The threaded Flanges is used for special circumstances
The Threaded flanges are usually supplied with a raised face (RF) or flat face (FF) sealing face. When a raised face is necessary for threaded pipe flanges, the standard height should be 1/16″ for the face under class400, If the threaded pipe flanges is same or more than class 400 , the standard threaded pipe flange raised face height should be 1/4″.
The A182 F53 150# RF Stainless Steel Threaded Flange commonly used in a small sizes and not very high pressure situation. The threaded flange is no welding in the joint ,it means the flange could be used for some situations which is not able to arrange a welding work.
These pressure classes also have differing pressure and temperature ratings for different materials. Unique pressure classes for piping can also be developed for a process plant or power generating station; these may be specific to the corporation, engineering procurement and construction (EPC) contractor, or the process plant owner. The ANSI/ASME pressure classes for Flat-Face flanges are 125# and 250#. The classes for Ring-Joint, Tongue & Groove, and Raised-Face flanges are 150#, 300#, (400# - unusual), 600#, 900#, 1500#, and 2500#.
The flange faces are also made to standardized dimensions and are typically "flat face", "raised face", "tongue and groove", or "ring joint" styles, although other obscure styles are possible.
Flange designs are available as "weld neck", "slip-on", "lap joint", "socket weld", "threaded", and also "blind".
ASME standards (U.S.)
ASME type flange on a gas pipeline
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