Do you recognize these 12 commonly used steel flanges in industrial projects

First, a basic introduction to flanges: Flanges, gaskets, and fasteners are generally referred to as flange joints.

Applications: Flange joints are a very common and widely used component in engineering design. They are essential parts for piping design, pipe fittings, and valves, and are also necessary components in equipment and equipment parts (such as manholes, sight glasses, and liquid level gauges). In addition, flange joints are frequently used in other disciplines such as industrial furnaces, thermal engineering, water supply and drainage, heating and ventilation, and automation.

Materials: Forged steel, WCB carbon steel, stainless steel, 316L, 316, 304L, 304, 321, chrome-molybdenum steel, chrome-molybdenum-vanadium steel, molybdenum-titanium steel, rubber-lined, fluoropolymer-lined materials.

Classifications: Flat-face flanges, neck flanges, weld neck flanges, ring flanges, socket flanges, and blind flanges, etc.

Execution Standards: Includes GB series (National Standard), JB series (Ministry of Machinery Industry), HG series (Ministry of Chemical Industry), ASME B16.5 (American Standard), BS4504 (British Standard), DIN (German Standard), and JIS (Japanese Standard).

International Pipe Flange Standard System: Internationally, there are two main pipe flange standard systems: the European system, represented by German DIN (including the former Soviet Union), and the American system represented by American ANSI.

Second, 12 Flange Types and Sealing Surface Forms:

1. Plate-type slip-on flange (Chemical Standard HG20592, National Standard GB/T9119, Machinery JB/T81).

Advantages: Easy to source materials, simple to manufacture, low cost, widely used.

Disadvantages: Poor rigidity, therefore it cannot be used in chemical process piping systems with supply and demand requirements, flammable, explosive, or high vacuum requirements, or in highly hazardous or extremely hazardous environments.

2. Neck slip-on flange belongs to the national standard flange system. This is one form of the national standard flange (also known as the GB flange), and it is one of the commonly used flanges on equipment or pipelines.

Advantages: Convenient on-site installation, eliminating the need for weld seam pounding.

Disadvantages: The neck height of the neck flange is lower, which increases the flange's rigidity and load-bearing capacity. Compared with the weld neck flange, it requires more welding work, consumes more welding rods, and cannot withstand high temperature, high pressure, repeated bending, and temperature fluctuations.

3. Weld Neck Flange

The sealing face forms of weld neck flanges include: raised face (RF), recessed face (FM), raised face (M), tongue and groove (T), grooved face (G), and flat face (FF).

Advantages: The connection is not easily deformed, the sealing effect is good, and it has a wide range of applications. It is suitable for pipelines with large temperature or pressure fluctuations, or for high temperature, high pressure, and low temperature pipelines. It is also used for pipelines transporting expensive media, flammable and explosive media, and toxic gases.

Disadvantages: Weld neck flanges are bulky, heavy, expensive, and difficult to install and position. Therefore, they are more susceptible to damage during transportation.

4. An integral flange is a type of flange connection. It belongs to the category of weld neck steel pipe flanges. Materials include carbon steel, stainless steel, and alloy steel. In domestic standards, integral flanges are represented by "IF". They are mostly used in high-pressure pipelines. The manufacturing process is generally casting. The type of integral flange is indicated by "IF". It is generally a raised face (RF), but in flammable, explosive, or highly hazardous applications, other sealing face types such as raised face (MFM) and tongue and groove (TG) can be selected.

5. A socket weld flange is a flange where one end is welded to a steel pipe, and the other end is bolted.

Sealing face types: Raised face (RF), raised face (MFM), tongue and groove (TG), ring joint (RJ)

Applications: Boilers, pressure vessels, petroleum, chemical, shipbuilding, pharmaceutical, metallurgy, machinery, stamped elbows, food processing, etc. Commonly used in pipelines with PN≤10.0MPa and DN≤40.

6. Threaded flanges are non-welded flanges where the inner bore is machined with pipe threads and connected to a threaded steel pipe.

Advantages: Compared to flat-welded or weld neck flanges, threaded flanges are easier to install and maintain, and can be used on pipelines where welding is not permitted on-site. Alloy steel flanges have sufficient strength but are difficult to weld or have poor weldability; threaded flanges can also be chosen in these situations.

Disadvantages: Threaded flanges are not recommended for use in conditions of rapid temperature changes in pipelines or temperatures above 260℃ or below -45℃ to prevent leakage.

7. Weld ring loose flanges are movable flanges, generally used with water supply and drainage fittings. Manufacturers typically ship expansion joints with one flange at each end, directly bolted to the pipelines and equipment in the project.

Function: The purpose of using weld ring loose flanges is generally to save materials. Their structure consists of two parts: one end of the steel pipe connects to the pipeline, and the other end has a weld ring. The flange uses a lower-grade material, while the steel pipe uses the same material as the pipeline, achieving material savings.

Advantages:

1. Cost savings. When the pipe material is special and expensive, welding flanges of the same material is costly.

2. Inconvenient for welding, processing, or requiring high strength. Examples include plastic pipes and fiberglass pipes.

3. Convenient for construction. For example, easy to align flange bolt holes during connection, or to prevent changes in flange bolt holes when replacing equipment later.

Disadvantages:

1. Low pressure resistance.

2. Low strength at the weld ring (especially when the thickness is less than 3mm).

8. Flat-faced weld ring loose flanges are movable flanges. They are directly bolted to pipes and equipment in the project. The purpose of using flat-faced weld ring loose flanges is generally to save materials. Their structure is divided into two parts: one end of the steel pipe is connected to the pipe, and the other end is made into a flange, with the flange fitting over the flange.

Advantages:

1. Convenient for welding, processing, or requiring high strength, such as plastic pipes and fiberglass pipes.

2. Facilitates construction; for example, the flange bolt holes are easy to align during connection, preventing changes in bolt hole alignment when replacing equipment later.

3. Saves costs when the price is high. Welding flanges of the same material to special pipe materials is expensive.

Disadvantages: Low pressure tolerance. Low strength at the weld ring (especially when the thickness is less than 3mm).

9. A flange cover, also called a blind flange or blind plate, is a flange without a central hole, used to seal pipe ends. Its function is the same as welded heads and threaded caps, except that blind flanges and threaded caps can be removed at any time, while welded heads cannot.

Flange cover sealing surfaces: flat face (FF), raised face (RF), male and female face (MFM), tongue and groove face (TG), ring joint face (RJ)

10. A lined flange cover is a type of blind flange where the side closest to the medium is welded with stainless steel, forming a single unit. Lined flange covers are used as blind plates on pipelines carrying corrosive media. The difference between a standard flange and a regular flange cover is the addition of a corrosion-resistant lining on the surface in contact with the medium.

11. American Standard (ASME) slip-on flanges are connected to pipe ends. They are primarily used to connect steel pipes. Slip-on flanges have holes for bolts to pass through, ensuring a tight connection between the two flanges. A gasket is used for sealing between the flanges. The gasket is placed between the sealing surfaces of the two flanges. After tightening the nuts, the pressure on the gasket surface reaches a certain value, causing deformation and filling any unevenness on the sealing surface, ensuring a tight, leak-proof connection. Flange connections are detachable. Based on the components being connected, they can be divided into vessel flanges and pipe flanges. Slip-on flanges are suitable for connecting steel pipes with a nominal pressure not exceeding 2.5 MPa. Slip-on flanges are used for butt welding between flanges and steel pipes. They have a reasonable structure, high strength and rigidity, and can withstand high temperature and pressure, repeated bending, and temperature fluctuations, ensuring reliable sealing. Slip-on flanges with a nominal pressure of 0.25–2.5 MPa use a raised face sealing surface.

12. ASME (American Standard) welding flanges are components used to connect steel pipes, attached to the pipe ends. ASME welding flanges are manufactured using two methods: forging and casting.

ASME welding flanges can be divided into necked and neckless types based on whether they have a neck. An ASME welding flange consists of two flanges with a gasket, fastened together with bolts to complete the connection. ASME flanges have perforations for the bolts to secure the two flanges tightly together.