Spectacle Blind
Spectacle Blinds find application in systems where frequent separation from other installations is required. Typically, a Spectacle Blind is initially fixed in the "open" position to allow flow through the pipe. However, if the Spectacle Blind is rotated into the "closed" position, it effectively blocks the pipe, preventing any flow from occurring. This mechanism provides the flexibility to control the flow of fluids through the system as needed.
Spades and Ring Spacers
Spades — Spades and Ring Spacers share similarities with Spectacle Blinds, except they are not connected to each other. These components are utilized in systems where frequent maintenance is not required, or in applications with large pipe sizes.
Spades and Ring Spacers can weigh hundreds of pounds, depending on the flange size and Pressure Class. To avoid adding unnecessary weight to flange connections, it's common to opt for two separate parts instead of a single Spectacle Blind. This approach ensures easier handling and installation, particularly in systems with significant size and weight considerations.
Ring Spacer — During maintenance of a pipe system, it may be necessary to temporarily replace a Ring Spacer with a Spade. This process typically involves loosening all bolts, removing half of them temporarily, and then placing the Spade or Spacer accordingly. Once the gaskets are replaced (it's advisable to use new gaskets), the bolts can be re-assembled and tightened.
One challenge is that Spades or Spacers fixed between flanges are often not visible. To address this, handles are often specially marked or designed differently. Clients may also provide their own specifications in this regard.
However, it's essential to ensure that the diameter and Pressure Class of a Spade or Spacer are engraved on the handle. This same practice applies to Spectacle Blinds as well. This ensures proper identification and helps prevent errors during installation or maintenance procedures.
Surfaces – Dimensions – Material
The sealing surfaces of a Spectacle Blind, Spade, or Ring Spacer are typically finished in accordance with the face finish of the flange. The diameter of these components is usually slightly larger than the Raised Face of a flange to ensure that, when correctly assembled, the bolts are not in contact with the Blind or Spacer.
The diameter of Spectacle Blinds, Spades, and Ring Spacers depends on the flange size and the thickness of the Pressure Class of the flange. ASME B16.48 provides specifications for pressure-temperature ratings, materials, dimensions, dimensional tolerances, marking, and testing for operating line blanks in sizes ranging from NPS 1/2 to NPS 24, for installation between ASME B16.5 flanges in Pressure Classes 150, 300, 600, 900, 1500, and 2500.
It's crucial that Spectacle Blinds, Spades, and Ring Spacers are made from a plate or forging specification approved for use by ASME B31.3. They should have essentially the same chemical composition as the mating flanges and piping involved to ensure compatibility and proper functioning within the system.
