Typical bonnet seal ring is applicable to the flange faces formed by pair of small grooves. Most of the small grooves have two angle faces and one flat bottom. Most of the gaskets have an octagonal cross section, but in some gaskets the small grooves are oval-shaped. The gasket can be fitted into the smasufficient size so that the ll groove, but the most are of two mating flange faces are separated. If the flanges do not coincide, the pipeline will be leaked during the feeding. Valve bonnet seal ring must be of full load and cannot touch the flange face, which shall cause the front gasket deformation. In addition, if the valve bonnet seal ring is not well aligned, it will occur that one face is sealed and the other face is leaked during the feeding.Because the levels of both internal and external should be accordance with the design requirements on both sides at the same time, prior art gaskets use face to face contact and cannot provide the effective seal.