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.

The measured inner wall has siltation layer or the pipe wall is worn, which changes the flow area and affects the measured value. This kind of fault only occurs after a period of operation. Please refer to fault case 8.
The deviation of the upstream flow condition of the flow sensor from the requirements is mostly caused by the improper installation of the sensor in the engineering design; However, it also happened that the engineering design installation was in good condition, but after a period of operation, there was a large error. According to common sense, it seemed impossible to judge that the flow condition was poor, but it did happen. Please refer to fault case 1.