How to Choose a Filter Bag for Industrial Filtration Systems

13 Apr.,2024

 

Industrial filtration systems are built to meet the specifications of your water purification needs. Choosing the correct filtration bag will assist in the removal of unwanted particles and microorganisms from your application. Depending on your application requirements, several styles of filter bags can be used.

Filter bag considerations include micron ratings, filter bag material and fabric requirements, and cost objectives. Since each industrial filtration system is unique to its direct application, the filter bags used within the system must also align with application parameters.

What is an Industrial Filtration System Filter Bag?

Bag filtration is among the most used ways to filter large quantities of water and other liquids. Depending on the liquid and application, some particle types may not need to be filtered, while other contaminants require at or near 100% removal. An absolute filter bag is often used for applications that require the removal of all particles. Absolute filters utilize a specific pore rating size that traps particles of a particular size or larger with defined efficiency.

Considerations When Choosing a Filter Bag

Several considerations should be met prior to choosing the right filter bag for your application. Each of the following characteristics must be considered to find the filter bag that will suit your application requirements.

  • Particle size
  • Flow rate
  • Pressure
  • Process conditions
  • Filter media types
  • Filter housing

Particle Size

The smaller the micron rating, the smaller the solid particles that will be prevented from passing through liquid filters. There are two ways to measure  the size and amount of particles removed, nominal and absolute. A nominal pore size rating refers to a filter capable of preventing the passage of an undefined percentage of solid particles greater than the stated pore size. Absolute filtration refers to retaining all particles of a certain pore size. For example, a 20 µm absolute rating means all particles with a 20 µm or larger pore size will be retained at 99% during one filtration process.

Flow Rate

The filtering area size will determine the speed at which the liquid flows through the filter bags. The liquid's thickness, material type, and viscosity will also affect the flow rate. Filter bags that are too small or with a material thicker than recommended can decrease the flow rate.

Pressure

Every filter bag is manufactured with a maximum operating pressure. If the maximum working pressure is exceeded, the filter can be damaged. Filter bags should be serviced when the pressure differential is 15 PSID.. Filter replacement or regeneration occurs over time once the filter becomes clogged.

Process Conditions

Process conditions are essential in determining the correct filter solution based on your specifications. Based on your project requirements, filter bags often require proper temperature resistance and high-pressure regulation, while process parameters also play a role in the specific sizing of the system.

Filter Media Types

Filter bags provide process filtering for water, paints, food liquid, chemicals, solvents, and more. The three basic media types include needle felts, woven monofilament meshes, and melt blown. Typical filter materials used within filter bags include:

  • Polypropylene
  • Polyester
  • Polyamide (nylon)

Filter Housing

Filter housings are casings that fit around a filter cartridge or bag in a liquid or gas stream. Filter bags are used to process and filter liquids in various housings. The application and liquid type will determine the housing material required. Housing material options include:

  • Stainless steel
  • Carbon steel
  • Aluminum
  • Exotic alloys
  • Plastic

Locate the Industrial Filtration System Filter Bags You Need at Rosedale Products

Rosedale Products is your source for high quality filter bags and components. Our filter bags are designed to remove contaminants and debris from liquids based on their specific micron ratings. Contact us for more information regarding our filter bag options, check out our replacement filter bag calculator, or learn more about Rosedale Products today!

 


How do you change a bag filter?

  1. Close all valves at the inlet and outlet ports.
  2. Ensure that the housing is not pressurized, by opening the pressure release valve.
  3. Remove the clamp (for clamp top style housings) or loosen the bolts (for bolt-down top housings) at the top of the housing.
  4. Remove the top of the housing.
  5. Remove the T-bolt at the top of the interior of the housing, allowing you to also remove the diffuser plate.
  6. Remove the dirty bag filter.
  7. Place a clean bag filter into the strainer basket, being sure that the bag filter extends straight down through the strainer basket.
  8. Place the diffuser plate back on top of the new bag filter.
  9. Screw the T-bolt back into the housing (it may slide into grooves on the interior of the housing), and tighten.
  10. Place the top back onto the top of the housing.
  11. Reattach the clamp (for clamp top style housings) and tighten; or tighten the bolts (for bolt-down top housings)

 

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Should I be using a #2 or #4 size bag filter?

Virtually all industrial and commercial applications utilize trade size #2 or trade size #4 filters, which correspond with #2 and #4 size filter housings. The correct housing for an application is mostly determined by the flow rate.

A #4 size housing is appropriate for most applications up to 40 gpm, and a #2 size housing is appropriate for most applications up to 100 gpm. Multi-bag housings can generally handle flow rates greater than 100 gpm.

Learn more about choosing the correct size bag filter/housing here, or speak with a PRM filtration expert.

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What type of bag filter material should I use?

Choosing the appropriate bag filter material depends on a number of factors, primarily chemical compatibility and temperature.

Polyester Felt Filter Bags:

  • High dirt holding capacity
  • Removes solids and gelatinous particles
  • Low cost
  • Chemical compatibility with wide range of contaminants
  • Maximum Temperature: 275° F
  • Welded Seam


Nylon Monofilament Mesh Filter Bags:

  • Provide extra strength and abrasion resistance
  • Produce predictable results for consistent performance
  • Chemical compatibility with a wide range of contaminants
  • Maximum Temperature: 275° F
  • Sewn seam using 5-line system


Nomex High Temperature Filter Bags:

  • Removes solids and gelatinous particles
  • Maximum Temperature: 425° F
  • Sewn seam using 5-line system
 Polyester Felt Nylon Mesh Nomex Material Mineral Acids Good Poor Fair Organic Acids Good Fair Fair Alkalis Good Good Good Oxidizing Acids Good Poor Poor Animal/Vegetable Petro Oils Excellent Excellent Excellent Organic Solvents Excellent Excellent Excellent Micro Organisms Excellent Excellent Excellent

 

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How long will my bag filter last?

The amount of contaminant as well as the micron rating of the bag will determine the life of the bag filter. Some applications may only allow the filter to last a few minutes, while other applications may be suited to last for weeks.

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When should I change the bag filter?

You need to be monitoring the inlet and outlet pressure on the vessel. The difference between the inlet and outlet pressure is referred to as “differential pressure” or “pressure drop”. You will want to change the bag filter when the differential pressure reaches a certain threshold that is dependent on your application or system. Often times this threshold can range from 5 to 20 psi.

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Are bag filters reusable?

Most bag filters are intended to only be used one time, including all PRM filter bags. Cleaning the bag filter can cause unintended damage, resulting in a change in the end product and/or malfunctioning of the filter bag.

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How do I choose the correct ring material for a bag filter?

Chemical compatibility: Bag filter rings are typically either polypropylene, carbon steel or stainless steel. The ring material should be chemically compatible with your application.

Temperature: If you are running liquids over 190° F through the system, you will want to be sure that the temperature will not affect the polypropylene ring by melting or softening. A steel ring bag filter may be more appropriate for applications involving hot temperatures.

Incineration: Some bag filters are disposed of via incineration, in which case you would not want to use a steel ring.

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What is the head loss across my bag filter housing?

An empty housing, at maximum flow rate, has no real measurable loss. With a clean bag(s), head loss is also negligible. It is not until the bag(s) begin to load that measurable loss occurs, increasing over time until the bag(s) needs to be changed.

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What is the maximum operating temperature of a bag filter housing?

The maximum operating temperature of a stainless steel or carbon steel bag filter housing is dependent on the type of bag filter material that will be used in the housing. A bag filter will begin to break down before any noticeable effects to a stainless steel or carbon steel housing.

PVC bag filter housings have a significantly lower maximum operating temperature compared their stainless steel and carbon steel counterparts. In general, PVC bag filter housings have a 100°-113°F maximum temperature rating, but be sure to check the exact specifications on the PVC housing in question.

Every bag filter has a specified maximum operating temperature. Most bag filters are rated for around 275°-300°F. If your application may exceed 275°F, High Temperature Nomex Filter Bags may be a good option.

You can always contact a PRM Filtration Expert for guidance in choosing the most appropriate bag filter housing and bag filter for your application.

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How to Choose a Filter Bag for Industrial Filtration Systems

How to Change, Size (#2 or #4), Type, and more