In the flange family, flat welding flanges have become an indispensable member of low-pressure pipeline systems due to their simple structure and economical cost. Flat welding flange, also known as lap welding flange, has an inner hole size that matches the outer diameter of the pipeline, a simple external design, and no complex flanges, making the installation process particularly convenient.

Flat welding flanges are mainly divided into two types: plate flat welding and neck flat welding. The plate type flat welding flange structure is the simplest and is suitable for pipeline systems with lower pressure levels and milder working conditions, such as civil water supply and drainage, HVAC, etc. The neck flat welding flange is designed with a short neck, which not only enhances the rigidity and strength of the flange, but also improves its load-bearing capacity, making it capable of withstanding higher pressure pipeline environments. It is widely used in the connection of medium and low pressure pipelines in industries such as petroleum, chemical, and natural gas.

The welding method for flat welding flanges adopts fillet welds, which fix the pipe and flange with two fillet welds. Although this type of weld seam cannot be detected by X-rays, it is easy to align during welding and assembly, and has a low cost. Therefore, it has been widely used in many situations where sealing performance is not required. The manufacturing of flat welding flanges follows multiple national standards, such as HG20593-2009, GB/T9119-2010, etc., ensuring the quality and performance of the products.