Pulse Jet Bag Filters: The Ultimate FAQ Guide

I know you’re looking for reliable pulse jet bag filters.

Today’s guide will take you through every aspect of pulse jet bag filter – from sizes, filter material, advantages, quality control, standards to filtration mechanisms, amongst others.

So, if you want to be an expert in pulse jet bag filters, read this guide.

Take a look:

What is a Pulse Jet Bag Filter?

The name pulse jet originated from using a jet pump (venturi) to create very high-pressure bag cleaning pulses.

Normally, the short burst (pulses) of compressed air that cleans the filters contributes the name.

You can use this device to remove particulate contaminants from the air in the workplaces, such as warehouses, factories, and plants.

It is a dry air filtration system that self-clean through removing retained impurities from surfaces of the filter medium by using compressed air.

Pulse jet bag filter

What is the Working Principle of a Pulse Jet Filter?

Dirty air enters the filter through the inlet port located in the lower section of the filter.

The large particles are blocked by the baffle plate and directed to the hopper below.

Remember, the air particles carry the fine particles into the bag filters.

As filtration proceeds, a filter cake forms which helps achieve maximum filtration.

The cleaned air enters the upper chambers of the filter, where it gets out through the outlet.

Continued deposition of dust particles leads to the development of resistance in the filter bags.

Consequently, the sequential time controller signaled the solenoid valve and compressed air header to release air pulses periodically.

Besides, the compressed air sends a shock wave through the filter bags in the opposite direction to normal airflow, forcing the dust cake to fall off into the hopper.

The short pulses last less than a second and hence happens simultaneously to air filtration.

How can you Size a Pulse Bag Filter?

The size of your pulse jet bag filtration system will depend on the design you select.

You can follow the steps below to determine the most appropriate size of your filters.

· Determine the Minimum Velocity (ft/m)

You should consult experienced professionals to work out the expected minimum conveying velocity for the process gas and dust you will be handling.

Different particle contaminants have different conveying velocity.

Usually, the conveying velocity will vary between 3,500 to 5,000 ft/m for most materials.

· Identify the Sources of Contamination.

Identify the primary sources which need constant venting and filtration when the application is running.

Also, count the secondary sources and note how frequently do they require venting.

This step will help you know how many vents you need to install in the workplace.

It also enables you to determine the quantity of airflow expected.

· Determine the Amount of CFM you Need for every Branch

Calculate the quantity of CFM you require at each branch of your system.

You should consult a dust collection expert experienced with similar applications.

Consult the OEM for determining CFC of large sources like furnace, kilns, or for custom made equipment.

· Create a System Plan and Layout

 Draw a floor plan indicating the positions of all materials and devices. Connect the pieces in a sketch up to the filter.

Work out the required CFC where two primary branches meet by combining the CFC for each branch at the required velocity.

· Determine the Static Resistance/Pressure (SP) of the System

Static resistance is the resistance created due to friction arising from airflow through the system.

You should add the SP of the following elements to come up with a total SP.

• The worst branch/ branch with highest SP
• Main trunk line SP
• The static pressure of main dust collector including any pre-filters

What are the Components of Pulse Jet Bag Filter?

Pulse-jet bag filter system

The main components of a pulse jet bag filter include;

• Inlet port: Directs the dirty air into the filter.
•  Outlet/Clean air plenum: Releases the cleaned air
• Hooper: Collects the dirt from the filtered air and cleaned filter bags
• Main Housing Protects the components of the filter.
• Venturi: Enhances the tube sheet seal to the cuff. It also creates a pressure shock wave on the compressed air.
• Solenoid valve: It opens and closes rapidly to release compressed air out of the tubes
• Filter bags: They remove the dirt from the raw air
• Nozzles: Attached to blowpipes and release the air into the filter bags
• Metal Bag cages: Holds the bags into place inside the housing and prevents them from collapsing.
• Blowpipes: It is connected to the valves outlet and transport the air to the bags.
• Air manifold: It holds a predetermined quantity of compressed air in the desired pressure for pulsed.
• Baffle plate: Is a protective layer that blocks the heavy particles which can damage the filter bags.
• Tube sheets: These are metal fittings where you attach the filter bags and cages.
• Sequential time controller: It controls the online cleaning cycle of pulse jet bag filters.

What Materials can you Choose to make a Pulse Jet Bag Filter Housing?

The choice of material to construct the pulse jet filter depends on the unique manufacturing need, resistance to abrasion, and chemical compatibility.

You can select from the following materials:

• Carbon steel
• Stainless steel
• Mild steel
• Aluminum
• Special alloys such as Hastelloy and Inconel

Pulse jet bag filter

How does Pulse Jet Bag Filter compare to other Types of Bag Filters?

Compared to mechanical and reverse air baghouse filters, pulse jet filters have reduced sizes and cost.

You will use less fabrics due to higher gas to cloth ratio.

Jet filters also do not need the additional space for offline cleaning compartment.

Where can you Use a Pulse Jet Bag Filter?

The filters are suitable but not limited to the following industries:

• Agriculture
• Chemical
• Energy
• Automotive
• Metallurgy
• Rubber and plastic
• Quarries
• Recycling industries etc.
• Cement manufacturing
• Electrical and electricity

What are the Advantages of Using a Pulse Jet Bag Filter?

These filters offer numerous benefits compared to other types of dust collectors.

They include;

• They are less costly to install and operate.
• These filters can remove particles of up to 2.5 microns at 99.99% removal efficiency.
• The screen can work uninterrupted even during cleaning.
• Pulse-jet filters automatically clean using a compressed air system that fitted above the bag filters.
• The pulse-jet filter requires less installation space.
• The filters come in a diverse range of design and construction materials, which can be customized to meet the specific requirements of the customer.

What factors should you Consider when Buying a Pulse Jet Bag Filter?

You should consider the following factors before you place a purchase order for the pulse jet filter.

Pulse jet bag filtration system

· Composition of the Process Air or Gas

Ensure that the chemical properties of your gas are compatible with the material you choose for constructing the filter.

If you are dealing with corrosive gas, then select inert material that is resistant to chemical degradation.

Ensure that your process gas is free of moisture as humid air/gas will lead to the fast deterioration of the fabrics.

· Nature and Particle Size of the Dust

You should know the size of particles suspended in the process gas.

Conduct a laboratory test to confirm the physical and chemical characteristics of the contaminants.

Are the contaminants corrosive, toxic, or saline?

If so, then coat your equipment with materials that are resistant to chemical degradation.

· Operation Conditions

You should take note of the flowrate and temperatures of the process gas before purchase.

You should also know whether the process gas is going to be disposed of or recycled into the system.

· Required Efficiency

You will select your filter elements depending on the level of filtration you want to achieve, although most filters can remove 99.9% of the contaminants.

· Nature of Operation

Is the operation process continuous or intermittent?

You also need to know if dust production is continuous or sporadic.

In non-continuous applications, you can clean the filters offline, which is not possible for continuous applications.

· Available Space

Conduct a process hazard analysis to determine where to station the filter house.

You can install the filter either inside or outside, depending on the nature and volume of contaminants.

If your filtration process is susceptible to fluctuation in temperature, then you should station the filter unit indoors with a connection to conditioned air.

Temperature fluctuations can alter the dust properties.

The location of the filter will also affect sizing and styles.

· Budget

Ensure that you choose a filter that fits into your budget.

Together with initial purchase cost, it also includes the cost of energy consumption, downtime, and replacement cartridges/bags.

Special conditions such as airlock or may cost you more in addition to supporting auxiliary equipment.

How can you Maintain a Pulse Jet Bag Filter to Extend its Longevity?

Pulse jet bag filtration system

You should schedule regular maintenance and service on a daily, weekly, and monthly basis to ensure smooth and efficient operation.

Below are some of the maintenance tips to ensure the sound performance of the filter:

• Check and take constant readings of the differential pressure gauge. It will let you rectify problems early enough in case the device malfunctions.
• Regularly clean the tubes lines and sensors of the device to avoid any damage and failure of the equipment.
• Perform regular leakage testing to detect potential filter failures in advance. Use leak detection powders and monochromatic lights to identify the exact point of leakage.
• Regularly check and service the exhaust fan in case of any sign of failures such as vibration, periodic squealing, and variation in operational standards.
• Conduct regular inspections and cleaning of the duct to avoid chocking the system.
• Ensure that the diaphragm valves are free from leakage.
• Replace any worn out diaphragm to prevent wastage of compressed air.
• Conduct regular inspections of the filter media to ensure proper functioning. Schedule a periodic test for leakages and the quality of the dust cake.
• Ensure that you replace the filters frequently, as instructed by the manufacturer. Always use filters from the original manufacturer for consistency in material quality and efficiency.

What are the Shortcomings of a Pulse Jet Bag Filter?

Pulse-jet filters also have some disadvantages including;

• The filter cannot function with process gas with high humidity.
• The concentration of effluents in the filters are likely to be higher in these filters compared to other bag dust collectors.
• The filters experience higher pressure drops and penetration because of the high filtration velocities.
• On line cleaning of pulse jet filters usually allows for dust re-deposition after pulse cleaning.
• Filters that use high velocities can also have the dirt transferred from a dirty bag to a clean bag during cleaning.

Consequently, causing the dust layers in the bags to become thicker, making it difficult to remove through using the compressed air system.

• The top of the filter bags is usually cleaned better than the lower part because of the loss of pulse energy as it travels from high to low-pressure zones.
• It requires an additional compressed air system, which will increase the time needed for maintenance.

Which Materials are Pulse Jet Bag Filters made of?

The properties of the gas/air you are filtering will determine the kind of material you choose to make the filter medium.

Also, the materials can be woven or non-woven. You can select from the following materials:

· Fiberglass

You can use this material when the application operating temperature is high because it can withstand up to 260°C.

The medium does not absorb moisture, it is noncombustible, and its dimensional stability is excellent.

It Is suitable for boilers fired with coal metal applications that require high temperatures.

· Teflon (PTFE)

You can use the material if you need a material that will resist chemical erosion throughout the pH range.

It can also withstand a temperature surge of up to 260°C.

It does not absorb moisture, is non-adhesive, and resistant to degradation by ultraviolet rays and mildew.

However, Teflon is highly susceptible to abrasion and very expensive.

· Ryton

You can use the material in combustion-control application because its resistance to alkalies and acid is excellent.

· Nomex

It is available in both felted and woven fabrics and produced either as a filament or staple fiber.

You can use it in operations with temperatures ranging between 135°C to 204°C.

It is resistant to flame and possesses excellent thermal stability.

However, it is less resistant to chemical attack, and the presence of moisture and Sulphur oxides usually results in unacceptable short bag life.

· Polypropylene

The material is non-hygroscopic, resistant to abrasion, and static build-up.

It offers a smooth surface that excellently releases cake during clean up.

Also, it has a low operating temperature of only 88°C.

· Polyester

You can use polyester if your application operates at 135°C. 

It can also sustain a temperature surge of up to 149°C.

It is highly resistant to many organic solvents and the majority of the oxidizing agents.

At low temperatures, the material is also relatively resistant to strong alkalis and has excellent resistance to weak alkalis.

However, polyester is very susceptible to degradation by water and concentrated nitric, sulphuric, and carbolic acids.

· Acrylic

A homopolymer version of acrylic provides better results when used as a filter medium.

It has excellent resistance to hydrolysis between the temperature range 127°C continuous to 135°C surge.

Besides, it is best suited in applications that process ferrous and nonferrous metal, lime, cement, carbon black, fertilizers, and wet filtration applications.

You can pre-coat the filter medium with a layer of inert dust such as calcium carbonate to prevent premature binding of moist, fine adhesive powder on the filter media.

In some cases, a thin layer of Teflon membrane is pre-coated on the side that performs filtration to prolong the life of the filters.

The filter medium is held in place by metal cages to prevent them from collapsing.

How do you Test the Quality of Pulse Jet Bag Filters?

There are four fabric quality tests that you can perform to verify the quality standards of the filters. They include:

· Permeability Test

You will use this test to determine the amount of air that can pass through a given cloth area.

Besides, you can achieve this by measuring the amount of air that will pass through one square foot of cloth at 125 Pa pressure drop.

· Mullen Burst Strength

This test will give the ability of a fabric to withstand pressure or pulse.

It can also indicate whether heat cleaning has compromised the integrity of new fiberglass fabrics.

· MIT Flex Test

The test indicates resistance to self-abrasion from flexing.

You can use this test the deterioration rate for fiberglass pulse jet filters installed in utility boilers powered by coal.

· Tensile Strength Test

This test measures the fabric elongation, stretch, and tear.

Different materials have different tensile strengths due to variations in fabric type and weight.

Generally, natural fabrics have lower elongation compared to synthetic material.

You can determine the rate of strength deterioration when you combine this test with the Mullen burst test.

How can you Install a Pulse Jet Bag Filter?

The large filter is shipped as isolated parts, while the small once can be sent as a complete unit.

You will bolt the pieces together at the installation site on a strong foundation.

The compressed air system comes with a general drawing that indicates the placements and pipe sizes.

Though the filter does not require lubrication, ensure to lubricate appropriate support devices such as a rotary clock.

The elements can be installed either horizontally or vertically, depending on the design of the filter.

You can use either bag or cartridge filters depending on the requirements of your operation and the design of the screen you are using.

The cages and bag or cartridge filters can either be bottom or top accessed. Each type of installation has a different installation procedure.

What are Pulse Jet Bag Filters Safety Precautions?

Pulse jet filter system

Ensure that everyone coming into close contact with the filters follow the instruction as prescribed in the safety symbols.

Place signal words such as WARNING, DANGER, NOTICE, and CAUTION appropriately and accompanied by appropriate safety messages.

Train all employees who work with the equipment on the procedures and related safety requirements.

Limit access of the filter to only authorized personnel.

Follow the instructions on the manual during installation, operation, and maintenance.

Avoid any unauthorized modification without prior written permission from the manufacturer.

Modification can impair the safety and operation of the machine as well as reduce its service life.

Ensure that safety decals are always clean and legible.

Replace missing and illegible decals with parts that have similar information as the originals.

You must shut down the power and release the pressure before servicing the machine.

Always ensure that the access doors, guards, and covers are secure when operating the filter.

Avoid the plenum when the system fan is on.

The airstream can close the door resulting in entrapment and injury.

Take strict caution while dealing with flying ash in the hopper as it takes quite a long time to cool down, sometimes even days after shutting down the system!

Put on protective gear for the whole body and eyes before you rod a hopper.

Don’t use a ladder to access a hopper that you need to open.

Avoid opening an ash-filled hopper unless it’s an emergency.

Stay away from the ash flow path at all times.

Ensure that the hopper is cold and ventilated before you get inside a hopper.

Always ensure that you have another person placed outside the hopper to respond appropriately in case of an emergency.

Are Pulse Bag Filters Cleanable?

Yes, pulse jet bag filters have a built-in automatic cleaning system called pulse jet cleaning.

The system uses a clean compressed air system that momentarily blasts in the opposite direction to the normal flow of air to dislodge the dust off the filter bags.

To avoid premature blinding, you should employ a random cleaning method where the bag row cleaning is non-sequential.

When you clean the bag rows sequentially, dirt from the adjacent bags will settle on already cleaned bags resulting in poor cleaning and retention of very fine particles.

How Long can Pulse Jet Bag Filters last before Replacement?

Pulse bag filters can take between 3 to 6 years before they require replacement under normal operations and proper maintenance.

What are the Industry Standards for Pulse Jet Bag Filters?

ISO 11057:2011 standards specify the procedure for testing quality standards and characterization of pulse jet cleanable filters.

The test methods will cover both particle emissions and the operational performance of the pulse jet filters.

How much can a Pulse Bag Filter Cost?

The cost of pulse bag filters varies greatly to size, filtration efficiency, capacity, and materials used for construction.

The small screens can cost as low as $600, while the sizeable industrial pulse filters for manufacturing plants can cost up to $454500 per set.

What Filtration Mechanisms are Employed by Pulse Jet Fibers in Cleaning Impurities?

The fibers remove dust from the process gas through impaction, direct interception, diffusion, and electrostatic forces.

With the information in this guide, you can probably choose the best pulse jet bag filter for your applications.

However, in case you have any question about pulse bag jet filter, contact us now.