This flange consists of two disc-shaped steel pieces that are connected to each other. One of these disks is solid and the other is hollow. Because the flange looks like glasses, it is known by this name.
Technical specifications of spectacle flange
This flange is a safety piece to insulate a part of a pipeline or equipment. It is installed between two flanges for use and a gasket is needed to seal the line. No welding is required to install these flanges, and a master bolt is used instead.