What’s the principle and characteristics of flat welding flange?

Flat welding flange is a kind of flange which is connected with vessel or pipe by Bai fillet weld, which belongs to arbitrary type flange. In the design, according to the integrity degree of the connection between flange ring and straight cylinder section, the integral or loose flange shall be checked respectively.

There are two kinds of flange ring with neck and without neck. Compared with the welding neck flange, the flat welding flange has the advantages of simple structure and less material consumption, but its rigidity and sealing performance are not as good as those of the neck welding flange. Flat welding flange is widely used in the connection of medium and low pressure vessels and pipes.

ANSI ASME B16.5 304 raised face plain flanges

ANSI ASME B16.5 304 raised face plain flanges

Sealing principle of flat welding flange:

The two sealing surfaces of the bolt squeeze the flange gasket and form a seal, but this also leads to the failure of the seal. In order to keep the seal, it is necessary to maintain a large bolt force, and for this purpose, the bolt must be made larger. To tighten the nut, a larger bolt diameter is required. However, the larger the diameter of the bolt, the applicable flange will become bent, and the only way is to increase the wall thickness of the flange part. The large size and weight of the entire installation will be a special problem in the offshore environment, where weight is always a major concern. Furthermore, a flat welded flange is essentially an ineffective seal, requiring 50% of the bolt load to be used to squeeze the gasket and only 50% to maintain the pressure.

Characteristics of flat welding flange:

The flat welding flange not only saves space and weight, but also ensures that the joint will not leak and has good sealing performance. The reduction in the size of the compact flange is due to the reduction in the diameter of the seal, which will reduce the cross-section of the sealing surface. Secondly, the flange gasket has been replaced by the sealing ring to ensure that the sealing face matches the sealing surface. As a result, only a small amount of pressure is required to compress the sealing surface. With the decrease of the required pressure, the size and quantity of bolts can be reduced accordingly. Therefore, a new product with small volume and light weight (70% – 80% less than the traditional flange) is designed. Therefore, flat welding flange is a relatively high quality flange product, which reduces the quality and space, and plays an important role in industrial use.

Haihao Group manufacture flange products more than 30 years,the products sells well all over the world for the high quality.If you have any question,please contact us! Email:sales@haihaogroup.com


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