In industrial pipeline connections, flanges are common and critical components used to connect pipes, valves, and equipment. Among various types of flanges, "lap joint flange" and "SO flange" (Slip-On Welding flange) are two common and widely used types. Although they may seem similar in name, they have significant differences in design, connection method, and applicable scenarios.

This article will delve into the differences between lap joint flanges and SO flanges, helping you understand how to choose the appropriate flange connection for the right scenarios to ensure the efficiency and safety of your pipeline system. Let's now begin our exploration of the subtle distinctions between these two types of flanges.

Lap Joint Flange

Lap joint flange is a straightforward flange connection. It usually consists of two parts: the flat ring-shaped flange itself and a lap joint stub end that complements it. The connection method of the lap joint flange involves aligning the flat end of the lap joint stub end with the end of the pipe and securing the flange to the stub end with bolts.

The flange's flat face creates a gap with the pipe end, and thus, it is called a lap joint. Lap joint flanges are suitable for pipe connections that require frequent disassembly, such as systems where pipes need to be replaced regularly. Only the lap joint stub end needs to be replaced and the entire flange does not require replacement. Lap joint flanges are typically used in low-pressure, low-temperature, or non-critical applications, as their sealing capability is relatively inferior.

Slip-On Welding Flange

Slip-on welding flange is a common type of flange connection. It has a flat end that can be directly inserted into the pipe and then welded to connect it with the pipe. The connection method of the slip-on welding flange involves welding the flange's neck to the end of the pipe to create a sealed connection.

Slip-on welding flanges are suitable for general industrial pipe systems, especially for high-pressure and high-temperature applications, as welding provides a more reliable sealing capability and connection strength. Slip-on welding flanges are also suitable for situations where easy disassembly is required, although they are slightly more complex to disassemble compared to lap joint flanges, as they require cutting and re-welding.

Reference to: Wiki-Flange

Differences between Lap Joint Flange and Slip-On Flange

Lap joint flange and SO flange (Slip-On Welding flange) are two different types of flange connections, and they have distinct differences in design and connection method.

1. Design and Shape >> 

Lap joint flange: Lap joint flange typically consists of two parts: the flat ring-shaped flange itself and a lap joint stub end that complements it. The flange itself is a flat ring-shaped disc.

SO flange: SO flange is a flange with a welding neck. The welding neck is a cylindrical structure on the flange used for welding connection with the pipe.

2. Connection Method >>

Lap joint flange: The connection method of the lap joint flange involves aligning the flat end of the lap joint stub end with the end of the pipe and securing the flange to the stub end with bolts. The flange's flat face creates a gap with the pipe end, and thus, it is called a lap joint.

SO flange: The connection method of the SO flange is by welding the flange's welding neck to the end of the pipe to create a sealed connection.

3. Applicable Scenarios >>

Lap joint flange: Lap joint flange is suitable for pipe connections that require frequent disassembly, such as systems where pipes need to be replaced regularly. It is typically used in low-pressure, low-temperature, or non-critical applications as its sealing capability is relatively inferior.

SO flange: SO flange is suitable for general industrial pipe systems, especially for high-pressure and high-temperature applications, as welding provides a more reliable sealing capability and connection strength. It is also suitable for situations where easy disassembly is required, although it is slightly more complex to disassemble compared to lap joint flanges, as it requires cutting and re-welding.

Conclusion

In summary, lap joint flange and SO flange have differences in connection method and applicable scenarios. Therefore, when choosing the appropriate flange connection, it is essential to consider the specific requirements and application scenarios of the pipeline system.