Air filtration systems contribute more than clean air
By Kevin Campbell, Senior Editor -- Plant Engineering, 1/15/2008 1:00:00 AM
While productivity, quality and the bottom line will never go away as the primary drivers of manufacturing processes, new focuses on safety and sustainability will have a growing impact on how those processes are executed. One area where plant managers can find real savings while addressing sustainability concerns is in their air filtration systems.
To optimize a plant’s air filtration system, it helps to first make some observations about the plant’s environment. Is it dry? Is it humid? Most important, identify pollutants generated through the manufacturing process and those present throughout the facility. Dust, gases, vapors, fumes and other substances – particularly volatile organic compounds – each require unique considerations to ensure they are sufficiently addressed.
According to Filter Selection: A Guide to Understanding HVAC Filter Selection, a white paper from Kimberly-Clark Filtration Products, “The first step in determining the best type of HVAC filter needed is to identify the types and sizes of particular pollutants in the building.” While filters made partially or entirely of natural materials have been available over the years, new synthetic media recently have proven to be more versatile solutions. Today’s filters more often are made of fiberglass, polyester and synthetic nonwovens.
“Unlike traditional cotton/poly media, the synthetic media in more modern filters can be made of thermally bonded, continuous, hydrophobic polyolefin fibers that resist shedding and do not absorb moisture,” the white paper added. “This is important in resisting bacterial growth, and it keeps shed fibers from getting into the HVAC coils or into the air space of the building.
“Moreover, synthetic filter media can be manufactured without the use of chemical binders, meaning that humidity will not affect the web structure and will not cause the glue to soften and thus the fibers to shed,” it added.
Once the type of filtration has been identified, the efficiency level of the filtration system must be considered. ASHRAE Standards 52.1-1992 and 52.2-1999 offer criteria and ratings that quantify filter efficiency. According to the white paper, Standard 52.1 defines four criteria that indicate a filter’s capability to remove contaminants.
Standard 52.2 provides means for measuring the particle size efficiency (PSE) of a filter and establishes a Minimum Efficiency Reporting Value (MERV) rating. The PSE, “indicates the filter’s ability to remove airborne particles of differing sizes between 0.3 and 10 microns in diameter,” the white paper said. “The MERV rating is a numerical system based on minimum PSE,” with efficiency ratings ranging from 5 to 16.
Keeping it optimized
Like any other plant infrastructure, air filtration systems must be maintained to remain efficient and effective. “An air filtration system’s maintenance schedule should be developed specifically for that environment,” said Charlie Wiles, executive director of the American Indoor Air Quality Council. “Preventive maintenance schedules will vary based upon activities conducted in that environment. It is sometimes necessary to observe an air filtration system in operation for many months before developing a maintenance schedule.”
New machinery or changes in processes may require users to modify the air filtration system, Wiles added. And sometimes the modifications can be substantial – due to new pollutants – to account for issues resulting from the machinery or process changes.
“It is not advisable to use pressure differentials as the sole basis for a decision to change filters,” Wiles said. “A filter that has ruptured, fallen out of the rack or become subject to seasonal airflow will falsify pressure differential readings. Hence, a visual confirmation of filter condition is necessary.”
Aside from correct installation, Kimberly-Clark Filtration Product’s Filter Maintenance: A Guide to Understanding HVAC Filter Maintenance white paper said users need to monitor filter media for tears and ensure that fasteners are in place. Cracks between filter frames and duct walls should be caulked, and filter frames should be reinforced to prevent collapse. Filter monitoring is key.
“(Filters) should be monitored and maintained to provide maximum filtration, while not overtaxing the supply fan capability or leading to 'blow-out’ situations with no air filtration. Scheduled maintenance or established pressure drops can be determining factors, along with specific variations in environmental conditions,” such as humidity or change of season, it said.
In addition to regular visual checks, users may find other techniques helpful in maintaining their air filtration systems.
“Those who have expertise in using infrared cameras may find them invaluable for observing air distribution, airflows, airflow cooling coil efficiency and water flow cooling coil efficiency,” Wiles said. Additionally, the white paper recommended the use of tools such as differential pressure measurement devices and pressure drop switches to help identify and alert personnel that filter changes are necessary.
Benefits go beyond good air quality
The correlation between good indoor air quality and energy efficiency is undeniable. With fewer contaminants in the air, machines are better ventilated and run more efficiently. Air filtration systems are obviously a central component to keeping the air clean and, in turn, creating a more energy-efficient facility.
“To look at HVAC filters as energy conservation tools, it’s first important to understand the cost of energy used by filters far outweighs the cost of the filter itself,” said Energy Efficiency, A Guide to Reducing HVAC Energy Costs, a white paper from Kimberly-Clark Filtration Products. “Energy costs can be 10 times the initial filter cost for a standard, pleated filter.
“Switching to a lower pressure drop HVAC filter is one of the easiest changes building owners and facility managers can make in an effort to reduce energy costs,” it added, citing that the lower pressure drop provides less resistance for the HVAC system motor to contend with in delivering required air flow, reducing the motor’s energy consumption.
“Indoor air quality and energy savings go hand in hand,” Wiles said. “The proper selection of air filters and development of PM schedules enhances the sustainability not only of HVAC equipment, but of all equipment in an environment.”
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