What are the 3 most common flange types?

Introduction

There is a myriad of piping flange varieties, each suited for different service conditions. The selection of flanges is determined by factors such as corrosion resistance, erosion resistance, pressure temperature rating (Class), the number of welds needed for attachment, physical size (some flange designs may not fit the designated space), and cost. Below are the most common types of flanges:

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Flange Types

Other types of flanges that engineers may encounter include the male and female and tongue and groove designs. Less prevalent types consist of the orifice, expander, reducing, and long welding neck flanges.

Flange ends can be screwed, welded, or lapped (where metal comes into contact) with their corresponding piping.

This section will cover the most popular flange types.

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Flange Types Overview

Key information about flange types is summarized in the table below. Although ASME standards are referenced, multiple international and national standards (like DIN, EN, etc.) are also applicable. ASME is the most universally acknowledged organization for piping standards; therefore, its standards have been highlighted.

The 'Faces' column indicates the typical sealing face for each flange type. However, exceptions may apply based on specific flange types. The table serves as a general overview; for precise information, consulting relevant standards is advised.

Flange Type Summary Table

Table Key:   FF​ flat face. ​ ​ RF​raised face. ​ ​ RTJ​ring type joint.

Special Flange Types

In addition to standard types, special flanges such as the reducer, expander, long welding neck, nipoflange, weldoflange, and swivel flange exist. Given their infrequent use, details on these special types are not included in this introductory material.

What Are The Most Common Flange Types?

This blog post will highlight the most widely used flange types in contemporary industrial applications. Flanges are fundamental components in various industries. Despite the multitude of flange designs, they all serve a shared purpose: to unite piping systems. Below, we shall delve into the specifics of the seven most recognized flange types, detailing their characteristics and uses across multiple sectors.

Weld Neck Flange:

Weld neck flanges excel in high-pressure environments. They rank among the most common types due to their long neck facilitating a seamless butt weld attached directly to the pipe, ensuring a smooth connection. Hence, they are ideal for applications in the oil and gas sector, where reliability under pressure is paramount. Typically, this flange type is intended for larger diameters and high-pressure ratings.

Slip-on Flange:

Due to their ease of installation, slip-on flanges are a favorite among manufacturers. These flanges lack a weld bevel and allow for pipe length adjustments regarding flange placement, making them a convenient alternative to weld neck flanges. The bore of the slip-on offers ample space for welders and fabricators to connect. Commonly utilized in shipbuilding and construction—a field demanding quick assembly—these flanges are usually deployed in low-pressure applications. Most slip-on flanges feature a hub resembling a raised face. In confined spaces that permit a 'ring style' slip-on, these flanges can be fitted without the hub. Although the hub style is frequently discussed, a ring-style slip-on without a hub is also valid as a slip-on flange. Higher-pressure class slip-ons are often designed with a lap joint height to enhance attachment.

Socket-weld Flange:

Socket-weld flanges are adept in withstanding high temperatures and pressures, making them suitable for power generation and chemical processing industries. These flanges come with a counterbore in their center, allowing for a clean weld of the pipe into the socket. Although less popular, socket weld flanges present a practical solution for situations requiring a compact assembly when compared to a traditional weld neck flange. Typically, they are found in smaller nominal pipe sizes and are a good alternative for tight spaces or extreme temperatures where the fluid is non-corrosive.

Threaded Flange:

Threaded flanges offer straightforward installation and function exceedingly well in low-pressure scenarios. These flanges play a crucial role in piping systems, ensuring tight seals are maintained without extensive welding processes. They feature a female NPT thread in the center for connectivity with male NPT threaded piping, and they are sometimes referred to as companion flanges, screw flanges, or NPT flanges. Often, they are employed to achieve reduced connections. Besides the standard NPT format as per ASME B16.5 specifications, various thread styles can be machined as well.

Blind Flange:

Blind flanges are vital for sealing off sections of piping systems. They serve as reliable barriers in industries involving petrochemicals or hazardous materials, ensuring worker safety while preventing leaks during maintenance or emergencies. Blind flanges commonly possess a slight indentation in the center, observed in standards like B16.1. This recess allows the pipe end to mate accurately with the connecting flange, creating a tight seal. In larger OD blind flanges, a concave recess appears through the body for a dished head formation at the top. Nowadays, modern blind flanges are produced with or without hubs, avoiding older cast iron specifications.

Lap Joint Flange:

Lap joint flanges, also known as backup flanges, loose ring flanges, or loose hubbed flanges, are easily disassembled and offer flexibility. This makes them particularly useful in sectors such as food and beverage, which require frequent maintenance or adjustments. The hubs can be set to user specifications and tend to be higher than slips on flanges. For higher-pressure class slip-ons, there is often a lap joint height for better attachment. If a lap joint is inaccessible, customers may opt for a slip-on flange modeled similar to a lap joint with a machined hub, assuming height isn't an issue.

Custom Flange:

Despite the name, custom flanges are frequently utilized across a variety of applications throughout different industries. Our machine shop can work with AIS and import materials to create products that comply with various specifications. We also adapt our inventory promptly to better serve our customers. Whether it's reverse engineering a sample or working from a CAD drawing, we help with prototypes, mass production, and product storage.

API’s Machining Capabilities:

• Machining inner diameter, outer diameter, gasket face, chamfers, and tapers up to 120’ outer diameter
• Single point threading of inner and outer diameter with standard or metric pitch
• Straight turning, tapers, and angles of inner and outer diameter face
• Profile milling, facing, contouring, pocketing, boring and threading
• Milling straight and tapered pipe threads
• Single-piece or large production orders
• Bolt-hole drilling up to 3’ diameter
• Turning shafts up to 60’ in length
• Steel, Aluminum, Duplex, Super Duplex, Alloy 20, and other exotic metals

Each flange type plays a specific role within its applications. At API International, Inc., we focus on providing a comprehensive array of fittings, including these essential flange types to meet diverse industry needs. If you have any questions or need a quote, please reach out to our sales team. They are eager to assist you in sourcing the industrial fittings essential for your projects.

For further information, please visit our website Flange Supplier.