Flange Faces An In-Depth Technical Guide to Types and Their Applications

Flange faces are integral components in the design and functionality of piping systems. A flange face refers to the area where the flange and the gasket meet to create a seal. The type of flange face used directly impacts the performance of the flange in sealing, pressure handling, and preventing leaks. In this guide, we will cover the different types of flange faces in-depth, supported by technical specifications, dimensions, and performance data.

Types of Flange Faces

Flat Face (FF):

• Description: A Flat Face (FF) flange has a completely flat sealing surface. The flange faces are at the same level as the flange’s outer diameter.
• Applications: Commonly used in low-pressure and non-critical applications, such as systems with cast iron piping.
• Key Dimensions:
  1. Pressure Rating: Typically used in systems up to 150 Class.
  2. Material Compatibility: Best suited for cast iron and low-pressure systems.
• Advantages: Easy to install, cost-effective for low-pressure applications.
• Disadvantages: Less effective in high-pressure or dynamic systems where sealing reliability is critical.

Raised Face (RF):

• Description: The Raised Face (RF) is the most widely used flange face type. It features a raised area around the bolt circle to improve sealing with gaskets.
• Applications: Most commonly used in ASME B16.5 and ASME B16.47 flanges for high-pressure applications.
• Key Dimensions:
  • Height of Raised Area: 1/16″ (for Class 150 flanges), 1/4″ (for Class 300-2500 flanges).
  • Pressure Rating: Suitable for pressure systems ranging from 150 Class to 2500 Class.
• Material Compatibility: Used with a wide range of materials, including Carbon Steel, Stainless Steel, and Alloy Steel.
• Advantages: Provides a reliable seal in higher pressure and temperature applications.
• Disadvantages: Requires precise alignment and flat surfaces for effective sealing.

Ring-Type Joint (RTJ):

• Description: Ring-Type Joint (RTJ) flanges feature a groove machined into the face of the flange, designed to accommodate a metallic ring gasket. This flange is commonly used in high-pressure and high-temperature applications.
• Applications: Primarily used in API and oil and gas industries where high sealing pressure is required.
• Key Dimensions:
  • Groove Depth: Typically 0.0625″ to 0.125″ depending on the flange size.
  • Pressure Rating: Can handle pressures up to 5000 Class or more.
• Material Compatibility: Best suited for stainless steel, duplex stainless steel, and alloy steels.
• Advantages: Capable of sealing at extremely high pressures and temperatures.
• Disadvantages: Requires precise machining for both flanges and gaskets.

Male and Female (M&F):

• Description: Male and Female (M&F) flanges feature a raised “tongue” on one flange and a corresponding groove or “female” portion on the other. This interlocking design improves sealing and enhances stability.
• Applications: Used in critical high-pressure systems where reliable sealing is essential.
• Key Dimensions:
  • Tongue Height: 0.0625″ to 0.125″.
  • Pressure Rating: Can accommodate pressure systems up to 1500 Class.
• Material Compatibility: Used with high-strength materials like Carbon Steel, Stainless Steel, Nickel Alloys, and Duplex Stainless Steel.
• Advantages: Superior sealing performance under high-pressure conditions.
• Disadvantages: Requires highly accurate machining to ensure interlocking fit.

Spiral Serrated Face:

• Description: Spiral Serrated flanges feature spiral grooves on the flange face, improving gasket grip and providing a higher sealability under dynamic conditions.
• Applications: Commonly used in high-temperature, high-pressure systems such as those found in power plants, refineries, and chemical plants.
• Key Dimensions:
  • Serration Depth: Approximately 0.125″.
  • Pressure Rating: Suitable for systems up to 2500 Class.
• Material Compatibility: Widely used with stainless steels, carbon steels, and alloy steels.
• Advantages: Enhances sealing capability in critical systems subject to high pressures and fluctuating temperatures.
• Disadvantages: Requires precise machining of grooves and accurate gasket selection.

Tongue and Groove (T&G):

• Description: The Tongue and Groove (T&G) flange face design consists of a raised “tongue” on one flange and a corresponding “groove” on the other flange, providing a mechanical interlocking effect that ensures superior sealing.
• Applications: Often used in high-pressure systems, especially in industries such as oil and gas, power generation, and petrochemicals.
• Key Dimensions:
  • Tongue Height: Typically 0.0625″.
  • Groove Depth: Typically 0.125″.
  • Pressure Rating: Suitable for systems up to 2500 Class.
• Material Compatibility: Suitable for alloy steels, stainless steels, and carbon steels.
• Advantages: Provides a more secure and leak-resistant seal than flat face and raised face designs.
• Disadvantages: Requires precise machining for accurate fitment.

Lapped Face:

• Description: The Lapped Face flange consists of one flange with a raised edge and the other flange with a corresponding flat face. This design is typically used in lower-pressure applications.
• Applications: Suitable for low to medium pressure systems, such as water and utility piping.
• Key Dimensions:
  • Raised Edge Height: Typically 1/16″.
  • Pressure Rating: Primarily used for 150 Class systems.
• Material Compatibility: Typically used with cast iron or low-strength materials.
• Advantages: Economical and easy to manufacture, ideal for lower-pressure applications.
• Disadvantages: Less effective for high-pressure systems due to the reduced sealing area.

Selecting the Right Flange Face

Choosing the right flange face is essential for system performance. Here are some key factors to consider:

1. Pressure and Temperature: For high-pressure and high-temperature systems, consider RTJ, M&F, or Spiral Serrated flange faces.
2. Sealing Performance: For reliable seals in demanding conditions, Ring-Type Joint (RTJ) and Male and Female (M&F) faces are ideal.
3. Material Compatibility: Ensure the flange face matches the material of the pipes and gaskets, especially for corrosive or high-temperature environments.

Flange faces are critical in ensuring the safety and efficiency of piping systems. By selecting the correct type, you can improve system performance, reduce leakage risks, and extend the lifespan of your equipment.

Contact Us:

For high-quality flanges and expert advice on selecting the right flange faces for your applications, contact Omaa Metal Sources at: sales@omaaforged.com