Spectacle Blind, Spacers and Spades

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Although they have different names, Spectacle blinds, Paddle Blinds, Figure Eight Blinds, Spacer and Spade and Disc and Donut are all functionally the same thing. However they do have some differences.

The first difference is in their configuration. The Spectacle Blind and the Figure Eight Blind are normally a one piece device. Think of the number eight ( except that one of the circles is not open. The Spacer and Spade and the Disc and Donut are two separate pieces.

The primary purpose for these devices is safety. They require intentional action and result in positive shut-off. Intentional because someone must shut off the flow in a section of pipe then unbolt a flanged connection to install the solid paddle or blind. It results in a positive shut-off because the solid blind acts as a gate which prevents flow.

Functionally they also have some differences. They are used for "Service Blinds" and they are used for :maintenance Blinds." In both cases the outside diameter of the solid side or item and the open spacer or disc part is the same outside diameter as the gasket for the specific flange rating where they are to be used. However, when they are planned for use as a "Service" Blind the thickness must be calculated to withstand the full design pressure and temperature. When then they are to be used only as a "Maintenance Blind" they may be thinner because they will only be used when the plant is shutdown and the plant is cold.