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Factors to Consider When Choosing Flanges for Your Project

Gas and oil plants are complex, large environments with thousands of miles of interconnected piping. For any flange or product to perform correctly, choosing the right type of flange for the job is fundamental. The flange must fit perfectly into the pipe joint to conduct its functions properly. A minor mistake during the flange selection may affect an application resulting in an expensive error.


This blog will discuss the factors associated with selecting the correct flange for the proper application to ensure maximum usability.


It is often easy to spot the flange type by the way it looks. First, you must classify the top of the flange by deciding whether the flange has a socket weld, flat flange, lap joint, threaded bore, welded neck, groove, and tongue flange. Next, the bottoms are identified with the evaluation of whether they have a flat face, which is entirely flat, or a raised face which is a slightly raised section on the face of the flange.

All of this information is usually defined by the stamping on the outside diameter of the flange, provided this has not been completely painted over. It is important to keep an archive of your assembly components for future reference and maintenance.


The flange size consists of factors that include the standard used (: JIS – Japanese International Standard, ANSI – American National Standards Institute, and DIN – Deutsches Institut für Normung / European), the pressure level needed, and the actual overall outside diameter and thickness of the flange. Other factors in determining the full call-out include the number of bolt holes, outer diameter, inner diameter, bolt circle, and bolt hole diameter, but the nominal pipe size is typically universal.


Depending on the flange thickness, it can be determined how high a pressure flange can handle, in any application thicker flanges can resist high pressures.

Bolt holes

Bolt holes help to measure the flange size and pressure class. The actual size of the bolt holes, the pitch circle diameter, and the number of bolt holes on the flange are three factors that need to be addressed. If the bolt is stronger and thicker, it can often correlate with higher pressure capabilities.


There are a lot of industry-defined standards from which you can choose the flanges. So the flanges help to choose based on the standard and application of the product. You can connect it to the three primary standards previously mentioned, including DIN, ANSI, and JIS.

Pressure class

Pressure class signifies the marginal pressure level under which the flange can safely function and sustain. Each standard comes with several pressure levels available, from high-pressure to low-pressure tolerance. The pressure levels of products connected to the flanges must be the same as those of valves and pipes in service. The most common industry pressure class is the modern ASME 150# per B16 spec.


It is crucial to choose a suitable material for a flange depending on the understanding and application the elements will encounter in an application that the piping system is using. The most common materials include chrome, nickel, carbon steel, duplex steel, stainless steel, etc.

Here are a few common ways to choose the flanges:

Define your specification and standard

Pipe flanges come in with standard blind, threaded, weld neck configurations. As fittings come into standard, oilfield dimensions become necessary for functional interchangeability.

Standard dimensions are the same for all materials used. However, the specifications are regularly updated, broadened, and revised.

Figure out the flange facing

Defining the facing of your flange is one of the first steps to order the industrial pipe fittings. The flange face is the sealing surface. The most common types of flange faces include:

. Full face
. Flat face
. Ring-type face
. Large female and male
. Lap joint
. Raised face

Pick put the correct pressure class

The pressure class of the flange standard determines its dimensions. The pressure class ratings may fall within 125 to 900 psi. The four factors which influence the pressure limits of the flange within the oil and gas industry include:

. Flange sizes
. Materials used
. External and internal temperatures
. Size of bolts, number, thickness, and dimensions


You may need to consult the fitting distributor to determine your project’s right flange pressure class. For more information on sourcing suitable flanges for your project, you can reach out to Texas Flange.

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