The filtration accuracy of a filter cartridge is usually divided based on the size of the particles it intercepts (in micrometers, μ m), and different materials and structures of the filter cartridge are suitable for different scenarios. The following are the classification and characteristics of filtration accuracy for common types of filter cartridges:

Accuracy and characteristics of common filter types

1. PP melt blown filter cartridge

Accuracy range: 1-100 μ m (commonly 1, 5, 10, 20, 50, 100 μ m).

Principle: Through hot melt winding of polypropylene fibers, particles are intercepted by deep filtration, and the accuracy is controlled by the fiber density.

Features: Low cost, high flux, but non washable, belonging to disposable filter element.

Application: Water filtration pretreatment, coarse filtration in the food and beverage industry, and initial filtration in air conditioning systems.

2. Wire wound filter element (cotton/synthetic fiber)

Accuracy range: 5~100 μ m (adjusted by winding density).

Principle: A deep filtration structure is formed by spiral winding textile fibers (such as cotton and polyester) around a porous skeleton.

Features: Can be cleaned and reused, with strong retention ability but high resistance.

Application: Industrial circulating water filtration, lubricating oil impurity removal, ship fuel filtration.

3. Folding membrane filter cartridge (microfiltration/ultrafiltration)

Accuracy range:

-Microfiltration (MF): 0.1-10 μ m (such as PES polyethersulfone membrane, PTFE polytetrafluoroethylene membrane);

-Ultrafiltration (UF): 0.01~0.1 μ m (such as PVDF polyvinylidene fluoride membrane).

Principle: Fold the microporous membrane into a wavy shape to increase the filtration area, with surface filtration as the main method and deep filtration as a secondary method.

Features: High precision, fast flow rate, high pollutant holding capacity, and some materials are acid and alkali resistant (such as PTFE, suitable for strong corrosion scenarios).

Application: Pharmaceutical industry drug sterilization (0.22 μ m filter membrane), electronic grade water filtration, sterile filtration of food and beverage.

4. Ceramic filter cartridge

Accuracy range: 0.1~10 μ m (commonly 0.2 μ m, 0.5 μ m, 1 μ m).

Principle: Sintered from porous ceramics such as alumina and silicon carbide, utilizing rigid pores to trap particles.

Features: High temperature resistance (up to 500 ℃), chemical corrosion resistance, backwash cleaning, long service life.

Application: High temperature fluid filtration (such as flue gas dust removal), chemical solvent filtration, and drinking water terminal purification (can remove bacteria).

5. Metal sintered filter element (stainless steel/copper)

Accuracy range: 0.5~100 μ m (controlled by pore size of metal powder).

Principle: Metal powder (such as 316L stainless steel) is sintered at high temperature to form a porous structure, which belongs to rigid deep filtration.

Features: High strength, high pressure resistance, corrosion resistance, can be repeatedly cleaned, and high cost.

Applications: aviation fuel filtration, chemical high-pressure systems, nuclear industry radioactive liquid filtration.

6. Activated carbon filter cartridge

Accuracy range: Broadly speaking, it is not directly divided by particle size and mainly adsorbs organic matter and odors (equivalent filtration accuracy of about 10-20 μ m).

Principle: Utilizing the microporous structure of activated carbon to adsorb molecular level impurities (such as residual chlorine, pigments, VOCs), with weak physical filtration effect.

Characteristics: Limited adsorption capacity, requiring regular replacement, often used in combination with other filter cartridges.

Application: Deodorization of drinking water, air purification, decolorization of chemical solvents.

7. Nanofiltration (NF) and reverse osmosis (RO) membrane filters

Nanofiltration accuracy: 0.0001-0.001 μ m, molecular weight cutoff of 200-1000 Da (Daltons), allowing monovalent ions to pass through.

Reverse osmosis accuracy:<0.0001 μ m, cut-off molecular weight<200 Da, almost all ions and organic matter are intercepted.

Principle: Depending on the pore size screening and charge repulsion on the membrane surface, pressure needs to be applied to drive fluid through the membrane.

Application:

-Nanofiltration: softening of drinking water (removal of calcium and magnesium ions), concentration of dyes, separation of antibiotics;

-Reverse osmosis: seawater desalination, lithium battery electrolyte purification, semiconductor ultrapure water.

Key factors affecting filtration accuracy

1. Material and Structure:

-Surface filtration types (such as membrane filters) have more stable accuracy, while deep filtration types (such as PP melt blown) may experience a decrease in accuracy due to usage time.

2. Operating conditions:

-Pressure, temperature, and fluid viscosity can affect the actual filtration effect (such as high temperature may cause deformation of polymer filters and loss of accuracy).

3. Characteristics of pollutants:

-Particle shape (spherical/fibrous), concentration, and viscosity can affect retention efficiency (such as fibrous particles easily clogging membrane pores).

Principles for selecting filter accuracy

1. Clearly identify the target pollutants:

-If bacteria (particle size about 0.5-5 μ m) need to be removed, a filter element with an accuracy of ≤ 1 μ m should be selected; If the virus (particle size about 0.02~0.3 μ m) is removed, ultrafiltration or nanofiltration level is required.

2. Matching system requirements:

-For front-end preprocessing, a coarse efficiency filter element can be selected to reduce costs, while for terminal precision filtration, a high-precision filter element should be selected according to process requirements.

3. Consider economy:

-High precision filter cartridges are expensive and prone to clogging, requiring a balance between filtration efficiency and replacement frequency (such as using a 5 μ m security filter before the RO membrane to prevent large particle clogging).

Based on the above dimensions, the most suitable filter type and accuracy can be selected according to specific operating conditions such as fluid type, temperature, and impurity composition.