The spectacle blind flange looks like the figure 8, so it is also known as figure-8 blind. This pipe fitting is generally machined from a piece of metal that is cut to fit between two pipe flanges and usually sandwiched between two gaskets when it is installed. In a piping system, this spectacle flange is mainly used to isolate a section of pipeline when the line requires inspection or maintenance.
One end of the spectacle blind flange will have an opening to allow flow through the pipe during operation and the other end is solid to block off flow during inspection or maintenance. In addition, the spectacle blind is provided with tapped holes that can make two flanges closely connected through screwed bolts.
Size of Spectacle Blind
American Series: CLASS 150, CLASS 300, CLASS 400, CLASS 600, CLASS 900, CLASS 1500 and CLASS 2500
Flange Facing Types
European Series: Raised Face (RF), Ring Joints Face (RJ)
Materials of Spectacle Blind
Carbon steel: A105
Alloy steel: A182 F 1-F 2-F 5-F 9-F 10-F 91-F 92-F 122-F 911-F 11-F 12-F 21-F 22
Stainless steel: A182 304-304H-304L-304N-304LN, 316-316H-316L-316N-316LN, 321-321H, 347-347H
Low temperature steel: A522 A707 Grade L 1-L 2-L 3-L 4-L 5-L 6-L 7-L 8
High performance steel: A694 F 42-F 46-F 48-F 50-F 52-F 56-F 60-F 65-F 70