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F

FABRIC FINISH
Top coating on fabric to assist in the filtering operation.

FABRIC FOLDER
A metal device used to fold moving fabric to a given shape automatically. Also prepositions the fabric.

FACE VELOCITY
The gas flow rate expressed in actual cubic feet per minute (ACFM) divided by the area of the filter element. For example, a 20 square foot filter element processing 2000 ACFM would have a face velocity of 100 feet per minute.

FAN
A device for moving air and dust through the system. If the fan is on the dusty side of the baghouse pushing the dusty air through the baghouse, it is called a positive system. If the fan is on the clean airside of the baghouse pulling the dusty air into the baghouse, it is called a negative system. (80% of all baghouses are negative systems.)

FDA
Food and Drug Administration.

FELLED SEAM
Vertical seam in a filter bag, typically a nonwoven, which requires an overlap of the material.

FELT (NEEDLED)
A fabric produced by using barbed needles to interlock carded fibers and, if applicable, a woven base fabric.

FIBER
Type and/or grade of fibers used in media.

FIELD (IN DEPTH)
An arrangement of bus sections perpendicular to gas flow energized by one or more high voltage power supplies.

FILL YARN
An individual yarn, which interlaces with the warp yarn at right angles in a woven fabric. Also known as a pick or filling yarn.

FILTER AID
Any material that assists in the separation of solids from liquids. Usually used on difficult filter applications.

FILTER CAKE
Solids deposited on the filter media.

FILTER DRAG
The ratio of differential pressure across the filters to velocity through the filters.

FILTER EFFICIENCY
A measurement of how well a filter retians particles. Usually expressed as a percentage of retention of particles of a specific size by a filter.

FILTER MEDIA
The permeable barrier employed in the filtration process; the fabric on which the filter cake is built.

FILTRATE
The end product of the filtration process; i.e., liquid exiting the filtrate outlet.

FILTRATION RATE
The volume of liquid that passes through a given area in a specified time. Usually expressed as gallons per square foot per minute (or hour).

FINGER LOOP
A loop sewn into the bag to assist in the installation of the bag.

FINISH, FINISHING
Physical (mechanical) or chemical fabric treatment to impart a desired surface property.

FIRE RETARDANT
Fabrics treated with special chemical agents or finished to make them retardant or resistant to burning. Many fabrics achieve this property by using fibers that have this property built directly into the polymer.

FLAT WIDTH
The distance across a bag or slit roll measured perpendicular to long side.

FLEX
The movement of filter media primarily during the cleaning cycles can lead to long term damage due to fiber-to-fiber abrasion. Also, new filter bags can be flexed (bent) by rough treatment during shipping and installation.

FLOW RATE
The speed at which a liquid flows and is measured in gallons or liters per minute. Flow rate of a liquid can be affected by the liquids' viscosity, differential pressure, temperature, and type of filter used.

FLY ASH
Dust from a furnace. The term distinguishes the ash that flies from that which drops to the bottom.

FUGITIVE DUST
Emissions from a process or control that occur at points other than stacks or vents.

FUMES
Small solid particles formed by the condensation of vapors of solid materials.