Blind Flange

A Blind Flange is a type of pipe flange that is used to close the end of a pipe system or pressure vessel opening. It is commonly used for maintenance purposes or to block off a section of piping that is no longer in use. The blind flange is typically bolted onto the end of a pipe or fitting with bolts, and it does not have a bore or an inside diameter, hence the term “blind.” This means that it effectively seals the end of the pipe or vessel, preventing the flow of fluids or gases. Blind flanges are available in various sizes, materials, and pressure ratings to suit different applications and operating conditions.

Material Grades

Stainless Steel: ASTM / ASME SA403 GR WP “S” / “W” / “WX” 304, 304L, 304H, 309, 310H, 316L, 316H, 317, 317L, 321, 321H, 904, 904L, 347, 347H.

Duplex Steel: ASTM / ASME SA815 UNS NO. S31803, S32205, S32550, S32750, S32760.

Carbon Steel: ASTM / ASME A234 WPB, WPC, ASTM / ASME A860 WHY42, WHY46, WHY52, WH60, WPHY65 & WPHY70

Alloy Steel : ASTM / ASME A234 WP1, WP5, WP9, WP11, WP 12, WP22, WP23, WP91

Sizes

Blind flanges are available in a wide range of sizes to accommodate different piping systems:

• Nominal Pipe Size (NPS): Typically ranges from ½ inch to 24 inches for standard applications. Larger sizes can be manufactured as needed.
• Diameter and Thickness: The outside diameter (OD) and thickness of the flange vary according to the pressure class and nominal size. Blind flanges are essentially solid disks, with dimensions specified by the relevant standards.

Pressure Ratings

Blind flanges are designed to handle various pressure ratings, indicating the maximum pressure they can withstand at a given temperature. The common pressure classes include:

• Class 150 (PN 20)
• Class 300 (PN 50)
• Class 400 (PN 64)
• Class 600 (PN 100)
• Class 900 (PN 150)
• Class 1500 (PN 250)
• Class 2500 (PN 420)

The pressure rating of a blind flange depends on the material, size, and temperature of the system. Higher pressure classes indicate the flange can withstand greater pressures.

Conclusion

When selecting a blind flange, it is crucial to consider the nominal pipe size, pressure class, material, and specific application requirements. Ensuring compliance with standards such as ASME/ANSI, MSS, or ISO guarantees compatibility and safety. Blind flanges are essential components in piping systems, providing effective sealing, easy access for maintenance, and flexibility for future system modifications.