How are Flanges Categorized Based on Their Faces?

As contact surfaces for seating the sealing gasket material, various flange faces are useful. ASME B16.47 and B16.5 describe many types of flanges, such as raised face, male, and female face flanges, and matching facings are made with identical dimensions to give a large contact surface.

The small and big tongue-and-groove flange facings, as well as the ring joint face designed for ring joint-type metal gaskets, are also covered by these standards.


Raised Face (RF)

The raised face flange, also known as a standard type used in process plant applications, is easy to identify. It is referred to mainly as the raised face because the gasket surfaces are raised above the bolting circle face. The face type allows wide combinations of gasket designs, including flat ring sheet metallic composites and double jacketed and spiral wound types.

The purpose of the RF flange is to concentrate more pressure on the smaller gasket area. It thereby helps to increase the pressure containment capability of the joint. Height and diameter are in the ASME B16.5, defined by diameter and pressure class. Flange pressure ratings determine the height of the raised face.

The typical flange face finish for the ASME B16.5 RF flange is 125 to 250 µin Ra (3 to 6 µm Ra).

Raised face height

If we talk about the height measures which is H and B of all described flange dimensions, if we keep in mind the exception of the Lap Joint flange, it is crucial to remember the following things:

. In pressure classes 150 and 300, the height of the raised face is approximately 1.6 mm (1/16 inch). In the two pressure classes, almost all the flanges suppliers are shown in the brochure and catalog; the H and B dimensions include the raised face height.

. In pressure classes of 400, 600, 900, 1500, and 2500, the raised face flange height is approximately 6.4 mm (1/4 inch). Many suppliers show the H and B dimensions in these p

Flat Face

The flat face flange’s gasket surface is in the same plane as the bolting circular face. Flat face flanges are widely used in applications where the flanged fitting or mating flange is constructed of a casting. Bolting flat face flanges to raised face flanges is never a good idea.

According to the ASME B31.1, when connecting flat face cast iron flanges to carbon steel flanges, remember to remove the full-face gasket. It prevents the thin, fragile cast iron flange from being sucked into the gap created by the carbon steel flange’s elevated face.

Ring type joint

At high pressures, ring-type joint flanges are used. They have grooves carved into their faces, and steel ring gaskets are included. The flanges seal with the tightening of bolts to compress the gasket between the flanges into the grooves. This process will deform the gasket to make intimate contact inside the grooves and create metal to metal seal.

A ring-type joint flange may come with a raised face with a ring groove machined into it. However, the raised face does not serve any part in the sealing mechanism itself.

Ring-type joint gaskets

Ring-type joint gaskets are metallic sealing rings that suit high-temperature applications and high pressures. They are always applicable to special, accompanying flanges, which ensure good, reliable sealing with the right material and profiles.

Ring-type joint gaskets are designed to seal by “initial line contact” or welding action between the mating flange and gasket. Then, with the pressure on the seal interface through bolt force, the ‘softer’ metal of the gasket flows into the microfine structure of the more complex flange material and creates an efficient and tight seal.

Tongue-and-groove (T&G)

The Tongue and Groove faces of the flanges need to match properly. One flange face has a raised ring (Tongue) machined onto the flange face, while the mating flange has a matching depression (Groove) machine into the face.

Tongue-and-groove facings are standardized in both small and large types. They differ from males and females in the inside diameter of the tongue, and the groove does not extend into the flange base. This helps in retaining the gasket on its outer and inner diameter.

Male-and-female (M&F)

A flange must match this flange category. For example, one flange face comes with an area that extends beyond the normal flange face (Male). However, the other flange or mating flange comes with a matching depression (Female) machined into its face.


The above description clearly shows the flange characterization based on their faces. If you want to learn more about flanges, can contact Texas Flange today!

How to Choose the Right Flange Type for Your Pipeline Industry Project?

A flange is a ridged fitting that increases a pipe or tube’s connection strength. Generally, it is used in pipeline works to make the system more rigid and stable. A flange plays a significant role in a variety of industries. Using different kinds of flanges can help you prevent the escape of gas, air or water, and any other fluids that are readily available in an industrial and commercial situation. Flanges are of different types and material grades and are used for various conditions and purposes. Here are the most common types of flanges used in pipeline projects:

Flat Face Flanges: The Flat-Face flanges have gasket surfaces in a similar plane as the flanges for the bolting circle face. Flat face flanges are almost never to be bolted to a raised face flange but should be connected to other flat face flanges, usually with flat face gaskets. Some old flanged fittings are made from cast iron, although this is a less common material for pressurized applications these days.

Raised Face Flanges: The most common type of flange used in process plant applications is the Raised Face Flange. You can also identify it quickly at the connection point. The reason behind the name “Raised Face” is that the gasket surfaces are raised above the bolting circle face. This face type allows using a comprehensive combination of gasket designs, including flat ring sheet types and metallic composites such as spiral wound and double jacketed types.


How to Choose the Right Flange Type for Your Pipeline Industry Project

Ring Type Joint Flanges: The Ring Type Joint Flanges are commonly used in high pressure and high-temperature services above 800°F (427°C). They have grooves cut into their faces with steel ring gaskets. The flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming (or Coining) the gasket to make intimate contact inside the grooves, creating a metal to metal seal. Gasket materials are almost always steel or alloy. API specifications require these seal types for all flanges (B and BX ring grooves.)

Tongue & Groove Face Flanges: The Tongue and Groove faces of alternate flanges must be correlated. One flange face has a raised ring (Tongue) machined onto the flange face, while the mating flange has a matching depression (Groove) machined into its face. Tongue-and-groove facings are standardized in both large and small types.

Male & Female Face Flanges: With the male and female types, the flanges also must be matched. One flange face has an area extending beyond the regular flange face (Male). On the other side, the female flange or mating flange has a matching depression similar to its face. The female face’s depth is 3/16 inches, and the male face’s height is 1/4 inches, and both are smooth finished. The outer diameter of the female face acts to locate and retain the gasket. There are two versions available – the Small Male & Female Flanges and the Large Male & Female Flanges. Custom male and female facings are commonly found on the Heat Exchanger shell to channel and cover flanges.

So if you are confused about how to choose the perfect flanges type for your particular projects, here are some tips for you:

1. First, you need to learn the configuration of your flange and its process of application. The main issue here is to choose the right flange instead of just defaulting to a simple flat face or raised face configuration slip-on. It will guarantee you that you will be able to prevent some stressful reworking of your pipeline assembly.

2. You need to study and identify the proper detail regarding your flange to secure your connections. This way, you can locate and select the right shape and flange material for your project. You will find it once you are well aware of the media flowing through your pipeline or vessel.

3. Now you have to choose the best alloy type for your project. Since most of these products are often made from different materials, you need to select which material grades you want. Your choices include flange types made from non-metallic, metallic, elastomeric materials, and fibrous.

4. In the next step, you need to evaluate the chemical resistance and corrosion requirements of the flanges to be installed. After you consider the materials, you also need to understand their chemical resistance levels by alloy. It ensures that you will adhere to the specific requirements of your application to suit your project demands.

5. Be sure to find a professional who can guide you properly. Often this is a member of your own staff. This helps to ensure the safety and practicality of your flanged assembly. A well-trained engineer will provide you with the correct information you need and work with you properly to apply the best fitting in the right service. By performing accurate testing and review of your design calculations, you will reliably test the performance of your entire assembly.

6. The next step is to choose the proper manufacturer. To provide you with the best flange that you are looking for, you should find the most reliable, reputable, and qualified manufacturer.

By following all these tips, you will find the perfect match of the flange for your project and have a better decision regarding your many options.

Understand the situation in its entirety and choose the right flange type for your pipeline project.