Butt-weld flanges are mainly used for gas valves and natural gas pipelines. The short neck improves the flange's stiffness and load-bearing capacity. Plate butt-weld flanges are used for general media. Welded neck flanges are suitable for flammable, explosive, corrosive, and toxic environments. The sealing surface of butt-weld flanges can be convex, concave-convex, and tongue-and-groove. They differ in structure, sealing effect, and strength.

Butt-weld flanges are generally called flat plates or lap-weld flanges. The connection between the butt-weld flange and the pipeline is achieved by inserting the pipeline into the flange bore to the appropriate position before lap welding. Characteristics of Butt-weld flanges: Butt-weld flanges not only save space and reduce weight but also ensure leak-proof joints with good sealing performance. The reduced size of compact flanges is due to the smaller diameter of the seals, which reduces the cross-section of the sealing surface. The advantages of butt-weld flanges are as follows:

1. Only minimal pressure is needed to compact the sealing surface of the butt-weld flange. As the required pressure decreases, the size and number of bolts required also decrease accordingly.

2. The production of butt-weld flanges can save materials and reduce costs. When the raw materials for the pipeline are special and expensive, the welding cost of the flange with the same raw materials will be high, and using this type of flange can effectively save material costs. It is conducive to construction; when the flange bolt holes are inconvenient to align during connection or to avoid replacing equipment flange bolt holes, etc., this type of butt-weld flange is very suitable.

3. Butt-weld flanges save space and reduce weight during application. The important thing is to ensure that the head does not leak. It has excellent sealing capabilities. The reduced size of compact flanges is because the diameter of the seal is reduced, which reduces the cross-section of the sealing surface. In addition, flange gaskets are now replaced by sealing rings to ensure excellent matching of butt-weld flange seals facing the sealing surface.

However, it also has some disadvantages: The disadvantages of butt-weld flanges:

The main disadvantage of butt-weld flanges is that they cannot guarantee leak-proofness. This is due to a lack of planning: The connection is dynamic, and factors such as thermal expansion and fluctuating cyclic loads can cause movement between the flange faces, affecting the flange's function, damaging its integrity, and leading to leaks.