When working with piping systems, flanges play a critical role in ensuring secure and leak-free connections. But with so many types of flanges available, identifying the right one can be overwhelming—especially when faced with technical drawings, specifications, or international standards. In this article, we’ll walk you through how to identify flange types based on shape, face type, pressure rating, material, and standards. This guide is ideal for engineers, procurement specialists, and technical buyers.

Throughout this article, we’ll also highlight how SASA FLANGE can support your flange needs with accurate identification, manufacturing, and custom solutions.

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1. Why Flange Identification Matters

Correct flange identification ensures:

• Compatibility with pipes, valves, and fittings

• Compliance with industry standards (ASME, DIN, EN, JIS, etc.)

• Prevention of leaks, system failure, or expensive rework

• Efficiency during procurement, inspection, and installation

Misidentifying flange types can result in mismatched connections, delayed projects, and increased costs. That’s why a clear understanding of the different types is essential.

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2. Key Factors to Identify Flange Types

2.1. Flange Face Type

The face type is the surface that comes into contact with the gasket. It plays a role in the sealing method and pressure containment.

Common face types include:

• Raised Face (RF): A small raised surface around the bore, most common in industrial piping.

• Flat Face (FF): Entire face is flat, often used with cast iron components.

• Ring Type Joint (RTJ): Features a deep groove and requires a metal ring gasket; used for high-pressure systems.

• Tongue and Groove (T&G): Each flange has a matching tongue and groove; offers accurate alignment.

• Male and Female (M&F): Similar to T&G but uses a wider sealing surface.

You can identify the face type by visually inspecting the sealing surface or checking engineering drawings.

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2.2. Flange Connection Type

Flanges connect to the piping system in different ways:

• Weld Neck Flange: Has a long tapered hub; welded to the pipe. Used in high-pressure and high-temperature applications.

• Slip-On Flange: Slides over the pipe and is welded inside and outside. Easier to align but less strong.

• Socket Weld Flange: Has a socket to insert the pipe before welding. Used for smaller sizes and high-pressure services.

• Threaded Flange: Screwed onto a threaded pipe; requires no welding.

• Lap Joint Flange: Used with a stub end; allows for easy alignment and rotation.

• Blind Flange: No bore; used to close off a pipeline or valve.

• Orifice Flange: Designed with pressure tap holes for flow measurement.

Each flange type has a distinct shape and installation method. Observing the flange neck, hub, and bore can help you identify the type.

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2.3. Material Type

Flanges are made from a range of materials depending on application needs:

• Carbon Steel – Common for general industrial applications.

• Stainless Steel (304, 316, etc.) – Used where corrosion resistance is essential.

• Alloy Steel – Suitable for high temperature and pressure.

• Duplex/Super Duplex – Excellent for offshore and corrosive environments.

• Copper-Nickel, Monel, Inconel – For marine, chemical, and specialty applications.

Material identification may require checking the markings on the flange or reviewing the mill certificate.

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2.4. Pressure Class / Rating

Flanges are classified by their pressure-temperature rating. The most common standard is ASME B16.5, with pressure classes:

• Class 150

• Class 300

• Class 600

• Class 900

• Class 1500

• Class 2500

Other standards like DIN PN (e.g., PN10, PN16, PN40) or JIS also apply.

The pressure class is typically marked on the flange along with the size and material grade.

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2.5. Standard and Specification

To identify a flange, check which standard it follows:

• ASME/ANSI B16.5 – Flanges from ½” to 24″

• ASME B16.47 – Flanges above 26″

• DIN EN 1092-1 – European standard

• JIS B2220 – Japanese flanges

• GOST – Russian flanges

• BS 4504 – British standard