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NAFA Guide To Air Filtration Chapter 3 Impingement Filters presented by the National Air Filtration Association Fourth Edition.

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Presentation on theme: "NAFA Guide To Air Filtration Chapter 3 Impingement Filters presented by the National Air Filtration Association Fourth Edition."— Presentation transcript:

1 NAFA Guide To Air Filtration Chapter 3 Impingement Filters presented by the National Air Filtration Association Fourth Edition

2 Impingement Filters Impingement- The process in which larger particles are removed from an air stream because of their (weight or size) inertia. Impingement- The process in which larger particles are removed from an air stream because of their (weight or size) inertia. Mechanical filters Mechanical filters whose principal whose principal mechanism of dust mechanism of dust capture is impingement. capture is impingement.

3 Impingement Filters  Most impingement filters are characterized by relatively high media velocities and by low pressure drops.

4 Impingement Filter Categories   Panel Filters  Roll Filters  Lint Filters  Washable Metal-Panel Filters

5 Panel Filters  Fixed-media air filters in which the face velocity and the media velocity are essentially the same.

6 Panel Filters Media velocity-the speed of the air as it moves through the filter media. Media velocity-the speed of the air as it moves through the filter media. Face velocity-the speed of the air as it approaches the filter face.

7 Panel Filters: Materials of Construction Metals Metals Spun-glass fiber media Spun-glass fiber media Synthetic Fibers Synthetic Fibers Foam Foam

8 Metal Washable Filters

9 Spun-glass media Used extensively in Impingement Filters Used extensively in Impingement Filters Usually adhesive coated to improve retention Usually adhesive coated to improve retention Media density varies ¼” to 5” Media density varies ¼” to 5” Can be used in pads or cardboard frames Can be used in pads or cardboard frames

10 Synthetic Fibers Polyester- Most popular material – ring and link panels, pocket filters Polyester- Most popular material – ring and link panels, pocket filters Also Polypropylene, Nylon Also Polypropylene, Nylon or other synthetic or other synthetic (usually meant to be (usually meant to be washed) washed)

11 Synthetic Fibers Fiber weight is measured in denier. Fiber weight is measured in denier. As a rule smaller denier fibers will do a better job capturing small dust particles. As a rule smaller denier fibers will do a better job capturing small dust particles. Dual denier media is commonly Dual denier media is commonly used. It incorporates a larger used. It incorporates a larger fiber on the air entry side and fiber on the air entry side and a smaller fiber on the exit side. a smaller fiber on the exit side.

12 Characteristics of Synthetic Fiber Media Fiber distribution consistency is the most important consideration when making synthetic media. Fiber distribution consistency is the most important consideration when making synthetic media. Tackifiers are commonly applied to the air exit side of some synthetic medias to prevent dust migration. Tackifiers are commonly applied to the air exit side of some synthetic medias to prevent dust migration. Electrostatic charge is present in some types of synthetic media to aid in particle capture. Electrostatic charge is present in some types of synthetic media to aid in particle capture.

13 Foam Usually polyurethane Usually polyurethane Classified by pore size Classified by pore size The more pores per inch (PPI) the higher the efficiency The more pores per inch (PPI) the higher the efficiency Can be washed and reused Can be washed and reused

14 Impingement Filter Media Performance Determined from independent filter testing Determined from independent filter testing ASHRAE standard 52.1 (now obsolete) ASHRAE standard 52.1 (now obsolete) ASHRAE standard 52.2 (MERV) ASHRAE standard 52.2 (MERV)

15 Method of Renewal Filter banks using panel filters are renewed by washing or replacing dirty filter media. Filter banks using panel filters are renewed by washing or replacing dirty filter media. The use of disposable The use of disposable materials has become materials has become the predominant method of renewal. the predominant method of renewal.

16 Filter Holding Systems

17 Roll Filters Devices in which clean filter media is unrolled at one end,exposed to a dirty air stream, and advanced at intervals to keep the pressure drop through the exposed air stream within a desired operating range. Devices in which clean filter media is unrolled at one end,exposed to a dirty air stream, and advanced at intervals to keep the pressure drop through the exposed air stream within a desired operating range.

18 Roll Filters: Media Advance and Control A motor driven system. A motor driven system. Manually operated chain drive. Manually operated chain drive. Can be controlled by an adjustable timer. Can be controlled by an adjustable timer.

19 Roll Filter Media Fiberglass roll (infrequent) Fiberglass roll (infrequent) Synthetic fiber rolls Synthetic fiber rolls

20 Lint Filters Use the automatic roll filter principle. Use the automatic roll filter principle. Filter material Filter material –Glass media with spun-bond backing –Thin 1,2, or 3 ply cellulose media

21 Grease Filters Devices installed in kitchen range hoods to prevent the accumulation of grease in hood exhaust ducts. Devices installed in kitchen range hoods to prevent the accumulation of grease in hood exhaust ducts. Usually made of steel Usually made of steel or aluminum or aluminum Grease filters do not Grease filters do not aid in smoke removal. aid in smoke removal. They can be washed. They can be washed. Must meet NFPA Std. 96 Must meet NFPA Std. 96

22 Sample Questions The velocity of the air through any one square foot of media in an extended surface filter is called? Media Velocity Having larger fibers on the air entering side and smaller fibers on the air exit side is called? Graduated density

23 Thank you. Other Questions Other Questions


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