2. Test results CTOD test system and weld CTOD sample after loading test. In the test, there are pop in HAZ samples, 8 effective samples in weld zone and 8 effective samples in HAZ, which meet the requirements of CTOD multi sample method. Wherein, the CTOD value of HAZ crack initiation point accounts for; C Critical CTOD value obtained by direct measurement= 0.05 Use the intersection point of multiple sample CTOD test regression line and crack growth 0.05mm vertical line to determine the CTOD value of the protrusion point; M is measured directly by the test. CTOD value of weld crack initiation point; C and critical CTOD value= 0.05 Determine the CTOD value of the protrusion point by the intersection of the regression line of the CTOD test of multiple samples and the vertical lines of the crack growth amount of 0.00mm and 0.05mm; M is measured directly from the test. See Table 1 for CTOD calculation results of welds and HAZ. Table 1 CTOD test results; c/ mm ; c/ mm ; C/mm heat affected zone 0.1970.240.53 weld 0.1960.230.91

2、 Operating principle of pneumatic actuator:
1. When the compressed air enters the pneumatic actuator from nozzle A, the gas pushes the double pistons to move in a straight line towards both ends (cylinder head end). The rack on the piston drives the gear on the rotating shaft to rotate 90 degrees counterclockwise, and the valve is opened. At this time, the gas at both ends of the pneumatic actuator valve is discharged with nozzle B. On the contrary, when the compressed air enters both ends of the pneumatic actuator from the nozzle B, the gas pushes the double plug to move in a straight line in the middle. The rack on the piston drives the gear on the rotating shaft to rotate 90 degrees clockwise, and the valve is closed. At this time, the gas in the middle of the pneumatic actuator is discharged with nozzle A. The above is the transmission principle of the standard type. According to the user's needs, the pneumatic actuator can be installed in the opposite transmission principle to the standard type, that is, the valve is opened when the alignment shaft rotates clockwise, and closed when it rotates counterclockwise. Single acting (spring return type) pneumatic actuator nozzle A is the air inlet, nozzle B is the exhaust hole (nozzle B should be equipped with a muffler). The air inlet of nozzle A is to open the valve, and the valve is closed by spring force when the air is cut off.
2. The single action here means that the cylinder is reset with a spring. When gas failure or power failure occurs, the valve is reset by the spring in the cylinder to close or open the valve. (Normally closed or normally open optional). Double acting means that the cylinder is opened and closed by compressed air.