Flanges are piping components used to connect pipes to each other, to fittings, valves, pressure vessels, and strainers. They are connected together by bolting and using a gasket in between as sealing. Technicians apply specific spray flanges or spray guards to prevent leaks.
There is a need for special protection against what is corrosive, flammable, toxic, or volatile. However, this article will focus on different types of flanges and their applications.
What are the different types of flanges?
There are around ten main types of flange in piping—each has a distinct purpose. They include;
- Slip-on flange
- Blind flange.
- Lap joint flange
- Weld neck flange
- Reducing flange
- Socket weld flange
- Threaded flange
- Long weld neck flange
- Orifice flange
- Swivel flange
Aside from these types, this article will also discuss different types of flanges based on their uses, standardization, materials, and manufacturing process.
Weld neck flange
This is the type of flange designed and developed to be joined in a piping system by welding it. Weld neck flange has different specifications, and it is expensive due to the cost of material used in production. It is mainly used in high-stress applications, such as pipelines.
Socket weld flange
Like the weld neck, socket weld flanges are used on high-pressure pipes that are smaller in size. This flange is mounted by inserting the pipe into the socket opening and doing a single fillet weld on the outside to hold the flange properly and prevent any form of leaks. This enables a smooth flow of gas or fluid inside the pipe.
As the name indicates, a blind flange is a strong disk used to create a stop or block off a pipeline. It is designed like other flanges with mounting holes to bolt it, and it has sealing rings to prevent leaks. The only difference is that they don’t have openings to allow fluids to flow through like other types. They can be mounted between two open flanges to block off the flow of fluid in a pipeline.
A slip-on flange is a type of flange that is connected to a fitting or pipe with two fillet welds. One on the inside, the other outside of the cavity of the flange.
The outside diameter of the connecting pipe is smaller than the bore size of the slip-on flange because the pipe has to be inserted into the flange by applying a fillet weld. This type of flange is known as a “Hubbed flange” and is easy to recognize due to its small and slim shape.
Threaded flanges have threads on their openings and are joined to pipes by screwing the pipes onto the flanges. These types of flange do not require welding. However, in some cases, small welds are applied to strengthen the connection.
These flange types are available in different pressure ratings and sizes up to 4 inches. They are, however, used mostly on low-pressure, low-temperature applications, such as air and water utility services.
Threaded flanges are also mandatory requirements in highly flammable areas, such as gas plants, as welding in such areas is extremely dangerous.
Lap joint flange
Lap joint flanges have a flat face and are always used along with a stub. Lap joints resemble a slip-on flange by design, except for the radius at the crossing of the flange. Another difference between them is that the lap joint has a bore where the flanged side of the stub end fits in.
The use of a lap joint flange and a stud is cost-effective for nickel alloy or stainless steel pipelines as the lap joint flanges are made of lower-grade material—carbon steel. The stub end has to match the pipeline material, which is usually of a higher grade than the lap joint flange.
As the name suggests, reducing flange is used to reduce the size of a pipe. You can safely reduce the size by 1 or 2. It is available in different material grades and sizes. However, they are not generally available in stock.
This is a special type of flange, and it is typically used in pairs. The Orifice flange is used together with the orifice plate for measuring the flow of gas or liquid in a piping system. They have drilled-tapped holes in the flange rims to connect with metering pipes. The orifice flange is usually made of a welding neck flange. Sometimes, the end connections are made of threaded or slip-on flanges.
Ring joint flange
A ring joint flange is designed with a groove slot where a metal ring gasket fits into it to create a sealing with the mating flange. This type of flange usually comes in two shapes—octagonal or oval.
It is typically used in corrosive applications because it is made of 316 stainless steel, a popular alloy with molybdenum. This alloy has enhanced corrosion resistance from chloride and other acids.
Long weld neck flange
The long weld neck flange is similar to the normal weld neck flange, but the neck is way longer than the flange. These types of flanges have different shapes and wall thicknesses. They are sometimes used as nozzles for a column or barrel. They usually come in two types—Equal long weld neck barrel (E) and long weld neck heavy barrel (HB).
Swivel ring flange
The swivel ring flange resembles the lap joint and stub end flange. The major difference is that the swivel is used on high-pressure and subsea and offshore applications. This flange is used to adjust bolt-hole misalignment via a rotational adjustment through the bolt-hole patterns.
This flange type is used for specific needs in oil and gas, petrochemicals, and many other industries to provide different solutions to piping systems
Types of flanges based on standardization
These are the types of flanges that follow certain standardizations.
ANSI flanges are types of flanges used to connect two pipes or fittings together. They are designed to provide secure and reliable connections. This type of flange follows the American National Standards Institute (ANSI) standards.
They come in different classes based on their pressure ratings and are used in different applications because of their standard capability and dimensions across different welding applications. ANSI class rating of a flange is the highest amount of increase in temperature a flange can withstand. There are 7 pressure classes, which include 150, 300, 400, 600, 900, 1,500, and 2,500.
Welding neck flange, slip-on flange, socket weld flange, lap joint flange, threaded flange, and blind flange are the most common types of ANSI flange.
PN stands for pressure normale and prefixes the pressure rating of the flange. For example, a PN25 is forged to work up to 25 bar effectively. The typical PN ratings are PN6, PN10, PN16, PN25, PN40, PN64, and PN100. They adhere to the European pressure rating standards and are mostly used in European piping applications.
The American National Standards Institute (ANSI) refers pressure/temperature rating to class.
The American Society for Testing and Materials (ASTM) is a specification that covers stainless steel and rolled or forged alloy pipe flanges, forged valves, fittings, and other parts of high-pressure piping.
So, ASTM flanges are flanges that comply with specific ASTM testing criteria and material and dimension standards. The American Society for Testing and Material Specifications ensures quality in piping applications.
DIN stands for Deutsches Institut für Normung, which is translated to German Institute for Standardization. DIN follows similar standards to the ANSI and ASME flanges. They set industry standards for quality safety and assurance, including material requirements, temperature, and pressure rating. They come in different shapes and sizes and are mostly used in European piping systems. DIN flanges can be blind flanges, slip-on flanges, lap joint flanges, or weld neck flanges.
Types Of Flange Based On Materials & Manufacturing Process
These types of flanges are grouped based on the materials used and their manufacturing process.
A metal flange is a term used to describe different types of flange forged with cast iron, carbon steel, stainless steel, and alloy steel. Metal or steel flange is used to join pipes or connect mechanical sections of pipes to a pump, valves, fittings, pressure vessels, or any other piece of piping equipment.
Flanges can either be forged or cast, and each method has its advantages and disadvantages, depending on the application you use them on. Casting is a process where a metalsmith heats up a metal until molten, then pours it into a vessel or a mold to create a designed shape. They are made with different materials, such as stainless steel, ductile iron, cast iron, or aluminum.
Some of the advantages of cast flanges are their low technical requirements, low cost, and a short mass production cycle.
Forged steel flange
This refers to any type of flange manufactured through a forging process. It could be a blind flange, welding neck flange, threaded flange, or any other flange that is manufactured by forging. Forged steel flanges are mostly used in high-pressure applications.
Types Of Flange Based On Speciality
These are special flanges designed for a specific purpose.
The split flange is designed for a specific purpose—to simplify installation and maintenance. It has two interlocking pieces bolted around a fitting or pipe. Split flanges are easier to install and remove. They are not welded or installed with several bolts. Instead, they are usually installed with one bolt to hold the two interlocking pieces together.
This flange type is commonly used in construction to prevent water from entering a concrete structure or building. They form a seal around pipes passing through concrete walls.
Other Types Of Flanges
These types can also be found as part of the first ten flanges above.
Plate flange, also called slip-on flange, flat flange, plain flange, etc., is a circular plate that is welded onto the end of another pipe and allows it to be bolted to another pipe. They are typically used in water or fuel pipelines. There’s always a gasket in between the two plate flanges before tightening them together.
Flanged pipe joint
As the name suggests, flanged pipe joints are essential for joining pipes or attaching to valves, fittings, and other piping components by using bolts and gaskets. They come in various types and sizes and are used for different purposes.
Steel lap joint flange
Steel lap joint flanges are typically used in applications that require frequent assembling and disassembling. They are best for easy piping alignment and bolting and are used in conjunction with a lap joint stub end. They come in different sizes, prices, and grades to meet different needs.
Round flanges are typically circular in shape and like other flange, they are used for connecting two pipes or connecting pipes to fittings, valves, or equipment. Their round and flat design ensures a leak-proof connection.
PTFE Lined Reducing Flange
As the PTFE (Polytetrafluoroethylene) lined reducing flange name suggests, it is a type of flange used to connect pipes of different sizes together. It is best used in corrosive material and high-pressure applications because it provides a non-reactive surface.
Flanges is like a plug-in the piping system that makes pipeline applications versatile and easy. From sturdy Weld neck to adaptable split flanges and puddle flanges, each serves a distinct purpose.
In piping applications, flanges ensure easy connections, precise measurements, and structural integrity. They are more than components; they are the solutions that hold piping networks together when the work becomes difficult.