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Actuator inspection 1. Inspection of the diaphragm chamber’s sealing performance: When the signal pressure range specified on the control valve’s nameplate is 0.2–1 kg/cm2 (the same applies throughout this text), compressed air at a pressure of 0.8 kg/cm2 is introduced into the diaphragm chamber. After the air supply is cut off, the pressure inside the diaphragm chamber should not drop by more than 0.007 kg/cm2 (5 mmHg) over a period of 5 minutes. 2. Inspection of the push rod’s movement and stroke: ① Apply a signal pressure in the range of 0–1 kg/cm2 to the diaphragm chamber; increase and decrease this signal pressure back and forth. The push rod should move smoothly and evenly, without any sticking or jumping. ② Adjust the preload of the compression spring so that the push rod starts to move when the signal pressure is 0.15 kg/cm2 (the starting signal pressure when used with a unit combination instrument is 0.2 kg/cm2). ③ Increase or decrease the signal pressure within the range of 0.2~1.0 kg/cm2; the stroke of the push rod should meet the maximum stroke requirement of the control valve. Inspection during assembly: 1. Before assembling the control valve, check whether the valve core, valve seat, and valve stem have any defects. The ground valve core should make tight contact with the valve seat, and the valve stem should be straight and smooth. 2. After the control valve and actuator are assembled, a signal pressure that causes the control valve to close is applied to the diaphragm chamber; the length of the valve stem is adjusted so that the valve core makes tight contact with the valve seat. For air-actuated shut valves, the signal pressure applied is 0.95 kg/cm2, while when used with unit combination instruments it is 1.0 kg/cm2. For air-actuated open valves, the signal pressure applied is zero.