Wear on the dirty side of the filter media due to the close contact with particulates from the dust laden gas.

Wear on filter media in a creased area due to flexing, normally associated with cage contact and filter bag cleaning process.

An opening in a dust collector or ductwork that allows workers to inspect and clean the system.

The rate at which air flows through the dust collection system, expressed in cubic feet per minute or CFM.

Filter media air permeability refers to the ability of a filter material to allow air or gas to pass through it. It is a measure of the ease with which air can flow through the fabric of a filter. The unit of measurement for air permeability is often expressed in cubic feet per minute (CFM), through a square foot of filter media at a differential pressure of 0.5” water gauge (w.g.).

A device that seals off a dust collector from the outside environment, preventing dust from escaping. Airlocks are typically used in dust collection systems that operate under pressure or vacuum.

Also known as the air-to-media ratio or filter velocity, air-to-cloth ratio is calculated by dividing the amount of airflow (CFM) by the amount of filter media in the dust collector. For example, if you have 10,000 CFM through your dust collector and 5,000 square feet of filter media area, your ratio is 2:1.

A property of a material that prevents the buildup of static electricity. Anti-static materials are often used in dust collection systems to prevent fires and explosions.

A baffle plate is a crucial component of a baghouse dust collector, and it is strategically placed in a baghouse to:

• Pre-separate larger and heavier particles from the air stream before it reaches the filter bags so that it reduces the load on the filter bags, extending their lifespan.
• Distribute the incoming contaminated air evenly across the filter bags, ensuring more consistent and efficient filtration.
• Prevent abrasive dust particles from directly hitting the filter bags, which can cause damage and tears.

A device that monitors the emissions from a baghouse to detect leaks. Bag leak detectors are typically required by law in many industries to ensure that dust collectors are operating properly.

The expected lifespan of a filter bag in a baghouse. Bag life is affected by a number of factors, including the type of dust being collected, the operating conditions of the dust collector, and the quality of the filter bags.

A baghouse is an air pollution control device and dust collector that removes particulates or gas released from industrial processes out of the air. Power plants, steel mills, pharmaceutical producers, food manufacturers, chemical producers and other industrial companies often use baghouses to control emission of air pollutants.

Particles of dust that are able to migrate through the filter media.

Filter media blockage by dust, fume or liquid not being discharged by the cleaning mechanism, resulting in a reduced gas flow because of the increased differential pressure across the filter media.

A fan that generates air pressure. Blowers are used in dust collection systems to move air through the ductwork and dust collector.

Also known as manifold. In pulse jet baghouses, a pipe in the plenum section that runs horizontally several inches over the tube sheet with a hole over each filter bag. It is responsible for distributing the compressed air pulses to each filter bag.

Also known as glazing, is the high-pressure pressing of the fabric by rollers to flatten or smooth the filter media. Calendaring pushes the surface fibers down onto the body of the filter media. It is typically used to produce filter media that is flat, smooth, and dimensionally stable. Calendaring process can be applied to various media such as polyester, polypropylene, and aramid.

Filter bag change-out refers to the process of replacing filter bags in a filtration system. Change-out involves removing the old filter bags and installing new ones to ensure optimal filtration performance. Regular filter bag change-out helps to maintain clean and safe working environments, improve equipment performance, and extend the lifespan of the filtration system.

Also known as resin treating, involves immersing the filter media in natural or synthetic resin. This process helps lubricate the fibers, helps the fibers to shed water and oils (hydrophobic & oleaphobic), and provides high-temperature durability and self-abrasion resistance.

A segmented filtering section of a baghouse that can be isolated from the others.

Also known as Inertial Dust Collector, a type of dust collector that uses centrifugal force to remove dust from the air.

Depth filtration is a method of capturing particles deep within the pores of a filter material. It can retain particles throughout its matrix, rather than solely on its surface.

In the context of dust emission control, desulfurization is a chemical process that removes sulfur or sulfur compounds from dust-laden air streams generated from industrial processes. There are mainly two desulfurization processes:

• Wet Scrubbing: This process uses a liquid absorbent to remove sulfur dioxide from flue gas.
• Sorbent injection: This process uses a dry powder to remove sulfur dioxide from flue gas.

Differential pressure (dP) is the pressure drop measured across the tubesheet (the metal plate from which the bags are suspended), from the dirty side of the filter bags to the clean air plenum.

In a genuin dual-density filter media, two medias of different density are separated by a scrim in the middle that provides dimensioinal stability and a densified central core which improves filtration efficiency by minimizing dust migration through the felt. The scrim structure offers a clear advantage over unsupported felts (without scrim) which are produced in a single process with a homogeneous fiber blend and filtration characteristics only.

The system of pipes that transports dust-laden air from the dust source to the dust collector.

Dust cake is a build up protective layer of dust that keeps particles from passing through the filter media. Adequate amount of dust cake increases filtration efficiency. However, excessive build up of dust cake decreases filtration efficiency.

A device that removes particulate matter from the air.

The quantity of dust in the gas stream, usually expressed as grains of dust per cubic foot of air.

An electrostatic precipitator (ESP), is a highly efficient device designed to remove fine particles from flowing gas. As the dust-laden gas passes through the ESP, it gets ionized by high-voltage electrodes, resulting in the particles within the gas becoming charged. The charged particles then migrate towards the collecting plates, which carry an opposite charge, due to the electrostatic attraction. The particles precipitate onto the collecting plates and build up over time, forming a layer of dust. Then the dust is periodically cleaned from the collecting plates, ensuring that the ESP operates efficiently.

Loss in pressure caused by air flowing into a duct or hood.

Filter bags are fabric filters used in baghouse dust collectors, which are industrial-scale dust collection systems used in manufacturing and other industrial operations to remove dust, gases, and solid particulates from the workplace and from being released into the atmosphere. Filter bags are made of filter medias of different materials, such as aramid, PPS, acrylic, polyester, PTFE, fiberglass, etc.

Or filter medium. Permeable material that separates the particles from the gas or fluid stream.

Filter media treatment is a series of processes that are applied to filter media in order to improve its performance and extend its lifespan. The specific treatments that are used will vary depending on the type of filter media and the application in specific industries.

Filtration efficiency is a measure of how well a baghouse filter bag can capture dust particles from a gas stream. It is usually expressed as a percentage of the inlet dust concentration that is removed by the filter bag. For example, if the inlet dust concentration is 100 mg/m³ and the outlet dust concentration is 1 mg/m³, the filtration efficiency is 99%.

The speed at which air travels through a filter media.

Also known as calendaring, is the high-pressure pressing of the fabric by rollers to flatten or smooth the material. Glazing pushes the surface fibers down onto the body of the filter media. Glazing can be applied to various media such as polyester, polypropylene, and aramid. This is done to increase and uniform surface life, improve stability and reduce shrinkage.

In dust collection, “grains” are often used to describe the concentration of dust particles within a given volume of air, typically in grains per cubic foot (gr/ft³).

This measurement helps to assess how much dust is present in the air stream and evaluate the effectiveness of dust collection systems. Lower grains per cubic foot indicate cleaner air, which is crucial for regulatory compliance and worker safety.

A category of filter media certified to capture at least 99.97% of particles with a diameter greater than or equal to 0.3 microns.

A container that collects dust particles that have been removed from the air by a dust collector.

Hydrolysis is a chemical reaction that causes water molecules to interfere with the fiber’s polymer and cause decomposition. High temperatures, humidity, and chemicals must exist to activate hydrolysis. Signs of hydrolysis include fiber color turbidity, reduced strength and can be easily torn by hand, and broken sewing thread.

Hydrophilic refers to filter materials that attract and absorb moisture from the air. It has the following characteristics:

• Moisture Retention: Hydrophilic filter media can retain moisture from humid or damp air streams, which may be beneficial in certain applications but can also lead to clogging or reduced filter performance in high-moisture environments.
• Dust Adhesion: Moisture can cause dust particles to adhere more firmly to the filter media, potentially impacting the efficiency of dust release during cleaning cycles.
• Potential for Caking: In some cases, especially with fine dust, hydrophilic media may lead to dust “caking,” where accumulated dust clumps and reduces airflow, necessitating frequent cleaning or maintenance.
• Special Applications: Hydrophilic filters might be used where dust collection processes involve water vapor or where moisture in the air is integral to the filtration process.

In many cases, hydrophobic (water-repellent) filters are preferred for dust collection to avoid these challenges, especially in humid environments. Hydrophilic media may still be useful, however, in applications where capturing both dust and water vapor is beneficial.

A unit of pressure (often abbreviated “wg”) equal to the pressure exerted by a column of liquid water one-inch-high at a standard temperature (usually 70°F).For conversions, 1.000 psi = 27.71″ wg.

Chemically inactive and un-reactive.

Pressure entering the inlet side of the filter. Also called upstream pressure or line pressure.

In dust collection it usually means the online cleaning procedure for vertically installed filter bags in built-in condition: filter bags and supporting cages are not dismantled.

Space or opening in a filter media. Also known as pore or void.

Leak detection refers to procedures that help to identify leakages in filter bags, such as holes and ruptures, or uncover a breach between the dirty air and clean air plenum in a baghouse system.

A manometer is an instrument used to measure the differential pressure across a dust collector, specifically the pressure drop between the clean side and the dirty side of the filter media. This pressure drop indicates how much resistance the dust-laden air faces as it moves through the filter, which is critical for monitoring the performance and efficiency of the dust collection system. Its key functions in dust collection:

• Monitoring Filter Condition: As dust accumulates on the filter, the pressure drop increases. A rising pressure differential on the manometer indicates that filters are becoming loaded with dust and may need cleaning or replacement.
• Optimizing System Efficiency: Maintaining the correct pressure range ensures the dust collector operates efficiently, with adequate airflow and minimal strain on the system’s fan or blower.
• Preventing System Downtime: By alerting operators when the filter is clogged or airflow is restricted, a manometer helps prevent system malfunctions or unplanned downtime due to excessive filter loading.
• Maintenance Scheduling: Using the readings from the manometer, maintenance can be scheduled proactively, which helps reduce wear on components and extend the system’s lifespan.

Manometers can be analog (U-tube or dial) or digital, and they are typically mounted on or near the dust collection unit to provide real-time monitoring of filter health and overall system performance.

Multi-stage dust collection is a system designed to remove dust and particulate matter from the air in multiple stages, typically using a combination of different technologies and components. A multi-stage dust collection system aims to improve efficiency in capturing and removing dust particles of varying sizes.

Offline cleaning involves shutting down the baghouse temporarily for cleaning purposes. This method is typically used when the process can tolerate intermittent periods without filtration.

In online cleaning, the cleaning process occurs while the baghouse is still in operation. This continuous cleaning method ensures that the filtration process is ongoing without the need to shut down the dust collection system.

A term to describe the percentage of light that cannot pass through an object; may be used to describe the degree of visibility of an exhaust plume.

Pressure exiting the outlet side of the filter.

A parallel web in the fiber carding process is a web in which the fibers are laid parallel to each other in the direction of the machine. This is achieved by passing the fibers through a series of carding rollers, which have thin wires on their surfaces. The wires comb and disentangle the fibers, and as they move through the rollers, the fibers are aligned in the direction of travel.

Solid particles suspended in the air.

Known as fabric or cloth permeability. The ability of air to pass through the fabric, given a 0.50″ wg pressure differential. Fabric permeability is expressed in units of cfm per square foot of fabric

The path taken by the gas discharge from a smoke stack or chimney.

Particulate matter with a diameter of 2.5 micrometers or less.

Particulate matter with a diameter of 10 micrometers or less.

Opening in a filter media. Also known as interstice.

Diameter of pore in a filter media.

In a positive pressure baghouse, the fan or blower is positioned at the inlet, pushing the dirty air through the filter bags. The positive pressure is maintained within the system, forcing the air through the bags and into the clean air outlet. Positive pressure systems can be advantageous in certain applications where maintaining a positive pressure is critical, such as preventing the entry of external contaminants into the baghouse.

Pressure drop refers to the pressure differential across the filter media, across the baghouse, or across the entire dust collection system. It is a good indicator of the amount of dust that the filter media is accumulating and, if regularly monitored, the condition of the filter bags.

In general, a sudden drop in the differential pressure denotes a leak in the dust collection system. Whereas a sudden or sharp rise in the differential pressure denotes that the filter bags are becoming blinded or “caked” with particulates.

In a baghouse dust collector, a pulse cycle is the process that uses brief bursts of compressed air to clean dust off the filter bags or cartridges, keeping them free of buildup and allowing continuous, efficient dust collection. This method, known as pulse-jet cleaning, is a self-cleaning mechanism that maintains airflow and prevents excessive pressure drop in the dust collection system. Key aspects include:

• Cycle Frequency: Pulse cycles are typically programmed based on dust load and system needs. Higher dust loads may require more frequent pulsing, while lower dust loads can use less frequent pulses.
• Cycle Duration: Each pulse cycle is brief, often only milliseconds in duration, but strong enough to dislodge accumulated dust effectively.
• Sequential Pulsing: In larger systems with multiple rows of filter bags, the pulse cycle usually operates sequentially, pulsing one or more rows at a time to maintain continuous airflow. In this context, a pulse cycle refers to time interval between one pulsing of a row of bags and the next pulsing of the same row.

Dust-laden gas enters the baghouse via an inlet entry. Clean air exits through the inside of the filter bags while the dust particles are collected on the outside of the filter bag surface. In a pulse jet baghouse, filter bags are cleaned by using high pressure compressed air. A support cage prevents filter bag collapse during filtration, and aids in the filter bag cleaning.

The greatest advantage of pulse jet baghouses is that the filter bags can be cleaned on-line without stopping or interrupting the air flow entering the baghouse.

The occurrence where dust is collected from the airstream but then returned to the airstream from the same device. This term is used to refer to the situation in baghouses where dust particles on the surface of the filter media are forced back into the air when the bags are cleaned.

Residence time in a waste incineration plant refers to the duration the combustion gases remain in the combustion chamber at a specified temperature to ensure complete combustion and the breakdown of hazardous compounds. Typical Residence Time in Waste Incineration:

• 2 Seconds at 850°C: This is the standard residence time required in most modern waste incineration plants. The exhaust gases must remain at or above 850°C for at least 2 seconds in the secondary combustion chamber. This is primarily designed to ensure that harmful organic compounds, such as dioxins and furans, are fully decomposed and do not escape into the atmosphere.
• 1100°C for Hazardous Waste: To incinerate more dangerous waste, such as medical or chemical waste, the residence time may also be 2 seconds, but at a higher temperature of 1100°C. This higher temperature helps ensure the complete destruction of highly toxic compounds.

In reverse-air baghouses, the bags are fastened onto a cell plate at the bottom of the baghouse and suspended from an adjustable hanger frame at the top. Dirty gas flow normally enters the baghouse and passes through the bag from the inside, and the dust collects on the inside of the bags.

Reverse-air baghouses are compartmentalized to allow continuous operation. Before a cleaning cycle begins, filtration is stopped in the compartment to be cleaned. Bags are cleaned by injecting clean air into the dust collector in a reverse direction, which pressurizes the compartment. The pressure makes the bags collapse partially, causing the dust cake to crack and fall into the hopper below. At the end of the cleaning cycle, reverse airflow is discontinued, and the compartment is returned to the main stream.

The flow of the dirty gas helps maintain the shape of the bag. However, to prevent total collapse and fabric chafing during the cleaning cycle, rigid rings are sewn into the bags at intervals.

In the context of filter media, a scrim refers to a supporting layer or substrate used in the construction of filters, typically made of synthetic fibers, woven materials, or non-woven fabrics. The primary functions of scrim in filter media include:

1. Structural Support: Scrim provides strength and stability to the filter, helping it maintain its shape during operation and ensuring that it can withstand the pressure of the air or liquid being filtered.

2. Layering: Scrims can serve as a base layer for additional filtering materials. They may be combined with other media, such as activated carbon or fibrous filter layers, to enhance filtration efficiency.

3. Filtration Performance: Depending on the material used for the scrim, it can help trap larger particles while allowing smaller particles to pass through to the primary filtration media, improving overall performance.

4. Durability: Scrim can enhance the durability of filter media, allowing for longer service life and better resistance to wear and tear.

Scrims are often used in various filtration applications, including air, water, and industrial processes, where reliable filtration and structural integrity are essential.

Dust particles are collected on the inside surface of the filter bags in a shaker style  baghouses. The dust-laden gas enters through the dirty side (inlet) of the dust collector and flows up through the bag. The particulate is filtered by the dustcake and the fabric, and clean air exits through the outside of the bag. A shaker baghouse utilizes an electric motor driven mechanical system to clean the filter bags by shaking them after dust particles are collected and accumulated on the inside surface of  the filter bags.

It refers to the process of lightly burning the surface of the filter media to remove microscopic fibers or filaments. This is done to improve the performance of the filter by increasing its surface area and making it more porous. The singeing process also helps to reduce the chance of fiber migration, which is the movement of fibers from the filter media into the filtered stream.

In needlefelt manufacturing, smile effect is a term used to describe the tendency of needlefelt webs to shrink in the cross-machine direction more than in the machine direction. This causes the web to curl at the edges, giving it the appearance of a smile.

Smile effect is caused by the needling process. The needles pierce the web and entangle the fibers, which causes the web to shrink in the cross-machine direction.

Surface filtration is a method used in dust collection systems to capture and remove particulate matter from the air by trapping dust particles on the surface of a filter medium. In contrast to depth filtration, where particles are captured within the filter material, surface filtration primarily relies on the outer layer of the filter to catch and hold contaminants. This type of filtration is commonly employed in baghouse systems, cartridge collectors, and other industrial dust collection units.

The gaseous form of substances which are normally in a liquid or solid phase at standard atmospheric conditions. This change of state is accomplished by either raising the temperature or lowering the pressure.

Speed of air, measured in feet per minute (FPM).

A device shaped like a converging-diverging nozzle inserted through the top of the bag openings in the tube sheet in some compressed air baghouses and used to increase the effectiveness of the compressed air blasts.

Waste incineration is a process of burning municipal and industrial waste materials at high temperatures to reduce their volume and potentially recover energy. It’s used as a waste disposal method and can help manage waste that is not easily recyclable or biodegradable.