FILTER MEDIASELECTION GUIDE

DUSTEX CORPORATIONFILTRATION MEDIA RESOURCES

for

Dustex Representatives and Distributors

Dustex Corporation has been recognized as an innovator in the design and manufacture of product recovery and air pollution control equipment for industry since 1947.

Through very close and long term working relationships with our primary suppliers of filtration fabrics, we have developed a wide range of media options to choose from when a filtration application dictates the use of any specific type of tubular or envelope bag, cartridge, and/or pleated element construction.

Through literally thousand of dust collector installation over our 60+ years of experience, we feel very confident in the technical expertise we have jointly developed in the recommendation of any particular fabric choices required in order to assure our clients that we have made the best selection of filtration media for each and every application we see.

Enclosed in the following pages you will find technical information relative to some of the media selections we have available to us.

So, whether the application calls for low or high temperature, sub-micron fume filtration, corrosion resistance, resistance to adhesive forming particulate or a combination of any of those, we have a fabric solution to present to our clients.

When you have any questions about any filtration media options and their suitability to a specific application, please don't hesitate to contact the factory.

POLYPROPYLENE

Temperature Tolerance: 190°F continuous 330°F melting point210°F surge

A synthetic fiber best know for its moisture resistance, polypropylene will withstand temperatures of only 190°F. However, it has a good resistance to a broad range of acids and alkalis.

Polypropylene is a non-hygroscopic. It does not absorb water. It stands along with only Ryton which has the same characteristic at a higher temperature in this respect. It is also not susceptible to hydrolysis.

Resistance Polypropylene has:

Very good resistance to both mineral and organic acid. It is attacked at high temperatures by nitric and chlorosulfonic acids.

Good resistance to alkalis, except high concentrations of sodium and potassium hydroxides at temperatures above 200°F.

Good resistance to most reducing agents.

Good resistance to many organic solvents, except Ketones, esters, aromatic, and aliphatic hydrocarbons at high temperatures. It is soluble in chlorinated hydrocarbons at 160°F.

Great resistance to static build-up and has the lowest static component of any current synthetic fiber.

The primary damaging agents to polypropylene are oxidizing agents and related salts.

POLYESTER

Some Fiber Trade Names: Dacron (Dupont)Enka Polyester (American Enka Corp)Fortrel (Fiber Industries/Celanese)Kodel (Eastman Chemical)

Temperature Tolerance: 275°F continuous 492°F melting point325°F surge

Polyester has become the workhorse in fabric filtration. It offers good resistance to most applications at ambient temperatures (90°F-120°F) or up to 275°F. It is also the most cost effective media in a broad range of applications.

Polyester is a thermoplastic and can be singed, glazed, treated with special coatings or PTFE Tetratex membrane to address specific requirements for better cake release, fine particulate, moisture, etc.

Chemical Resistance:

Good resistance to most mineral and organic acids, except high concentrations of nitric, sulfuric, and carbolic acids.

Good resistance to weak alkalis and fair resistance to strong alkalis at low temperatures. It is dissolved at high concentrations and temperatures.

Good resistance to most oxidizing agents.

Excellent resistance to most organic solvents, but is unsuited for some phenolic compounds and is affected by cyclohexanone at 313°F.

Hydrolysis:

Polyester is subject to hydrolysis, the reaction being most likely at 210-220°F and accelerated in acidic atmospheres. There is no color change, but total loss of strength, board hand (feel), and fiber shrinkage are all evidence of hydrolytic attack.

The primary damaging agents to polyester are hydrolysis, concentrated sulfuric acid and heat in excess of 275°F for extended periods of time.

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Example Applications:

Steel Reverse AirCement Pulse-jetFoundry ShakerGrain Milling Pulse-JetFlour Milling Pulse-Jet

POLYESTER MICROFELTTM

Style: PE-16/M-SPEG (MicroFeltTM)

Construction: Scrim-supported needle felt

Composition: 100% polyester using micro-denier and standard fiber deniers with proprietary manufacturing technique

Finish: Heat set, glazed one side

Weight: 15.0 - 17.0 oz/sq.yd.Thickness: 0.055" - 0.075"Air Permeability: 15 - 25 cfmMullen Burst Strength: 400 psi minimumDimensional Stability: 3% max. shrinkage at 300°F for 2 hours

Temperature resistanceContinuous: 275°FPeaks: 300°F

Resistance to acids: FairResistance to alkalis: FairResistance to oxidation: GoodResistance to organic solvents: Good

ARAMID

Some Fiber Trade Names: Nomex (Dupont)Conex (Tejin Ltd., Japan)

Temperature Tolerance: 400°F continuous700°F Char. (does not melt)425°F surge

Aramid is the media used to solve problems of high temperature and excursions where polyester becomes brittle and fails. Aramid has excellent abrasion and flex endurance. It also has good resistance to many chemicals and is highly resistant to hydrocarbons and many other organic solvents.

Finishes such as singing, Defender, and Tetratex membrane are available for improved cake release or to address a specific need.

Concerning Thermal Stability:

Aramid has excellent thermal stability, shrinking less than 1% at 350°F and only 2.5% at 545°F. It does not melt, but it will degrade rapidly and char at temperatures above 700°F. It is permanently flame resistant, but fabrics which have become impregnated with non-combustible dusts are ignited they may exhibit "afterglow" for considerable time, which can lead to complete destruction of the fabric.

Concerning Hydrolysis:

The rate at which hydrolysis occurs depends on the amount of water present, temperature, and the presence of acids in the gas stream.

It is revealed by a color change to red-brown. Hydrolysis is accelerated with any of the following combination of conditions:

10% relative humidity, presence of SO, NO, HCl acid components, and temperature of 375°F.

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Chemical Resistance:

Poor acid resistance, although superior in this respect to Nylon.

Excellent resistance to alkalis at room temperature, but is degraded by concentrated alkalis at high temperatures.

Poor resistance to oxidizing agents.

Excellent resistance to most hydrocarbons and many other organic solvents.

Example Applications:

Steel Pulse-Jet/ShakerAsphalt Pulse-JetFoundry Pulse-Jet

RYTON

Fiber Name: PPS (Polyphenylene Sulfide)

Temperature Tolerance: 375°F continuous 545°F melting point450°F surge non-flammable

Under severe chemical and temperature demands, Ryton is quickly becoming the fiber of choice. Ryton is a high temperature synthetic fiber. It will withstand continuous temperature of 375°F. It is chemically resistant to a broad range of acids, alkalis, and oxidizing agents.

Most significantly, Ryton will not hydrolyze and thus replace Nomex under these types of conditions at elevated temperatures. Ryton also has a low rate of moisture absorption.

The following parameters can be used to identify filtration applications where Ryton fiber excels:

1. Where temperature is 375°F continuous or less.

2. Where the oxygen content is 9% or less.

3. If sulphur is present in the fuel or oxides of sulphur may exist.

4. Where moisture is present in the flue gas.

P-84

Temperature Tolerance: 460°F continuous no melting point500°F excursions non-flammable

P-84 is a synthetic fiber with a very high temperature resistance. Unfortunately, P-84 is a condensation polymer and is subject to hydrolysis if chemistry or moisture is present at these elevated temperatures.

P-84 is a tri-lobal fiber and provides a very efficient media due to the larger surface area of each individual fiber. Therefore, P-84 is one of the more efficient synthetic fibers available.

It is intended for use in situations where high temperature, acid attack, and flex abrasion occur simultaneously.

Long exposure to alkaline conditions, especially at higher temperatures should be avoided.

GLASS, WOVEN (FIBERGLASS)

Some Fiber Sources: Owens CorningPPG

Temperature Tolerance: 500°F continuous 700°F 50% loss of strength

This material offers outstanding performance in high temperature applications. The properties of glass fiber, such as good acid resistance, good heat resistance, and high tensile strength solve many inherent baghouse problems.

Fiberglass has poor flex abrasion resistance and is subject to failure if pulsed or cleaned too vigorously. It is resistant to most chemicals except strong alkalis, hydrochloric acid, hydrofluoric acid, and sulfuric acid.

Fiberglass fabric must always be finished with a protective coating. The primary function of all such coatings is to give the glass fibers a high level of abrasion resistance through lubrication which they naturally do not possess. While fiberglass itself will withstand almost any operating condition in pollution control equipment, the various finishes all have specific capabilities and limitations. A successful fiberglass installation is dependent on the appropriate finish because once the finish breaks down the fiberglass will lose its protection from internal and external abrasion and fail mechanically.

These are four commonly used finishes:

"T" for non-acidic conditions

The triple finish was one of the earliest finishes developed for filtration fabrics. It consists of a blend of silicone, graphite, and Teflon. The three finish components combine to protect the glass fabric from abrasion, but offer only limited protection from chemical attack. The triple finish is now used primarily in cement production and metal foundry applications.

Dustex / M - "E"

A 10% add-on of Dupont's PTFE, Teflon B. The PTFE particles encapsulate the glass fibers to prevent abrasion. However, because the PTFE does not bond to the glass, fabric with a Teflon B finish can be attacked chemically by acids or alkalis. Fabric with Teflon finish is recommended for use with utility base load boilers operating under mild pH conditions.

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Dustex / M - "I" Burlington I-625 / "F" JP Stevens

A proprietary finish consisting of acid resistant polymers, PTFE, graphite and silicone oils. The acid resistant polymers form a covalent bond with molecules on the surface of the glass. The bonded polymer forms a protective barrier around the glass surface to shield it from chemical attack. The acid resistant finish is recommended for filtration of the flue gases in an acid environment such as Carbon Black, most utility boilers, incinerators, and cement.

Dustex / M - "373" (BHA refers to as Blue Max finish)

A proprietary formulation of a polymer which prevents the chemical attack of glass fabrics and PTFE to provide superior abrasion resistance. It is based on a unique PTFE dispersion that has been formulated to promote covalent bonding and coalescence of the PTFE particles. This finish is resistant to both acid and alkali attack and provides superior abrasion resistance. Recommended for any fabric filtration application.

Concerning Resistance Fiberglass has:

Noncombustible

Zero moisture absorption, therefore, it is not subject to hydrolysis.

Good resistance to acids, but is attacked by hydrofluoric, concentrated sulfuric, and hot phosphoric acid.

Poor resistance to alkalis.

Poor resistance to acid anhydrides and metallic oxides (fluorides, sulfur oxide).

(Do not use EAF applications where adding fluorospar during melts.)

Example Applications:

Cement Kiln D/C Reverse AirIndustrial Boilers (coal, rice, hull) Pulse-JetLead-Reverb D/C ShakerSteel-EAF Pulse-Jet/Reverse Air

WHAT IS TETRATEX?

Expanded PTFE (polytetrafluoroethylene) Extremely Thin Microporous Fine Fiber / Small Pore Size Chemically Inert Clean, non-shedding Bonded to Variety of Support Materials

o Thermobondingo Adhesive Bonding

WHY USE TETRATEX FOR AIR FILTRATION?

Reduced Emissions Surface Filtration Superior Cake Release Lower Pressure Drop Higher Air-to-Cloth Ratios Longer Filter Life Functional Equivalent to Gore-Tex

PHYSICAL PROPERTIES OF PTFE MEMBRANE

Fine Fiber Structure Small Pore Size Excellent Release Properties Chemically Inert High Temperature Limit (550°F) Hydrophobic (rejects water)

INDUSTRIES USING PTFE MEMBRANE

Chemical Processing Food Processing Metals Processing Minerals Boilers Incinerators Other

PERFORMANCE TESTS

Fabric Dust Penetration Outlet Loading(dimensions x 10-5) (gr/ft3)

Tetratex 0.1 0.000003Gore-Tex 0.9 0.00003Acrylic - coated 4.1 0.00012Dual Density 10.2 0.00032PTFE - finished 11.2 0.00042Standard Felt 37.2 0.00112P-84 Composite 158 0.00502