The socket weld flange with neck and the butt weld flange with neck have significant differences in terms of weld form, material, nominal pressure, connection method, structural stiffness, manufacturing cost and inspection requirements. The detailed analysis is as follows:

Weld form

1. Socket weld flange with neck: The welding weld form between the pipe and the flange is fillet weld. This weld form is relatively simple, but the sealing performance and strength are relatively low.

2. Socket weld flange: The welding weld form with the pipe is circumferential weld. This weld form is more complex, but it can provide higher sealing performance and strength, and is suitable for harsh working conditions such as high pressure and high temperature. Material

1. Necked flat weld flange: The material is usually machined from ordinary steel plates that meet the required thickness. This material has a relatively low cost, but its strength and corrosion resistance may be relatively weak.

2. Necked butt weld flange: The material is mostly machined from forged steel parts. Forged steel parts have higher strength and corrosion resistance, and can better adapt to harsh working conditions such as high pressure and high temperature.

Nominal Pressure

1. Necked flat weld flange: The nominal pressure range is usually 0.6 - 4.0 MPa. This pressure level is suitable for medium and low-pressure pipeline systems.

2. Necked butt weld flange: The nominal pressure range can reach 1 - 25 MPa. This pressure level can meet the requirements of high-pressure pipeline systems, and is suitable for high-temperature, high-pressure, low-temperature, and working conditions with severe temperature and pressure fluctuations. Connection method

1. Necked plain weld flange: Generally, it can only be connected to the pipeline, but not directly to the butt-welding pipe fittings. Its connection method is relatively simple, but the flexibility is lower.

2. Necked butt-welding flange: It can be directly connected to all butt-welding pipe fittings (including elbows, trisets, reducers, etc.) and even the pipeline. This connection method is more flexible and can adapt to more complex piping systems.

Structural stiffness and strength

1. Necked plain weld flange: Although the neck design increases the strength of the flange, compared with the necked butt-welding flange, its structural stiffness is still lower.

2. Necked butt-welding flange: Through the conical neck structure, it is welded to the pipeline, which has higher structural stiffness and strength. The neck height increases with the nominal pressure, reaching up to 89mm, and the structural stiffness is increased by approximately 50% compared to the plain weld flange.

Manufacturing cost and inspection requirements

1. Necked plain weld flange: The manufacturing cost is relatively low because its material and manufacturing process are relatively simple. Additionally, necked plain weld flanges with a nominal diameter greater than 250mm usually do not require non-destructive testing, further reducing the cost.

2. Necked butt-welding flange: The manufacturing cost is relatively high because its material and manufacturing process are more complex. Moreover, necked butt-welding flanges with a nominal diameter greater than 250mm require 100% radiographic testing and 20% ultrasonic testing to ensure the weld quality. These inspection requirements increase the manufacturing cost and time.