A butt weld flange is a flange that is connected to a vessel or pipe through fillet welding. It can be any flange. Depending on the integrity of the flange ring and straight section during design, inspect the integral flange or loose flange respectively. Butt weld flanges have both neck and no-neck types. Compared with neck weld flanges, butt weld flanges have a simpler structure and less material, but their rigidity and sealing performance are not as good as neck weld flanges. Butt weld flanges are widely used in the connection of medium and low pressure vessels and pipes.

Butt weld flanges not only save space and weight, but more importantly, they ensure that the joint does not leak and has good sealing performance. Due to the reduction in the diameter of the sealing element, the size of the compact flange is reduced, which will reduce the cross-section of the sealing surface. Secondly, the flange gasket has been replaced by a sealing ring to ensure that the sealing surface matches the sealing surface. In this way, only a small amount of pressure is needed to tightly compress the cover. With the reduction of the required pressure, the size and number of bolts can be reduced accordingly. Therefore, a new type of butt weld flange with small size and light weight (70% to 80% lighter than traditional flanges) has been designed. Therefore, the butt weld flange is a relatively high-quality flange product, reducing quality and space, and playing an important role in industrial applications.

Sealing principle of butt weld flange: The two sealing surfaces of the bolt squeeze the flange gasket to form a seal, but this will also cause seal damage. In order to maintain the seal, a huge bolt force must be maintained. Therefore, the bolt must be made larger. Larger bolts must match larger nuts, which means that a larger diameter bolt is needed to create conditions for tightening the nut. However, the larger the bolt diameter, the more the applicable flange will bend.

This method increases the wall thickness of the flange part. The entire equipment will require huge size and weight, which is a particular problem in marine environments, as in this case, the weight of the butt weld flange is always a major concern.