What are the different types of flanges?

Weld Neck Flange (WN)
WN flanges are identified by their tapered hub. It is designed to be full penetration welded to the piping system. The pipe schedule will need to be specified.

Long Weld Neck Flange (LWN)
Like WN except the hub is extended. The LWN was designed to take the place of WN and pipe coming off a pressure vessel.

Blind Flange (BL)
A blind flange is designed to terminate/close the end of a piping system.

Slip On Flange (SO)
An SO flange is designed to slip onto the pipe and welded on the inside and outside with fillet welds.

Socket Weld Flange (SW)
Like an SO flange, the pipe is inserted into the flange; however, they only have one external fillet weld securing the flange. Corrosion may be an issue since there is a crevice between the pipe and the flange. The pipe schedule will need to be specified.

Lap Joint Flange (LJ)
LJ flanges are designed to be used with a Stub End. They look like a SO flange; however, it has a radiused bore to accommodate the insertion of the stub end. For stainless steel or nickel alloy pipelines, lap joint flanges are a cost-effective solution since the lap joint flange material can be of a lower grade.

Threaded Flange
Threaded flanges use NPT threads to connect to the piping system without the need for welding.

Orifice Flange
Orifice flanges are used with orifice plates to measure or restrict the pressure or flow. The flanges are typically sold as a pair and are equipped with a set of bolts called jack screws that help separate the two flanges for removal and/or insertion of the orifice plate. Additionally, each flange has two external taps (Either SW or NPT) for instrumentation and monitoring. The flanges are available in weld neck, slip-on, and threaded end configurations.

Paddle Blind (AKA Line Blank, Spade Flange)
This product is designed to be inserted between two flanges and isolate the piping system. Often used during maintenance and repair operations (MRO), it provides a positive shut-off. It is considered a safety device since it avoids issues with degraded valve seals or operator error. The paddle blind will be replaced with a spacer when the MRO is complete.

 Paddle Spacer
This product is designed to be inserted between two flanges and allows for the free flow of media through the flanges.

Spectacle Blind (AKA Spec Blind)
This product is designed to be inserted between two flanges and is a combination of the blind and spacer. The blind and the spacer are connected in the middle and the appearance resembles a set of spectacles.

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