faq banner
  • Home
  • FAQ
  • What is a flange? What are the types of flanges?

What is a Flange? What are the types of flanges?

When the pump is connected to the pipeline, we generally use flanges, unions or hoses for connection. For the application of medium and large pumps, we often use flanges as the main connection method. Flange refers to the disc-shaped parts used to connect pipes, containers, or fix the shafts. Usually, there are screws and threaded structures to fix them. Flanges are generally used in pairs, the most common in pipeline engineering. The typical connection consist of flanges, gaskets and screws. Gaskets are added to the two flanges and tightly fixed with screws. Widely used in chemical industry, petrochemical industry, firefighting, drainage or water treatment application for liquid transfer solution.


There are countless types of flanges. The commonly used materials are carbon steel, stainless steel, alloy steel, etc. In addition, the thickness, the number of screw holes, and the diameter of the flange need to be selected according to the operation requirements.


The common types of flanges can be divided into Slip On Flange(SO), Weld Neck Flange(WN), Threaded Flange(THDF), Lap Joint Flange(LJ), Socket Weld flange(SW), Blind Flange(BL), and other special types(Specialty Flange), the following basically introduces several main flange types.


Slip On Flange(SO)

A fairly common type with lower installation costs and lower requirements for precise pipe cutting. The steel pipe, pipe fittings are inserted into the inner hole of flange and connected to the pipe through a fillet weld at the flange top and bottom. Since the flange hole is larger than the pipe diameter, it usually requires more welding action than other flanges, so it can effectively prevent leakage. Compared with weld neck flange, it is only suitable for low and medium pressure applications due to the lower neck height.


Weld Neck Flange(WN)

It is a flange that is butt welded to the pipe or fitting, and its installation cost is higher. In contrast to the slip on flange, the distance between the welding joint and the joint surface is large, and the joint surface will not be deformed by the welding temperature. Weld neck flanges are not easily deformed and have high sealing properties, making them suitable for high temperature and high pressure, even for pipelines that transport flammable and toxic fluids.


Threaded Flange(THDF)

The inner hole of the flange is processed into a screw thread and connected with a threaded pipe, which belongs to a non-welded flange. The main feature is easy installation, disassembly and maintenance. However, considering the characteristics of thread structure, it is strongly influenced by the environment, and the temperature in the threaded pipe fluctuates greatly, so it is not suitable for high temperature and high pressure applications.


Lap Joint Flange(LJ)

It consists of two parts, the Stub End and the Backing Flange. The flange is placed on the stub end, and the stub end is butt welded to the pipe joint. The flange can move on the pipe joint. It is mainly used for pipe systems that need to be disassembled frequently for inspection and maintenance. The flanging of the stub end is the sealing surface, and the flange is used to clamp the end of the pipe and the stub end. Because flanging stub end can isolate the flange from medium, it is suitable for conveying corrosive fluids.


Socket Weld flange(SW)

The inner hole of flanges has a socket and is connected by inserting the pipe into the socket and fillet welding around the top. Usually used in smaller, high-pressure pipelines, but not for highly corrosive fluids.


Blind Flange(BL)

It is a flange without a hole in the middle for closing the end of the pipe, with mounting holes around the perimeter and the gasket sealing rings are machined into the mating surface. The function is the same as the head and the cap, and the blind flange is fixed with screws for easy disassembly.


PTCXPUMP sealless magnetic drive pump provides standard flange specifications(ANSI,JIS,DIN) for easy pipeline connection. It can adjust screw hole position to avoid leakage of inlet and outlet.

Best Solution For Chemical Transfer 
 PTCXPUMP Sealless Magnetic Drive Pump