Grading and Excavation Contractor | MOBILIZING FOR POWER AND LIGHT

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When it comes to lighting up your job site or providing auxiliary power for tools and equipment, you enjoy a wide variety of choices. Here’s a guide to help focus your selection.

By Greg Northcutt

Completing a grading or excavating project usually requires more than the power to dig, push, grade, load and otherwise handle dirt efficiently and productively. Often it takes other types of power, as well—like the power to extend your workday and help keep the site secure during hours of darkness. Or, the power to operate tools, ranging from electric breakers to air compressors, and even to keep the lights and computers on in a job shack. That’s where portable lighting systems and mobile generators can save the day as well as the night.

Like any piece of equipment, getting the most for your money from a set of lights or a genset means selecting the unit that best fits your grading and excavating needs. Here are some tips to help you make that decision.

Lighting Up With Light Towers
Mounted on a trailer, a typical light tower features a telescoping mast, which rotates 360 degrees and usually extends about 30 feet above the ground, topped by a set of four adjustable 1,000-watt metal halide bulbs. Other usual standard features include an 1,800-rpm diesel engine running a 6-kW diesel generator set to power the bulbs, a control panel for the engine, and lights and a set of four outriggers for stability in uneven terrain and windy conditions. Such a system can be used to illuminate an area as large as about 7 acres.

Lighting fixtures—Metal halide lamps, which produce high light output for their size, provide a bright white light. They are, by the far, the most popular choice of bulbs. However, some manufacturers also offer high-pressure sodium lamps, which produce light that is more pink in color.

Light fixtures that are elliptical in shape allow light to travel directly to the work area for brighter illumination than round fixtures. For ease of adjusting light coverage, look for lights that can be individually adjusted up and down and to either side without tools. An individual circuit-breaker switch for each light adds to flexibility of power use.

Masts—Extendable masts include a hand-operated dual winch for raising and lowering and a self-braking system to prevent it from free falling. Look for winch handles that are easy to reach and operate and aircraft-quality cables. Some manufacturers also offer available electric winches for faster, easier operation and dual brakes.

Outriggers—While outriggers enable light towers to withstand winds, usually between about 50 and 65 miles per hour, the design and wind ratings can vary. In the case of Wacker light towers, for example, the outriggers are attached directly underneath the tower rather than at the back, as on other makes. “This design directly supports the load of the mast to provide more stability,” says Marc Leupi, utility group product manager for Wacker. “With the outriggers fully extended and all jacks in place, the light towers are rated to withstand winds up to 65 miles per hour.”

Size—The length and width of the light tower trailer varies from one manufacturer to the next. The more compact the design, of course, the easier to keep it out of the way on the job site. A smaller unit also takes up less space on a trailer and in the storage yard.

“If you have a number of light towers to transport to a job site and if you can fit two of them side by side on a flatbed trailer, you can reduce freight costs,” Leupi says. “Models with a removable tongue can allow you to save even more transport or storage space.”

Other features, like forklift pockets and a crane attachment point, make loading and loading units easier.

Fuel tank—The larger the fuel tank, the less time and money spent to refuel the engine. Depending on make and model, fuel capacities can range from around 30 gallons to more than 60 gallons. The largest tanks can provide for as much as 100 hours of continuous operation.

Engine—A glow-plug preheat system makes cold-weather starting easier and lengthens service life. At the same time, an automatic engine shutdown feature can protect the engine from damage caused by low oil pressure or high coolant temperatures.

Control panel—Some models offer a separate engine control panel for more convenience in monitoring engine performance and full diagnostics for added engine protection. 120V/A GFCI and 240V/30A receptacles with separate circuit breaker give you the power for other equipment, tools or other job site needs.

Engine noise—Depending on local rules, the amount of noise made by tower’s engine could be a problem. Noise output is affected by the type of engine and how well it is shrouded, and decibel ratings for most models are in the 68- to 72-decibel range, Leupi notes. “To check noise levels, it’s best to run the machine on concrete or asphalt,” he says. “Hard surfaces amplify engine noise the most.”

Maintenance—Features that can simplify engine servicing include large access doors that eliminate the need to climb on top of or under the tower unit and drainage openings. For added durability, look for such features as zinc dichromate–treated masts and lamp-mounting bars, zinc-plated leveling jacks and steel genset cabinets protected polyester powder coat or polyurethane paint.

Heavy-duty construction of the trailer, including features like heavy-gauge steel, beefy axles and impact-resistant foam core polyethylene plastic fender, can increase reliability while decreasing maintenance costs.

Options—In addition to the popular four-light, 6-kW light tower, manufacturers also offer 8-kW and 20-kW models as well as those with six or eight lights.

Depending on brand, other choices include cold-start packages, sound-attenuated gensets, fuel-water separators, engine fluid containment systems, and a ball or pintle trailer hitch.


	A Look at Some Lighting and Genset Choices

Lighting Without Shadows
Originally developed for the film industry, balloon lights are becoming more common on grading and excavation job sites. This type of light features a halogen or metal-halide bulb encased within a self-inflating balloon made of a translucent, white ripstop fabric that resists rain or snow mounted and mounts on a telescopic tripod or mast. The balloon fabric diffuses the light evenly, eliminating glare and shadows.

“This produces a homogenous light over 360 degrees without hot points,” says John Wessels, a national sales manager with Airstar America Inc. “Thanks to this unique technology of balloon lights, you can see perfectly and work in comfortable conditions without strain on the eyes. A driver or a passerby can see the balloon and not be dazzled or blinded. These are big advantages compared to traditional lighting systems such as light towers.”

Because balloon lights resist damage from vibrations, they can also be mounted on construction equipment. In fact, when Airstar introduced this technology to the construction industry, its first balloon lights were used on mobile pavers and rollers.

The maximum recommended mounting height for the company’s 1,000- or 2,000-watt lights is 16 feet. “There’s no increase in the light intensity on the ground as you raise the light higher,” Wessels says. Maximum height for the company’s 4,000-watt balloon light is 35 feet.

Depending on type of bulb, wattage, and mounting height, Airstar balloon lights can be used to illuminate areas ranging in size from 1,000 to 108,00 square feet, he reports.

Those designed for construction work range in diameter from 3.1 to 7 feet and are designed to withstand winds up to 65 miles per hour, Wessels notes. “An elliptical or tubular shape gives them better wind resistance,” he says. “Also, a safety system switches off the power in case the balloon loses air pressure.”

Balloon lights are lightweight and easy to transport, set up and take down. Some features to consider in selecting a balloon light include the following:

Type of light—Choice of light sources include halogen bulbs that fire up immediately, eliminating the need for ballast and space to store it, and higher-priced metal halide bulbs. Metal halide bulbs, which require several minutes to reach full light output and longer to cool down, produce more intense light than a halogen bulb.

Balloon inflation—Depending on manufacturers, these lights can be inflated with several different methods, including a built-in fan or a rechargeable air blower. The latest development is a mechanical system that opens like an umbrella, eliminating fan noise. With no fan to draw in dirt, the balloon reportedly stays cleaner.

Mobility—Some manufactures offer cart-mounted models with a telescopic mast, four pneumatic tires, handlebars for steering along and a portable generator.

Storage—The various components of balloon lights—such as the fabric envelope, the bulbs, blower, ballast and power cord—require minimal storage space.

Economics—Because a balloon light system typical doesn’t include a generator, the purchase price can range from about one-third to three-fourths the cost of standard light tower, reports Leupi with Wacker, which makes both balloon lights and light towers.

“If your main concern is to eliminate glare or you want a softer light for general illumination, a balloon light is probably a more economical choice,” he says. “However, for illuminating a larger area, a light tower is definitely more cost effective.”

Generating Power
Typically, a towable generator, is powered by a diesel-engine operating at 1,800 rpm and has a four-pole alternator producing single-phase and three-phase power at a frequency of 60 Hz. Models are available in sizes ranging from about 20 kW to 250 kW or more to meet a variety of job-site needs. The selection can also features like automatic remote start for standby operations, dual-axle trailers or programmable control panel, depending on make and model. Here are some tips to help you sort through your choices.

Know your load—The key to satisfaction with any generator, say the experts, is buying one that best matches your power requirements.

Buy too small, of course, and you won’t have the power when you need it. To figure the right size generator your job sites, total up the wattage of all lights, tools and other equipment that you’ll be connecting to the generator. Usually, that information is on the equipment name plate. If amps and volts are shown, but not watts, you can determine your wattage needs with this formula: Amps x Volts = Watts (VA)

Your calculations should also allow enough reserve power to handle the extra amperage that electric motors require when starting. Small tools may draw two to three times the amps to get started than when running. Induction motors, like those on compressors and submersible pumps, may need as much as four to five times their operating amps for starting. To boost the generator’s ability to respond to the surge in power demand for starting electric motors, some generator manufacturers use alternators with a separate excitation winding and an automatic voltage regulator.

Depending on your job site and equipment conditions you may need to add even more reserve power. For example, because of leakage, older, worn equipment may draw more amps than when new. Hot weather can also take its toll on a generator’s efficiency due to the way generators are designed. The power-generating ability of some generators begins to drop off around 100°F to 105°F. Others can tolerate higher temperatures before their power output starts to decline.

Buying or renting more generating power than you need has its drawbacks, too. You not only spend more money than necessary to purchase or rent the unit, you’re also wasting money on extra fuel. In addition, you’re adding to maintenance costs while reducing the useful life of the generator’s engine.

Operating a generator below 50% capacity on a regular basis can lead to a condition called wet stacking. “Carbon builds up inside the cylinders and valves of the engine, causing it to run inefficiently,” Leupi says. “Over time, this will not only reduce the generator’s performance but also shorten the engine’s lifespan.”

The remedy, he notes, is to connect the generator to a heavy load, either to a tool or construction equipment or to a load bank, a piece of equipment that simulates a heavy load. “This causes the engine to run hot and burns off the carbon inside the cylinders,” Leupi says.

Fuel tank—The larger the fuel tank capacity, the less time spent refueling. Wacker offers an optional long-run fuel tank for its larger generators that allows the generator to run about three days at full load between fill-ups. “That’s especially handy for running a piece of equipment, like a submersible pump, over a long weekend or to power load in a remote location,” Leupi says.

Engine noise—As with generators on light towers, the amount of noise produced by a towable generator could be an important factor to consider, depending on location of your job sites. If so, look for units with sound attenuated enclosures.

Engine governor—By controlling engine speed, the governor responds to loads imposed on it by the generator to regulate frequency and voltage output. If you’re using the unit to power hand tools, a mechanical governor is probably sufficient, notes Leupi. However, if you’re connecting the generator to computerized or electronically operated tools and equipment, an electronic governor is a better choice because it produces a rapid, more stable engine response.

“The frequency can vary by as much as 5% or so with a mechanical governor,” he reports. “An electronic governor responds to loads faster and more precisely to better manage the interface between the generator and engine in regulating the frequency and help prevent damage to electronics.”

That’s a moot point if you’re buying a new 50-kW or larger generator. “Almost all these units are equipped with Tier III engines which come equipped with electronic governors to meet the newest EPA diesel engine emission control standards,” Leupi says.

Control panel—In addition to gauges and meters or LED displays for monitoring engine and generator performance, other control-panel features can enhance operating convenience and safety. Depending on manufacturer, they may include automatic engine shutdown in the event of low radiator fluid, low engine oil and engine overspeed or underspeed; and a lockable voltage selector switch to prevent damage by changing voltages while the unit is running.

Maintenance—Among the various features that can reduce maintenance costs are sealed generator bearings, fuel water separator to protect the engine from water and other contaminants; and large removable enclosure doors.

Some manufacturers offer features designed to keep the generator up and running in extremely cold temperatures. For example, Wacker has a cold-weather package that includes a shutter system for regulating temperatures inside the engine enclosure. “The shutters stay closed, recycling the air inside while the engine is warming up,” Leupi says. “Once the engine reaches operating temperature, the shutters open up to slowly release warm air to the outside as needed.”

Options—Depending on make and model, you can outfit towable generators with a dozen or more options ranging from an engine block heater and electronic governor to a fluid containment system.

Installing options at the factory provides some advantages over adding them in the field, Leupi reports. Wacker is one of a few manufacturers that offer factory installation of its options. “This way you can have a generator made to your specific needs,” he says. “It’s more efficient than adding the options later. Also, the machine is fully tested at the end of the production with all the options integrated to make sure they all function together as designed.”

Greg Northcutt writes on construction and business issues.

GEC - May 2008

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