Cangzhou Avant International Trade Co., Ltd. is one of the leading manufacturers and suppliers of large diameter flange in China. We are committed to providing high quality customized products with competitive price. Welcome to wholesale cheap large diameter flange in stock here from our factory. Also, free sample is available.
While the standard ASME B16.5 covers sizes up to NPS 24, projects adhering to US standards typically utilize ASME B16.47 for larger sizes. This standard comprises two series: Series A (derived from MSS SP-44) offers higher structural strength and is commonly used for high-pressure process piping, whereas Series B (based on API 605) is lighter and more cost-effective, making it suitable for long-distance utility pipelines. Domestic projects follow the GB/T 13402 standard for large-diameter steel pipe flanges; European-standard projects utilize EN 1092-1; and chemical industry projects may employ the HG/T 20592 or HG/T 20615 systems. Specifications range from DN 500 to DN 3000 (or even larger non-standard sizes), with pressure ratings spanning from low-pressure water service (PN 6, PN 10, PN 16) to high-pressure industrial applications (up to PN 100), as well as US-standard classes (Class 75, 150, 300, 600, and 900). Raised Face (RF) is the predominant sealing surface type, though Ring Joint (RJ) faces are available for high-pressure applications, and Flat Face (FF) or Male-Female (MFM) faces can be manufactured upon request.
Regarding materials, carbon steels such as A105, Q235, 20#, and the A694 series are the most common choices for long-distance pipelines. Stainless steels (304, 316L) are selected when corrosion resistance is required, while duplex steel and low-temperature carbon steel (LF2) are utilized in specific marine projects. For low-pressure, large-diameter plate flanges, rolled steel plate construction offers a significant cost advantage; however, high-pressure, large-diameter weld-neck flanges require forged blanks to ensure structural integrity. Heat treatment is performed during production to relieve machining stresses and prevent warping or deformation during lifting or hydrostatic testing. Factory inspections include dimensional verification and visual/surface flaw detection; high-pressure orders require additional Ultrasonic Testing (UT) and Magnetic Particle Testing (MT). Comprehensive Material Test Reports (MTR) and heat treatment records are provided upon request to meet material traceability requirements for overseas projects. Carbon steel flange surfaces can be treated with black paint or anti-rust oil to prevent moisture-induced corrosion during maritime transport.
Incorrect installation or improper positioning of large-diameter flanges entails extremely high rework costs; therefore, several key points require attention:
Never mix standard systems: Dimensional differences are more pronounced in large-diameter flanges than in smaller ones. For instance, a DN600 flange may have completely different outer diameters and bolt hole spacings depending on whether it follows the Chinese National Standard (GB), ASME (US), or HG (Chemical Industry) standard. It is crucial to strictly verify the standard designation and pressure rating specified in the drawings before procurement.
Special design considerations for large-diameter blind flanges: When using large-diameter blind flanges for sealing, the large contact area makes bolt tightening extremely labor-intensive. For pipelines DN400 and larger-or those with high rigidity-engineering specifications often recommend installing "jacking bolts" on the blind flange. These allow the threaded jacking force to separate the gasket during disassembly, preventing damage to the sealing surface caused by forceful prying.
Safety during installation and lifting: Large-diameter flanges are exceptionally heavy; the center of gravity must be accurately identified during lifting to prevent the flange from flipping in mid-air, which could cause injury or damage the sealing surface. During fit-up, using bolts to forcibly pull the flange into alignment to correct pipe misalignment is strictly prohibited; the flange face must be perpendicular to the pipe and precisely centered.
Protection of sealing surfaces: Large-diameter flanges feature extensive sealing surface areas (such as Raised Face/RF or Ring Type Joint/RTJ), making them highly susceptible to scratches during machining and transport. Thorough inspection prior to installation is essential, with localized repairs performed if necessary; otherwise, leakage is highly likely under high pressure.
Our large-diameter flanges are regularly exported to the Middle East, Southeast Asia, and South America, with a track record of supplying major water treatment plants, long-distance natural gas pipelines, storage tank projects, and power plant circulating water systems. While some standard specifications are available from stock, we also offer custom manufacturing for oversized or non-standard dimensions based on your drawings. For export, products are packed in solid wood crates, with protective film applied to sealing surfaces and protective sleeves fitted to bolt holes to prevent damage during transit. We provide complete documentation for customs clearance and accommodate third-party on-site inspections.
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