1、Bonnet is the type of mechanical compression, 

2、Valve bonnet seal ring is used in 6B flanges with standard flanged connections, it has the face seal with good seal performance, but it should have high accuracy.

3、 Valve bonnet seal ring can be reused in the field in the case of  the appearance with no damage.

4、 The hardness of valve bonnet seal ring must be15~20HB lower than the mating flange face hardness.

5、 The seal faces of valve bonnet seal ring, including the bevel faces, shouldn’t have the scratches, knock marks, cracks and defects. Its surface roughness shouldn’t be larger than Ra1.6.