Floodlighting shall not produce a disabling glare condition for approaching road users, flaggers, or workers.” In addition, “The adequacy of the floodlight placement and elimination of potential glare should be determined by driving through and observing the floodlighted area from each direction on all approaching roadways after the initial floodlight setup, at night, and periodically.” These somewhat subjective guidelines make such lighting a somewhat subjective endeavor and, as a result, light towers are fairly standardized pieces of equipment. According to one industry expert, future advances will focus mainly on glare reduction.
Most Units Are Similar
Don Cruikshank, vice president of Newhall, CA–based A.V. Rentals, says the brands stocked there have similar specifications. “The typical unit is a 6-kW generator, a 6,000-watt unit firing 4,000 watts of lighting, and the bulbs are 1,000-watt metal halides. Typically, there’s a receptacle somewhere on the unit that has a couple of thousand watts of power left over to power small tools,” he says. “Two thousand watts is not going to take you very far in powering equipment, and the units typically don’t have the capability of being run as a 6,000-watt generator, and they typically don’t have multiple connectors so you can hook into 10 power boxes.” Other standard features of A.V. Rentals units are diesel-driven generators and Kubota motors.
“We’re pretty standard on lighting,” echoes Jeff Schmidt, inventory manager at Ziegler Equipment in Bloomington, MN. “Our packages cover seven acres if you set them right. The light plant is pretty versatile—you can change the pitch of the light, the angle; you can turn them. Usually what we find is that when contractors are using them during the day they use them for saws and small hand tools—nothing major. The biggest one you see is an 8-kW generator, so you’re not usually going to power much off of that anyway.”
Because most contractors rent instead of own lighting units, rental equipment managers might be more selective than contractors in regard to brands. “Parts orders are huge,” Cruikshank says of selecting a brand to carry. “When we get on the phone, we want a quick turnaround on parts. If we have a tower go down, we need something that’s proprietary. I can usually get a bulb anywhere else if I need to, but if I need a part, I can call and pretty much get a turnaround where they ship it today and I get it in a day or two at most,” he says of his vendors. “I’m down two or three days on the high end. We’ve had some other manufacturers come in and try to get us to sell their towers; they’re a little cheaper, but I don’t like mixing up my fleet. I’ve got a good source for parts and I’ve got a good relationship, so I leave it alone.”
Cruikshank and Schmidt add that deploying light towers for maximum illumination of an area is not an exact science. “It really depends on how intense you want the lighting to be,” Cruikshank says of the number and spacing of light towers on a job site. “In general terms, we say that a light tower will light up, give or take, a 20- or 30-yard radius around the unit. That’s going to give you about 100 feet.
“It’s more of a gut feel,” Cruikshank says of positioning units to illuminate a site. “It comes down to where are you going to position the unit and how are you going to set it up. It becomes the call of the inspector; if you’re on a public works job, you’ll have an inspector out there who will say you’ve got enough light or you don’t have enough light, or they’ll want the angle of the light changed because oncoming traffic may be blinded.”
Schmidt adds, “It’s a just a matter of spacing out the lighting, depending on how much lighting you want. In certain places, where they’re working at night, they may just want to put a light on a loading and dumping area, or they may want to light the whole roadway.”
Probably the most important safety issue related to light towers is stability, notes Steve Petrehn, a manufacturer’s representative who supplies light fixtures to light tower companies and who is owner of Performance Power & Light in Roland Park, KS. “There have always been outriggers designed to make a circle around the unit, roughly a third of the height of the tower,” he says. “If you have 12 feet for a 30-foot tower, that’s the combination that gives you stability for winds up to 60 miles an hour.”
Contractors may have to make a choice in regard to the wheels on a light tower, Petrehn explains. “Features to look for are good-size tires, the wide track—they tow a little better if you’re going to be doing a lot of long-distance towing,” he says. “The smaller trailers with narrow tracks on the tires aren’t as easy to tow. If they’re just going to be loaded or unloaded off of a rental center’s trailer, then the compact ones are the solution.”
Parallel Fixtures Differentiate
One major differentiating feature offered by a few major manufacturers of light towers currently on the market is that of a light fixture that makes use of more light output and protects the bulb from breaking during transport. The parallel fixture, which was designed by Petrehn, positions bulbs horizontally and is designed to provide improved performance compared with coaxial fixtures that position bulbs vertically.
Photo: Allmand Brothers Inc.
|Studies indicate that when a parallel fixture is angled at 20 degrees below horizontal—a common position on a job site—97% of its light is output. The result is more even lighting of the job site and elimination of “dead spots” within the combined beams from multiple bulbs in a tower.|
Originally designed for use in applications such as warehouses and stadiums, lights equipped with coaxial fixtures are not ideal for job sites. Nearly all of the light output is indirect; that is, it shines directly off of the reflector that encloses the fixture, resulting in a loss in output of up to 30% for some coaxial lights. In comparison, a bulb sitting in a parallel fixture shines nearly 50% of its output directly through the lens. A bulb sitting in a parallel fixture, when the lens is completely horizontal (zero-degree angle), is considered to project 100% of its lumens.
On the job site, however, it is unlikely that a light tower would ever be deployed with the lens completely horizontal. Studies by Allmand Brothers Inc. indicate that at a more realistic angle, 20 degrees below horizontal, a bulb in a parallel fixture outputs 97% of its rated lumens. On the job site, this design eliminates the bright spot–dull area–bright spot phenomenon, providing better illumination and more even distribution of light.
A good analogy is pointing two types of adjacent desk lamps at a wall—one with a round bulb and another with a fluorescent light tube—and comparing the different beam shapes. The round bulb produces a spotlight-shaped beam; if this bulb were combined with other round bulbs, a series of round beams—with dead spots among them—would result. The fluorescent light tube produces a larger, even beam.
The parallel fixture also provides support for both ends of the bulb, keeping it secure during transport. “It seems to support the bulbs better,” says Cruikshank. “Sometimes you break bulbs just driving down the street. It sits sideways in the can. It screws into one side and then it has a spring-tension support on the other side. It holds the other side of the bulb so that both sides are supported instead of going down the road and you hit a bump and the bulb shakes like crazy and sometimes it’ll break—it just seems more stable.”
Other Unique Features
A few other differentiating features are available on some light towers and may be worth an inquiry.
|Parallel-mounted light fixtures not only increase light output, but they also prevent bulb breakage during transport.|
Getting a site illuminated can be a time-consuming, tedious process, according to Cruikshank and Schmidt. “You have to adjust them and then put them up, and if they’re not right you bring them back down again,” Cruikshank says of most light towers, although he knows of a unit on the market that can be adjusted while elevated. Schmidt adds, “One thing we do that other companies don’t is we put electric winches on our towers. Instead of having to crank them up, they just hit a button.” Schmidt adds that according to the manufacturer, Allmand Brothers, Ziegler Equipment is one of only two distributors in the nation to include this factory-installed option on its light towers.
One option that helps prevent damage and makes it easier to start and stop the units is automatic turn-on and shutoff. “It’s photoelectric and timer controlled,” says Petrehn. “At night, if you’ve got a large site, instead of a man driving from light tower to light tower when it starts to get dark, they’ll light up and the engine will warm up. They will ‘cycle up.’ It’s important for the light to be turned on when the generator has steadied itself and is running at the right revolutions per minute and electrical output. Then, when they’re shut down, it’s important to shut the lights off and then shut off the generator, too—otherwise, you get equipment damage. Most of them are photo-controlled, where the sun going down is what turns them on.” Alternatively, adds Petrehn, remote-controlled starting and stopping may be available.
Independent switch control of lights on a unit can also be an advantage, Petrehn explains.
“If you’re turning the lights on one at a time, maybe you just need one or two or three of them on a time,” he says. “If you want more precise control over the levels of lighting, there’s an advantage there. If you have a malfunction in one of the lights, you can isolate it from the circuit by leaving it off, whereas if one switch controls two and there’s a short in the light bulb, you’re taking both of them out. If you have four isolated circuits, there are four isolated lines.”
Petrehn is not so quick to discount the value of utilizing the light tower generator for other purposes on the job site; that is another benefit of independent switch control of lights, he says.
“Some manufacturers have two lights per switch and then auxiliary electrical outlets are also a good feature because these light towers have the potential to be good daytime portable generators for a job site—I don’t think they get utilized that way enough,” he says. “I think that end users and rental companies don’t think of them as that kind of an asset. When you’re running all four lights, there’s not much extra power in reserve, but in the daytime or sometimes during the day they might be inside a building, they have all 6,000 or 7,000 watts available to them and several different tools could be running or an air conditioner.”
Inquiring about using bulbs other than metal halides—which, for starters, take a relatively long time to warm up—also might be worthwhile, Petrehn indicates. “It’s also possible to fit light towers with high-pressure sodium lights, which are a little more orange, like you see on street lights,” he says. “It’s perfectly good lighting—it’s actually more light for the same wattage. Orange light can glare less in traffic situations. Another thing that’s coming down the road in this industry is more highway and road repair going on at night, and the white lights that are traditionally used tend to shine in the eyes of drivers and have a little more glare. The safety folks at the federal and state level are starting to recognize that lights that have reduced glare are much safer.”
In coming years, as nighttime roadwork becomes more common, Petrehn expects light-tower manufacturers to focus on glare reduction. “I think one of the things that is going to be coming is low-glare lighting—bigger, heavier towers with low-glare lighting,” says Petrehn. He predicts that, in coming years, more manufacturers will offer light towers with shrouding that reduces glare, similar in design to smaller “balloon” lighting units currently used inside buildings. Petrehn knows of one French company, Airstar, that is developing a shrouded light unit for light tower manufacturers.
Don Talend specializes in covering sustainability, technology, and innovation.