Figure 8 blind flanges (also known as spectacle blinds) are essential components in piping systems for isolating sections of a pipeline. They consist of a solid disc (blank) and a spacer ring (open) connected by a central web, resembling the figure 8 shape. This design allows quick switching between isolation and flow positions without removing the flange. For global EPC projects, proper procurement of these components is critical to avoid leaks, pressure failures, or non-compliance.
Production Process Overview
Understanding the manufacturing steps helps buyers evaluate supplier capabilities.
Material Selection
Materials must match the service conditions – pressure, temperature, and corrosiveness. Common grades include:
- Carbon steel: ASTM A105, A350 LF2 (low temperature)
- Stainless steel: ASTM A182 F304/F316
- Alloy steel: ASTM A182 F11/F22
Buyers should request material certificates (MTCs) and verify traceability to mill test reports.
Forming
Blanks are cut from plate or forged bar, then machined to final dimensions. CNC machining ensures accurate facing, bolt holes, and web thickness. For high-pressure designs (e.g., Class 900+), forging is preferred over plate cutting for better grain flow and strength.
