How Should the Flange of a Stainless Steel Filter Housing be Selected?

In any industrial fluid handling system, stainless steel filters are core components that ensure media purity and protect critical equipment. However, an often overlooked yet crucial detail is the flange connecting the filter. Far from being a simple connector, it is the cornerstone of the entire system's sealing, structural integrity, and long-term stable operation. Improperly selected flanges can lead to persistent leaks, reduced efficiency, and even safety risks, significantly undermining the value of high-performance filters.

1. Core considerations for flange selection

Flange standards and specifications: These are fundamental to project design. Currently, mainstream standards include the American Standard (ASME B16.5), the German Standard (DIN), the Chinese Standard (GB/T), and the Japanese Standard (JIS). These standards vary in dimensions, tolerances, and testing requirements. When selecting flanges, ensure that the filter flanges and pipeline flanges meet the same standards. It's also important to note that some projects may require a unique combination of standards, requiring the supplier to possess the corresponding production capabilities.

Pressure rating: This is a key parameter in flange selection. Common ratings, such as Class 150, 300, 600, or PN 10, 16, and 40, reflect the flange's pressure-bearing capacity. When selecting a flange, consider the system's maximum operating pressure, temperature fluctuations, and safety factors. Especially in high-temperature operating conditions, material strength decreases, necessitating the selection of flanges with higher pressure ratings. When selecting a supplier, ensure their flanges are clearly labeled with pressure ratings and rigorously tested to ensure system safety.

Material selection: The flange material must be fully compatible with the working conditions. 304 stainless steel is suitable for general corrosive environments, 316L stainless steel has better chloride ion corrosion resistance, and special alloys such as Hastelloy are used in extreme corrosive environments. It is also necessary to consider the electrochemical compatibility of the flange material and the pipe material to avoid galvanic corrosion problems. To ensure optimal performance, it is recommended to select products with both the filter body and flange made of high-quality stainless steel to avoid potential compatibility issues.

Size and diameter: The flange size needs to match the system design flow rate. Standard sizes such as DN50, DN80, and DN100 correspond to different flow ranges. When selecting a model, the flow rate at the maximum flow rate of the system needs to be calculated, which is generally controlled within a reasonable range of 1-3m/s. Too small a diameter will result in increased pressure drop, while too large a diameter will increase unnecessary costs. The product lines of mainstream manufacturers generally cover a wide range of sizes and can meet various needs from laboratories to large-flow industrial scenarios.

2. Application scenarios and selection recommendations

2.1 Flange selection for stainless steel filters under high pressure conditions

In high-pressure applications (such as petrochemical, energy, and pumping systems), the flange selection for stainless steel filters is directly related to system safety and sealing reliability. In such environments, flanges must possess exceptional structural strength and pressure stability to prevent leakage or connection failure.

First, the pressure rating needs to be significantly higher than the conventional requirements. Usually, flanges of Class 600 and above (American standard) or PN 100 (European standard) need to be selected to ensure that the seal is maintained in high-pressure fluctuations. Secondly, the sealing surface type should preferably be a ring joint (RTJ). Its metal ring gasket design can withstand pressures of up to hundreds of bars, which is far superior to soft gasket sealing methods such as raised face (RF). In addition, the flange material also requires special consideration. Although the filter housing is stainless steel, the flange still needs to be made of forged 316L or duplex steel, and the mechanical properties must be improved through precise heat treatment process. The number and distribution of bolt holes and the grade of the bolts themselves (such as ASTM A193 B7) also need to be enhanced accordingly to provide uniform and sufficient sealing pressure ratio.

For stainless steel filter housings, flange selection must also match the filter's design pressure, housing thickness, and internal support structure. Hongtek's Multi High Flow Filter Housings, multi bag filter housings and Multi Cartridge Filter Housings commonly used in high-pressure and high-flow applications, utilize thickened housings to minimize flange deformation under high pressure, ensuring long-term sealing.

2.2 Corrosive environment: an important factor affecting flange material selection

In corrosive environments such as chemical processing, marine engineering, and electroplating, the choice of stainless steel filter flange material directly determines the equipment lifespan and system safety. Focusing solely on the corrosion resistance of the filter housing while ignoring the flange can make the connection the weakest link in the system, leading to leaks and even structural failure. 316L stainless steel, due to its excellent corrosion resistance, is the material of choice for most corrosive environments.

Compared with 304 stainless steel, the key advantage of 316L stainless steel is the addition of 2-3% molybdenum (Mo) element. The addition of molybdenum significantly improves the material's ability to resist pitting and crevice corrosion, especially in chloride ion media (such as seawater, bleach or chloride solutions). This enables 316L flanges to effectively cope with common corrosion challenges in chemical production, extending equipment life and reducing maintenance requirements. In addition to the selection of the material itself, it is also necessary to pay attention to the risk of galvanic corrosion.

It is recommended that the flange, filter housing and connected pipes be made of the same grade of material (such as 316L) to avoid electrochemical corrosion caused by potential difference between different metals. For a few extreme corrosive conditions (such as strong oxidizing acids or high temperature and high concentration chlorides), special materials such as duplex steel or nickel-based alloys can be considered. However, for most application scenarios, 316L stainless steel achieves the best balance between performance and cost, and is the most reliable and economical choice for stainless steel filter flanges in corrosive environments. Our Hongtek stainless steel filter can choose the material according to the customer's working conditions.

Hongtek Multi Bag Filter Housing and Multi Cartridge Filter Housing are designed for high-flow filtration needs. They utilize high-precision filter elements and a reinforced housing structure, providing a larger filtration area and higher dirt-holding capacity. These filters are equipped with precision-machined 316L stainless steel flange interfaces that support various standards, including ASME, DIN, and GB, to meet the interface requirements of diverse projects. This ensures sealing reliability in corrosive environments. The optimized flow path design significantly reduces system pressure drop, improves operational efficiency, and significantly reduces maintenance time and costs.

2.3 Frequent maintenance scenarios: Consider the easy-to-disassemble design and the durability of the gasket

In applications requiring frequent cleaning or filter media replacement, the flange design of stainless steel filters directly impacts maintenance efficiency and operating costs. Traditional flange connections require the removal of multiple bolts, which is time-consuming and labor-intensive, and can easily damage the sealing surface due to repeated tightening. Therefore, ready-to-disassemble flanges offer the optimal solution. These flanges utilize hinged bolts or quick-release clamps, allowing for simple opening and sealing, significantly reducing maintenance time.

At the same time, the durability of the gasket is also crucial. New materials that are resistant to aging and compression set, such as reinforced EPDM rubber or flexible graphite composites, should be selected to ensure a reliable seal even after dozens of disassemblies. Furthermore, the surface treatment of the flange sealing surface is also important. Fine polishing or plating can reduce wear on the gasket and extend its service life.

Regarding flange selection for this factor, Hongtek's multi-bag filters feature a unique quick-opening top cover design, coupled with precisely machined flange sealing surfaces and highly durable food-grade sealing rings. This allows for quick opening and bag replacement without tools. The large manhole design further facilitates maintenance personnel, significantly reducing equipment downtime. Furthermore, the multi-core filter utilizes a modular filter element design and quick-release flange connections, equipped with durable metal spiral wound gaskets or reinforced rubber sealing rings, capable of withstanding frequent disassembly without compromising sealing performance. The precision-machined flange sealing surfaces are polished to effectively reduce wear on the sealing elements and extend replacement cycles.

3. Conclusion: Make Smart Technology Decisions

Flange selection is a technical decision that requires comprehensive consideration of multiple factors, including standards, pressure, sealing, material, and size. The right choice not only ensures safe and stable system operation, but also reduces ongoing maintenance costs and improves system efficiency. We recommend thorough consultation with the supplier's technical staff during the selection process, providing detailed operating parameters and usage requirements.

If you have any questions about flange selection for stainless steel filters, Hongtek's technical team is ready to provide professional consultation and help you find the most suitable solution for your system. With extensive project experience and a comprehensive technical support system, we can provide the optimal connection solution for your filtration system.