What is a filter

What is a filter?

The filter is an indispensable device in the pipeline for transporting media and is usually installed at the inlet end of other equipment such as pressure reducing valves, pressure relief valves, constant water level valves. The strainer is composed of a barrel, a stainless steel screen, a drainage part, a transmission device and an electrical control part. After the water to be treated passes through the cartridge of the filter screen, its impurities are blocked. When cleaning is needed, it is only necessary to take out the removable cartridge and reload it after treatment, so it is extremely convenient to use and maintain.

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Structure of the filter

In plumbing systems, a strainer is a porous metal screen used to filter or strain solid debris from water systems. Different varieties are used for residential and industrial or commercial applications. This filter element is usually made of stainless steel to protect against corrosion.

The strainer is composed of the shell, multi-purpose filter element, backwashing mechanism, and differential pressure controller.

Filter screen

The filter screen is mainly stainless steel wire mesh.

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Stainless steel wire mesh (stainless steel mesh)

  • Material: SUS201, 202, 302, 304, 316, 304L, 316L, 321 stainless steel wire.
  • Weave: plain, twill, dense weave.

Specification of stainless steel wire mesh 1 mesh – 635 mesh. In the case of dense twill weave can reach up to 2800 mesh.

  • 304 stainless steel wire mesh is generally referred to as “18-8” (18% chromium, 8% nickel) most of which is a basic stainless steel alloy, ideal for netting. It can be exposed to the outdoors and will not rust or oxidize when the outside temperature rises to 1400 degrees Fahrenheit.
  • 304L stainless steel mesh is very similar to T-304, with the difference that the carbon content is reduced, making it easier to weave and re-weld.
  • 316 stainless steel mesh can be stabilized by adding 2% molybdenum, T-316 is an “18-8” alloy. It is less susceptible to corrosion in salt water, sulfur water or in brine salts than other chromium-nickel stainless steels. The most valuable feature of T-316 is its greater creep resistance at elevated temperatures. Other mechanical properties and structural characteristics are the same as T-304.
  • 316L stainless steel wire mesh is very similar to T-316, with the difference that the carbon content has been reduced, making it easier to weave and re-weld.

Application: Because of its acid resistance, alkali resistance, wear resistance, temperature resistance and other properties, stainless steel is commonly used in acid and alkali environmental conditions for sieving (sieve) and filtering (strainer), the petroleum industry for mud mesh, chemical fiber industry for sieve mesh, electroplating industry for pickling mesh

Cartridge

As the name implies, the precision cartridge is the heart of the filter, and the cartridge is generally mainly used in the filtration industry such as oil filtration, water filtration and air filtration.

  1. Precision cartridge breathability: the cartridge adopts the strong hydrophobic and oleophobic fiber filter material of the United States, and at the same time adopts the skeleton with good permeability and high strength to reduce the resistance caused by the crossing.
  2. Precision cartridge high efficiency: the cartridge adopts the German fine open pore sponge, which can effectively prevent the oil and water from being entrained by the high-speed airflow, so that the fine oil droplets down the road will gather at the lower end of the cartridge sponge and be discharged to the bottom of the filter container.
  3. Precision cartridge airtightness: the combination point of the cartridge and the filter shell adopts a reliable sealing ring to ensure that the airflow is not short-circuited and prevent impurities from entering the downstream directly without the filter core.
  4. Precision cartridge corrosion resistance: the cartridge adopts corrosion-resistant reinforced nylon end cap and corrosion-resistant cartridge skeleton, which can be used in harsh working conditions.

Working principle of the filter

When the filter works, the water to be filtered enters from the water outlet, flows through the filter screen and enters the pipeline required by the user through the outlet for process circulation, and the particles and impurities in the water are trapped inside the filter screen. With such a continuous cycle, more and more particles are retained and the filtration speed becomes slower and slower, while the imported sewage still enters continuously, the filter hole will become smaller and smaller, thus generating a pressure difference between the inlet and outlet, and when the large difference reaches the set value, the differential pressure transmitter transmits an electric signal to the controller, and the control system starts the drive motor to drive the shaft rotation through the transmission component, while the discharge port opens and is discharged by the discharge port. When the filter is cleaned, the differential pressure drops to the minimum value, the system returns to the initial filtration state, and the system operates normally. The filter consists of a shell, a multi-purpose filter element, a backwashing mechanism, and a differential pressure controller. The horizontal partition inside the shell divides the inner cavity into upper and lower cavities, and the upper cavity is equipped with multiple filter cartridges, which fully fills the filtering space and significantly reduces the volume of the filter, and the backwashing suction cup is installed in the lower cavity. When working, the turbid liquid enters the lower chamber of the filter through the entrance, and then enters the inner chamber of the filter element through the hole of the partition. Impurities larger than the gap of the filter cartridge are retained, and the net liquid goes through the gap to the upper chamber and is finally sent out through the outlet. The filter adopts a high-strength wedge-shaped screen, and the filter element is automatically cleaned through differential pressure control and timing control. When the impurities in the filter accumulate on the surface of the cartridge causing the differential pressure between the import and export to increase to the set value or the timer reaches the preset time, the electric control box sends a signal to drive the backwashing mechanism. When the backwashing suction cup mouth is directly opposite to the cartridge inlet, the drainage valve opens, at which time the system releases pressure and drains, and a negative pressure zone with a relative pressure lower than the water pressure on the outside of the cartridge appears between the suction cup and the inside of the cartridge, forcing part of the net circulating water to flow into the inside of the cartridge from the outside of the cartridge, and the impurity particles adsorbed on the inner wall of the cartridge flow into the disc with the water and are discharged from the drainage valve. The special design of the filter screen makes the jet effect inside the cartridge, and any impurities will be washed away from the smooth inner wall. When the differential pressure between the inlet and outlet of the filter returns to normal or the timer sets the time to end, the whole process is continuous with no material flow and little water consumption for backwashing, realizing continuous and automatic production. The filter is widely used in the fields of metallurgy, chemical industry, petroleum, paper making, medicine, food, mining, electric power and urban water supply. Such as industrial wastewater, filtration of circulating water, regeneration of emulsion, filtration treatment of waste oil, continuous casting water system and blast furnace water system in metallurgical industry, and high pressure water descaling system for hot rolling. It is an advanced, high-efficiency and easy-to-operate fully automatic filtration device.
The water to be treated enters the body through the water inlet, and the impurities in the water are deposited on the stainless steel screen, resulting in a pressure difference. When the differential pressure reaches the set value, the electric controller gives the hydraulic control valve and drives the motor signal. After the equipment is installed, the technician will commission it, set the filtering time and cleaning conversion time, the water to be treated will enter the body from the inlet, the filter will start to work normally, when the preset cleaning time is reached, the electric controller will give the hydraulic control valve and drive motor signal, which will trigger the following action: the motor will drive the brush to rotate and clean the filter element, while the control valve will open to discharge, the whole cleaning process will only last for When the cleaning is finished, the control valve is closed, the motor stops rotating, and the system returns to its initial state and starts the next filtration process. The interior of the filter housing is mainly composed of coarse and fine screens, suction pipes, stainless steel brushes or stainless steel nozzles, sealing rings, anti-corrosion coatings, and rotating shafts.
A simple filter is formed by separating the container into upper and lower chambers with filtration media. Suspension is added to the upper chamber, under pressure through the filter media into the lower chamber to become filtrate, solid particles are trapped in the surface of the filter media to form filter residue (or called filter cake). During the filtration process, the slag layer accumulated on the surface of the filter media gradually thickens, and the resistance of the liquid passing through the slag layer increases and the filtration speed decreases. When the filter chamber is full of slag or filtration speed is too small, stop filtration, remove the slag, so that the filter media regeneration to complete – a filtration cycle.
Liquid through the slag layer and the filter media must overcome the resistance, so there must be a pressure difference between the two sides of the filter media, which is the driving force to achieve filtration. Increase the pressure difference can accelerate filtration, but the deformation of the particles under pressure in the large pressure difference is easy to block the pores of the filter media, but slow down the filtration.
There are three types of suspension filtration: slag layer filtration, deep filtration and sieve filtration.

  • ① Slag layer filtration: At the beginning of filtration, the filter media can only retain large solid particles, and small particles pass through the filter media with the filtrate. After the formation of the initial slag layer, the slag layer plays a major role in filtration, at which time both large and small particles are retained, such as the filtration of plate and frame filter press.
  • ② Deep filtration: the filter medium is thicker, the suspension contains less solid particles, and the particles are smaller than the pore of the filter medium. When filtering, the particles enter and are adsorbed in the pore channel, such as the filtration of porous plastic tube filter and sand filter.
  • ③ Sieve filtration: filtration retains solid particles are larger than the pores of the filter media, and the solid particles are not adsorbed inside the filter media, such as rotary filter sieve to filter coarse impurities in the sewage. In the actual filtration process, the three ways often appear at the same time or one after another.

Filtration speed of the filter

When the solid particles in suspension are large and uniform in size, the pores of the filtered slag layer are smoother and the filtrate passes through the slag layer at a greater speed. The application of coagulant to collect the microfine particles into larger clumps is conducive to improving the filtration speed.
For suspensions with fast settling speed of solid particles, the application of the filter media in the upper part of the filling filter, so that the direction of filtration and gravity – the same direction, the coarse particles first settled, can reduce the filter media and filter slag layer clogging; in the difficult to filter suspensions (such as colloids) mixed with coarser solid particles such as diatomaceous earth, expanded perlite, etc., can make the filter slag layer become loose; filtrate viscosity is large, the suspension can be heated to reduce the viscosity. All these measures can accelerate the filtration speed.

Performance characteristics of the filter

  • 1. High-efficiency and precise filtration: The filter disk filtration technology with special structure has precise and sensitive performance, ensuring that only particles with a particle size smaller than that required can enter the system, making it the most effective filtration system; there are various specifications such as 5μ, 10μ, 20μ, 55μ, 100μ, 130μ, 200μ, etc., and users can choose filter disks with different precision according to water requirements. The system flow can be flexibly adjusted according to the needs.
  • 2. Standard modularization, save area: The system is based on standard disc filter unit, designed according to modularization, users can take or leave as needed, flexible and interchangeable. The system is compact and occupies a very small area, and can be flexibly installed in the corner space, such as the treatment of water volume of about 300m3/h equipment occupies only about 6m2 (- general water quality, filtration grade 100μ).
  • 3. Fully automatic operation, continuous water discharge: between each unit in the filter combination, the backwashing process alternates in turn, and the working and backwashing states switch automatically to ensure continuous water discharge; backwashing consumes very little water, accounting for only 0.5% of the water discharge; with air-assisted backwashing, the self-consumption of water can be reduced to less than 0.2%. High speed and thorough backwashing, only tens of seconds to complete
  • 4. Long life: The new plastic filter element is strong, non-abrasive, non-corrosive, very little scaling, proven by years of industrial practice, no wear and tear for 6 to 10 years, no aging, filtering and backwashing effect will not deteriorate due to the use of time.
  • High quality, low maintenance: The products meet the corresponding quality standards, all products are tested and tested by simulated working conditions before leaving the factory, no special tools and few parts are needed; easy to use, only regular inspection is needed, almost no daily maintenance is required.

Classification of filters

Filters are divided into three categories: gravity filters, vacuum filters and pressurized filters, depending on the method of obtaining filtration impetus.
Gravity filter
The pressure formed on the filter medium by the gravity of the suspended liquid and the difference in position is used as the driving force of filtration, and is generally operated intermittently, such as sanders.
Vacuum filter
The negative pressure at the outlet of the filtrate is used as the driving force for filtration. The absolute pressure of the industrial vacuum filter operating vacuum is (2. 5 to 8. 0) × 105 Pa. The temperature of the suspension during filtration should be lower than the vaporization temperature of the filtrate under the operating vacuum. This kind of filter is divided into two kinds: intermittent operation and continuous operation. The intermittently operated vacuum filter can filter suspensions of various concentrations. The vacuum filter is filled with the suspension in the vessel housing. The filter leaves covered with filter cloth on both sides are immersed in the suspension and the inner chamber of the filter leaves is connected to the vacuum system. The filtrate is sucked out and led by a conduit, and the residue accumulated on the surface of the filter leaves is removed after shutdown. The vacuum filter with continuous operation is suitable for filtering thick suspensions with more solid particles. The working principle of rotary drum vacuum filter, internal filter surface rotary drum vacuum filter, disc vacuum filter and hopper vacuum filter are all similar. The whole filtering surface is divided into several separated filtering chambers, and each rotating filtering chamber is connected to each fixed tube in sequence through distribution valves to suck out the filtrate and washing liquid in the filtering chamber or to feed compressed air. Each filtration chamber rotates to complete the whole process of filtration operation, and the operation of multiple filtration chambers is connected to form continuous filtration. The structure of belt vacuum filter is similar to that of belt conveyor, with a continuous filter belt, which is suitable for easy filtration of suspensions. Belt vacuum filter, internal filtering surface drum vacuum filter and tipping bucket vacuum filter are all charged on the upper part of the filtering medium (filter cloth), which is especially suitable for suspensions with high density of solid particles and fast settling.
Pressurized filter
It uses the pressure applied at the inlet of the suspension or the mechanical pressing force applied to the wet material as the filtration driving force, and is suitable for suspensions requiring a large filtration pressure difference, and is also divided into two types of intermittent operation and continuous operation. Intermittently operated tubular filter presses and pressurized filters are used for filtration of low concentration suspensions. The filter is also a kind of intermittently operated pressurized filter, which is divided into three kinds: plate and frame, chamber and vertical, and is very widely used. The oil filter is a plate and frame filter press unit equipped with oil pump, vacuum evaporator and other accessories. The continuously operated drum pressurized filter and disc pressurized filter carry out pressure filtration in a closed shell, and their structure is similar to that of drum vacuum filter and disc vacuum filter. Due to the complex structure, they are less used.
Commonly used pressurized filtration is filtration by using the volume of the filter chamber to become smaller or by applying mechanical pressing force, and the moisture content of the filter residue is low, which is suitable for suspensions with high concentration of solid particles. In a belt press filter, the wet filter residue, after initial de-liquefaction by gravity or vacuum, is sandwiched between two filter belts and then de-liquefied by roller extrusion. The screw press filter has a cylinder with pores, in which there is a rotating screw, the depth of the screw groove varies, the material is added from the deep groove end and pushed to the shallow groove end, the space of the filter chamber is gradually reduced, the material is pressed, the filtrate is discharged from the pores of the cylinder, and the filter slag is discharged from the small end.
Precision filter
Precision filter is for filtration precision, generally between sand filtration (coarse filtration) and ultrafiltration. Under the action of pressure, the raw water passes through the filter element, impurities are retained on the wall of the filter element, and water flows out through the filter core, thus achieving the purpose of filtration. The scale of manufacturers of filter equipment in China is mainly small and medium-sized enterprises. The products use high-quality stainless steel, hard PVC, engineering plastics, organic glass and other corrosion-resistant materials to do the shell, which is mainly based on high-quality stainless steel, built-in cartridge of different media. The built-in cartridge has PE core, beehive core, folded core, titanium tube sintered core, activated carbon core, ceramic core, polypropylene fiber cartridge and so on. Different filter elements have different filtration effects, so the precision filter can remove suspended matter, certain colloidal substances and fine particles in water according to the requirements of raw water quality, effluent water quality and water quantity to achieve different filtration precision. The filtration precision of precision filters in the market ranges from 0.2-100um. Precision filters are often used as protective filters for electrodialysis, ion exchange, reverse osmosis, ultrafiltration and other devices, and can be applied to water treatment in food, wine, pharmaceutical chemical, electronic and other industries, such as:

  • Food industry: fine filtration of mineral water, clarification and filtration treatment of beverages and liquors. Pharmaceutical industry: water treatment of sterile water, oral liquid, infusion, injection, etc;
  • Electronic industry: semiconductor, instrumentation, picture tube and other production plants pure water preparation, washing water filtration;
  • Chemical industry: organic solvents, esters, alcohols, acids, bases and other chemical materials, oil purification;
  • Environmental protection: treatment of various industrial wastewater such as electroplating wastewater, printing wastewater, pharmaceutical wastewater, etc. Water quality treatment of seawater, brackish water desalination, water supply treatment of hotels and apartments, etc;
  • Gardening: park yard, greenhouse greenhouse, animal husbandry, industrial places that need to artificially create ultra-fine water mist, and the irrigation maintenance of high-grade flowers.

Classification according to the performance of the filter

  • Pipeline filters
  • Double cartridge filter
  • High pressure filter

The above-mentioned filter should be a mesh filter, in fact, there are many kinds of filters, such as stacked filter, sand rod filter, carbon filter, plate and frame filter, activated carbon filter, diatomaceous earth filter, microporous filter, etc. The main principle is to use the pore size of the filter media to retain substances smaller than the pore size of the media, of course, some filter media also have special effects such as adsorption. Most filters are not that troublesome to backwash, as long as the media in the reverse backwash filter is introduced from the – end of the filtered water to achieve a good backwashing effect.

According to the classification of filter industry

Hydraulic oil filter: mainly used in oil filtration industry, including oil suction filter, oil return filter, pipeline filter, etc.

  • Food filters: dust filters, air filters, air conditioning filters.
  • Filter for medicine: medicine liquid filter, breathing filter, blood filter, bacteria filter.

According to the function of the filter classification

Self-cleaning filter
It is a kind of precision equipment that uses the filter to directly intercept the impurities in the water, remove the suspended matter and particles in the water, reduce the turbidity, purify the water quality, reduce the generation of system dirt, bacteria and algae, rust and corrosion, etc., in order to purify the water quality and protect the normal work of other equipment in the system.
The main components are: motor, electric control box, control pipeline, main tube assembly, filter element assembly, 316L stainless steel brush, frame assembly, transmission shaft, import and export connection flange, etc.

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It overcomes many shortcomings of filtration products such as small dirt-holding capacity, easy to be clogged by dirt, the filtering part needs to be disassembled and cleaned and the state of the filter cannot be monitored, etc. It has the function of filtering the raw water and automatically cleaning and discharging the filter element. The system provides uninterrupted water supply during cleaning and discharging, and the working status of the filter can be monitored, so the degree of automation is very high. It covers the needs of various filtration precision from 10um to 3000um. Adopting the advanced technology of international water treatment industry equipment, it can be installed in any position in any direction vertically, horizontally and upside down, and can be used for water filtration in various industries such as industry, agriculture, municipal electricity, electronics, medicine, food, printing and dyeing, construction, steel, metallurgy, paper making, etc.
Automatic filter
It is a set of equipment widely used in the filtration industry, which overcomes many shortcomings of traditional filtration products such as small dirt-holding capacity, easy to be clogged by dirt, the filtering part needs to be disassembled and cleaned and the state of the filter cannot be monitored, and has the function of filtering raw water and automatically cleaning and discharging the filter element. It is composed of shell, multiple filter elements, backwashing mechanism, electric control box, reducer, electric valve and differential pressure controller. The horizontal partition inside the shell divides its inner cavity into upper and lower cavities, and the upper cavity is equipped with multiple filter cartridges, which makes use of the filtering space and significantly reduces the volume of the filter, and the lower cavity is installed with backwashing suction cups. When working, the turbid liquid enters the lower chamber of the filter through the entrance, and then enters the inner chamber of the filter element through the hole of the partition plate, and the impurities larger than the gap of the filter core are retained, and the net liquid reaches the upper chamber through the gap and is finally sent out through the outlet.

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Advantages: the automatic filtration precision is 100 microns by default, and it can be selected from 10 to 3000 microns, with large filtration area and high dirt-holding capacity, which can be customized by users according to actual working conditions. The cleaning method is simple, and the cleaning cycle is electronically monitored, which can realize automatic cleaning and discharging. All parameters in the control system of automatic self-cleaning filter can be adjusted, etc.
Brush filter
The types of stainless steel brush filter are: automatic stainless steel brush filter, hand-operated stainless steel brush filter. Its main function is to get rid of suspended matter in water, reduce the concentration of suspended matter in water, particulate matter, reduce turbidity, purify water quality, reduce system dirt, bacteria and algae, rust and corrosion, purify water quality, etc.
The stainless steel brush filter adopts the internal mechanical structure of patented technology to realize the high pressure backwashing function in the real sense, which can easily and thoroughly remove the impurities retained by the filter screen, with no dead angle of cleaning and no decay of flux, guaranteeing the filtration efficiency and long service life.
The stainless steel brush filter achieves automatic backwashing through its own retrieval and strain function, and can cope with unstable water quality fluctuations without manual intervention.
During the backwashing process of stainless steel brush filter, each (group) screen is backwashed in turn; ensuring safe and efficient cleaning of the screen, while the other screens are not affected and continue to filter.
Stainless steel brush filter adopts automatic drainage valve, with short backwashing time, low water consumption for backwashing and environmental protection and economy. There are few wearing parts, no consumables, low operation and maintenance costs, and simple operation and management.

According to the classification of filtering media

According to the filtration medium is divided into: air filter, liquid filter, network filter, light filter.
Air air filter
Development of air filter
The prototype of air filter is the respiratory protection apparatus used by people to protect their breathing. According to records, as early as – century Rome, people in the purification of mercury when the protection of the mask made of coarse hemp. In 1827, Brown discovered the law of motion of tiny particles, and the mechanism of air filtration was further understood.
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Schematic diagram of filter structure
The rapid development of air filters was closely related to the development of the military and electronics industries. During the First World War, due to the use of various chemical agents, asbestos fiber filter paper as a smoke filter layer of military gas masks came into being. Glass fiber filter media for air filtration was patented in the United States in October 1940. 50s, the United States on the production process of glass fiber filter paper for in-depth research, so that the air filter has been improved and developed. 60s, HEPA filter was introduced; 70s, the use of micro-fiber glass filter paper as a filter media HEPA filter, 013 micron particle size particle filtration efficiency up to 99. 9998%. Since the eighties, with the emergence of new test methods, the use of evaluation and the improvement of filtration performance requirements, HEPA filters were found to have serious problems, and ULPA filters with higher performance were produced. Countries are still working on the research and it is estimated that more advanced air filters will appear soon.
Performance of air filters
To make the contaminated air be cleaned to the state needed for production and life, that is, to make the air reach – a certain degree of cleanliness. How air filters filter air.
-The general air purification equipment filtering air is roughly divided into the following methods and steps.
1. Multiple filters – to prevent dust and germs in the air from entering the room
Multiple activated carbon filters effectively intercept dust and germs, filter the air, and ensure the clean air entering the room.
2. Titanium oxide to kill toxins – degradation of indoor air pollution of formaldehyde, benzene and other organic toxic gases nanoscale titanium dioxide activated by ultraviolet light, to filter the air to effectively degrade the air of formaldehyde, benzene and other organic toxic gases radioactive pollution.
3. Anion oxygenation – increase the amount of oxygen in the indoor air to the right amount and keep the content stable anion generator to indoor air oxygenation, to ensure that the air entering the home to maintain a sufficient amount of oxygen, vibrant, enhanced filtered air.
4. PTC ceramic heating – heating indoor air to a comfortable temperature
PTC ceramic heater to the winter into the indoor fresh air for auxiliary preheating, appropriate to increase the indoor temperature, thereby filtering the air, so that the home warm and comfortable.
5. UV sterilization – strong to kill the air in the epidemic virus bacteria
Ultraviolet light source has a strong effect to kill the epidemic virus bacteria in the air, so that people away from the source of infection, to filter the air and take care of the health of the whole family.
The filter is an indispensable device on the pipeline for transporting media, usually installed at the inlet end of pressure reducing valves, pressure relief valves, constant water level valves or other equipment to eliminate impurities in the media in order to protect the normal use of valves and equipment. When the fluid enters the filter cartridge with a certain specification, the impurities are blocked, and the clean filtrate is discharged from the filter outlet.
High efficiency air filter

High-efficiency air filters are generally used as the end of filtration, so the requirements for high-efficiency filters are the most stringent, and the factory needs to test each unit. As the end of the high efficiency filter is the most critical level of the filter at all levels – level, the need for additional “lookout”. To extend the service life of the high efficiency filter, the most fundamental way is to keep the dust in the pre-filter. Replacement of pre-filters generally requires no downtime or commissioning, so experienced owners will focus their attention and money on the pre-filter. For class 10000 and 100000 clean plant. Pre-filter can choose F8 filter, so that the end of the high efficiency filter life – generally up to five years. In foreign projects and new projects in China, F8 filters are the most common pre-filter for non-uniform flow cleanrooms. For chip factory 100, 10 or higher level clean plant, the common efficiency level of pre-filter is H10, and many new projects simply choose HEPA. in the domestic clean room air conditioning system design in the past, the common configuration of the filter is: coarse effect of high efficiency. At that time, the service life of high-efficiency filters was only 1 – 3 years, and the worst was only a few months. It can be seen that the efficiency of the pre-filter determines the life of the end filter use.

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Liquid filter

So that the contaminated liquid is cleaned to the state needed for production and life, that is, to make the liquid reach – a certain degree of cleanliness.

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The main liquid filter is common: the pool – the body of the filtration equipment.
Pool – the body of the equipment in the modern pool industry market belongs to – a mainstream product selection direction. Pool – the body of the equipment with its technical content, its design concept, the pool equipment market to the brainstorming – a new impact. Pool – body of equipment is a pool filtration, disinfection, circulation – pool equipment, has become a mainstream product in today’s pool equipment market.
Pool – integrated equipment, in the operation of modern pools play an irreplaceable role. Its characteristic role has the following three points.
1. Its location can be placed in the vicinity of the pool, low noise, high safety factor.
2. The installation is simple, reduce the workload, high efficiency.
3. The small size, buried in the ground, which can be vacated to the pool to do the beautification effect.
Network filter
Set to block spam by setting to make out the information on the computer screen as much as possible to meet the requirements.
Light filter
The same principle of absorption separates different colors of light and absorbs some unwanted light.

Classification according to the role of the filter

Oil suction filter
The filter is located in the suction line of the pump, filtering out the residual contaminants in the oil tank through the air holes into the pollutants, there is a role in protecting the pump. However, in order to avoid the cavitation phenomenon of the pump, full attention must be paid to the pressure loss, – generally use 100-200 purpose coarse metal mesh or notched metal wire material. Therefore, it is not a filter to control the pollution concentration of the system.
High pressure line filter (A)
Set on the outlet pipe of the pump, it has the function of protecting the contaminants from entering the system. Therefore, it can control the contaminant concentration of the system. However, because it is a high-pressure main line, it is subject to the pulsation and pressure impact of the pump, so the material and strength of the filter element should be carefully considered.
High pressure line filter (B)
In the system, this filter, also called terminal filter, is installed to protect the hydraulic parts that are particularly sensitive to contamination. Therefore, it often has a smaller filter size than other filters. Therefore, choose the one with large capacity when using it. In addition, the material and strength of the element should be considered as well as (A).
Return filter
Set in the return line of the system, its role is to capture the contaminants generated or invaded in the system before returning to the oil tank. Therefore, it is the most effective and important filter to control the pollution concentration of the system. Although it is a low pressure pipeline, but according to the operation of the transmission device, there will be pulsation or pressure shock, so the component material and strength should be fully considered. Imported pump
Circulation filter
Set in the oil tank circulation of the return path, the capacity of the system is large, so it is often used when requiring strict cleanliness, even if the system is not working, it can also trap the contaminants in the tank, so the best efficiency in reducing the concentration of pollution. In addition, a cooler is installed, and it has the advantages of being able to cool at the same time and easy to maintain. However, a special pump and motor are required, and the cost is high.
Air filter
It is installed on the tank to prevent contaminants from being mixed into the tank with air due to changes in the oil volume of the tank. Therefore, the filtration accuracy should have the same performance as the filter, and the capacity should be left sufficient to prevent the internal pressure of the tank from becoming negative due to hole blockage, causing the cavitation phenomenon of the pump. Particular attention should be paid when the surrounding environment is harsh.

Other types of filters

Used for filter performance test bench above, this test bench in the test before the system to be strictly purified, so the test system and the test system for the service of pollution injection system are required to be equipped with filters, this filter and the filter being tested are two different things, its precision requirements, dirt holding capacity requirements than the filter being tested high precision, in order to distinguish the same – test system in the two types of filters, this filter This filter is called the test bench filter, and the tested filter is called the tested filter.
Fiber filter
Mechanical filtration is the most common method of sewage treatment, according to the different filtration media, mechanical filtration equipment is divided into two types of granular media filtration and fiber filtration, granular media filtration mainly uses sand and gravel and other granular media as filtration media, through the adsorption of granular media and the pore space between the sand particles on the water body solids in suspension to achieve filtration, the advantage of easy backflushing, the disadvantage is that the filtration speed is slow, – generally not more than 7m/h. The core filtration layer is only the surface of the filter layer; the filtration precision is low, only 20-40μm, which is not suitable for rapid filtration of sewage containing high turbidity.
High efficiency asymmetric fiber filtration system adopts asymmetric fiber bundle material as filter media, its filter media is asymmetric fiber, on the basis of fiber bundle filter media, adding – a nucleus, so that it has the advantages of both fiber filter media and particle filter media, due to the special structure of the filter media, so that the filter bed porosity soon forms a gradient density of the upper large and lower small, so that the filter filter speed is fast, large dirt interception, easy backwashing, through the special design, so that the dosing, mixing, flocculation, filtration and other processes Through the special design, the processes of dosing, mixing, flocculation and filtration are carried out in one reactor, so that the equipment can effectively remove the suspended organic matter in the breeding water and reduce the COD, ammonia nitrogen and nitrite in the water, which is especially suitable for the filtration of suspended solids in the circulating water of the temporary breeding pool.
The scope of use of fiber filter

  • Aquaculture circulating water treatment.
  • Cooling circulating water, industrial circulating water treatment.
  • River, lake, family water features and other eutrophic water treatment.
  • Water reuse.

Fiber filter mechanism of action
1. Asymmetric fiber media structure of high-efficiency

Automatic gradient density fiber filter core technology is the use of asymmetric fiber bundle material as the filter media, the – end of the loose fiber bundle, the other end of the fiber bundle fixed in the specific gravity of the solid body, filtration, the specific gravity of the solid nucleus plays a role in the pressure of the fiber bundle, at the same time, due to the small size of the nucleus, the uniformity of the distribution of the filtration section void rate does not affect At the same time, due to the small size of the nucleus, it has little effect on the uniformity of the distribution of the void ratio in the filter section, thus improving the interception capacity of the filter bed. It makes the filter bed have the advantages of high porosity, small specific surface area, high filtration speed, large dirt interception and high filtration precision of fiber filtration. When the suspended matter in water flows through the surface of fiber filter media, the adhesion force of suspended solids and fiber bundles is much larger than that with quartz sand under the effect of Van der Waals gravitational force and transelectricity, which is conducive to improving the filtration speed and filtration precision.
When backwashing, due to the specific gravity difference between the core and fiber filaments, the comet tail fiber spreads and swings with the backwashing water flow, producing a strong throwing force; the mutual collision between the filter media also intensifies the mechanical force on the fiber in the water, and the irregular shape of the filter media makes the filter media rotate under the action of backwashing water flow and airflow, which strengthens the mechanical shear force on the filter media when backwashing, as a result of the joint action of the above forces The result of the combined action of the above forces is that the solid particles attached to the fiber surface are easily removed, thus improving the cleanliness of the filter media, so that the asymmetric fiber filter media also has the backwashing function of granular filter media.
2. Continuous gradient density filter bed structure with sparse top and dense bottom
Asymmetric fiber bundle filter media filter bed in the compaction of water flow, water flow through the filter layer resistance, from top to bottom, the head loss gradually reduced, the water speed is faster and faster, the degree of compaction of the filter media is higher and higher, the porosity is smaller and smaller, so that along the direction of water flow, the automatic formation of continuous gradient density filter layer distribution, the formation of an inverted pyramid structure. This structure is very conducive to the effective separation of suspended solids in water, i.e., the particles that are detached from the upper part of the filter bed are easily captured and retained in the lower narrow channel of the filter bed, realizing the unity of high filtration speed and high precision filtration, improving the filter’s filtration capacity and extending the filtration cycle.
Features of fiber filter

  1. High filtration accuracy: the removal rate of suspended matter in water can reach more than 95%, and the removal of impurities such as macromolecular organic matter, viruses, bacteria, colloids, iron, etc. is certain, and the treated water after good coagulation treatment, when the influent water is 10NTU, the effluent water is less than 1NTU.
  2. Fast filtration speed: generally 40m/h, up to 60m/h, more than 3 times that of ordinary sand filter.
  3. Large dirt-holding capacity: generally 15 to 35 kg/m3, more than 4 times that of ordinary sand filters.
  4. Low backwashing water consumption rate: backwashing water consumption is less than 1-2% of the cycle filtration water.
  5. Low dosing, low operating costs: due to the structure of the filter bed and the characteristics of the filter media itself, the flocculant dosing is 1/2 to 1/3 of the conventional technology. the cycle of water production increases, the ton of water operating costs are also reduced.
  6. Small footprint: the same amount of water is produced, and the footprint is less than 1/3 of that of ordinary sand filter.
  7. Strong adjustability. The parameters such as filtration precision, interception capacity and filtration resistance can be adjusted as needed.
  8. The filter media is durable, with a life of more than 20 years.

Process flow of fiber filter
After the raw water is pressurized by the booster pump, the flocculant is mixed evenly with the fine solid particles suspended and colloidal substances in the raw water after being stirred by the pump impeller, and the flocculant with a volume larger than 5 microns is quickly generated, which flows into the high-efficiency asymmetric fiber filter through the pipeline of the filtration system, and the flocculants are filtered and retained by the filter material.
Y-type filter

Y-type filter (water filter) belongs to the series of coarse filter of pipeline, also can be used for gas or other media large particles filtration, installed in the pipeline can remove large solid impurities in the fluid, so that the normal work and operation of machinery and equipment (including compressors, pumps, etc.), instruments, to stabilize the process, to ensure the role of safe production. It has the advantages of simple production, easy installation and cleaning, large dirt-holding capacity, etc.

20221105233030 18098 - What is a filter

Disc filter
Disc filter is a device composed of filtration units applied in the filtration system.
The filter unit is mainly composed of a group of annular reinforced plastic filter discs with grooves or ribs. When filtering, the sewage enters from the outside and the solids in the water are retained by the rim formed by the grooves and ribs on the adjacent filter discs; when backwashing, the water flows from the inside of the annular filter discs to the outside and the dirt retained on the discs is washed off and discharged through the drainage port.
Y type fillet filter

The discs are compacted and stacked together in the unit, and the grooves in the middle of the upper and lower layers of discs play the role of filtering and intercepting. The raw water flows from outside to inside when passing through the filter unit, and the impurities larger than the groove will be intercepted outside. The core part of the disc filter is the plastic filter discs stacked together, with special grooves or ribs on the discs, and the grooves or ribs on the adjacent discs form a channel of a certain size, so that suspended matter with particle size larger than the channel size is intercepted to achieve the filtering effect. This product can largely replace the traditional mechanical filtration devices such as sand filters, and its performance is superior and its water and electricity consumption is much lower than other products.

20221105233121 40218 - What is a filter

The disc filter is designed with different structured ribs on both sides of the filter disc, and these ribs are superimposed together to form the intercepting surface, among which the curved ribs mainly play the role of intercepting and storing the suspended matter. filtration accuracy. When raw water enters the middle of the two filter discs, it first flows into the discs along the curved ribs, but on closer inspection it cannot enter directly. Impurities smaller than the size of the groove in the ring can enter the curve along the ring, and larger impurities are intercepted.
The unique structure of the filter disc also makes the backwashing process of flushing out the dirt simpler and easier, without the need for complicated mechanisms such as motors and drives, and a simple flow of water is sufficient to flush the dirt out of the filter element. This excellent performance reduces the backwashing time of the filter; at the same time, the filter can hold more dirt because the dirt is stored not only between the filter disc set and the housing, but also more inside the filter disc set.
Primary filter

FA-PF primary filter

20221105233216 67085 - What is a filter

Before pleating the filter material, the FA-PF primary filter is firstly laminated with a layer of galvanized iron mesh on the air outlet surface of the filter material. This layer of iron mesh not only protects the filter material from being blown through, but also prevents the filter material from being deformed due to wind pressure, thus ensuring that all surfaces of the filter material can be fully utilized.
The special needle-punching method is used to treat the filter fibers to form a gradual structure, so that the filter has a high dust catching capacity and a long service life.
The outer frame of the filter is made up of a sturdy waterproof board to hold the folded filter media. The diagonal design of the outer frame provides a large filter area and allows the inner filter material to adhere tightly to the outer frame. The filter is bonded to the outer frame with a special professional adhesive to prevent air leakage or breakage caused by wind resistance pressure.
Characteristics of the primary filter.
The filter is divided into three sizes: 1”, 2” and 4” in depth, and its filtering area is five times that of a normal flat filter, which has a longer service life and higher filtering efficiency than a glass fiber filter or a synthetic fiber filter.
It can be used directly or as a primary filter to protect the middle and high efficiency filters in the latter part of the air conditioning system.
The fibers are treated with a special needle technique to form a gradual structure, so that the filter has low pressure loss, high dust catching capacity and long service life.
Application of primary filter.
Coarse filtration system for general air conditioners, to extend the service life of bag type and HFPA filters Coarse filters for factory exhaust gas and processing dust collection.
Faucet filter
Basic information
Specifications: 60mm high color: light blue, light pink, white (randomly issued);
Composition: 1 filter, 1 coupling.
Material: PS plastic, zeolite, activated carbon (coconut shell), PVA non-woven fabric.
Features of the faucet filter
The material requirements and water quality requirements are produced according to the “Drinking Water Processor Health and Safety and Functional Evaluation Regulations”.
Can remove residual chlorine, heavy metals and other impurities from tap water. Make the water quality sweeter and more hygienic.

The product is through the internal layer of water filtration organization to achieve the effect of rapid layered filtration and purification:

  1. Non-woven fabric: filter out iron slag and visible impurities in water pipes; coconut activated carbon reduces alkaline substances in water.
  2. Silicate ionized zeolite: it can remove some heavy metal impurities such as residual chlorine, residual ammonia and odor, making the water sweeter and more hygienic.
  3. Coconut shell activated carbon: high quality coconut shell is the material, the product has good adsorption power, high strength and uniform particle size. Appearance is black, with well-developed voids, high adsorption rate, good strength, stable performance, easy to regenerate, durable and other characteristics. It can effectively remove the odor and color of water, can effectively help people remove carcinogenic substances, make the water clear and soft taste. It is widely used in the deep purification of drinking water.
  4. The product is compact in size, easy to load and unload, and suitable for all kinds of faucets, both old and new.
  5. After using this product, it can also slow down and control the water flow of faucet immediately, prevent splashing and save water.

Scope of application of the faucet filter
Because faucet specifications vary, in order to enhance the sealing effect of the installation
Raw material tape (sealing tape) can be used appropriately in the installation process.
Caution
Avoid prolonged use under hot water, preferably below 50 degrees.
There will be black water outflow at the first time of use, which is caused by the powder of basic activated carbon, and can be used normally after 5-10 seconds of water discharge.
Installation methods of filters
There are three types of installation: flange connection, threaded connection and welding connection.

Industry standards for filters

CJ/T 3068-1997 High polymer sintered microporous tube filter

GB/T 13554-2008 High-efficiency air filter

GB/T 14295-2008 Air filter

GB/T 14382-2008 Tee filter for pipeline

GB/T 17486-2006 Hydraulic filter

HG/T 21637-1991 Chemical pipeline filter

HG/T 4085-2009 Pressure type fiber bundle filter

JB/T 7538-1994 Basket filter for pipeline

SY/T 0523-2008 Oilfield water treatment filter

YY-T 0142-1994 Air filters for single-use infusion and blood transfusion instruments

JB-T 7374-1994 Pneumatic air filter

HG-T 20570.22-1995 Pipe filters

JB-T 6417-1992 Air filters for air conditioners

JB-T 9044-1999 High gradient magnetic filters

YY0286.1-2007 Disposable precision filter infusion sets

JB/T 10410-2004 Automatic backwashing filters for industrial water

Maintenance of filters

Rough filter
1. The core part of the filter is the filter core, which is composed of the filter frame and stainless steel wire mesh, and the stainless steel wire mesh is a wearable part and needs special protection.
2. When the filter works for a period of time, the filter core precipitated a certain amount of impurities, then the pressure drop increases, the flow rate will drop, the need to promptly remove the impurities in the filter core.
3. When cleaning impurities, pay special attention to the stainless steel wire mesh on the filter core can not be deformed or damaged, otherwise, the filter installed again, the purity of the filtered media can not meet the design requirements, compressors, pumps, instruments and other equipment will be damaged;.
4. If the stainless steel wire mesh is found to be deformed or damaged, it needs to be replaced immediately.
Precision filter
1. The core part of the precision filter is the filter element, the filter core is made of special materials, which is a wearable part and needs special protection.
2. When the precision filter works for a period of time, the filter cartridge intercepts a certain amount of impurities, then the pressure drop increases and the flow rate decreases, the impurities in the filter need to be removed in time, and the cartridge should be cleaned at the same time.
3. When removing impurities, pay special attention to the precision filter element, which must not be deformed or damaged, otherwise, the filter element installed again, the purity of the filtered medium will not reach the design requirements.
4. Certain precision cartridges, which cannot be used repeatedly for many times, such as bag cartridges, polypropylene cartridges, etc.
5. If the cartridge is found to be deformed or damaged, it needs to be replaced immediately.
Pay attention to rust prevention, paint or grease at the flange piece, and also do insulation.

What is filter used for?

  • Garden lawn, irrigation of agriculture.
  • Food, textile, mining, electronics, casting industry’s total water supply filtration system.
  • Filtering of water for nozzles in the pulp and paper, metallurgy, and machinery industries.
  • Singing and general water filtration in the food, power, mining, and smelting industries.
  • Careful filtration of circulating water in cooling towers for pharmaceutical, petrochemical refining, air conditioning systems or heating systems.
  • Select ion exchange pretreatment of wastewater for petrochemical, electromechanical, and pharmaceutical industries.

How to select the correct filter?

Selection principle of filter

1. Diameter of inlet and outlet:
In principle, the inlet and outlet diameter of the filter shall not be smaller than the inlet diameter of the matching pump, which is generally consistent with the inlet pipe diameter.
2. Nominal pressure:
The pressure rating of the filter shall be determined according to the highest possible pressure of the filter line.
3. Selection of hole number:
The particle size of impurities to be intercepted is mainly considered, which is determined according to the process requirements of the medium process. The particle size that can be intercepted by various specifications of screen can be found in the following table “Screen Specifications”.
4. Filter material:
The metal material of the filter is generally the same as that of the connected process pipe. For different service conditions, the filter made of cast iron, carbon steel, low alloy steel or stainless steel can be considered.
5. Calculation of filter resistance loss
The pressure loss of water filter is 0.52-1.2KPa under the rated flow rate generally calculated

Installation position of filter

(1) In general low pressure devices with pressure below 140kg/cm2, only suction filters are usually installed, but return filters and air filters should also be installed.
(2) In general medium and high pressure liquid devices with a pressure of more than 140kg/cm2, return filters are commonly used to control the pollution concentration. However, when there are special requirements for reliability, high pressure pipeline filter shall be used.
(3) To increase the reliability of electromagnetic proportional control valve or micro flow regulating valve, terminal filter shall be set.
(4) When using servo valves, efforts should be made to reduce the pollution concentration of the system. Therefore, high pressure and reflux filters should be used together; In case of large capacity, circulating filter shall be set, and terminal filter shall be installed on auxiliary pipeline.

Precautions for installing the filter

The installation positions of the oil filter in the hydraulic system are generally as follows:
(1) It shall be installed at the oil suction port of the pump:
The oil suction path of the pump is generally equipped with a surface type oil filter to filter out large impurities and particles to protect the hydraulic pump. In addition, the filtering capacity of the oil filter should be more than twice the pump flow, and the pressure loss should be less than 0.02MPa.
(2) Installed on the outlet oil circuit of the pump:
The purpose of installing oil filter here is to filter pollutants that may invade valves and other components. The filtering accuracy shall be 10-15 μ m. It shall be able to withstand the working pressure and impact pressure on the oil circuit, and the pressure drop shall be less than 0.35MPa. At the same time, a safety valve shall be installed to prevent the oil filter from clogging.
(3) Installed on the oil return circuit of the system: this installation plays an indirect filtering role. Generally, a back pressure valve is installed in parallel with the filter. When the filter is blocked and reaches a certain pressure value, the back pressure valve opens.
(4) It is installed on the branch oil circuit of the system.
(5) Separate filtering system: a hydraulic pump and oil filter can be specially set for large hydraulic system to form an independent filtering circuit.
In addition to the oil filter required by the whole system, a special fine oil filter is often installed in front of some important components (such as servo valve, precision throttle valve, etc.) to ensure their normal operation.

Key points for filter selection

When selecting oil filter, the following points shall be considered:
(1)The filtering accuracy shall meet the predetermined requirements.
(2) Sufficient flow capacity can be maintained for a long time.
(3) The filter element shall have sufficient strength and shall not be damaged due to hydraulic pressure.
(4) The filter element has good corrosion resistance and can work at the specified temperature for a long time.
(5) The filter element is easy to clean or replace.
Therefore, the model of the oil filter shall be selected according to the technical requirements of the hydraulic system, filtering accuracy, flow capacity, working pressure, oil viscosity, working temperature and other conditions.

Filter precision conversion

Mesh number μm Mesh number μm
2 8000 100 150
3 6700 115 125
4 4750 120 120
5 4000 125 115
6 3350 130 113
7 2800 140 109
8 2360 150 106
10 1700 160 96
12 1400 170 90
14 1180 175 86
16 1000 180 80
18 880 200 75
20 830 230 62
24 700 240 61
28 600 250 58
30 550 270 53
32 500 300 48
35 425 325 45
40 380 400 38
42 355 500 25
45 325 600 23
48 300 800 18
50 270 1000 13
60 250 1340 10
65 230 2000 6.5
70 212 5000 2.6
80 180 8000 1.6
90 160 10000 1.3

Test method of filter

  1. Bubble point method test: When the filter membrane and filter element are completely soaked with a certain amount of solution, then the air source is used to pressurize on one side (our instrument has an air inlet control system, which can stabilize the pressure and regulate the air inlet). With the increase of pressure, the gas is released from one side of the filter membrane, indicating that there are bubbles of different sizes and numbers on one side of the membrane. The instrument judges that the corresponding pressure value is the bubble point.
  2. Diffusion flow method test: Diffusion flow test refers to that when the gas pressure is 80% of the bubble point value of the filter element, a large amount of gas has not yet perforated, but a small amount of gas is dissolved into the liquid phase membrane first, and then diffuses from the liquid phase to the gas phase on the other side. This part of gas is called diffusion flow. Why the diffusion flow method is better? the bubbling point value is only a qualitative value, and it is a long process from the beginning of bubbling to the final group bubbling, which cannot be accurately quantified. The measured diffusion flow value is a quantitative value, which can not only accurately determine the integrity of the filter, but also reflect the problems in the membrane porosity, flow rate and effective filtering area, which is why foreign manufacturers use the diffusion flow method to test the integrity.
  3. Water intrusion method test: the water intrusion method is specially used for the test of hydrophobic filter element. The hydrophobic film resists water. The smaller the aperture, the greater the pressure required to squeeze water into the hydrophobic film. Therefore, under a certain pressure, measure the water flow squeezed into the filter membrane to determine the pore diameter of the filter element.

Source: China Industrial Filters Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.com)

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