Advantages: Easy to source materials, simple to manufacture, low cost, and widely used.
Disadvantages: Poor rigidity, unsuitable for use in chemical piping systems with high demands for safety, flammability, explosiveness, or high vacuum, as well as in high-risk environments. Seal face forms include flat and raised faces.
Type 2: Necked Flat-Welded Flange
A necked flat-welded flange is part of the national standard flange system (also known as GB flange), commonly used in equipment or piping.
Advantages: Convenient for on-site installation, eliminating the need for additional welding steps.
Disadvantages: The neck height is relatively low, which increases flange stiffness and load-bearing capacity. Compared to butt-welded flanges, it requires more welding work, consumes more welding rods, and is not suitable for high temperatures, high pressures, or repeated bending and temperature fluctuations.
Type 3: Necked Butt-Welded Flange
The seal face forms of necked butt-welded flanges include raised face (RF), flat face (FF), concave face (FM), convex face (M), tongue and groove face (TG), and groove face (G).
Advantages: Difficult to deform, excellent sealing performance, widely applied, and suitable for pipelines subjected to large temperature or pressure fluctuations, as well as high temperature, high pressure, and low temperature pipelines. It is also used for transporting expensive media, flammable and explosive substances, and toxic gases.
Disadvantages: Bulky, heavy, expensive, and challenging to install. Due to its size, it is more likely to be damaged during transportation.
Type 4: Integral Flange
An integral flange is a type of necked butt-welded steel flange, made from materials such as carbon steel, stainless steel, and alloy steel. It is represented by "IF" in domestic standards and is primarily used in high-pressure pipelines. The manufacturing process generally involves casting.
Advantages: Suitable for high-pressure pipelines.
Disadvantages: Seal faces are generally raised (RF), but for hazardous environments, other sealing faces like concave-convex (MFM) or tongue and groove (TG) can be selected.
Type 5: Socket-Welded Flange
A socket-welded flange has one end welded to a steel pipe, while the other end is bolted.
Seal face forms: Raised face (RF), concave-convex face (MFM), tongue and groove face (TG), and ring joint face (RJ).
Flange uses: Commonly used in boiler pressure vessels, petrochemical, shipbuilding, pharmaceuticals, metallurgy, machinery, stamping elbows, and food industries. Typically used for pipelines with PN ≤ 10.0 MPa and DN ≤ 40.
Type 6: Threaded Flange
A threaded flange has an internal thread that matches with a pipe's external thread for connection. This is a non-welded flange.
Advantages: Easier to install and maintain compared to flat-welded or butt-welded flanges, and suitable for pipelines where welding is not allowed. Alloy steel flanges are strong but difficult to weld, so threaded flanges are a good alternative.
Disadvantages: Not recommended for pipelines subjected to rapid temperature changes or where temperatures exceed 260°C or drop below -45°C, as leakage may occur.
Type 7: Butt-Welded Loose Ring Flange
A butt-welded loose ring flange is a movable flange plate, commonly used in drainage and water supply fittings. It is designed for cost-saving applications.
Flange Uses
Typically used in situations where material savings are required. The structure consists of two parts: one part welded to the pipe, the other as a butt-welded ring.
Advantages
Cost savings, especially when pipe material is expensive.
Convenient for construction, as flange bolt holes are easier to align.
Disadvantages
Low pressure tolerance.
Low strength at the weld ring, especially for thicknesses under 3mm.
Type 8: Flat-Welded Loose Ring Flange
A flat-welded loose ring flange is a movable flange plate, directly bolted to the pipe or equipment in engineering systems. It is used for cost-saving applications.
Advantages
Easy to weld and process, suitable for pipes like plastic or fiberglass.
Convenient for construction, as flange bolt holes are easier to align.
Cost-effective, especially when pipe material is expensive.
Disadvantages
Low pressure tolerance.
Low strength at the weld ring, especially for thicknesses under 3mm.
Type 9: Flange Cap
Also known as a blind flange, this type of flange does not have a hole and is used to seal the end of a pipeline. It serves the same purpose as a welded end cap or threaded pipe cap, but can be removed easily, unlike welded caps.
Seal face forms: Flat face (FF), raised face (RF), concave-convex face (MFM), tongue and groove face (TG), and ring joint face (RJ).
Type 10: Lined Flange Cap
A lined flange cap is a type of blind flange with a welded stainless steel lining on the side exposed to the medium. It is used in corrosive pipelines.
Advantages: The additional corrosion-resistant layer improves durability, especially in aggressive environments.
Disadvantages: Slightly more complex and costly than standard flange caps.
Type 11: ANSI Necked Flat-Welded Flange
A necked flat-welded flange is connected to the pipe ends. This type of flange features holes that allow bolts to connect the two flanges, with a gasket placed between the flanges for sealing. Once tightened, the gasket deforms, filling in the irregularities of the sealing surface to ensure a tight, leak-proof connection. This type of flange is a removable connection.
Flange uses: Suitable for pipe connections in pipelines with nominal pressure up to 2.5 MPa.
Advantages: Strong structure, good rigidity, and resistance to high temperatures, high pressures, and bending.
Seal face: Typically uses a concave-convex seal face (MFM).
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