How to Identify a flange?

- Aug 30, 2017-

How to Identify a flange?


Whether a flange will function properly all goes back to whether the flange was the right one for the job in the first place. A flange must fit in pipe joints just right in order for it to perform properly. A small error in choosing a flange can effect an application resulting in a costly mistake. These 7 factors are all involved in choosing the right flange for the right application to maximize its functionality.



Its pretty easy to identify the type of flange by how it looks. First, identify the tops by determining whether a flange has a flat face, threaded bore, lap joint, weld neck, socket weld, or tongue and groove. Next is identifying the bottoms by determining whether it has a flat face, which is completely flat or a raised face which is a slightly raised section on the face of the flange.



The size of a flange is comprised of factors that include the standard used (ANSI/DIN/JIS), pressure class needed, and the actual measurements of a flange. Factors include the outer diameter, inner diameter, number of bolt holes, bolt hole diameter, and the bolt circle.



Thickness play a vital role in identifying a flange by how high of a pressure it can withstand because thicker flanges can withstand higher pressures in an application.


Bolt Holes

This component helps determine the size of a flange and pressure class. 3 factors that need to be considered are the amount of bolt holes, pitch circle diameter, and actual size of the bolt holes on a flange. The thicker the bolt the stronger the bolt is, resulting in a higher pressure that the flange can withstand.



There are a number of standards that can be selected from.  The selection will most likely be based upon the application and standards of the other components that this flange will be connected to. (i.e. valves) 3 main standards used are: ANSI American National Standards Institute, DIN Deutsches Institut für Normung / European, and JIS Japanese International Standard.


Pressure Class

Pressure class represents the nominal amount of pressure that the product can support or operate under safely.  Each standard has multiple pressure classes available ranging from low pressure tolerance to high pressure tolerance.  The pressure class of products working together should be the same matching the pressure class of the pipes and valves in the system that it is connected to.



It is important to choose the right material for a flange and understand the elements that it will face in an application the piping system is being used. (corrosion, pressure, moisture, temperature) Common materials include steel, stainless steel, carbon steel, and copper nickel.


To see our selection of slip-on, weld neck, blind, bulkhead, and manifold covers in ANSI, DIN, and JIS standards, visit the product page of the Glen Flange Ltd. For convenience, we also offer this helpful Quick Reference Flange Image! But if you’d like to speak to an experienced sales person who can help you find the flange with the right job, contact Glen Flange Ltd by mail: