Weld Neck Flange not only saves space, reduces the weight, the more important is to ensure that the joints do not leak, has good sealing performance. The reason for the reduction in the size of the compact flange is that the diameter of the seal is reduced, which will reduce the cross section of the sealing surface. Secondly, the flange gasket has been replaced by the seal ring to ensure that the sealing face matching face. This way, in order to compress the sealing surface requires only a small pressure. With the required reduction of the pressure, the size of the bolt and the required number can be reduced accordingly. So a new product, which has a small size and light weight (less than the weight of the traditional 70%~80%), is designed. Therefore, a relatively flat welding flange flange high-quality products, reducing the quality and space, which plays an important role for industrial use.