What is a spectacle blind?
A spectacle blind or spec blind, abbreviated as SB, is a safety device used to isolate a section of line or piece of equipment when the line or equipment needs to be inspected or removed from service.
It is different than a valve in that the blind is a permanent or long term isolation device
Jointly they perform the same function as a Spectacle Blind as essentially a simplistic valve. The Spade or Spacer is fitted in the line between two flanges and is bolted in place. The Spacer is used when the line is required open and the Paddle Blind or Spade is installed when the line is required blocked or closed.
Adjusting spectacle blinds is straightforward. Simply loosen the bolts around the flange leaving the bolt running through the spectacle blind in place, rotate the desired face into the space between the pipes, and tighten the flange bolts again, some piping applications will require new gaskets to be installed.
Spectacle blind, spades, and spacers are also known as figure-8, paddle blank, Slip blind, and spacer. These are three different components that used in piping for positive isolation of the section of a line or equipment during maintenance and shutdown.