Overview
As a core device for industrial fluid processing, stainless steel bag filters have become the preferred choice for chemical, water treatment, food & beverage, and other industries, relying on their all-stainless steel corrosion-resistant structure and flexible high-efficiency filtration performance. Their working principle is based on the precise interception of filter bags, achieving efficient removal of particulate impurities in liquids through the combination of a stainless steel housing and filter bags. Compared with traditional filters, stainless steel materials (commonly 304/316L) give them outstanding performance in chloride ion resistance, high-temperature tolerance, and structural strength, especially suitable for filtering strong acid-alkali, high-salinity, or high-temperature media. The equipment realizes high-flow processing through standardized design, with a single unit capable of handling tens of cubic meters per hour, serving as a key link to ensure medium cleanliness in modern industrial processes.
Core Working Principle and Structural Design
I. Filtration Mechanism Analysis
Stainless steel bag filters adopt an inside-out fluid path: The liquid to be filtered enters the housing from the top inlet, penetrates from the inner side to the outer side of the filter bag, with impurities intercepted inside the bag and clean liquid flowing out from the bottom outlet. Filter bags are typically made of polypropylene, polyester, or nylon, with pore sizes ranging from 0.5-600μm, achieving deep filtration through a gradient fiber structure—the inner dense fibers capture tiny particles, while the outer loose structure accommodates more impurities, increasing dirt-holding capacity by over 30% compared to traditional cartridges.
II. Structural Advantage Analysis
1. All-Stainless Steel Housing: Made of 316L stainless steel by seamless welding, with a pressure resistance of 1.6MPa, it can withstand media with Cl⁻ concentration >20,000ppm (such as seawater and chemical waste liquid). The surface is electrolytically polished to a roughness of Ra≤0.8μm, complying with food-grade hygiene standards while reducing microbial growth.
2. Quick-Opening Sealing Design: The top head uses clamp or flange connection with O-ring sealing, requiring no special tools for disassembly. A single person can replace the filter bag within 15 minutes, improving efficiency by 50% compared to traditional bolt connections.
3. Filter Bag Support System: A built-in stainless steel basket with pores matching the filter bag avoids bag collapse during filtration, ensuring uniform fluid passage, eliminating bypass flow, and maintaining stable filtration precision.
Typical Application Scenarios
1. Chemical and Petrochemical Industries
In pesticide intermediate production, stainless steel bag filters (paired with 10μm polypropylene filter bags) intercept catalyst particles and polymer impurities in reaction liquids, providing clean media for subsequent distillation processes. A herbicide production line case shows that using 316L filters extended the scaling cycle of the distillation column from 2 months to 6 months, saving ¥800,000 in annual cleaning costs. For hydrofluoric acid-containing etching solution treatment, a combination of corrosion-resistant 316L and PTFE seals allows the equipment to operate continuously for 3 years without housing corrosion.
2. Water Treatment and Environmental Protection
- RO Reverse Osmosis Pretreatment: Municipal wastewater treatment plants use stainless steel bag filters with 5μm filter bags to intercept colloids and suspended solids, protecting RO membrane elements. Data from a coastal water plant shows this solution extended the RO membrane replacement cycle from 4 months to 10 months, saving ¥1.5 million annually in membrane costs.
- Oily Wastewater Treatment: In metallurgical cold rolling wastewater treatment, paired with oleophilic filter bags (such as polyester fiber), it efficiently removes emulsified oil, reducing effluent oil content to <5mg/L, meeting reuse standards.
3. Food & Beverage and Pharmaceuticals
- Beer Clarification: A craft brewery uses stainless steel filters with 0.45μm nylon filter bags to intercept yeast and proteins, with filtrate turbidity <0.5NTU, eliminating the need for filter aids and saving 30% in consumable costs compared to traditional diatomite filtration.
- Water for Injection Pretreatment: Pharmaceutical factories use 316L stainless steel filters (paired with 0.22μm polyethersulfone filter bags), combined with steam sterilization (121℃/30min), to ensure water quality meets GMP standards, with a bacterial interception efficiency >99.99%.
4. New Energy and Electronics Industry
In lithium battery electrolyte filtration, stainless steel bag filters (double-layer bag design: inner 1μm PP, outer 5μm PE) remove nanoscale metal particles, ensuring stable electrolyte conductivity. After adoption by a power battery factory, the cell short-circuit failure rate decreased by 60%. In semiconductor cleaning liquid filtration, 316L material with a polished inner wall avoids metal ion contamination, meeting the ultra-pure water requirements for 14nm processes.
Performance Characteristics and Technical Advantages
1. Corrosion & High-Temperature Resistance
316L stainless steel has an annual corrosion rate <0.1mm in 10% sulfuric acid and 40% sodium hydroxide solutions, and can operate stably in 80℃ high-temperature media, suitable for pharmaceutical and food scenarios requiring steam sterilization. For high-temperature oil media (such as heat-conducting oil), customized filters can withstand 150℃, expanding application scenarios.
2. High Flow & Low Energy Consumption
Pressure loss of a single 5th-size filter (processing capacity 40m³/h) is <0.1MPa, reducing energy consumption by 20% compared to traditional cartridge filters. The large-flow design reduces equipment quantity— a chemical park replaced 30 traditional filters with 10 stainless steel bag filters, reducing floor space by 60%.
3. Convenient Maintenance & Environmental Protection
Filter bag replacement does not require system emptying, and the quick-opening structure shortens maintenance time; stainless steel housings can be 100% recycled, and if washable materials (such as polyester) are used, filter bags can be reused over 50 times, reducing solid waste discharge. Compared with disposable cartridges, comprehensive operation and maintenance costs are reduced by 40%.
Selection and Maintenance Guidelines
I. Key Selection Factors
- Material Matching:
Choose 304 stainless steel for conventional water quality, 316L for chloride ion-containing (>1000ppm) or highly corrosive media, and customize 316L + high-temperature fluororubber seals for high-temperature scenarios (>100℃).
- Filter Bag Precision:
Select 5-20μm for pretreatment, 0.22-1μm for precision filtration (such as electronic-grade water), and 10-100μm for high-viscosity fluids (such as syrup), based on the medium particle distribution curve.
- Flow Design:
Configure at 1.3 times the system's maximum flow. For example, a 20m³/h RO system should use a filter with a processing capacity of 26m³/h, reserving redundancy to avoid rapid pressure drop.
II. Maintenance Highlights
1. Daily Monitoring:
Monitor pressure loss through inlet and outlet pressure gauges. Replace filter bags when the pressure difference >0.2MPa to avoid bag damage from high pressure difference. It is recommended to record pressure loss data daily and establish a trend analysis model.
2. Cleaning Specifications:
Filter bags can be backwashed (water pressure 0.2MPa) combined with ultrasonic cleaning; oil contamination can be cleaned by circulating 10% sodium hydroxide solution; wipe the housing surface with a neutral cleaner to prevent medium residue corrosion.
3. Integrity Testing:
Conduct bubble point tests quarterly for precision filter bags (<1μm). For example, the bubble point pressure of a 0.22μm filter bag should be ≥3.2Bar to ensure no precision degradation due to damage.
Industry Development Trends
With the advancement of Industry 4.0 and green manufacturing, stainless steel bag filters are developing toward intelligence and functional compounding:
- Intelligent Monitoring Integration: Some manufacturers have introduced models with built-in pressure sensors and IoT modules, enabling real-time upload of pressure loss data and prediction of filter bag replacement cycles. Combined with AI algorithms to optimize maintenance plans, unplanned shutdowns are reduced by 30%.
- Modular Functional Design: Integrating activated carbon adsorption and filtration into the same housing. For example, a certain model has a built-in activated carbon fiber layer, removing residual chlorine in water while intercepting particles, simplifying the water treatment process and reducing system investment costs by 15%.
- Nano-Coating Application: After coating the filter bag surface with superhydrophobic nano-coating, anti-fouling ability is increased by 50%, and the cleaning cycle is extended to 1.5 times that of traditional filter bags, especially suitable for high oily wastewater treatment.
Conclusion
Stainless steel bag filters have become the mainstream choice for industrial fluid filtration due to their core advantages of corrosion resistance, high flow, and easy maintenance. From harsh chemical environments to precision electronics manufacturing, their reliable performance provides solid support for production processes. In the future, with the deep integration of material technology and intelligent control, this equipment will meet more precise filtration needs in high-end fields such as semiconductors and hydrogen energy, promoting the continuous evolution of industrial filtration toward efficiency and greenness.
