How to debug a pneumatic shut-off valve

In my opinion, this issue should be understood in the following way: the debugging rules for electric valves and pneumatic valves are basically the same. When debugging a pneumatic programmable valve, one usually turns the electromagnet on or off to observe how the valve responds, and then checks whether the feedback signal from the sensor is normal. For pneumatic control valves, signals of 4, 8, 12, 16, and 20 mA are sent to determine whether the valve’s opening degree corresponds to 0%, 25%, 50%, 75%, or 100%. If a positioner is used, the debugging is carried out automatically; whereas with a mechanical positioner, it is necessary to adjust the zero-setting screw and range-setting screws inside the valve positioner

Agree with the second floor’s opinion. Electric and pneumatic systems differ only in their power source, which in turn leads to different components being used; the principle of their actuators remains the same. Pay attention to the following aspects during debugging: 1. Quality and pressure of the gas supply ； 2. Calibration of the valve positioner, that is, whether the conversion of electrical signals to pneumatic signals is accurate ； 3. Selection and performance of solenoid valves ；

The 2nd and 3rd floors are discussing pneumatic control valves, while the original poster is asking about shut-off valves; I think those are simply on/off valves, which should have two states – open and closed. A solenoid valve needs to be added for this.

Use a signal generator to output 4-20MA, and check whether the valve opening is correct as well as whether the valve’s fault status is accurate.

Debugging isn’t that simple; the position of the handwheel also needs to be taken into account.

I. Composition of the pneumatic diaphragm-type pneumatic control valve: It consists of an actuator and a valve body. Among them, the actuator is the driving device of the control valve; it generates a corresponding thrust based on the level of the signal pressure, causing the push rod to move accordingly, and thus enabling the valve core of the control valve to operate. Operating steps for pneumatic diaphragm-type pneumatic control valves: 1. Before checking the control valve, it is necessary to inquire with the process department about the properties of the medium in the pipeline, coordinate with them to switch to manual operation and connect the appropriate bypass lines, and obtain the relevant work permits. 2. Check whether the signal from the on-site control valve matches the DCS output, in order to determine if there are any faults with the DCS output module or the output safety barrier. It is also necessary to verify that the spring pressure of the control valve corresponds to that specified by the positioner. 3. Understand the operating principle of the control valve, send a signal to verify it, and confirm that the control valve operates properly. 4. When replacing the positioner, attention must be paid to its mode of operation. 5. Check whether the diaphragm is leaking air. When replacing the diaphragm of the actuator, be sure to turn off the air supply first. When removing the bolts, release pressure slowly, and be careful not to get injured by residual pressure when lifting the upper diaphragm cover. 6. Check whether the valve stem is stuck. When removing the control valve, the process team must close the upstream and downstream valves, open the vent valve, ensure that all fluid in the pipeline of the control valve has been drained, and wait until the temperature and pressure have returned to normal before proceeding with removal. II. Working principle of the cylinder-type control valve: Principle of two-position on/off operation (taking a small model as an example): It is controlled by a two-position three-way solenoid valve or a two-position five-way control valve; when the solenoid valve is energized, it changes the position of the valve spool relative to the air outlet holes, thereby enabling adjustment of the air flow path. Cylinder-type control valves can be operated remotely, manually opened and closed, or quickly activated and deactivated on-site using pneumatic buttons. 1. Components: The cylinder-type control valve consists of three parts: the valve body, the actuator, and the manual operating mechanism. 2. Cylinder-type control valves are generally classified into control type, on-off type, and quick shut-off control type. Steps for troubleshooting cylinder-type control valves: When checking such valves, note that the air supply pressure should be around 0.4–0.7 MPa; also ensure that there are no leaks or blockages in the instrument pipelines and connections. 1. Solenoid valves come in DC and AC types; attention should be paid to their supply voltage during inspection. 2. Some cylinder-type control valves do not have auxiliary lines or handwheels that can be modified; therefore, it is essential to coordinate with the process team during inspections to avoid disrupting the normal operation of the process. 3. When removing the solenoid valve, be sure to turn off the power first. When removing a cylinder-type control valve, it is essential to relieve pressure first.