3、 CTOD (Crack Tip Opening Displacement) test As mentioned above, the welded joint of the all welded valve body pipeline pneumatic ball valve body is the biggest hidden danger for the integrity of the valve pressure boundary. However, the Charpy impact test, the traditional test method for evaluating the toughness of welded joints, is actually an indicator to measure the impact resistance of welded joints, It can not fully reflect the true toughness of welded joints, nor can it explain the failure mechanism of welded joints, nor can it reflect the impact of welding residual stress, geometric size constraints of welded joints and other factors on toughness. Therefore, the Charpy impact toughness value used to evaluate the toughness of welded joints has obvious limitations.

2、 There are many kinds of butterfly valves, and there are many classification methods.
1. Classification by structure
(1) Center sealing butterfly valve
(2) Single eccentric sealing butterfly valve
(3) Double eccentric sealing butterfly valve
(4) Triple eccentric sealing butterfly valve