Industrial Air Filter Elements

A Comprehensive Guide to Types and Applications

Industrial filter elements are essential in a multitude of processes, encompassing a broad range of devices with filtering materials.

This article provides an in-depth look at the different types of industrial filter elements, including equipment-type, frame-type, and pipeline filters, and categorizes them based on their filtering performance.

characteristics and applications

Hydraulic Oil Filters
Hydraulic oil filters are predominantly used in the oil filtration industry, including suction oil filters, return oil filters, and pipeline filters.
Industrial Filters
Includes dust filters, air filters, and air conditioning filters.
Medical Filters
Covers liquid medicine filters, breathing filters, blood filters, and bacterial filters.
Drinking Water Filters
Includes tap water filters and sewage filters, etc.
Special Focus: Air filters, including primary, secondary, and highefficiency filters, as well as activated carbon filters.

Industrial Air Filter Elements Primary Filters

The recommended maintenance and replacement cycle for primary filters is generally between 3 and 6 months. However, the specific cycle may vary depending on factors such as the pollution level of the working environment and the material and quality of the primary filter. In harsher environments or with poorer air quality, it is recommended to shorten the replacement cycle to ensure filtering effectiveness. In dust-free workshops, the replacement cycle of primary filters may be shorter, around 1-2 months. However, some sources also suggest cleaning the primary filter once a week and replacing it every six months.

There are significant differences in performance and application scenarios among plate, pleated, and bag-type primary filters.

Plate Filters

Characteristics: Plate filters typically use galvanized steel frames and synthetic fiber filtering media, offering high coarse particle filtration efficiency (about 55%) suitable for low to medium-efficiency air filtration. They are easy to disassemble and clean, with readily available spare parts, high regenerability, and can be cleaned with warm water and household detergent.
Application Scenarios: Plate filters are commonly used for pre-filtration to maintain the efficiency of subsequent filters. For example, they are used as primary filters in air conditioning systems to filter larger particles.

Pleated Filters

Characteristics: Pleated filters increase the filtration area through a folded structure, thereby improving filtration efficiency. However, their performance can be affected by the permeability of the support layer, which may significantly reduce filtration performance if it varies drastically.
Application Scenarios: Pleated filters are suitable for applications requiring a larger filtration area, but their design is not primarily intended to reduce system resistance, so they may not perform as well as non-pleated filters in practical applications.

Pocket Filters

Characteristics: Pocket Filters use natural or synthetic fiber-woven fabrics as the medium. Their efficiency significantly improves as an initial dust layer accumulates on the surface media. Bag filters cannot withstand extreme temperatures, corrosive environments, or excessive mechanical stress, and they have high maintenance costs and expensive filter bag replacements.
Application Scenarios: Pocket Filters are typically used in situations where waste gas undergoes multiple filtration processes, such as removing airborne particles from gas streams in the nuclear industry. They are also suitable for applications requiring efficient removal of submicron-sized particles, but the overall process efficiency is slightly lower because some dust is lost during the initial layer formation.

In summary, plate filters are suitable for low to medium-efficiency air filtration scenarios requiring pre-filtration; pleated filters are suitable for applications requiring a larger filtration area but may be limited by support layer permeability; and bag filters are suitable for special industrial applications requiring efficient removal of fine particles, despite higher maintenance costs.

Specific Working Principle of Primary Filters in Air Purification Systems

The specific working principle of primary filters in air purification systems is mainly based on physical filtration. When particulate matter in the air enters the primary filter, it is blocked by the filter media, thereby purifying the air. Primary filters usually consist of one or more layers of fibrous materials, such as non-woven fabrics or glass fibers, woven into a dense filter mesh. When air passes through the filter mesh, larger particles are intercepted, while smaller particles may penetrate the mesh.

Additionally, primary filters use interception and adsorption principles to purify the air. Interception is the primary method; when airflow passes through the filter, the filter mesh structure inside the filter blocks larger particles of dust, hair, etc. Adsorption refers to the ability of the primary filter mesh to not only adsorb small dust particles but also effectively remove larger particles such as hair, as well as odors such as sweat, pet odors, and tobacco smoke.

How to Select Appropriate Materials and Structures for Primary Filters Based on Different Application Environments

Selecting suitable materials and structures for primary filters involves considering multiple factors, including the application environment, filtration efficiency, resistance, dust holding capacity, and specific functional requirements. Here are some key points

Specific Working Principle of Primary Filters in Air Purification Systems

Filter Media

Common filter media for primary filters include non-woven fabrics, glass fibers, nylon mesh, and activated carbon filter materials. Non-woven fabrics are a common filtering medium with good filtration performance and cost-effectiveness. Activated carbon filter materials are suitable for applications requiring the removal of gaseous pollutants, such as in air conditioning units, purification equipment, or upstream of high-efficiency filters in cleanrooms.

Frame Materials

The frame materials for primary filters include paper frames, aluminum frames, and galvanized steel frames. Aluminum frames and galvanized steel frames are typically used for plate filters, while paper frames are more commonly used for pleated filters.

Structural Design

Primary filters come in plate, pleated, and bag types. Plate filters use multiple layers of aluminum or stainless steel mesh rolled into a wavy shape and interleaved within the frame to form different densities and pore sizes. Pleated filters are folded and installed within high-strength cardboard to increase the windward area and improve filtration efficiency. Bag filters feature a unique bag structure that ensures balanced airflow throughout the bag, reducing resistance and maximizing dust holding capacity.

Realizing Specific Functions

In addition to basic filtration functions, specific extra functions can be achieved by adding antibacterial agents, selecting appropriate flame-retardant materials, or choosing salt spray-resistant formulations.

Performance Optimization

Optimal structural design of filters can be achieved using Computational Fluid Dynamics (CFD) simulation technology to obtain the best combination of efficiency, resistance, and dust holding capacity (lifespan) with appropriate materials, achieving energy savings and lifecycle cost optimization.

Citation: Air filters for general ventilation — Part 2: Measurement of fractional efficiency and air flow resistance. ISO (International Organization for Standardization)