are generally applied to permanently separate pipe systems, or just to connect with each other. A spectacle blind is machined from a single piece of metal that is cut to match the pipe size, fit between two pipe flanges and requires an additional gasket when it is installed. Also, the bolts will need to be lengthened depending on what piping class and size blind is used. The thickness of the spectacle blind is specified based on the line pressure and pipe size.
One end of the blind will have an opening to allow flow through the pipe during operation and the other end is solid to block flow.