Light towers

|  October 01, 2003 |

The vast majority of light towers illuminating construction sites are the basic four-light, 30-foot models with 6-kilowatt generators. This gets the job done in most applications, providing light at night and powering tools by day.

But if you want to use your light tower’s generator to power more than a small drill, saw or coffee maker, you will be better off selecting a tower with a larger capacity generator. Motor-starting loads, for example, typically take three to six times the current to start as they take to run. So an item that pulls 10 amps could draw 30 to 60 amps to start.

For this type of application, Doug Dahlgren, product manager for Allmand Brothers, recommends specifying a light tower with an automatic-voltage-regulator generator rather than the standard capacitor generator. “When you start trying to run a 2-horsepower electric motor on a pump and the pump has to start with a load on it, it’s going to fall on its face,” he says. “Not that it can’t be done with a light tower, but if you want to do that type of function, manufacturers offer avr-regulated generators and light towers with generators up to 20 kilowatts.”

Larger-generator light towers have been introduced in recent years and allow you to power such things as offices or trailers in remote areas in addition to the small construction tools a 6-kilowatt generator can support.

Six-light towers are also available and work well for large projects that require a lot of light. Because you get 50 percent more light out of each tower than you would with four-light towers, you can eliminate several units from your requirements if the job is big enough.
You need to choose a mechanism for raising and lowering the towers that will work best at your jobsite. Three kinds are available: a hand-crank winch, electric winch or hydraulic tower. See the chart below for the pros and cons of each tower type.

Once you have decided which type of towers to rent or buy, you’ll have to figure out how many lights your project will require. If you are working on a state highway, this is particularly important because state departments of transportation usually set light requirements in their job specifications. If light levels are not prescribed in your project’s specs, you can get a feel for how many towers you need from the Illuminating Engineering Society’s recommendations. You’ll find IES light level suggestions for various applications and charts to help you calculate how many floodlights will provide those levels on page 70.

Bob Schaefer, director of sales, marketing and customer support for Terex Light Construction, says light towers are not good items to consider when trying to trim spending at the construction site. “The better lit a jobsite is, the safer your workers will be,” he says.

TIP: Before erecting a light tower, inspect the tower and winch cables for wear, make sure the safety pins for the mast and telescoping locking pins are present and secured with the chain and ensure the springs located in the mast and telescoping locking pins are not broken or missing.

Avoiding operator error
When operating your light towers, you can keep the jobsite safe and prolong the life of the equipment by following a few simple guidelines and paying attention to what you are doing.
Light towers should not be placed near any obstructions, such as trees or power lines. “The electrical hazard from overhead power lines is very real, and care must be taken to avoid this potentially fatal hazard,” says Mark Conrardy, sales engineering manager for Wacker. “The lamps also create a lot of heat, so any combustible obstruction, such as trees, can catch fire if they are too close to the lamps.”

Extending and locking in place the telescoping outriggers to both level and stabilize the towers is vital as well. Still, many people neglect to do this because they are in a hurry and are trying to cut corners, Schaefer says.

“They say, ‘Oh, it’s hooked up to the pickup truck – that’s good enough,'” says Jim Roberts, marketing manager for Magnum. “I’ve seen sites where light towers have tipped over because someone took a shortcut. These things weigh 2,000 pounds. If it tips over, you’re in trouble. It’s a piece of equipment.”

Another common mistake is not grounding the units. Any power-generating machine should be grounded, and most manufacturers provide a ground stud with their light towers.
If you are not paying attention to what you are doing when you crank a tower up or down with an electric winch, you could spool extra cable off the drum that can then get knotted and tangled, Roberts says. If someone releases the mechanical pin that holds up the tower, the tower could fall until that slack is taken up.

Always turn off the lights and unplug items from the accessory outlets before shutting down the generator. “Most of the warranty or service issues we have with generators are from people shutting the engine off without turning the load off first,” Dahlgren says. “So as the engine rpm is dropping the generator regulation system is trying to maintain the voltage and it can’t do that.” Eventually this will destroy the generator’s capacitor. The capacitor could also be damaged if you turn the generator on with the lights switched on or tools plugged into the accessory outlets.

During the past two years, several manufacturers have introduced management systems that automatically turn off the load on the generator before shutting it down or prevent the unit from starting when the main breaker is on or accessory items are plugged in.

Running out of fuel will impose the same strain on the generator regulation system and in most cases will require you to reprime the engine. If you over crank the engine when repriming it you could damage the starter motor or fuel solenoid. Some of the new
management systems have a feature that will initiate the shutdown sequence when the fuel level drops to 10-percent capacity.

Many of these automatic systems also give you the ability to program the lights to turn on or off at particular times each day or operate them remotely with wireless devices such as cell phones. Photocell technology can turn the lights on at nightfall as well.

Make sure you raise your towers to their full 30-foot height because the higher the tower, the more light coverage you will get. Rita Moore, marketing product manager for Ingersoll-Rand, says workers at road sites sometimes raise towers only 12 feet because they can tow them under bridges at that height. “They’re just trying to get the light up and on so they just take it up to its first level and they don’t take it any further,” she says. “I just don’t think they realize they could probably eliminate a light tower out of their requirements if they just use their towers’ total capacity.”

You should angle your lights down 20 to 30 degrees. This reduces glare, keeps the light out of drivers’ eyes if you are working on a road project and puts brighter light on the work surface. You’ll also get broader coverage if you angle your lights to the right and left a bit instead of having them all pointed in the same direction, Moore says.

TIP: Prior to each use, check tires for proper pressure and inspect trailer lamps.

Safety depends on frequent maintenance checks
Because light towers may run constantly at a jobsite for a week at a time, maintenance is particularly important. You or your maintenance manager should visit the light towers on your jobsites when making rounds to other machines, says Tim Gunnels, manager of engineering for Terex Light Construction.

The majority of the maintenance procedures light towers require involve the engine. Follow the manufacturers’ recommendations for changing oil and replacing oil and air filters, making sure you accelerate the air filter schedule if you are working in a dusty environment. Check fluid levels every time you fuel the unit.

Before each use, inspect the tower and winch cables for wear, make sure the safety pins for the mast and telescoping locking pins are present and secured with the chain and ensure the springs located in the mast and telescoping locking pins are not broken or missing. Also check tires for proper pressure and inspect trailer lamps.