Grading and Excavation Contractor | Let There Be Light Towers

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When it absolutely, positively has to be done overnight...

By Daniel P. Duffy

Nighttime construction, grading, and excavation activities have always been potentially more dangerous than daytime construction due to obvious reasons of limited visibility. This limited visibility can be caused by both darkness and its opposite, excessive glare. However, nighttime construction efforts (including those related to highway construction or repair projects) have become more common so as to not interfere with the daily activities of motorists and pedestrians (especially the morning and evening commutes). Any such night work requires a well-thought-out and prepared lighting plan that provides adequate illumination for each specific scheduled nighttime task while supplying a reasonable level of uniform lighting over the rest of the site. Such light should be planned and provided without generating significant glare that would affect equipment operators on the site and passing motorists. In addition to a well-executed plan for utilizing light sources, an equally important plan for supplying the energy required by these light sources is essential. Light sources cannot be considered independent of the mobile power generators that accompany them. Together the two should be considered one piece of equipment. They are no more independent than the drive train and hydraulic systems on a tracked dozer. Both are required for proper functioning.

Lighting is one of the main factors affecting worker safety, quality of workmanship, reduced costs, and productivity as measured in effective use of man-hours and equipment hours. Standards for the lighting of nighttime construction projects have been established by most state departments of transportation, and such standards are usually applied even to no-roadway construction. Once these standards have been applied, a lighting plan can be developed. This lighting plan will depend on the performance characteristics of multiple light sources being used independently or together across the job site. The energy needs of the individual light sources will be provided by the mobile power sources used at the site.

Light-Tower Standards
This article will focus on all aspects of outdoor job-site lighting (lighting used to illuminate the interiors of buildings under construction or lighting used in underground tunneling and excavation jobs is a separate application). Outdoor lighting fixtures usually utilize directional shielding. This allows the light to be contained and directed toward only that part of the job site that needs illumination. Limiting stray light goes a long way toward limiting glare. At no time should high-intensity lights, such as lasers or strobes, be used to illuminate a job site as they can cause temporary night blindness or even damage to the retina. Even the use of flashing lights should be minimized to prevent distraction.

In addition to being located specifically to illuminate certain areas of the job site or certain work activities, lighting fixtures should be set to an appropriate height. The site’s lighting plan should designate both the location and height of the lamps. No more than 40–50 above the finished grade at the bottom of the light-source pole or fixture is a typical height standard. In addition to this height standard, there are several others affecting the proper use of outdoor area lighting. Height combined with the horizontal distance of the light source from the point of illumination provides the position and aiming angle of the light. Aiming angle and rotational angle determine how flexibly the lighting can be used from a fixed position so that one light can illuminate multiple tasks or follow the operations of equipment working over a large area.

These factors are applied individually to the number of lights of all kinds (trailer-mounted light towers, equipment-mounted luminaries, and even equipment and vehicle headlights) being utilized at the site.
In addition to quantity, the quality and power of the lighting will have a significant effect on its overall usefulness. These qualitative factors include the type of light being used (e.g., metal halide lamps or halogen lamps), the lumen output per light and its resultant intensity and energy requirements, how the light is distributed in different directions, and the fading of the light over time with each hour of usage.

The overall lighting system takes all of these factors into account to develop a plan that optimizes average illumination to ensure adequate lighting on the site, lighting uniformity to reduce areas of shadow or blackness, and glare minimization to reduce annoyance, discomfort, temporary blindness, and eyestrain. At a minimum, lighting equivalent to 5 foot-candles should be provided for the entire work area.

A foot-candle is defined as the even illumination of 1 lumen applied to a 1-square-foot surface. For comparison, a standard 100-watt lightbulb emits approximately 1,700 lumens. Equipment-mounted lighting systems generating 10 or 20 foot-candles are usually connected directly to the construction equipment.

Photo: Terex

It's important for equipment to stand out at night.

Light Towers and Suppliers
Multiquip is the manufacturer of the Night Hawk series light towers. Set atop masts 30 feet high, the lights can be rotated 360 degrees to wherever illumination is needed. The mast structure is sturdy enough to withstand wind gusts up to 65 miles per hour without bending or overturning. The company’s models LT-12D and LT-12P each shine with four metal halide floodlights. Over 60 hours of operating time is made possible by an integral 30-gallon fuel tank. The tank is made of polyethylene and includes a fuel control system that ensures high-temperature and low-oil-pressure shutdowns. Power is supplied by a 10.7-horsepower to 12-horsepower diesel engine. Additional self-lighting is provided by lamps that illuminate the tower itself and the power receptacles that are integral to the light tower. Small (only 1,550 pounds each) but powerful, the light towers can emit 6,000 watts of light, and eight of them can be carried on a single flatbed truck.

Baldor manufactures compact, mobile light towers that are easy to transport and set up. The smaller models provide up to 4,000 watts of light from metal halide lamps. Its Pow’r Lite model can illuminate up to 7 acres. These models are powered by a Baldor 6,000-watt light-tower generator. These generators are powered by Kubota diesel engines with 50-gallon fuel tanks that provide for 100 hours of operation.

Bossltg provides a telescoping light-tower kit that allows the support pole to expand to a maximum height of 28 feet. Affixed to this telescoping pole are four 1,000-watt floodlights. The assembly consists of a supportive frame design that can be attached to an existing trailer or delivered with its own trailer. This allows for flexibility of operations so the user can install the genset package of his choice to supply the electrical power. In addition to the light fixtures, the unit includes a plug-in control panel that operates off a 125/250-V, 50-amp, spider-model receptacle. This can be used for plugging in power tools or even other light fixtures.

Controls that minimize manual operation are a key feature of the Terex AL 4000. These controls include a timer mode that automatically turns the lights on and off at set times and a photocell mode that automatically turns the lights on and off depending on the amount of natural light measured by the photocells. At full height, the expandable tower mast can reach up to 30 feet and can rotate 360 degrees. Attached to each tower are four 1,000-watt halide lamps. Each tower can provide sufficient lighting for an area of up to 7.5 acres. It is powered by a 10.5 Kubota diesel engine whose 30-gallon fuel tank allows for 60 hours of continuous operation.

In addition to its famous lines of earthmoving equipment, Caterpillar manufactures and supplies towable light towers. Each tower comes equipped with four 1,000-watt metal-halide floodlights. The towers are telescoped and can extend up to 25 feet in height and can rotate 360 degrees. Capable of illuminating between 5 and 7 acres of area, the unit comes with a control panel equipped with individual light switches, hour and amp gauges, and a pair of 120-V GFCO receptacles for operating auxiliary power tools. The unit is sturdily built on a reinforced galvanized-steel trailer frame with a 3,500-pound-rated axle supporting 15-inch-diameter radial towers.

Photo: Mobilight

Setup of lights is critical: Look for blind areas.

Bull Dog’s Power Tower is well-designed for large-scale applications. For a light tower with a relatively modest power output of 2,000 watts it can illuminate up to about 4 acres of area with an output of 220,000 lumens. Its illumination is provided by a pair of 1,000-watt metal-halide bulbs. Durable and easily portable, the Power Tower meets or exceeds OSHA workplace safety requirements. Requiring a 20-amp, 120-V power source, its tower mast has urethane spring-mount cushions to handle the jolts that come with rigorous use.

Ingersoll-Rand offers a new kind of portable lighting unit, the “balloon light.” This light is designed as an inflatable, opaque “balloon.” With this configuration, a balloon light evenly diffuses light (with an almost shadowless illumination) from 1,000-watt lamps. The lack of shadow is made possible by diffusing the light through the envelope of its balloon-like cover. Not only are shadows virtually eliminated, but glare is also significantly reduced. Balloon lights offer the advantages of easy portability and operational flexibility since they can operate off any welder, portable generator, or 20-amp circuit. Popular in Europe, balloon lighting is making inroads on the American market. Design refinements include toolless adjustment positioning that allows for the purely manual installation of the lights, flexible use of available electrical power via additional receptacles that can supply power to hand tools, and the use of electrical or hydraulic winches to raise and lower the tower, which eliminates much of the grunt work involved in light-tower installation. The light-tower operations are automatically regulated by photocells, which turn a unit on as darkness falls and turn it off as the sun rises.

Airstar America’s glare-free lighting is particularly suited to nighttime roadwork because the company’s lighting balloons—emitting high-wattage, 360-degree, shadow-free illumination—offer increased safety to work crews and motorists alike. Lightweight and mobile, the self-inflating balloons are easy to set up and immediately operational.

Specific lighting of discrete areas can be provided by the light tower’s smaller cousin, the portable work light. Though often used for emergency lighting or even recreation, these handheld units can occupy useful niches in the nighttime work environment. Being relatively cheap compared to tower lighting, multiple portable work lights can provide much-needed flexibility to a job site’s lighting plan. One example is the LumaPro portable work light, capable of providing illumination with a single 1,000-watt halogen-bulb floodlight. It has a lightweight, die-cast aluminum housing with a convenient S-shaped handle for manual movement and placement. Its waterproof gasket lens allows for safe use in wet environments.

If maximizing illumination is the goal of your site lighting plan, the Allmand Brothers lines of high-illumination light towers should meet your needs. The company’s Super High Output (SHO) lighting tower generates 50% more lumens than comparable light towers. This output is provided by the ML6 and ML8 models, utilizing four 1,250-watt lights and six 1,000-watt lights, respectively. Utilizing an Isuzu 4LE1 liquid-cooled diesel engine, greater operational flexibility is provided by the ML15 and ML16 towers with their multiple outlet capabilities and 15-kW and 20-kW generators. The SHO comes standard on the Night-Lite Pro with its parallel lamp fixtures, which are powered by a Kubota D905 liquid-cooled diesel engine.

Portable-Generator Standards
The electrical power supply needed to run light stands and other sources of illumination is typically provided by portable generators (also known as “gensets”). These power units can be easily hauled out to a job site, set up, and operated as needed. They consist of several components mounted on a metal chassis. These components include an internal-combustion engine, which varies in size and power output and utilizes various types of fuel (gasoline, diesel, or propane). The internal combustion engine drives an alternating current (AC) alternator that translates the mechanical energy of the engine into the electrical power that turns on the lights. This power is managed by a key starter and a system of manual starting and regulating controls. Connections to the power generated by the alternator are provided by multiple electric power outlets located on the generator’s chassis. Since electrical power generation at a work site can be potentially dangerous (especially in rainy weather), the generator comes equipped with safety devices, such as ground-fault circuit interrupters and circuit breakers.

Sixty-Hertz current is the standard for power generation in the United States. This requires a mechanical power source that operates at a minimum of 1,800 rpm (or multiples thereof). High-rpm, air-cooled engines tend to run light-duty generators with relatively short operational lifetimes of up to 500 hours of use. They are mostly used as emergency backup generators. Long-service generators suitable for lighting operations tend to be powered by liquid-cooled, low-rpm, diesel-fueled engines capable of providing up to 30,000 hours of use.

The fuel used to run a portable generator can be biodiesel, diesel gasoline, propane, or natural gas. It can be supplied from an attached fuel tank for operating cycles less than 12 hours or via a fuel line for continuous operation. Tank-supplied generators need to be stopped and refueled at regular intervals if used for continuous lighting. Fortunately, few lighting projects will require an operating cycle greater than 12 hours. Gasoline-operated gensets are the least expensive, but they come with significant drawbacks. Stabilized gasoline will be required for onsite storage for long-term projects. Cold-weather startup problems could also occur. Diesel-powered engines are more efficient, have longer operating lifetimes, and tend to be quieter. Propane can also be conveniently stored in tanks and has an unlimited shelf life. Many portable generators are flex-fuel-capable and can be run with a variety of fuels.

Portable Generators and Suppliers
In addition to light towers, Baldor manufactures portable gensets that are easily towed to a job site. Their design emphasizes quiet operation and rugged dependability even in the roughest work environments. Utilizing state-of-the-art electronics and controls, these units can be used with an automatic transfer switch for standby applications. The models range from 25-kV-A/20-kW to 400-kV-A/320-kW units. Flexibility of operation is provided by a three-position voltage-switch selector that allows for single-phase and three-phase power generation. The gensets are provided with a large integral fuel tank equipped with fuel-water separators, water-temperature automatic shutdowns, low-oil shutdowns, and other features that ensure smooth and safe operation. The units can be customized either by field installation or factory modifications to include such features as battery chargers and block heaters.

As a matching power source to its light towers, Caterpillar’s 8-kW genset is powered by a water-cooled diesel engine that can provide up to 50 hours of continuous operation. These gensets supply 8-kW, 120/240-V, single-phase, 60-Hz, 1,800-rpm electrical power. The 25-gallon diesel fuel tank allows for extended, nonstop operations. The system is equipped with a complete array of automatic safety shutdowns. The genset cabinet is painted with a powder-coat, corrosion-resistant paint. Naturally, being Caterpillar, the color is yellow.

Honda is an industry leader in the manufacture of gensets, earning a well-deserved reputation for rugged reliability. All of its EB-series generators come standard with full GFCI circuit protection, making them compliant for all regulated job sites. EB generators provide 5,000 watts of electrical power with such standard safety features as a steel fuel tank, a four-step oil-and-gas filter, an automatic throttle for smooth running, and an automatic voltage regulator for even power generation. In addition to its main power line, the generator includes a GFCI 120/240-V receptacle. Use of the voltage switch allows for total generator output to be available through the pair of 120-V outlets. Physical safety features are provided by strong frame protection, a bale hook, and a wheeled axle for ease of mobility. Honda’s new i-Pro series provides up to 6,500 watts of portable inverter power. The “i” in i-Pro in effect stands for “intelligent,” utilizing Honda’s proprietary i-Monitor technology. This system provides information to the operator concerning hours of operation, power output, engine speed, and other diagnostics needed for proper servicing of the unit. Utilizing this technology, the Honda EB7000i also comes with such features as Honda’s Eco-Throttle for up to 14 hours of run time on a single tank.

Kubota brings 80 years of experience to the field of generator manufacture. It manufactures sturdily built, one-side maintenance, diesel engines emphasizing long-term operating life and reliability in the field. Its SQ series is designed for very quiet operation, whether delivering single-phase (up to 25 kW) or three-phase (up to 28 kW) power. The SQ offers clean-burning emissions with diesel engines that produce far less soot, hydrocarbons, and carbon-monoxide emissions from Kubota’s original E-TVCS combustion. The silent operation is provided by an over-sided engine silencer (some models have a second silencer) and an ultra-quiet cooling fan. The company’s GL series is low and compact, designed for installation in tight operating conditions. It produces single-phase (11 kW) power. The generator and engine of this design are directly coupled to ensure dependable operation. This direct-coupling design also allows for compact construction and makes the model’s space-saving characteristics possible. Like the SQ model, its diesel engine is designed for low emissions. Heavy-duty power generation is provided by Kubota’s KJ series. Operating in either single-phase (up to 17.5 kW) or three-phase (up to 21.6 kW) mode, the KJ utilizes a brushless, self-excitation-type alternator.

This allows the generator to be used in a wide variety of difficult starting conditions. Larger load impacts can be managed by the KL due to its Load Acceptance Module (LAM), which allows it to quickly regain its rated speed. Worldwide use is made possible by its ability to convert between 50-Hz and 60-Hz frequencies. Safety features include automatic air bleeding to remove air bubbles from fuel lines, an automatic shutdown mechanism triggered by adverse oil-pressure or water-temperature conditions, an emergency unit that combines three different relays (emergency, timer, and safety) into one space-saving unit, and improved protection against water, dust, and vibration. Finally, Kubota’s simple all-purpose J series provides flexible energy production in a variety of environments by using either single-phase or three-phase (both up to 18.8 kW) modes. Steady current flow is ensured by the use of an automatic voltage regulator and skewed rotor and damper winding that minimizes waveform distortion.

Daniel P. Duffy, P.E., is with the URS Corp. in Akron, OH.

GEC - September/October 2007

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