Thirteen Common Types of Flanges and Their Properties

A flange is a method of connecting pipes, valves, pumps and other equipment to form a piping system. A flange also provides easy access for cleaning, inspection or modification. Flanges are usually welded or screwed, and the flanged joints are made by bolting together two flanges with a gasket between them to provide a seal.

  There are many various types of flanges, today we will be looking into some of the most common types of flanges as well as their properties to help you understand flanges better: –

1. Slip-on Flanges

  • Slip-on flanges are also known as “Hubbed Flanges” and they are easy to identify because of their slim and compact shape.
  • The type of flange is slipped over the pipe and is settled by welding at both top and base side of the flange. 
  • Slip-on flanges are used to provide sufficient strength to the connection and prevent leakage. 
  • This type of flange is generally favored over weld neck flanges as less accuracy is required when cutting pipe to length, the cost of manufacture is lower but there is almost the same outcome.

 2. Blind Flanges

  • This is a flange without a bore. 
  • Blind flanges are also known as a blanking flange, it is used to fix or seal an end of a piping framework or shut off a piping system or vessel opening. 
  • Inspection of vessels or piping system is easier and simpler to access it. 
  • A blind flange can be supplied with or without hub varying on the requirements.


3. Lap-Joint Flanges

  • A lap-joint flange is similar to a slip-on flange, but it has a radius at the intersection of the bore and the flange face to accommodate a lap stub end.
  • The face on the stub end of a lap-joint flange forms the gasket face on the flange.
  • This type of flange is used in applications in which the section of piping systems needs to be dismantled quickly and easily for inspection or replacement.


4. Socket Weld Flanges

  • A Socket Weld Flange is similar to a slip-on flange in outline, but the bore is counter-bored to accept pipe.
  • The diameter of the remaining bore is similar to the inside diameter of the pipe.
  • The flange is attached to the pipe by a fillet weld around the hub of the flange.
  • An optional interval weld may be applied in high stress applications.
  • A socket weld flange’s biggest use is in high pressure systems like hydraulic and steam lines.


5. Threaded Flanges

  • A threaded flange is similar to a slip-on flange in outline, but the bore is threaded, thus enabling assembly without welding.
  • The bore will obviously restrict its application to relatively low-pressure piping systems.
  • The flange may be welded around the joint after assembly, but this is not considered a satisfactory method of increasing its applications.


6. Weld-Neck Flanges

  • As its name suggests, a weld-neck flange is a flange attached by welding neck of flange to a pipe.
  • This type of flange is expensive because of its long neck, but it is more suitable for high stress applications as the neck provides important reinforcement to the flange.
  • The bore of the flange matches the bore of the pipe, lowering turbulence and erosion.


7. Orifice Flanges

  • The function of an orifice flange is to give access to a line for metering of gases or liquids.
  • An orifice plate is clamped between a pair of flanges when installed in a line and the whole assembly is referred to as an orifice flange union.
  • Jack-screws within the assembly enable removal of the orifice plate.
  • The orifice plate, the metering device, consists of a thin plate with a concentric, square edge, circular hole in the center.
  • Two pressure tap-holes are drilled in each flange to determine the pressure difference through the orifice.


8. Groove Flanges / Tongue Flanges

  • A groove flange is constantly paired with a tongue flange.
  • The tongue flange has the face with a raised ring (the tongue). One flange has a machined raised ring (also called the tongue) and the other one has machined groove depression (also called the groove). Those two flanges should match with each other perfectly.
  • Tongue-and-groove facings are regulated in both large and small types. These two flanges are mainly used for pump covers and valve bonnets.
  • Tongue-and-groove joints have the benefit of being self-aligning and act as a reservoir for the adhesive. Major machining operations are not necessary especially thanks to the scarf joint keeping the axis of loading in line.


9. Long Neck Flanges

  • Long neck flanges are unique due to their simple connectivity with other pipes.
  • Moreover, these flanges are extensively used in refining industries for linking purposes.


 10. Spectacle Flanges

  • A spectacle flange is a pressure retaining plate with one solid end and one open end connected with a web or tie-bar.
  • The open end forms the seal between two flanges and permits normal flow of fluid through pipe work in normal operation.
  • If the solid end is swung into position, the flange will effectively blanks the pipe and halts the flow.


11. Expanding Flanges

  • Expanding flanges, also known as “expander flanges”, are used to increase the bore of the pipeline from a specific point to another or to connect pipes to other mechanical devices like pumps, compressors, and valves that have different inlets sizes.
  • An expanding flange has a welding neck flange with a larger bore on the non-flanged end.
  • Expanding flanges can be used to increase the run pipe bore only by one or maximum two sizes and not more.
  • Expander flanges are a cheaper and lighter solution compared to the combination of a buttweld reducer and a standard flange.


12. Reducing Flanges

  • Reducing flanges, also known as reducer flanges, have the opposite function as expander flanges, this is because reducer flanges are used to decrease the bore of a pipeline.
  • The bore of the run pipe can be safely reduced by only 1 or 2 sizes; an otherwise solution based on the combination of a butt weld reducer and a standard flange has to be used.
  • Reducing flanges are available in many sizes and material grades, and are not usually available from stock.
  • Reducing flanges follow the same procedures in terms of specifications, sizes and material grades as expander flanges.


13. Swivel Ring Flanges

  • Swivel ring flanges assist the alignment of the bolt holes between the two mating flanges, a feature that is helpful in many circumstances, like the installation of large diameter pipelines, subsea and offshore pipelines, pipe works in shallow waters and similar environments.
  • Swivel flanges are used to suit oil, gas, hydrocarbons, water, chemical and other demanding fluids in petrochemical and water management applications.
  • In the case of a large diameter pipeline, the pipe is fitted, at one end, with a standard welding neck flange, and with a swivel flange at the other end: by simply rotating the swivel flange on the pipe, the operators can achieve a perfect alignment of the bolt holes in a much easier and faster way.


Overall, there are many different types of flanges available and manufactured by Shinsei Industry Sdn Bhd. By knowing different types of flanges, you will have a vast variety and be able to make a well-informed decision when you are purchasing flanges for your project next time.