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.
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 available?
There are numerous flanges developed to support varying pipelines and plumbing works. Some of the most commonly accessed flanges include slip-on flanges, weld neck flanges, socket weld flanges, and blind flanges.
Let’s look at the detailed explanation of the working of these flanges.
Weld Neck Flange
A weld neck flange is also commonly called a tapered or high-hub flange. A pipe with a weld neck flange can move the tension within the pipe. This helps avoid pressure from accumulating and gathering at the bottom of the flange. Weld neck flanges are operable and compatible with high -and low-pressure pipelines. These pipes have a long and tapered ending that passes through the pipes.
Weld neck flanges consist of a circular fitting and a protruding edge around the circumference of the pipe. The maximum pressure yielded by a weld neck flange is 5000 psi.
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
A slip-on flange in nothing but a ring placed over a pipe end. The flange face extends a distance to apply a welded bead to the pipe’s inner diameter or ID. As the name suggests, these flanges slip over the pipe. Thus, the flange size is larger than the OD or outer diameter of the pipe such that the ring of the flange sits perfectly around the pipe. These flanges, known as slip-on flanges, cannot withstand high-pressure flow. Thus, slip-on flanges are ideally used for low-pressure applications.
Threaded Flange
Threaded flanges are extremely similar to slip-on flanges in terms of appearance. However, one of the major differences between a threaded and a slip-on flange is that threaded flanges have a bore that matches the ID or inner diameter of the pipe. Threaded flanges, as their name suggests have tapered pipe threads on the bore of the flange. These flanges are ideal for pipes with small diameters and a high-pressure flow of gases and liquids. The main and most important advantage of threaded flanges is that it does not require any welding.
Socket Weld Flanges
Socket weld flanges are a distinctive type of flange used in piping systems, offering advantages over other flange types. Unlike slip-on flanges that require two welds, socket weld flanges only need a single fillet weld on the outer side of the flange for a secure connection.
As per ASME B31.1 guidelines, connecting a socket weld flange involves inserting the pipe into the socket of the flange until it rests at the bottom. Then, the pipe should be slightly raised by 1.6 mm before welding. This deliberate gap ensures proper pipe positioning within the flange socket once the weld solidifies.
Blind Flange
In contrast to the various flange types discussed earlier, blind flanges stand apart as they lack a central opening. Their primary purpose is to seal off or “blind” a pipeline, valve, or pressure vessel or block the flow of fluids.
Blind flanges are crucial in withstanding substantial mechanical stress, primarily from system pressure and the required bolting forces.
One noteworthy advantage of blind flanges is their ability to provide easy pipeline access. They can be readily unbolted, allowing operators to perform tasks within the terminal end of the pipe. This versatility also extends to their use as manholes for pressure vessels on occasion.
Other Special Types of Flanges include:
- Spectacle Blind Flange
- Lap joint Flange
- Reducing Flange
- Square Flange
- Expander Flange
- Spade and ring spaces Flange
- Weldo Flange
- Nipo Flange
- Orifice Flange
- Loose Flange
- High Hub Bling Flange
- Screwed Flange
- Plate Flange
While flange shape is the most apparent classification method, several alternative approaches exist for categorizing flanges:
By Material Grade:
Flanges can be classified based on the type of material they are constructed from, such as stainless steel, carbon steel, or alloys, which is critical for their performance in different environments.
By Flange Face Type:
Flanges can feature various face types, including raised, flat, ring joint, male and female, tongue and groove, and lap joint. Each face type serves a specific purpose and suits different sealing requirements.
By Flange Finish:
Flanges can have different finishes, including smooth and serrated. The finish affects the sealing capability and is chosen based on the application’s needs.
By Dimensions:
Flanges are categorized by nominal size and pressure rating, ensuring compatibility and safety in various piping systems.
