Paint Spray Booth Lighting: Safety and Effectiveness|
Article- November 2011 By Larson Electronics.com
Larson Electronics Explosion Proof Fluorescent Lights for Paint Booths
Producing effective illumination in a paint spray booth entails more than just bright lighting. In order to provide illumination that is effective as well as safe, paint booth lighting must be considered for its general characteristics as well as approvals for use in a hazardous atmosphere. While it is certainly important that the lighting in a spray booth allows you to produce the best possible application of materials, this importance is rendered moot if the useful life of the booth is drastically shortened by a fire or explosion, not to mention injuries to yourself or others. As you can imagine, the twofold requirements of both safety and effectiveness mean there is a whole lot of information to be taken in when outfitting a paint spray booth with lighting equipment. For our purposes, we’ll run through a few of the basics and leave the technical aspects to organizations such as OSHA since they have the final say on whether your lighting is up to meeting compliance or not.
In order for spray paint booth lighting to be effective it must produce light in a uniform manner. This means you want fixtures that will distribute light as evenly as possible over a wide area. Light that produces “hotspots”, shadows, and irregular patterns of lightness and darkness are obviously to be avoided. For this reason, fluorescent lighting is usually the preferred choice for paint booths. Since fluorescent tubes emit light evenly over the entirety of their surface, they are effective for producing a wide flood of light with few irregularities. Additionally, fluorescent tubes produce a much “cleaner” and brighter color of light than traditional incandescent bulbs, which is important when considering the ability of your lights to reproduce colors accurately and provide a clear contrast between finishes and surface irregularities.
This light color quality is usually represented by what’s known as a lamp’s “CRI” or Color Rendering Index. Rather than delve into a lengthy discussion of what CRI is and how it applies to different lamps, suffice it to say that a CRI of around 80 or better is preferable for paint booth use. As if that weren’t enough, it’s also important to take into account the color temperature as well which is represented in Kelvins. A fluorescent tube with a CRI above 80 and a color temperature of around 6000Kelvin or higher is generally considered adequate for most spray booths although many operators will go even higher to wring out the best performance possible. It should be noted, that as CRI and color temp goes up, the efficiency of the lamp tends to go down, so these high performance lamps can be expected to have shorter lifespans, run a bit hotter, and use more electricity. Like most things in life, it’s a compromise to find what works best for you.
Another thing to consider when looking for a goof performing fluorescent paint booth fixture is light intensity. Unlike spotlights, fluorescent tubes emit light over a 360° radius from their surface. As a result, a lot of the light produced by a fluorescent tube is going to be emitted in directions of completely no use to the paint booth operator, like up at the ceiling and walls. In order to concentrate the light from a fluorescent lamp, fixtures designed for the paint spray booth will incorporate reflector assemblies that help to redirect and focus much of the light back towards where you need it, namely onto the working surface of the object being treated. The problem here is that a poor reflector design can cause the aforementioned bright and dark spots as well as create irregular light patterns that can make accurately inspecting a prepped surface difficult. Good reflectors will be smoothly contoured and have a strong durable white finish that reflects light evenly. Reflectors with sharp angles, uneven surfaces, and that do not encompass the entire length of the fluorescent tube are a sign that the fixture in question may not perform very well and should be avoided.
Producing enough light in and of itself can sometimes be a challenge as well, particularly in larger paint spray booths. While the exact size and shape of a booth will have a great deal to do with how many fixtures and of what size are needed, it should be remembered that it is possible to go overkill. The ideal scenario is a paint spray booth with lighting that closely mimics the color and intensity of the light outside on a bright and sunny day. Anything of a greater intensity is likely to not be of much benefit since such high levels would likely be uncomfortable to work with. Instead, concentrate on good CRI and Kelvin numbers, and shoot for around 3 foot candles of light reaching the work surfaces. Most average sized paint booths reach this level using fixtures containing 4 - 40 watt, 4 foot lamps which are spaced evenly overhead and to the sides. Again, how many fixtures you will need will be determined by the size of your booth, and in some large booths operators will utilize 8 foot 110 watt lamps to achieve the necessary foot candles at 3 feet.
No discussion of paint booth lighting would be complete without mentioning a bit about safety compliance. In truth, considering the flammable and explosive nature of the chemical, finishes and fumes present in a paint spray booth, safety and compliance should be more than just an afterthought and one of the first considerations when evaluating fixtures.
Lighting for paint spray booths must adhere to federal and local regulations regarding the use of lighting in hazardous locations. OSHA offers a wealth of information on explosion proof lighting and hazardous locations and it is never a bad idea to familiarize yourself with what they have to offer if you’ll be operating a paint booth. Lighting for spray paint booths must be approved for hazardous locations and carry certification proving its suitability for use in a particular environment. Paint spray booths typically require Class I, Division 2 or Class I, Division 1 approved fixtures that are certified for use around chemicals, vapors and gases. Generally speaking, Class 1 Division 1 explosion proof light fixtures offer the highest protection and are normally used inside the booth where flammable gases and vapors are regularly present. Class 1 Division 2 fixtures are for use in areas where flammable vapors and gases are NOT normally present, such as immediately outside of the booth or in areas where chemicals are stored and normally sealed.
The highest protection is had with paint spray booths that actually mount the light fixtures outside of the booth in panels that allow the light to shine into the booth without the fixture ever contacting the atmosphere inside. However, even though these types of setups remove the fixture from inside the booth, they will likely still need to be at least Class1 Division 2 rated in order to be compliant with OSHA and local regulations. The only way to be entirely certain your lighting is compliant is to discuss your particular needs with the lighting manufacturer and consult with your local fire and safety authorities in order to ensure your chosen equipment will meet compliance, not to mention protect the hefty investment a paint spray booth represents and your own well being.