Basics of Selecting Effective Paint Booth Lighting|
Article- August 2012 By Larson Electronics.com
Larson Electronics Low Profile Explosion Proof Paint Booth Light with Emergency Backup
Paint spray booth lighting is without any doubt the most critical part of any paint booths design features. There are few items that can affect the productive capability as well as the quality of product coming out of a paint booth as drastically as lighting. The type of lighting used, the quality of the lamps themselves, the color temperature of the bulbs, and how the lights are positioned within the booth can significantly affect your perception of prepped surfaces and the finished color of paints once they are applied. Additionally, lighting equipment plays a large role in paint booth safety as well since the solvents, paints, and chemicals used with the booth are usually flammable and give off vapors and gases that can be ignited when exposed to an ignition source such as a spark or a hot bulb.
The lighting of choice for most paint booths is standard four foot long fluorescent bulbs, usually arranged in fixtures containing either two or four bulbs grouped together. Fluorescents are popular because they produce a very wide spread of light output, which helps to evenly and uniformly illuminate the irregular surfaces of vehicles and thus better reveal imperfections in the surface to be coated. Fluorescent lamps are also popular because they can be had in a variety of color temperatures, which allows paint booth operators to choose lamps according to how well they mimic the natural color of daylight, or how accurately they render the color of the paints being used.
For most paint booth lighting applications, operators prefer a fluorescent lamp with a high color temperature and high color rendering index. The color temperature rating of a lamp denotes where in the light spectrum it radiates the majority of its light output. An incandescent lamp for example has a color temperature of around 2700 Kelvin, which is close to the red end of the light spectrum, hence the yellow or orangish color of the light they produce. A natural white fluorescent on the other hand has a color temperature of around 5500-6000 Kelvin, thus putting its light output closer to the middle of the light spectrum. When we view objects under these different lamps, their colors will appear different due to the spectral properties of the light the lamps produce.
An incandescent lamp with its output heavily skewed into the red end of the light spectrum will tend to reproduce red, orange, and yellow colors well, but do poorly when it comes to rendering blues, greens and whites. The natural white fluorescent on the other hand produces light near the middle of the light spectrum and thus will generally reproduce all colors fairly well, with some exceptions. Because of how a bulb produces light, how much of the light spectrum it actually radiates can vary greatly. Although a fluorescent lamp may radiate in the 6000k end of the light spectrum, this does not automatically mean it radiates all the colors of the light spectrum. A fluorescent lamp may be rated at 6500K, but it can also be red deficient, resulting in a lamp that produces somewhat bluish light that poorly renders the true red coloring of an object. In these cases, it is best to choose a lamp that is “full spectrum” with a middle of the range color temperature, meaning it produces the widest possible range of color wavelengths across the light spectrum.
As a result, it is also necessary to consider the color rendering index of a lamp as well. The color rendering index tells us how well a lamp renders the colors of its spectrum. Incandescent lamps have a CRI of 100 despite having poor light quality because they reproduce the colors of their spectrum very well. Thus, if we choose a fluorescent paint booth light with both a mid range color temperature and a high CRI, we can be reasonably assured of good quality light output that will reproduce colors accurately. Generally speaking , for paint booth light it is best to look for lamps with a color rendering index of at least 80 and a color temperature in the 5500-6000K range.
Positioning of lamps within the paint booth also plays a critical role in how effectively the work space will be illuminated. Since fluorescent lamps are typical long and thin, arranging them around the booth vertically can make it difficult to illuminate the work space effectively. With the lamps arranged vertically, it is easy for the paint booth operators’ body to block most of the output of a lamp when he moves in front of it. Fluorescent paint booth lights are best positioned horizontally, which allows more of their light to radiate onto the work surface even when an object is in front of the fixture. Another good practice is to mount overhead lighting across the upper corners of the booth rather than flat on the ceiling, thus providing the maximum amount of coverage with less potential for shadowing or obstruction.
Above all else, a lighting that will be installed within the confines of the booth must be approved for use in hazardous locations. The nature of the materials used and the type of work performed gives paint booths a Class 1 Division 1 rating, meaning lighting approved for regular exposure to flammable or explosive gases and vapors must be used. While it is also popular to install lighting outside of the booth in panels in order to avoid the expense of explosion proof compliant lighting, there are some special considerations that must be considered. For instance, some areas, door openings and exhaust vents for example, pose the potential to allow flammable gases and vapors to escape. As a result, when the spraying system cannot operate unless the ventilation system is switched on, then any lighting within 5 feet horizontally and 3 feet vertically of the opening must be Class 1 Division 2 approved.
For safety purposes, paint booth operators would be best served to consult with the NEC guidelines, particularly articles 500 through 516 in order to be certain their booth is compliant with all current regulations as well as safe for operation.