1) Fabric Selection
Media performance is a function of fiber properties, fabric construction, and fabric finishes.
HL Filter’s extensive knowledge and experience of how these variables interact allows us to determine the most effective filter media solution to meet your requirements related to flow rate, filtrate clarity, product dryness, cake release, and resistance.
Because each baghouse has its own set of characteristics and system parameters, it is important to evaluate each of the following variables in order to choose a fabric best suited to the system:
- Temperature - do your bags need to withstand extreme temperatures?
- Product/Particulate size - what are you filtering?
- Humidity-what moisture conditions within which the filters must withstand?
- Chemistry - can your bags withstand the chemical make up of the dust particles?
- Resistance- is the filter media able to resist the wear and tear of the dust particles?
- Air-to-cloth ratio
- Particulate abrasiveness
- Mechanical factors, such as cleaning style, installation, etc.
1.1 Fiber Properties
Fiber Characteristics
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Fiber
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Max. Continuous Temperature℉ (℃)
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Max. Surge Temperature
℉ (℃)
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Tensile Strength
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Resistance
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Sypport Combustion
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Special Properties
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|
Abrasion
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Moist Heat
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Acid
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Alkaline
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Nylon (PA)
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|
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Excellent
|
|
|
|
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Yes
|
|
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Polypropylene (PP)
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194 (90)
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230 (110)
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Excellent
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Very Good
|
Excellent
|
Excellent
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Excellent
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Yes
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Excellent cake release. Lowest temperature
|
|
Acrylic
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260 (127)
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284 (140)
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Fair
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Good
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Excellent
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Good
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Fair
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Yes
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A type of acrylic, functions at higher temperatures
|
|
Polyester (PE)
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265 (130)
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302 (150)
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Excellent
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Excellent
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Poor
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Fair
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Fair
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Yes
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Most versatile, cost effective, and widely used
|
|
PPS
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374 (190)
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392 (200)
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Very Good
|
Good
|
Good
|
Excellent
|
Excellent
|
No
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Excellent chemical resistance (except for oxidation)
|
|
Aramid (Nomex)
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400 (204)
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465 (240)
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Very Good
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Excellent
|
Good
|
Fair
|
Good
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No
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Best used in dry conditions at high temperatures
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|
Polyimide(PI/P84)
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465 (240)
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500 (260)
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Good
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Fair
|
Good
|
Good
|
Fair
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No
|
Non-flammable and thermostable organic fiber
|
|
PTFE (Telfon)
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500 (260)
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536 (280)
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Fair
|
Good
|
Excellent
|
Excellent
|
Excellent
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No
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Expensive-excellent chemical and thermal resistance
|
|
Fiberglass (GL)
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500 (260)
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536 (280)
|
Excellent
|
Fair
|
Excellent
|
Fair
|
Fair
|
No
|
Finishes limited, maximum temperature range.
|
- This table serves only as a guide for the selection of engineering materials and filter media
- Testing in accordance with the end user’s safety guidelines is recommended
- P84, PTFE, and Fiberglass: sentitive bag to cage fit for good energy performance
1.2 Fabric Construction
Nonwoven: The felt constrfuction is scrim supported or self-supported. Packing of scrim supported felts is a woven scrim. Self Supported needle felts , where the backing is a batt of the same fiber as the felt itself.
There are some distinct advantages to having a self-supported compared to one with a scrim:
• Since the scrim does not aid in the filtering process, not all of the weight of a scrim-supported felt contributes to filtering. In a scrimless needle felt, all fibers, including the backing, are available for filtration.
• Fiber-supported needle felts are stronger than those with scrims, since stitching weakens scrims, but strengthens fibers.
• Fiber-supported needle felts are usually less expensive, since scrims typically cost more to produce than the fiber backing.
• Scrims can blind if dust completely penetrates the fiber mat.
• Fiber-supported needle felts flex better than those with scrims, providing for better pulse cleaning.
Woven: Woven fabrics are not as efficient as felted fabrics. Fiberglass is most commonly used as a woven, rather than felted fabric, but this material is fragile.
1.3 Fabric finishes
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Fabric- Finishes/Surface Treatments
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Features & Benefits
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|
Mechanical Finishes
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Plain
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Natural finish. General purpose material
|
|
Heat Set
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Passing media over a heated blanket. Surface remaining intact, without fiber melting or burning. Provides dimensional stability, resist changing shape, and eliminates shrinkage
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Singed (one side or both sides)
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Exposing media to open flame to burn off any loose fibers. Benefits: improved abrasion resistance, reduced fiber shedding, and in some cases improves the filtration performance. Singeing the surface of felt reduces fiber ends protruding from the surface
|
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Glazed/Eggshell (one side or both sides)
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Running the felt over heated rollers, which melts fibers and results in a smooth "eggshell" finish, which will enhance cake release (may impede airflow) . With the pressure between the rolls will adjust the permeability as well as impart stability to the fabric.
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Chemical Treatments
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PTFE Impregnation (Bath/Penetrating)
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Applied to high temperature filtration fabrics by full impregnation of fabrics in PTFE dispersion.
Imparts high level of oil and water repellency. Improves fabric cleanability and lowers operation pressure drop. Improves abrasion resistance. Prevents moisture and acids formed during dew point transitions from being absorbed by the filtration fabric. Limited cake release
|
|
PTFE Membrane
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Increases collection efficiency and cake discharge. Protects the filter against chemical attack. Improves blinding resistance and bag life. Membrane provides an extremely smooth, high efficiency finish and the greatest cake release. For capture of fine particulate, improved filtration efficiency, cake release and airflow capacity
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Flame Retardant
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Retards combustibility (not flame-proof)Reduces flammability of fabrics.
Slows spread of fire in situations when a flammable dust is ignited inside the dust collector system.
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Water & Oil Repellent
( Hydrophobic & Oleophobic)
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Provides a durable, clear protective barrier, characterized by extremely low surface tension; which improves cake discharge and enhances water and oil repellency. Main purpose is to prevent filter bags from binding caused by the accumulation of wet, sticky or agglomerating dust.
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Anti-static filter media (use when static dissipation is required): Improves conductivity of fibers.
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Stainless steel scrim supported felt
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A woven scrim comprised partially of stainless steel yarns.
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Stainless steel fiber blend felt
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Use of stainless steel fibers blended with standard fibers.
|
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Epitropic fiber blend felt
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A blend of standard and epitropic (carbonized) fibers.
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> Other special finishes (Silicone, Acid Resistant, Flame Retardant, PTFE/Acrylic Coatings...) are customized on request
> Applicable media: Fiberglass with limited finishes. For more, please contact us
Benefits:PTFE Membrane
Near zero emissions meet or exceed the strictest regulatory standards while providing greater product collection
Excellent dust release characteristics
Increased bag life
Less frequent cleaning required
Reduced pressure drop results in energy savings
Lower maintenance costs lead to increased profitability
2) Selecting a Filter Bag
You should choose the media from which your filter bags will be constructed based on the type of application they will be used for and fabric selection guide provided.
Accurate measurements for your filters before ordering replacement filter bags are necceassry for the performance of the filter bags.
Bag reconfiguration includes:
- Overall Length
- Flat Width or Circumference
- Top and bottom construction of a filter bag involves a variety of possible configurations. The type of cleaning process used by the dust collector determines which configurations will be used in the design of the filter bag.
Please contact us for further information
