water intake screen

I. Basic Definition and Core Functions A water intake screen is a filtration device installed at the inlet of a water extraction system. It is primarily used to intercept solid impurities in the water (such as silt, algae, floating debris, and biological remains), preventing them from entering subsequent pipes, pumps, heat exchangers, or treatment equipment. It is a key pretreatment component ensuring the stable operation of water treatment systems, industrial circulation systems, and water supply systems. Its core functions can be summarized in three points: Protecting core equipment: Preventing impurities from wearing down pump impellers, clogging heat exchanger pipes, or damaging precision instruments, thus extending equipment lifespan; Improving treatment efficiency: Reducing the load on subsequent filtration units (such as filter cartridges and membranes), lowering the frequency of consumable replacement and operating costs; Ensuring water quality safety: Intercepting suspended pollutants that may affect water quality, providing basic filtration protection for drinking water treatment, industrial process water, and other scenarios. 

II. Common Types and Applicable Scenarios Based on different structural designs, filtration principles, and application scenarios, water inlet filters can be divided into the following categories, with significant differences in the characteristics and applicable scope of each type: 

1. Classification by Structural Form (1) Basket Screen Structural Features: Funnel-shaped or basket-shaped, the filter material is mostly stainless steel (304/316), nylon, or polyester fiber. It is fixed to the water inlet by bolts or clips, and impurities are intercepted inside the filter. It needs to be disassembled and cleaned regularly. Applicable Scenarios: Suitable for small and medium flow systems (such as the inlet of household water purifiers, the inlet of small industrial pumps), especially suitable for water bodies with larger impurity particles (diameter ≥1mm) and lower content, such as tap water and shallow groundwater. (2) Cylindrical Screen Structural Features: The filter is cylindrical, divided into internal suction type and external suction type. It is usually equipped with a backwashing device (such as a high-pressure water gun or an automatic rotating brush), which can clean impurities online without stopping the machine for disassembly. Applicable scenarios: Industrial circulating water systems, cooling water inlets of large central air conditioning systems, and front-end pumps of sewage treatment plants. Suitable for water bodies with medium to high flow rates (≥50m³/h) and moderate impurity content (such as river water and lake water). (3) Self-Cleaning Screen Structural features: Integrated differential pressure sensor and automatic scraping/backwashing mechanism. When the filter screen intercepts impurities and the differential pressure reaches the set value, the system automatically starts the cleaning program to discharge the impurities. No manual intervention is required throughout the process. Applicable scenarios: Large unattended systems (such as circulating water systems of thermal power plants and municipal water supply pumping stations), and water bodies with high impurity content (such as river estuary water and industrial wastewater pretreatment). Especially suitable for scenarios where continuous operation is required and frequent shutdowns are not possible. (4) Belt Screen Structural Features: Composed of a stainless steel mesh belt, drive motor, and flushing device. The mesh belt operates continuously, collecting impurities (such as weeds and plastic fragments) from the inlet and conveying them to the outlet. Simultaneously, high-pressure water flushing restores the mesh belt's filtration capacity. Applicable Scenarios: Intakes of natural water bodies (such as reservoirs and rivers), especially suitable for intercepting fibrous and ribbon-like impurities, avoiding clogging of traditional filters. 

2. Classification by Filter Material Stainless Steel Filter: High corrosion resistance and strength, wide applicable temperature range (-20℃~400℃), suitable for corrosive water bodies such as industrial wastewater and seawater. Common specifications are 304 (for general applications) and 316L (for highly corrosive applications). Nylon Filter: Lightweight, flexible, and with high filtration accuracy (up to 50μm), but poor temperature resistance (≤80℃), suitable for drinking water and ambient temperature freshwater filtration, such as household water purifiers and aquarium water changing systems. Polyester fiber filter screen: Superior acid and alkali resistance compared to nylon, high tensile strength, suitable for filtering industrial process water at medium and low temperatures (≤120℃), such as in the pretreatment stages of textile mills and food processing plants. Metal sintered filter screen: Made from sintered metal powder, with uniform pore size and stable filtration accuracy (1~100μm), it can withstand high temperatures and pressures, suitable for harsh environments such as petrochemical plants and high-temperature boiler feedwater applications. III. Key Technical Parameters and Selection Considerations

1. Core Technical Parameters

Filtration Accuracy: Refers to the smallest particle diameter of impurities that the filter screen can intercept, measured in micrometers (μm) or mesh size. Selection must be based on the requirements of subsequent equipment (e.g., pumps typically require ≥100μm, while membrane filtration requires ≤50μm).

Rated Flow Rate: The maximum water throughput of the filter screen under normal operating pressure, measured in cubic meters per hour (m³/h) or liters per minute (L/min). A 10%~20% flow margin should be reserved during selection to avoid overload.

Operating Pressure and Temperature: Must match the actual operating pressure of the system (typically 0.1~1.6MPa) and water temperature (selected based on material, e.g., nylon ≤80℃, stainless steel ≤400℃).

Pressure Difference Loss: The water flow resistance under clean filter conditions, typically required to be ≤0.02MPa. Excessive pressure difference will increase pump energy consumption; selection must be combined with the system head.

Material Compatibility: Based on water composition (e.g.,...) 1. Select corrosion-resistant materials based on pH value and chloride ion content. For example, 316L stainless steel is required for seawater applications, while PTFE (polytetrafluoroethylene) coated filters are needed for highly acidic water.

2. Core Selection Principles

Matching System Requirements: Prioritize determining the filtration accuracy based on the impurity tolerance of downstream equipment (pumps, heat exchangers, membrane modules), then combine this with flow rate, pressure, and temperature to determine the filter specifications.

Adapting to Water Characteristics: Select belt filters for waters containing a large amount of fibrous impurities (e.g., river water), 316L stainless steel for highly corrosive waters (e.g., seawater), and large-pore self-cleaning filters for high-viscosity waters (e.g., industrial syrup).

Balancing Cost and Maintenance: Basket filters (low cost) are suitable for scenarios with convenient manual maintenance (e.g., small workshops), while self-cleaning filters (lower long-term costs) are suitable for unattended or high-frequency maintenance scenarios (e.g., large water plants). IV. Maintenance and Solutions to Common Problems

1. Key Points of Daily Maintenance

Regular Inspection: Non-self-cleaning filters need to be inspected weekly to observe the accumulation of impurities on the filter surface. Self-cleaning filters need to have their backwashing mechanism checked monthly to ensure it is functioning properly.

Timely Cleaning: When the accumulation of impurities in basket/cylinder filters reaches 30%, the machine must be stopped and the filters disassembled. They should be rinsed with high-pressure water (pressure ≤ 0.5MPa, to avoid damaging the filter) or cleaned with a soft brush (hard brushes are prohibited for nylon filters).

Regular Replacement: Nylon and polyester fiber filters typically have a service life of 6-12 months. They should be replaced immediately if damaged or deformed. Stainless steel filters can be repeatedly washed and have a service life of 3-5 years. Replace them when corrosion or perforation is observed.

Winter Protection: For filters used outdoors (such as river intakes), antifreeze measures should be taken in winter. Insulation cotton can be wrapped around the outside of the filter, or antifreeze can be added to the system to prevent the filter from freezing and cracking.