Heavy Duty Light Tower Basics|
Article- June 2012 By Larson Electronics.com
Larson Electronics 30' Telescoping Light Tower - 6 Metal Halide Fixtures
Illuminating work sites and construction areas during evening hours is a critical part of safe and effective work operations and is normally accomplished through the use of high power light towers. Operators have several light tower options available to them, but each has its own advantages and disadvantages that should be taken into consideration before any type of tower is settled upon as the best choice. Different tower configurations and lamp types offer distinctly different operating properties that make the choice of lamp greatly dependent upon the type of application they will be used in.
In order to make the best choice of light tower an operator should be familiar with some of the most common tower and lamp combinations. Metal halide lamps currently dominate the tower lighting industry due to their high output and good light quality, while high pressure sodium lamps offer poor light quality but excellent efficiency. LED lamps are quickly gaining in popularity due to their high output, good light quality, and extreme long life and durability, but bring with them a higher price tag. There are mobile light towers, portable light towers, and massive self contained units which incorporate everything from the trailer and generator, to the tower and lamp assemblies into one convenient package.
The following are some basics regarding tower and lamp types that may make choosing a tower easier and will certainly help build familiarity with the most common light tower types available.
Portable Light Towers:
Portable light towers are units that can typically be set up and taken down by one person and easily deployed in small and midsized work areas. These towers normally range from an adjustable 4 to 14 feet in height, and are often equipped with either wheels or collapsible legs that allow stable setup and easy movement of the tower. Although they can be constructed of steel, aluminum is normally a better material choice as it is much lighter and aids in how easily the portable light tower is transported and handled. Portable towers typically require an external power source such as a generator or local power outlet although some smaller units may incorporate a rechargeable battery pack which allows limited runtimes without the need for external power. Portable towers have typically lower to mid power light output with coverage for areas up to 20,000 square feet the average high end.
Mobile Light Towers:
Mobile light towers represent the high end of the light tower spectrum. These units are typically mounted to a trailer which can be towed behind vehicles or heavy equipment and are designed to provide a self contained lighting solution that can be operated in just about any outdoor location. These units usually include towers that can reach anywhere from 15 to 35 feet or more in height and are deployed with either electrical or mechanical winches. Power is normally provided with onboard diesel or gasoline powered generators, and some newer versions are now incorporating solar panels and battery banks for a more environmentally friendly and efficient power source. Mobile light towers are intended for large scale applications such as large construction sites, open pit mining operations, large scale entertainment events, and emergency response centers such as those set up after earthquakes or other natural disasters. These systems typically cover areas anywhere from 2 to 10 acres in size depending upon lamp configuration.
Light towers can be equipped with Metal Halide, LED, or Incandescent Halogen lamps depending upon the operator’s preference and the work areas’ requirements.
Metal Halide lamps tend to produce the highest light output and are usually used on larger portable towers where a large amount of space needs to be illuminated. Metal Halide lamps are efficient and long lived, with around 100 lumens per watt produced and an average operating life of 10,000 hours. Metal Halide lamps run very hot and are easily damaged if protective lenses and covers become damaged or allow contaminants such as water to contact the bulbs. MH lamps also require additional ballast and ballast housings which increase weight and add to cost. They also normally require a warm up and cool down period between power cycles, meaning the lamp takes a few minutes to reach full output when switched on, and must be allowed to cool for several minutes before being restarted after switching off.
LED lamps have become very popular for use with portable towers due to their extreme high efficiency and high light output as well as their excellent durability. LEDs are nearing Metal Halide in terms of lumens per watt of output averaging 60 to 90 lumens per watt. LEDs produce intense white light with good color rendering and contrasting and have operational lives averaging 25-50,000 hours, making them the longest lived of the available tower lamp choices. LED lamps are good choices for small to midsized work areas and can typically cover areas up to 18,000 square feet in size depending upon the tower configuration. LEDs are excellent choices for portable towers equipped with rechargeable batteries as they have low amp and current draw, allowing them to run for extended periods with limited power supplies. LEDs run cool and have no glass or filament in their construction, making them ideal for use in light towers where the unit could possibly be tipped or knocked over. Unlike traditional MH or incandescent lamps, an LED lamp will not shatter if subjected to significant impacts and will oftentimes withstand repeated abuse without any reduction in performance. LEDs do cost more than other lamp types, however, they have operational lives up to three times that of other lamp types, helping to offset their higher cost with fewer required lamp replacements.
Halogen lamps are still commonly used in light towers primarily because of their cheap purchase cost. Halogen lamps are the least efficient of the lamp types and typically produce about 17 lumens per watt. The light produced by halogen lamps is yellowish in color and tends to have poor color rendering properties. Towers fitted with halogen lamps tend to be used in smaller scale applications and are best suited to illuminating areas 10,000 square feet or less in size. They have a short 500 to 1,500 hour operational life and are sensitive to contamination from moisture and dusts, with abrupt and oftentimes catastrophic failure of the lamp taking place once the lamp is subjected to water or dampness. Halogen lamps require frequent servicing and lamp replacement and are highly susceptible to damage from tipping or knocking over of the tower.