Displaying items by tag: airflow
Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent air flow principles. Laminar, or unidirectional, air flow systems direct filtered air downward or in horizontal direction in a constant stream towards filters located on walls near the cleanroom floor or through raised perforated floor panels to be recirculated.
Specifying lighting systems for cleanroom facilities requires considerations beyond energy and maintenance savings. While lighting for cleanrooms should be energy efficient and provide proper illumination for the task at hand, it is crucial that lighting coordinates with air-supply systems and minimizes any chances for contamination.
In an industrial cleanroom environment, unidirectional air flow can provide a component or process with protection from airborne contaminants, but additional measures may be required to block these types of contaminants in certain applications. Barriers between the contamination source and the process, product, or personnel in the cleanroom can effectively shield sensitive elements. In addition to cleanroom garments, curtains, and structures, clean air devices, such as transfer hoods, safety cabinets, and isolators can be used to achieve the necessary level of contaminant control. These devices usually have their own air filtration units independent of cleanroom ventilation and can provide workspaces that are some degree cleaner than the larger cleanroom itself.
There are basically three different air flow systems in cleanrooms: pressurized plenum, ducted supply and ducted return, and ducted supply and open return. Pressurized plenum essentially means you pump the air into the plenum, push it through the filters and down on into the cleanroom. With a ducted supply and ducted return, you’re doing just that; you’re ducting the air delivered to the cleanroom and you’re ducting the air back out of the cleanroom. This last design is prevalent in a pharmaceutical cleanroom arrangement where you have to control the air. The most efficient from a cost and operational standpoint, is the ducted supply and open return. This involves ducting the air into the cleanroom though you let the air flow into an open return, which is essentially an return air plenum.
It does, and actually in opposite ways. A single pass cleanroom is going to cost you less to construct because you don’t need that return air path, or that secondary containment, and you need secondary walls to do that. However, the problem with it is you cannot control the outside environment as well.
Air Flow Rates
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There are basically three different air flow systems in cleanrooms: pressurized plenum, ducted supply and ducted return, and ducted supply and open return. Pressurized plenum essentially means you pump the air into the plenum, push it through the filters and down on into the cleanroom. With a ducted supply and ducted return, you’re doing just that; you’re ducting the air delivered to the cleanroom and you’re ducting the air back out of the cleanroom.
High efficiency particulate air (HEPA), originally called high-efficiency particulate absorber but also sometimes called high-efficiency particulate arresting or high-efficiency particulate arrestance, is a type of air filter. Filters meeting the HEPA standard have many applications, including use in medical facilities, automobiles, aircraft and homes. The filter must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE).
Everything in the cleanroom, including the lighting fixtures, is designed to ensure successful air filtration and maintain the laminar airflow in a contamination-free environment. Depending on the function of the controlled environment, a cleanroom will use either HEPA or ULPA filtration. These air-filtering systems are typically an expensive component and one of the first to be considered in construction. They take up a majority of the ceiling space, which leaves a real challenge for lighting the environment.
Clean rooms need a lot of air and usually at a controlled temperature and humidity. This means that in most facilities the cleanrooms Air Handling Units (AHU) consume over 60% of all the site power. As a general rule of thumb, the cleaner the cleanroom needs to be, the more air it will need to use. To reduce the expense of modifying the ambient temperature or humidity, AHU or systems are designed to recirculate (if product characteristics permit) about 80% air through the room, removing particulate contamination as is it generated and whilst keeping the temperature and humidity stable.