What is a strainer filter?

Divided by application field

Industrial sector

Air filter: In industrial production, air filters are used to remove particulate matter such as dust and impurities from the air. For example, in the dust-free workshop of an electronics factory, air filters can ensure the cleanliness of the air in the workshop and prevent dust from polluting the production of electronic components. It intercepts particles of different sizes through multiple layers of filters, such as primary filters, medium filters, and high-efficiency filters. The primary filter mainly filters larger dust particles, such as hair and larger dust particles; Efficient filters can filter out tiny particles such as bacteria, viruses, etc.

Liquid filter: used to filter impurities in liquids. In the chemical industry, liquid filters can remove solid impurities from chemical raw materials, ensuring the smooth progress of chemical reactions. For example, in the pharmaceutical process, a liquid medicine filter can remove insoluble impurities from the liquid medicine, ensuring the quality of the drug. The working principle is generally to use a filter membrane or filter cartridge. The pore size of the filter membrane can be selected according to the particle size of the impurities that need to be filtered, while the filter cartridge intercepts impurities through its internal porous structure.

domestic sphere

Water purifier (water filter): This is a common filtration device in households, used to remove impurities, harmful substances, etc. from tap water. It usually includes multi-stage filtration, with the first stage possibly being a PP cotton filter element, used to filter out large particles of impurities such as sediment, rust, etc. in water; The second stage may be an activated carbon filter, which mainly adsorbs odors, pigments, and some organic matter in water; The third level may be reverse osmosis membrane or ultrafiltration membrane, which is used to remove bacteria, viruses, heavy metal ions, etc. from water, making the water quality reach drinkable standards.

Air purifier: used to improve indoor air quality. It can filter pollutants such as dust, pollen, smoke, bacteria, etc. in the air. The air purifier has a fan inside that draws in air and filters it through a filter. Some high-end air purifiers are also equipped with HEPA filters (high-efficiency air filters), which can effectively filter out small particles such as PM2.5, which is very helpful for people with allergic rhinitis or respiratory diseases.

Divided by working principle

mechanical filter

Sieve filtration: This type of filter uses the aperture of the sieve to intercept particles larger than the aperture. For example, the vibrating screen used on construction sites separates large and small particles in sand and gravel through the vibration of the screen. The large particles are intercepted above the screen, while the small particles fall through it. The effectiveness of screening and filtering mainly depends on the pore size of the sieve and the integrity of the sieve.

Deep filtration: It uses the pore structure inside the filter medium to intercept impurities. For example, a sand filter is a typical deep filter. In a sand filter, water flows through the sand layer, and impurities in the water are adsorbed on the surface of the sand particles or intercepted by the pores between the sand particles. This type of filter has a good filtering effect, but over time, the sand layer will gradually clog, and regular backwashing is needed to restore the filtering performance.

 Membrane filters

Microfiltration membrane filter: The pore size of the microfiltration membrane is generally between 0.1-10 μ m. It can remove larger particles such as suspended solids and bacteria from water. For example, in some small water treatment equipment, microfiltration membranes are used for initial purification of water quality, removing most impurities from the water. The filtering principle is mainly through physical interception. When the water flows through the microfiltration membrane, particles larger than the pore size are intercepted on the surface of the membrane.

Ultrafiltration membrane filter: The pore size of ultrafiltration membrane is smaller, generally between 0.001-0.1 μ m. It can remove tiny particles such as bacteria, viruses, colloids, etc. from water. During the purification process of drinking water, ultrafiltration membranes can effectively remove microorganisms from the water and improve the safety of water quality. It is also achieved through physical interception, and the surface of the ultrafiltration membrane may also carry charges, which can adsorb some charged impurity particles through electrostatic interactions.

Reverse osmosis membrane filter: The pore size of the reverse osmosis membrane is very small, generally between 0.0001-0.001 μ m. It can remove almost all impurities such as dissolved solids, microorganisms, viruses, etc. from water. In the process of seawater desalination, reverse osmosis membrane filters play a crucial role. It utilizes the selective permeability of semi permeable membranes, allowing water molecules to pass through the membrane under pressure, while impurities such as salt in seawater are trapped on the other side of the membrane, thus achieving the production of fresh water.