Energy Efficient Solutions for Cleanroom Illumination
Cleanroom illumination is critical to process function and operator awareness to prevent errors in production, contamination of products, and interference with diagnostic equipment. It must work in harmony with cleanroom ceiling HEPA filtration system layouts to minimize any shadow or disorientations to process functions and operators.
Cleanroom lighting specifications and layout must take into account the HEPA filtration module layout, process equipment floor plan and work bench layouts, any process equipment or diagnostic equipment that may be affected by electromagnetic field generation, and cleanability of the lighting fixtures. Light fixtures must provide adequate illumination, access for maintenance, energy efficiency, and sealing against contamination control or loss of pressurization.
Cleanroom lighting systems represent less than 1% of the cleanroom budget and when compared to the HVAC mechanical systems minimal operating cost. Still, a larger cleanrooms with numerous light fixtures should utilize the highest energy efficient light fixtures operated at the most advantageous voltage. Though watts are watts and the voltages do not actually represent any energy savings the number of light fixtures on a circuit is greater with a 277v system versus a 120v system which can allow for more light fixtures on a circuit reducing installation cost.
The unit of lighting luminance in the United States is the foot-candle, which equals 1 lumen per square foot. Lumens are used to describe the light output (luminous flux) of the source. The foot-candle level required in cleanrooms has been historically high due to precision demands or the extremely small size of the object that requires attention. Illumination levels vary depending on the different process areas within the cleanroom. The engineer or lighting designer is encouraged to review each process area within the cleanroom to determine the type of task to be performed and the illumination levels desired at specific areas.
The HEPA filtration module layout, depending on the ISO cleanliness classification of the cleanroom, can occupy for 15% to 100% of the cleanroom ceiling area. There are thee basic lighting fixtures utilized in cleanrooms which are as follows:
Troffer style florescent cleanroom light fixtures can be specified with a number of options for sterile and non sterile cleanroom operations and process applications.
Fluorescent lamps are nearly always used in cleanroom environments due to their energy efficiency, low maintenance and long life. High intensity discharge lamps may be required for high bay facilities. Lamps with temperatures around 3500K are considered "neutral" and often specified in cleanrooms. The number of light fixtures and their spacing should be reviewed to produce a uniform lighting level throughout the space.
Fluorescent lamps produce some energy in the ultraviolet (UV) spectrum, which can be detrimental to certain cleanroom processes. UV filtering can be accomplished with lens shielding or tubes to cover the lamps. However, this shielding converts the visible light to yellow color, which is not as pleasing to the occupant. While the shielding may reduce illumination levels by only 10 to 20 percent, the perceived lighting levels can seem less due to the color shift.
Lumen ratings can vary depending on the lamps used. Specifying lamps with higher initial lumens will reduce the number of fixtures required to achieve a desired foot-candle level. However, foot candle (fc) requirements vary throughout cleanroom facilities, from 30 fc in mechanical/electrical rooms to 100 fc or more in the cleanroom. Some cleanroom applications that involve food inspection and grading require at least 150 foot-candles. The engineer should work with the cleanroom staff to determine the proper foot-candle requirements in each of the areas within the space.
Revision B of Federal Standard 209 (now 209E) originally contained a requirement for 100 fc in main cleanroom areas. In practice, 100 fc has been viewed as excessive and detrimental to eye comfort levels in most cleanroom applications. In addition, it can be difficult to obtain 100 fc in ISO Class 4 (Class 10) and lower cleanrooms, since most of the ceiling space is dedicated for air filters.
An increase in the illumination levels may be required to achieve the desired visual acuity. In some cleanroom applications, lamps that produce high levels of UV to reduce bacteria or other biological contaminants may be required.
Cleanroom Lighting Design and Engineering We Offer:
Florida Cleanroom Systems lighting designs deliver cleanroom regulatory compliance, operational illumination levels, and energy efficient designs and engineering to mitigate process errors, operator fatigue, and contamination of the cleanroom environment.
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