Stainless steel flanges, ubiquitous components in the industrial sector, serve as the primary connection method in piping systems, with their quality directly impacting the safety and reliability of the entire pipeline infrastructure. Whether in chemical plants, water supply systems, or energy sectors, these disc-shaped connectors silently perform their crucial duties.
1. Flange Fundamentals: More Than Just a Connector
Flanges, also known as flange plates or collars, are components that connect pipes to other pipes or equipment. Featuring bolt holes that allow two flanges to be tightly joined with gaskets providing sealing, stainless steel flanges offer excellent corrosion resistance, high-pressure tolerance, and impermeability, along with smooth inner surfaces, reasonable cost, long service life, and easy installation.
A complete flange connection consists of three fundamental elements: the flange itself, sealing gaskets, and connecting bolts. Together, these form a reliable sealing system that enables convenient installation, disassembly, and maintenance of piping systems.
2. Key Characteristics of Stainless Steel Flanges
The exceptional material properties of stainless steel flanges make them the preferred choice for demanding environments:
Corrosion Resistance: Stainless steel material enables flanges to withstand various chemical erosions, extending pipeline system service life.
High-Pressure Capability: Stainless steel flanges can withstand pressure ranges from 0.25Mpa to 250Mpa, meeting diverse industrial application requirements.
Temperature Adaptability: Stainless steel material maintains stable performance in both high and low-temperature environments.
Hygienic Properties: Non-toxic and pollution-free stainless steel flanges are suitable for food, pharmaceutical, and drinking water systems.
These characteristics make stainless steel flanges ideal for multiple industries including chemicals, petroleum, power generation, and water supply.
3. Diverse Types of Stainless Steel Flanges
Based on structure and connection methods, stainless steel flanges come in various types, each with unique application scenarios:
Plate Welding Flange (PL): Suitable for steel pipeline connections with nominal pressure not exceeding 2.5MPa.
Slip-On Welding Flange (SO): Features a low neck height that improves flange rigidity and load-bearing capacity.
Weld Neck Flange (WN): Known as “high-hub” flanges, they transfer stress to the pipes, reducing high stress concentration at the flange base.
Socket Welding Flange (SW): Features a counterbore matching the pipe size, allowing pipes to be inserted into the flange.
Threaded Flange (TH): Uses threads for connection, with the main advantage being assembly without welding.
Loose Flange: Includes welding neck loose flanges with loose collars and other variants designed for material savings.
Additional special types include blind flanges (for sealing pipe ends) and reducing flanges.
4. Manufacturing and Quality Standards
Stainless steel flange production primarily involves four processes: forging, casting, cutting, and rolling. Each method produces flanges suitable for different scenarios, with forged flanges typically offering better mechanical properties and tighter grain structure for high-pressure environments.
Common materials used in stainless steel flange production include 304, 304L, 316, and 316L, each with specific corrosion resistance and mechanical properties for different environments.
Flange production and inspection follow various standards including:
- Chinese National Standards: GB/T9112-2010 series
- American Standards: ANSI B16.5
- Chemical Industry Standards: HG20592-2009 series
- Mechanical Industry Standards: JB/T79-94 series
The newly implemented T/CECS 10363-2024 standard specifically addresses flanges and flange joints for thin-walled stainless steel pipes, specifying technical requirements for flanges with nominal sizes not exceeding DN300 and nominal pressures of PN10, PN16, PN25.
International standards continue to evolve, with ASTM A 961/A 961Mb:2024 specifying general requirements for steel flanges, forged fittings, valves, and piping components, while ASTM A182/A182M:2024 specifically addresses forged or rolled alloy and stainless steel pipe flanges for high-temperature service.
5. Sealing Design and Gasket Selection
The sealing performance of flange connections largely depends on proper gasket selection. Different gasket types are required based on medium, temperature, and pressure conditions:
Ordinary Rubber Gaskets: Suitable for temperatures below 120°C.
Asbestos Rubber Gaskets: Applicable for steam temperatures below 450°C, oil temperatures below 350°C, and pressures below 5MPa.
Metal-Clad Gaskets: Made by wrapping non-metallic materials like asbestos with thin metal plates.
Spiral-Wound Gaskets: Created by co-winding thin steel strips with asbestos strips.
Metal Gaskets: Employed in high-pressure equipment and pipelines, made from copper, aluminum, or stainless steel in lens-shaped or other configurations.
Flange sealing face types also vary, including flat face (FF), raised face (RF), male-female face (MFM), tongue-groove face (TG), and ring joint face (RJ), each suitable for different working conditions and sealing requirements.
6. Installation and Usage Guidelines
Proper installation is crucial for ensuring safe and reliable flange connections. Stainless steel flange installation requires specific steps:
Preparation: Clean contaminants from stainless steel pipes or fittings before flange connection.
Pipe End Treatment: Perform 90° flanging process on both pipe ends, ensuring flanged ends are vertically smooth, burr-free, and without deformities.
Sealing Ring Installation: Embed stainless steel sealing rings with pre-installed O-rings into grooved flange plates.
Bolt Tightening: Connect flange plate holes with bolts, tightening bolt components symmetrically to ensure even compression of sealing rings.
Special attention is also required during welding:
- Use lower welding currents (approximately 20% less than carbon steel electrodes) to prevent intergranular corrosion
- Maintain electrode dryness during use
- Avoid repeated heating during welding, which can precipitate carbides and reduce corrosion resistance and mechanical properties
7. Application Fields and Market Overview
Stainless steel flanges find extensive applications across multiple industries:
- Chemical equipment, pressure vessels, and pipeline engineering
- Boiler pressure vessels, petroleum, chemical, shipbuilding, pharmaceutical, metallurgy, machinery, and food industries
- Water conservancy, power generation, power stations, pipeline components, industry, and pressure vessels
- Fire protection, gas, hot and cold water, air conditioning, air compression pipes, oil pipes, instrumentation, and hydraulic pipes
According to December 2022 market information, stainless steel flange prices vary by specification:
- DN15 stainless steel flange plates range approximately 10-20 RMB
- DN20 stainless steel flanges reference market price: 51.19 RMB/piece
- DN200 stainless steel flange prices are significantly higher
Notably, stainless steel flange prices in third-tier cities are relatively lower, though specific prices depend on order quantity and flange location.
8. Development Trends and Innovations
The stainless steel flange industry continues to innovate, introducing new materials, processes, and technologies. The newly implemented 2024 standard for flanges and flange joints for thin-walled stainless steel pipes provides clear guidance for the design, manufacture, and acceptance of flanges with nominal sizes not exceeding DN300 and nominal pressures of PN10, PN16, PN25.
The industry is also working to address limitations of traditional flanges. For instance, conventional stainless steel flanges often use fixed clamping rings when connecting external pipes, which may damage pipe outer walls and shorten service life.
New designs incorporate detection components, sealing elements, and silicone gaskets, enabling timely leak detection by monitoring fluid appearance at potential leakage points.
As industrial development demands higher safety, environmental protection, and efficiency standards, technological innovation and standard updates for stainless steel flanges will continue advancing to meet more challenging working conditions and stricter safety requirements.
The future development of stainless steel flanges will increasingly focus on innovations in materials science to adapt to more demanding working conditions; improvements in sealing technology to enhance system safety and reliability; integration of standardization and customization to meet special industry requirements; and incorporation of intelligent monitoring functions to enable predictive maintenance.
With the advancement of Industry 4.0 and smart manufacturing, the development of stainless steel flanges as critical components of industrial piping systems will be closely linked to progress throughout the entire industrial ecosystem.