Raised Face Flange


ASME / ANSI B16.5 Raised Face Flange Manufacturer In India

The Raised Face flange is the most common type used in process plant applications, and is easily to identify. It is referred to as a raised face because the gasket surfaces are raised above the bolting circle face. This face type allows the use of a wide combination of gasket designs, including flat ring sheet types and metallic composites such as spiral wound and double jacketed types. The purpose of a RF flange is to concentrate more pressure on a smaller gasket area and thereby increase the pressure containment capability of the joint. Diameter and height are in ASME B16.5 defined, by pressure class and diameter. Pressure rating of the flange determines the height of the raised face.

The typical flange face finish for ASME B16.5 RF flanges is 125 to 250 µin Ra (3 to 6 µm Ra).Perhaps the most common type of flange facing is the raised face flange. It is used in almost all applications in high and low pressures and temperatures.

rf raised face flange manufacturerThe face of the flange is either 1/16” or 1/4” depending on the pressure class. ANSI 300 and under have a 1/16” raised face and ANSI 400 and above have a 1/4” raised face. The mating face is machined to have shallow grooves in it to ensure a positive grip with the gasket. The

Raised face flanges are available in most types of flanges. Some of these are blind flanges, lap joint flanges, slip on flanges, socket weld flanges, threaded flanges and weld neck flanges. All of the ANSI pressure classes are available with raised face flanges.

Gaskets for a raised face flange can be whatever is suited for the process.  They can be spiral wound gaskets or non metallic gaskets.  This is fully dependant on whatever is required by the process stream.

DESIGN CONSIDERATIONS

As with all the other flange facings, it is important to ensure that the mating flange is compatible with whatever flange you are using. For example, flanges that are built to AWWA standards are different than flanges that are built to ASME B16.5, although they look similar.

When looking at flange tables, the dimension of the face is not always included in the dimensional data. Always be sure whether or not the length dimension is included. The dimensional data at Piping Designer does not include the dimension of the raised face.

It is important to take note of whether the raised face is included within dimensions charts when dealing with pipeline components as Pipe Drafting and Design warns:

“The 1/4″ raised face thickness is not always included in the length dimensions for 400# and higher pound ratings. To assure accurate dimensioning, always determine if the dimensioning chart being used includes the 1/4″ raised face thickness for the larger pound rating flanges. The 1/4″ raised face thickness must be added to the dimensioning chart measurement to obtain the overall flange length if the dimensioning chart indicates it has not been added.”