Read more about Sly Inc. via the blog articles below:

How to Select the Correct Filter Media

Posted on October 26, 2020
4 minute read

Dust collectors are the primary choice for industrial air quality control. By increasing the safety of your site, protecting the health of your workers, and helping you to maintain regulatory compliance, dust collectors are vital to the success of your business. A baghouse can be structurally perfect but still fail if you choose the wrong filter media. But, how do you know what media is the right choice?

Choosing the correct filter media for your baghouse is essential to making sure that your dust collection system is operating at maximum efficiency, properly removing particulate, and maintaining draft from your process. Without the right media, your baghouse could lose permeability quickly, or even fail. If this happens, a baghouse can become one of the most high-maintenance pieces of equipment at your plant, requiring repairs, unscheduled downtime, and emergency maintenance.

Here at Sly, we know that this simply can’t happen. The right filter media inside a Sly baghouse is a key component to predictable dust collection performance.


Selecting the Correct Filter Cloth Types

When it comes to selecting a filter media, there are three main filter media categories to choose from. These include:

  • Woven media
  • Non-woven felts 
  • Synthetics

Finding out which bag filter media is best for your baghouse will largely depend on your application. That’s because the performance of your filter bag is directly related to its ability to withstand and operate in the environment that it’s being used in.

There are three modes of failure for filter media that must be considered:

  • Thermal
  • Chemical
  • Mechanical

Preventing Thermal Failure

For temperature, you need to know the continuous operating temperature of your airstream at the inlet of your baghouse. Ask yourself:

  • What’s the average temperature?
  • Are there any temperature surges?
  • What’s the frequency and duration of those surges and how hot does it get?

The answers to these questions will determine what fibers you can use for the filter media. If you have an ambient operating temperature around 120°F with no surges, then most industrial-grade natural and synthetic fibers would work. However, if you have an operating temperature above 400°F with frequent 500°F surges, then you’ll need a specialty media. Make sure that the filters can handle these higher temperatures without breaking down or compromising baghouse performance, like PTFE or P84® (Polyimide), or fiberglass.

If these conditions are violated, the filter media will experience thermal failure. This will manifest as media strength loss, shrinkage or elongation of the media, or even loss of protective finishes on the media.

Preventing Chemical Failure

Once you know how the baghouse will operate thermally, you’ll want to consider the chemical nature of the dust and gas stream. Take the time to ask:

  • Are there any common chemical reactions that I should expect in the baghouse?
  • Am I injecting gas stream conditioning agents that may react in the collector?
  • Will I need to start-up and shut-down frequently, which passes the baghouse through the dew point?

If these factors are not considered, chemical failure could occur due to an improperly applied filter media. This failure could be from an acid attack on individual fibers, alkalinity weakening the overall media, or other issues from the amount of oxygen in the gas stream. Any of these things can lead to the premature failure of the baghouse filter media, forcing you to shut down operations and perform unscheduled maintenance.

Preventing Mechanical Failure

Once you’ve chosen the right filter media from a thermal and chemical standpoint, you still need to consider the operating conditions to which the baghouse will be exposed. Even when you do everything right, filter media will eventually fail. It’s similar to mileage on a car tire; once you hit that mileage mark, the tread is gone and it’s time for them to be replaced.

With regard to mechanical failure, all of the following can affect a filter’s performance:

  • Dust particle size – Is it small and embedded in the fabric, leading to non-recoverable high dP?
  • Dust characteristics – Is it “sticky” and difficult to clean? Does the dust have high moisture content?
  • Abrasiveness – Is it going to wear out the fabric with its abrasiveness, leading to holes in the fabric and causing emissions?
  • Faulty construction – Did a damaged or defective filter get installed in the baghouse, leading to mechanical issues with the filter, or surrounding filters?
  • “Normal” operation – You may have done everything perfectly, but filter bags will hit their “mileage” limit and begin to fail mechanically.
  • Dust combustibility  

That last point is especially important with the September 7, 2020 DFPA 652 deadline to complete your Dust Hazard Analysis. Beyond lowering your baghouse’s efficiency and performance, not having a filter that can handle explosive or combustible dust can be devastating, both from a safety and regulatory standpoint. If you’re dealing with combustible dust, you’ll need a filter that can mitigate the risk of an explosion. Period.

Types of Filter Media 

For the above dust considerations, the following table shows the main types of filter media that Sly offers, along with their key features and best-suited operating parameters:

 

Type  

Common Finishes  

Operating Temp.  

Key Features  

Cotton  

flame retardant  

180°F  

resistant to flex and flat abrasion, excellent clean-down  

Polyester  

ePTFE membrane, singed, glazed, oleophobic  

275°F  

great resistance to chemicals, abrasion, dry heat degradation, will fail from hydrolysis  

Polypropylene  

singed, glazed, SlyTech-01  

170°F  

high strength, excellent resistance to most acids and alkalis  

Nylon  

singed, glazed  

250°F  

good resistance to alkalis, holds up well to organic solvents  

Acrylic  

ePTFE membrane, singed, glazed, SlyTech-01  

275°F  

good acid, heat, and hydrolysis resistance  

Aramid*  

ePTFE membrane, singed, glazed, SlyTech-01  

375°F  

good resistance to alkalis, holds up well to organic solvents, resists abrasion  

Fiberglass*  

Acid resistant, ePTFE membrane, lubricity coating     

450°F  

excellent resistance to most acids, excellent with high heat and moisture conditions

P84®

ePTFE membrane, singed, glazed, SlyTech-01  

500°F  

non-flammable, resistant to flex abrasion  

PPS*  

ePTFE membrane, singed, glazed, oleophobic  

375°F  

excellent resistance to both acids and alkali, great in applications where emissions standards are tight  

PTFE

ePTFE membrane

500°F  

impervious to chemical attack, resists abrasion   

*considered high-temperature media, best suited for applications with high heat operating conditions

Always one to innovate, Sly also offers Sly High Efficiency Felts (SlyHe). With both regular and high temperature (Aramid) designs, these innovative felts have several advantages over both commodity felts and ePTFE membrane laminates, including lower emissions, higher efficiencies, and an extended bag life.

How Sly Can Help

Beyond providing high-quality fabrics and filter media for your dust collector, Sly also offers a number of baghouse analysis services to make sure that you maintain a highly-optimized system. Our particle analysis service allows us to better understand the characteristics of your dust by measuring bulk density and particle size distribution. Then, with our filter bag failure analysis, we can analyze any filters that have failed in the past and combine that with your system’s operating data in order to recommend the best bag type for your specific application.

With the combination of Sly’s superior products and expert knowledge, we’ll help you to get the most out of your air pollution control system, no matter what industry you’re in.


designing a dust collection system

Tags: dust collectors

Subscribe to Our Blog

Recent Posts