In many industrial production and daily water use scenarios, self-cleaning filters have become important equipment for ensuring water quality due to their efficient and convenient filtration characteristics. However, in the face of complex and diverse working conditions, how to accurately select suitable self-cleaning filters has become the key to maximizing their performance
Working condition analysis
（1） Industrial circulating water system
The industrial circulating water system has a large scale and high water flow rate, and the water often contains various impurities such as sediment, rust, microbial sludge, etc. There are significant differences in water quality requirements among different industrial fields. For example, in the circulating cooling water of the power industry, if there are too many impurities, it is easy to scale on the surface of equipment such as condensers, affecting heat transfer efficiency and even causing equipment failure in severe cases; The circulating water in the chemical industry has extremely high requirements for the corrosion resistance of filter materials due to the possibility of contact with corrosive media.
（2） Municipal water supply system
Municipal water supply needs to meet the domestic water needs of residents, with continuous and stable water volume, strict water quality requirements, and compliance with national drinking water hygiene standards. The impurities in water mainly include natural organic matter, colloids, bacteria, and rust generated during pipeline transportation. Once there is a problem with the water quality of the supply, it will directly affect the health of residents and trigger social problems.
（3） Sewage treatment system
The sewage treatment system covers various types of sewage, including domestic sewage, industrial wastewater, etc. The composition of sewage is complex. In addition to containing a large amount of suspended solids, oil, and microorganisms, industrial wastewater may also contain heavy metal ions and toxic and harmful substances. During the treatment process, it is necessary to select self-cleaning filters with appropriate filtration accuracy in stages according to different sewage properties and treatment processes, to ensure that sewage treatment meets discharge standards or achieve water reuse.
（4） Agricultural irrigation system
Agricultural irrigation requires a large amount of water, and the water source is mostly surface water or groundwater. The water often contains impurities such as sediment, algae, and plant residues. Different irrigation methods (such as drip irrigation, sprinkler irrigation, etc.) have different water quality requirements. Drip irrigation systems require extremely high filtration accuracy, and small impurities may clog the drip heads, affecting irrigation uniformity and system service life; Sprinkler irrigation systems require slightly lower filtration accuracy, but still need to effectively remove larger particle impurities to prevent nozzle clogging.
Key factors for selection
（1） Filtering accuracy
1,Determining accuracy based on working conditions: In industries such as pharmaceuticals and electronic chip manufacturing that require extremely high water quality, it may be necessary to achieve a filtration accuracy of 1 micron or even lower to ensure that the product is not contaminated by tiny particles; In general industrial circulating water cooling systems, a filtration accuracy of 20-100 microns is sufficient to remove large particle impurities and prevent equipment scaling; In agricultural irrigation, drip irrigation systems typically require a filtration accuracy of 50-150 microns, while sprinkler irrigation systems can be relaxed to 150-300 microns.
2,The impact of precision on the system: If the filtration precision is selected too low, it will not be able to effectively remove key impurities from the water, resulting in subsequent equipment wear, blockage, or product quality decline; However, excessively high filtration accuracy will increase the cost of the filter and may also cause a decrease in water flux, affecting the system flow rate.
（2） Traffic volume
1,Matching operating condition flow requirements: Accurately calculating the maximum flow required for operating conditions is the basis for selection. For large-scale industrial circulating water systems, flow rates can reach thousands of cubic meters per hour, and self-cleaning filters with large diameters and high flow rates should be selected; The municipal water supply system needs to accurately calculate the flow rate based on factors such as the number of service population and peak water usage periods, to ensure that the filters can meet the uninterrupted water supply demand; The agricultural irrigation system should determine the flow rate based on factors such as irrigation area, irrigation cycle, and crop water demand, and select appropriate filter specifications.
2,Flow margin design: In order to cope with possible flow fluctuations in working conditions (such as load changes in industrial production, peak water usage in municipal water supply, etc.), the rated flow rate of the filter should be 20% -50% higher than the actual maximum flow rate to ensure stable operation of the filter in extreme situations and avoid deterioration of the filtration effect due to flow overload.
（3） Work pressure
1,Adapting to the pressure range of the system: There is a significant difference in system pressure under different operating conditions. The pressure of the industrial high-pressure boiler feedwater system can reach several megapascals, while some low-pressure agricultural irrigation systems may only have a pressure of a few tenths of megapascals. The working pressure range of the self-cleaning filter must match the operating system pressure to ensure that the filter structure is safe and reliable under the operating pressure of the system, and there are no problems such as leakage or deformation.
2,Consideration of pressure loss: Filters will generate certain pressure losses during operation. If the pressure loss is too large, it will increase system energy consumption and affect the economic efficiency of system operation. Therefore, when selecting, attention should be paid to the pressure loss index of the filter, and products with lower pressure loss should be selected, especially for long-distance water transmission or high energy consumption systems. Reducing pressure loss is of great significance.
（4） Material
1,Corrosion resistance: In working conditions with corrosive media such as chemical engineering and seawater desalination, the parts of the filter that come into contact with water (such as filter screens, cylinders, flushing devices, etc.) should be made of corrosion-resistant materials, such as 316L stainless steel, Hastelloy alloy, etc., to prevent equipment from being corroded and perforated, and to extend its service life; In industrial circulating water and municipal water supply systems with generally neutral water quality, ordinary 304 stainless steel material can usually meet the requirements.
2,Strength and durability: For working conditions that can withstand high pressure or water flow impact, the material should have sufficient strength and toughness to ensure that it does not rupture or damage during long-term operation. For example, at the outlet of a large industrial circulating water pump, the water flow rate is fast and the pressure is high. The filter material needs to be made of high-strength stainless steel to ensure the stability of the equipment structure.
（5） Cleaning method
1,Suitable cleaning types for working conditions: Common cleaning methods for self-cleaning filters include brush cleaning, suction cleaning, backwash cleaning, etc. In working conditions with high impurity content, large particles, and easy adhesion, such as sewage treatment systems, backwashing cleaning combined with air-water mixed backwashing can more effectively remove impurities from the filter screen; In the pharmaceutical industry, which requires extremely high water quality and does not allow impurities to remain, brush cleaning can ensure the cleanliness of the filter surface, but it may not be suitable for conditions with high impurities, as its cleaning efficiency is relatively low.
2,Cleaning effect and frequency: The cleaning effect is directly related to the filtering performance and service life of the filter. Excessive cleaning frequency will increase equipment wear and energy consumption; If the cleaning frequency is too low, it will cause the filter screen to become clogged, affecting the filtering effect. Therefore, it is necessary to choose a cleaning method that has good cleaning effect and can reasonably control the cleaning frequency based on the impurity content, properties, and filter operating parameters in the working conditions.
Selection case analysis
（1） Industrial circulating water system of a certain steel plant
The flow rate of the circulating water system in the factory is 3000 cubic meters per hour, and the main impurities in the water are iron oxide scale, sediment, etc. The system pressure is 1.2 MPa. After analysis, a high flow backwash self-cleaning filter with a filtration accuracy of 80 microns was selected. The filter screen material is 316L stainless steel to adapt to impurities and system pressure in water, while resisting trace corrosive media in circulating water. The rated flow rate of this filter is 4000 cubic meters per hour, which meets the requirements of flow margin. It adopts a gas water mixed backwash method to effectively remove impurities from the filter screen, ensure the quality of circulating water, reduce equipment scaling and wear, and has a good operating effect.
（2） Municipal water supply system in a certain city
The city has a water supply population of 500000, with a peak water supply flow of 2000 cubic meters per hour, and the water quality requirements meet the national drinking water standards. Considering the types of impurities in water and flow stability, a suction self-cleaning filter with a filtration accuracy of 20 microns is selected, and the cylinder and filter screen are made of 304 stainless steel material. The rated flow rate of the filter is 2500 cubic meters per hour, which can cope with changes in peak water supply flow. The suction cleaning method can accurately remove impurities on the filter screen, ensuring stable water supply quality, and the cleaning process has little impact on the system flow, ensuring the safety of urban residents' water use.
（3） A certain agricultural drip irrigation system
The drip irrigation system irrigates an area of 500 acres, with groundwater as the water source. The water contains a small amount of sediment and algae, and the system pressure is 0.3 MPa. According to irrigation needs, a brush type self-cleaning filter with a filtration accuracy of 100 microns is selected. The material is a combination of engineering plastic and 304 stainless steel, which ensures corrosion resistance and reduces costs. The rated flow rate of the filter meets the irrigation flow requirements, and brush cleaning can effectively prevent droplet clogging, ensure irrigation uniformity, improve water resource utilization efficiency, and assist crop growth.
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