What are the functions of industrial dust removal filter cages?

The industrial dust removal filter cage, commonly referred to as the filter bag frame or cage, is a key component in a bag filter (also known as a baghouse or bag filter). It does not directly filter dust, but rather provides structural support for the filter bags. The cage ensures that the filter bags are properly installed and fully extended within the housing, maximizing their usable surface area.

1. Function of Industrial Dust Removal Filter Cages
Supporting the Filter Bags: During dust collector operation, dust-laden gas passes through the filter bags, creating a pressure differential (negative pressure) between the inside and outside of the bags. Without the support of the cage, the bags would collapse due to this pressure differential, resulting in reduced filtration efficiency or even failure. The cage ensures that the bags maintain their original shape and filtration area.

Optimizing Cleaning Efficiency: Baghouses typically use pulse jets or backflush cleaning methods to shake off dust accumulated on the filter bag surfaces. The filter cage helps the filter bag expand and contract rapidly during cleaning, generating effective vibration, which more thoroughly removes dust and maintains the bag's optimal filtration performance.

Extends filter bag life: The filter cage reduces mechanical stress on the filter bag caused by airflow impact, friction, or pressure changes during use, effectively extending the bag's service life and reducing operating costs.

Ensures filtration effectiveness: By maintaining the integrity and effective filtration area of the filter bag, the filter cage indirectly ensures that the dust collection system effectively captures industrial dust and meets environmental emission standards.

2. Dust Collection Filter Cage Shapes and Applications
Filter cages come in a variety of shapes to accommodate different filter bags and dust collector designs:

Round: The most common shape, widely used in various pulse-jet baghouses.

Oval: Suitable for compact dust collection systems with limited space.

Flat or envelope: Found in certain air handling units or applications requiring maximum filtration area.

Star/pleated: Provides a larger filtration surface area.

Split Filter Cage: When the dust collector's height is limited or transportation is inconvenient, a segmented design can be used for on-site assembly.

3. Common Problems with Industrial Dust Cage Filters During Use
Cage Corrosion and Rust
Cause: Filter cages are typically made of metal. If the flue gas in the operating environment contains moisture, acidic or alkaline substances, or if the temperature is too high, the surface coating of the cage may be damaged, leading to corrosion. Corrosion can make the cage's steel wire brittle, thin, or even break.

Impact: A rusted or corroded cage surface becomes rough, increasing friction with the filter bag, causing wear and perforation. Furthermore, corrosion reduces the mechanical strength of the cage, making it prone to deformation or collapse during pulse jet cleaning, ultimately causing the filter bag to break or even fall out.

Cage Deformation and Collapse
Cause: External impact: Improper handling during installation, maintenance, or cleaning can cause the cage to bend or become damaged.

Design Defects: The filter cage's wire diameter, rib spacing, or overall strength are improperly designed, making it unable to withstand the pressure shocks of pulse cleaning.
Corrosion or Wear: As mentioned earlier, severe corrosion can weaken the filter cage, making it unable to withstand normal operating loads and causing deformation or collapse.

Impact: Once the filter cage is deformed, it will change its fit with the filter bag, preventing some areas of the filter bag from fully expanding, affecting cleaning performance. Severe collapse can lead to direct filter bag failure or even detachment, causing dust leakage.

Problems with the Fit of the Filter Cage and the Bag
Cause: Dimensional Mismatch: A filter cage diameter that is too large or too small can cause problems. An oversized cage makes installation difficult and may break the filter bag; a undersized cage causes the bag to loosen, swing excessively under airflow, and increase wear.

Surface Roughness: The welds on the filter cage are not smooth, or the surface has burrs or sharp objects. When the filter bag expands and contracts during cleaning, these rough spots can cut the filter bag like a knife, causing localized wear or perforations.

Impact: Any defect in the fit will shorten the life of the filter bag, increase replacement frequency, and thus increase operating costs.

Welding or Cracked Joints
Cause: Poor welding quality: Weak welds during the manufacturing process are the primary cause.
Fatigue Stress: During long-term pulse jet cleaning cycles, welds are subjected to repeated mechanical stress, which can lead to metal fatigue over time, causing cracking or breaking of the welds.

Impact: A single weld may loosen a wire, compromising the support strength of the entire filter cage and potentially directly damaging the filter bag. If multiple welds are loose, the filter cage may become partially deformed or even fail completely.

Dust Accumulation and Clogging
Cause: Faulty cleaning system: If the pulse jet pressure is insufficient or the pulse cycle is improperly set, dust cannot be effectively removed from the filter bag surface, causing the dust layer to accumulate and even form clumps, resulting in "bridging" (a phenomenon known as "blocking").

Wet or sticky dust: When handling high-humidity or sticky dust, dust tends to adhere to the filter bags and cage surfaces, making it difficult to shake off.

Impact: Heavy dust accumulation on the cage increases the load on the filter bags, impairs cleaning performance, and may alter the cage structure. This increases system operating resistance, reduces handling airflow, and ultimately affects the efficiency of the entire dust removal system.