What Are the Different Types of Flange? . Flanges are essential components in various industries, serving as connectors between pipes, valves, and other equipment. These mechanical devices ensure a secure, leak-proof joint, allowing fluid or gas to flow efficiently in pipelines. But what are the different types of flange, and how do they meet specific industrial requirements? This article delves into the various flange types, their features, applications, and why they’re integral to modern engineering.
Read More : How to Clean Oxygen Sensor Without Removing It?
There are many different types of piping flange due to the different service conditions in which they operate. Flanges are chosen based on their corrosion resistance properties, erosion resistance properties, pressure temperature rating (Class), number of welds required for attachment, physical size (some flange designs may not fit into the space allowed) and cost. The most common flange types are:
- Welding Neck Flange
- Slip-on Flange
- Socket Weld Flange
- Lap Joint Flange
- Threaded Flange
- Blind Flange
What exactly is a Flange?
Flanges are crucial for linking valves, pipes, pumps, and other plumbing equipment. These forged rings come in many shapes and sizes, making it imperative to determine the most suitable option for your needs. With the vast range of varieties and specifications available, selecting the right flange may initially pose a challenge. The two main categories of flanges are welded and threaded types of flanges.
Key Components of a Flange
Every flange consists of several critical parts:
- Flange Face: The surface that makes contact with a gasket.
- Bolt Holes: Ensure a secure connection with other components.
- Hub or Neck: Adds structural stability.
Read More : How to Clean Hydraulic Lifters?
How are flanges connected to one another or various other pieces of equipment?
Connections are developed between two flanges or between a flange and another piece of equipment using a bolt. The two pieces are bolted together, making them a single unit. Bolting a flange to a pipeline provides an easily accessible seal.
Types of Flanges
Welding Neck flange
Welding Neck Flanges are easy to recognize at the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting.
The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero and / or elevated temperatures. The smooth transition from flange thickness to pipe or fitting wall thickness effected by the taper is extremely beneficial, under conditions of repeated bending, caused by line expansion or other variable forces.
These flanges are bored to match the inside diameter of the mating pipe or fitting so there will be no restriction of product flow. This prevents turbulence at the joint and reduces erosion. They also provide excellent stress distribution through the tapered hub and are easily radiographed for flaw detection.
This flange type will be welded to a pipe or fitting with a single full penetration, V weld (Buttweld).
Read More : Why Seals Play a Critical Role in Preventing Leakage: An In-Depth Guide
Long Welding Neck Flange
“Long Welding Neck” refers to a type of flange used in piping and industrial applications. This elongated flange design is characterized by its extended neck, which allows for a strong, secure weld connection to the piping system.
Slip On flange
The calculated strength from a Slip On flange under internal pressure is of the order of two-thirds that of Welding Neck flanges, and their life under fatigue is about one-third that of the latter.
The connection with the pipe is done with 2 fillet welds, as well at the outside as also at the inside of the flange.
The X measure on the image, are approximately..
Wall thickness of pipe + 3 mm.
This space is necessary, to do not damage the flange face, during the welding process.
A disadvantage of the flange is, that principle always firstly a pipe must be welded and then just a fitting. A combination of flange and elbow or flange and tee is not possible, because named fittings have not a straight end, that complete slid in the Slip On flange.
Read More : mechanical design textbooks
Socket Weld flange
Socket Weld flanges were initially developed for use on small-size high pressure piping. Their static strength is equal to Slip On flanges, but their fatigue strength 50% greater than double-welded Slip On flanges.
The connection with the pipe is done with 1 fillet weld, at the outside of the flange. But before welding, a space must be created between flange or fitting and pipe.
ASME B31.1 1998 127.3 Preparation for Welding (E) Socket Weld Assembly says..
In assembly of the joint before welding, the pipe or tube shall be inserted into the socket to the maximum depth and then withdrawn approximately 1/16″ (1.6 mm) away from contact between the end of the pipe and the shoulder of the socket.
The purpose for the bottoming clearance in a Socket Weld is usually to reduce the residual stress at the root of the weld that could occur during solidification of the weld metal. The image shows you the X measure for the expansion gap.
The disadvantage of this flange is right the gap, that must be made. By corrosive products, and mainly in stainless steel pipe systems, the crack between pipe and flange can give corrosion problems. In some processes this flange is also not allowed. I am not an expert in this matter, but on the internet, you will find a lot of information about forms of corrosion.
Also for this flange counts, that principle always firstly a pipe must be welded and then just a fitting.
Read More : mechanical engineering books pdf
Lap Joint flange
Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a “Lap Joint Stub End”.
These flanges are nearly identical to a Slip On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End.
Their pressure-holding ability is little, if any, better than that of Slip On flanges and the fatigue life for the assembly is only one tenth that of Welding Neck flanges.
They may be used at all pressures and are available in a full size range. These flanges slip over the pipe, and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).
Lap Joint flanges have certain special advantages..
- Freedom to swivel around the pipe facilitates the lining up of opposing flange bolt holes.
- Lack of contact with the fluid in the pipe often permits the use of inexpensive carbon steel flanges with corrosion resistant pipe.
- In systems which erode or corrode quickly, the flanges may be salvaged for re-use.
Read More : Top 10 Popular Software for Mechanical Engineers
Stub End
A Stub End always will be used with a Lap Joint flange, as a backing flange.
This flange connections are applied, in low-pressure and non critical applications, and is a cheap method of flanging.
In a stainless steel pipe system, for example, a carbon steel flange can be applied, because they are not come in contact with the product in the pipe.
Stub Ends are available in almost all pipe diameters. Dimensions and dimensional tolerances are defined in the ASME B.16.9 standard. Light-weight corrosion resistant Stub Ends (fittings) are defined in MSS SP43.
Threaded flange
Threaded Flanges are used for special circumstances with their main advantage being that they can be attached to the pipe without welding. Sometimes a seal weld is also used in conjunction with the threaded connection.
Although still available in most sizes and pressure ratings, screwed fittings today are used almost exclusively in smaller pipe sizes.
A threaded flange or fitting is not suitable for a pipe system with thin wall thickness, because cutting thread on a pipe is not possible. Thus, thicker wall thickness must be chosen…what is thicker ?
ASME B31.3 Piping Guide says..
Where steel pipe is threaded and used for steam service above 250 psi or for water service above 100 psi with water temperatures above 220° F, the pipe shall be seamless and have a thickness at least equal to schedule 80 of ASME B36.10.
Read More : 15 Essential Mechanical Engineering Skills You Must Master for a Successful Career
Blind flange
Blind Flanges are manufactured without a bore and used to blank off the ends of piping, Valves and pressure vessel openings.
From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed flange types.
However, most of these stresses are bending types near the center, and since there is no standard inside diameter, these flanges are suitable for higher pressure temperature applications.
Read More : Mechanical Design Explained: Principles, Applications, and Emerging Trends
Applications of Flanges in Different Industries
Oil and Gas Industry
- Used in refineries, pipelines, and offshore rigs.
- Withstands high pressure and corrosive environments.
Chemical Industry
- Resistant to chemical corrosion.
- Ensures safe transport of hazardous materials.
Power Generation
- Used in cooling systems, steam lines, and turbines.
- Handles high temperatures and pressures.
Water Treatment Plants
- Suitable for handling water and waste.
- Often made from corrosion-resistant materials.
Read More : Mechanical Engineering vs. Civil Engineering: A Comprehensive Comparison
How to Select the Right Flange?
Choosing the right flange depends on several factors:
- Material Compatibility: Ensure compatibility with the pipeline material.
- Pressure Rating: Check the flange’s pressure and temperature limits.
- Application Requirements: Consider ease of assembly, disassembly, and maintenance.
- Industry Standards: Adhere to standards like ASME, ANSI, or DIN.
Common Materials Used in Flanges
Flanges are crafted from a variety of materials, depending on the application and required properties.
Popular Materials Include:
- Carbon Steel: Ideal for high-temperature applications.
- Stainless Steel: Offers corrosion resistance.
- Alloy Steel: Suitable for heavy-duty operations.
- Plastic and PVC: Used in low-pressure systems.
Read More : Problem And Solution To Mechanical Engineering
Flange Types Overview
Some important information concerning flange types has been compiled into the below table. Although ASME standards are cited in the table, alternative international and national standards are available (DIN, EN etc.). ASME is however the most widely accepted piping standards organisation, and for this reason its standards have been cited.
In the below table, the ‘Faces’ column indicates the usual sealing face chosen per flange type. However, there may be exceptions to the rule depending upon the flange type. The table should be treated as a general overview table, whilst specific information should be sought in relevant standards.
| Flange Type | NPS (inch) | ASME Class | Faces | Joint Integrity | Weld | ASME Standards |
| Welding Neck Flange | All | All | All | High | One butt weld. | B16.5, B31.3 |
| Slip-on Flange | Many | Generally, ≤ 600 | FF, RF | Medium | One or two fillet welds. | B16.5, B31.3 |
| Socket Weld Flange | Generally, ≤ ½ to 2. Max ≤ 4 |
≤ 600 | FF, RF | Medium | One fillet weld. | B16.5, B31.3 |
| Lap Joint Ring Flange | Not used for small sizes. | NA | FF | NA | None | B16.5, B31.3 |
| Stub End of Lap Joint Flange | 150 to 2500 | FF, RF, RTJ | High | One butt weld. | B16.9, B31.3 | |
| Threaded Flange | Generally, ≤ ½ to 2. Max ≤ 4 |
≤ 300 | FF, RF | Low | None | B1.20.1, B31.3 |
| Blind Flange | All | All | All | NA | None | B16.5, B31.3 |
Flange Type Summary Table
Table Key: FF– flat face. RF–raised face. RTJ–ring type joint.
Read More : The Mechanical And Thermodynamical Theory Of Plasticity
FAQs About Types of Flange
Q1: What are the most commonly used flanges in the industry?
The most common types are weld neck, slip-on, blind, and threaded flanges. Each serves a specific purpose, depending on the application and pressure requirements.
Q2: How do I know which flange to choose for my system?
Consider the operating pressure, temperature, and compatibility with your pipeline material. Consulting industry standards can help guide your decision.
Q3: Can flanges be used in high-pressure applications?
Yes, flanges like weld neck and socket weld flanges are designed to handle high-pressure systems effectively.
Related Topics
-
Why Seals Play a Critical Role in Preventing Leakage: An In-Depth Guide
-
Top 10 Popular Software for Mechanical Engineers
-
15 Essential Mechanical Engineering Skills You Must Master for a Successful Career
-
Mechanical Design Explained: Principles, Applications, and Emerging Trends
-
Mechanical Engineering Handbook 3rd Edition
-
Objective Mechanical Engineering
-
Mechanical Engineering vs. Civil Engineering: A Comprehensive Comparison
-
Heat Transfer Principles in Mechanical Engineering
