Oil and Gas

Spectacle Blind Flange

Spectacle and line blind flanges are similar to a blind flange but different because they fit between two flnges. Spectacle blind gets their name from similarity to pair or eye glasses. Once side of spectacle blind is fully closed for complete flow shutt off, whereas the other end is open for full flow. In this setup the blinds can be rotated without having to take the system apart. It also gives visual confirmation if the line is open or close.

Reducing Flange

A reducing flange changes the line size without adding an extra fitting. The reduction in a reducing flange is always abrupt compared to a reduction that can be achieved by concentric butt weld reducer. A reducing flange is commonly available as threaded reducing flange or slip on reducing flange. A 6" by 4" reducing slip on flange will have the flange dimension (outer diameter, bolt circle diameter) of a 6" flange but the hole of a 4" flange. This allows it to mate to a 6" pipe via flanged connection but connect a 4" pipe instead.

Flange Faces

Flange face provides a mean to mate the flange with sealing element, usually a gasket. Even though there are many face types, most common flange face types are following;

• Raised Face
• Flat Face
• Lap Joint
• Ring Joint
• Tongue and Grove

There are two type of flange face finishes for Raised Face and Flat Face Flanges;

• Smooth finish
• Serrated finish (serrated concentric grooves, serrated spiral grooves)

Both serrated finishes have grooves 1/16" deep with 24 to 60 groves per inch.