Needlefelt filter bags are made from nonwoven synthetic fibers (such as polyester or polypropylene) that are mechanically entangled to create a depth filtration structure. These bags provide depth filtration, meaning they capture particles throughout the media thickness. They are best for applications requiring high dirt-holding capacity, such as:

• Paints, inks, and coatings
• Water treatment
• Food and beverage processing
• Chemical processing

Mesh filter bags are woven materials, typically made from nylon or polyester, that offer surface filtration by trapping particles on the material’s surface. They are best for applications where precise particle size retention is needed, such as:

• Bulk solids separation
• Fine particle classification
• Viscous liquids with minimal particulate load
• Pharmaceutical and high-purity applications

The best choice depends on the filtration goal: needlefelt bags are better for capturing a high volume of contaminants, while mesh bags are ideal for retaining specific particle sizes and offering easy cleaning/reusability.

Polypropylene, Polyester, Nylon, Nomex, Teflon

Selecting the right filter bag material depends on the substance being filtered, operating temperature, chemical compatibility, and filtration efficiency required. Common materials include polyester, polypropylene, nylon, and PTFE, each suited for different applications such as chemicals, food processing, or water treatment.

The replacement frequency depends on factors like the type of contaminants, flow rate, operating conditions, and differential pressure buildup. Regular monitoring of pressure drop and inspecting the filter bag for clogging or damage will help determine the optimal replacement interval.

The primary indicator of filter performance is pressure drop across the filter. A rising pressure differential suggests clogging and reduced efficiency. Visual inspections and scheduled maintenance also help ensure consistent performance. Always change bags out when they reach the changeout differential pressure specified by the manufacturer.

Bag filters are typically disposable items, but in certain industrial applications can be cleaned and their life extended. Some industrial systems use pulse jet cleaning, where compressed air pulses remove collected particles from the filter media, extending its lifespan. Other systems may use mechanical shaking or reverse air cleaning.

Proper installation involves ensuring a secure fit in the housing, checking for correct sealing to prevent bypass, and confirming that the system is operating at the right pressure and flow rate. Maintenance includes regular inspections, timely bag replacements, and keeping the housing and sealing surfaces clean.

Check the chemical compatibility of the filter media with the liquid or gas being filtered. Reference chemical resistance charts provided by manufacturers, and consider temperature and pH factors that could affect material integrity over the exposure time. Read our blog: Choosing The Right Filter Bag For Your Application for more information. 

Lifespan varies based on application, contaminant load, temperature, and operating pressure. Some filter bags last only a few days in high-load environments, while others can last weeks or months in low-contaminant applications. Monitoring pressure drop and conducting periodic inspections will help optimize lifespan. However it is also worth noting that under sizing of bag filters will also cause frequent change out and short service life.

• Regularly monitor pressure drop and change bags before excessive clogging occurs.
• Use proper pre-filtration if necessary to extend bag life.
• Ensure a proper seal to prevent bypass.
• Store replacement bags in a clean, dry environment.
• Choose the right micron rating for your specific application needs.