What is a standard SS 304 flange?

A standard SS 304 flange is a pipe connection component made of austenitic stainless steel 304 (UNS S30400, Werkstoff Nr. 1.4301), manufactured according to international or national standards. It is mainly used to connect pipes, valves, pumps, containers, and other equipment, achieving a seal through bolt tightening. It is widely used in petrochemical, food and beverage, water treatment, pharmaceutical, and construction industries.

Its core material advantage stems from the classic 18% chromium + 8% nickel ratio, which forms a dense passivation film on the surface, effectively resisting corrosion from atmospheric, fresh water, and weak acid media. It also possesses good tensile strength (≥515MPa), elongation (≥40%), and processing performance, meeting various processing requirements such as welding and stamping. Its cost-effectiveness far exceeds that of ordinary carbon steel flanges and other stainless steel flange materials.

International Standards

ASTM/ASME Standards: The most commonly used international standards. ASTM A182 Grade F304 is the core standard for SS 304 flanges, corresponding to pressure ratings of Class 150~2500. Dimensions follow ASME B16.5 (DN15~DN600) and ASME B16.47 (large diameter flanges). Suitable for projects exported to Europe, America, and Southeast Asia, it is the most frequently searched standard type by global buyers.

DIN Standards: Follow DIN EN 1092-1, with pressure ratings of PN6~PN40. Dimensions differ slightly from ASTM standards. Primarily used in piping systems in Europe, characterized by high precision and excellent sealing performance, suitable for high-pressure and high-temperature applications.

BS Standards: Follow BS 4504, with pressure ratings of PN6~PN100. Commonly used in Commonwealth countries. Material requirements are consistent with ASTM A182 F304, but dimensional details have specific specifications, adapting to British piping connection methods.

JIS Standard: Complies with JIS B2220, corresponding material SUS 304, pressure rating PN10~PN40, smaller size, mainly used in Japan, South Korea and parts of Southeast Asia, suitable for small equipment and precision pipeline connections.

Sealing Surface Types:

Raised Face (RF): Most commonly used, suitable for medium and low pressure, ordinary media. The sealing surface is flat, and can be used with rubber gaskets or asbestos gaskets. Low cost, easy installation, suitable for most working conditions.

Flat Face (FF): Suitable for low pressure, corrosive media. The sealing surface has no protrusions. Suitable for soft gaskets, preventing media corrosion of the sealing surface. Commonly used in chemical and municipal sewage treatment pipelines.

Matching Face (MFM), Tongue and Groove Face (TG): Dedicated for high pressure and highly corrosive conditions. Excellent sealing performance, preventing media leakage. Suitable for chemical reactors and high-pressure steam pipelines. Requires the use of corresponding matching matting face flanges.

Ring Joint Face (RTJ): Dedicated for ultra-high pressure conditions. Suitable for metal ring gaskets. Extremely strong sealing performance. Suitable for pipeline systems with pressure ≥10.0MPa, such as high-pressure pipelines in petrochemical industries.

The core advantages of standard SS 304 flanges:

Excellent corrosion resistance: Thanks to the compositional advantages of 304 stainless steel, it resists corrosion from the atmosphere, fresh water, and common acid and alkali solutions. Its salt spray corrosion resistance reaches level C5 (ISO 12944 standard). In chemical and municipal wastewater treatment applications, the maintenance cycle can be extended from 1 year to over 5 years, significantly reducing maintenance costs.

Stable mechanical properties: Tensile strength ≥515MPa, yield strength ≥205MPa, elongation ≥40%, operating temperature range -196℃~800℃. Under extreme conditions such as high-temperature steam and low-temperature liquid nitrogen, there is no cold brittleness. The sealing surface deformation rate is <0.5%, far superior to the 3%-5% of ordinary carbon steel flanges. High cost-effectiveness: Compared to 316L flanges, the procurement cost is 30%-40% lower (for example, the price difference for a DN200 flange is approximately 800-1200 RMB per piece), and it meets the needs of most working conditions. It is also 100% recyclable, with a residual value of 40%-50% of the original price after disposal, aligning with green manufacturing trends and offering significant advantages in total life-cycle cost.

Standardized specifications and strong interchangeability: Adhering to unified international and domestic standards, standard SS 304 flanges from different manufacturers are interchangeable, eliminating the need for separate customization. The procurement cycle is short (standard specifications are readily available), adapting to globally compatible piping systems and reducing procurement and installation risks.

Extremely wide range of applications: Covering multiple fields such as chemical, power, food and pharmaceutical, municipal engineering, marine engineering, and machinery manufacturing, it can be used for various scenarios including pipe connections, equipment docking, and sealing. From deep-sea platforms to food processing plants, its presence is ubiquitous, ensuring stable procurement demand.

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