Regarding the commissioning of control valves

Generally, that’s how two limit switches are adjusted; if the switching time is required, the sensitivity also needs to be adjusted

Accuracy, hysteresis, starting air pressure, leakage test, pressure resistance test, etc.

Is the construction team also responsible for debugging?

Of course it needs to be debugged; we usually test the fully open and fully closed positions as well as the 50% position. Are there any experts?

Commissioning of control valves: Instrumentation equipment is subjected to mechanical stresses caused by handling or assembly during installation, which can alter its performance; generally, however, this impact is relatively minor. However, for reliability reasons, after the control valve is installed, on-site commissioning should be carried out prior to starting up production, in two steps: line-by-line commissioning and system commissioning. 2.1 Line debugging: Line debugging is used to check whether the connections of the signal lines, air supply pipelines, or hydraulic pipelines connected to the control valve are correct. 1) Connection of the control valve input signal: Usually, it is checked together with the valve positioner. The input signal for the control valve comes from the controller; a start signal is sent out by the controller to check whether the control valve is in the starting position ； Output an end-position signal to check whether the control valve is at the end position. To this end, it is necessary to check the pressure of the air supply source, the proper operation of the filter regulator, the oil pressure supplied by the hydraulic system, whether the power supply is functioning properly, and whether the output signals are correct. Additionally, at least 5 points within the measurement range should be selected to verify that the required relationship between the input signals and the valve position holds true. It is necessary to check whether the operation mode of the air-open and air-close functions is correct, and whether it meets the process requirements of the production process. 2) Connection of the control valve’s output signal: The control valve’s output signal is a valve position signal, which can be either an analog signal or a digital signal. While checking the input signal to the control valve, it is necessary to verify whether the valve position signal is correct. When using a HART or intelligent electric valve actuator to electronically control the valve positioner, it is necessary to check whether the valve position information is transmitted correctly. During the full stroke operation of the control valve, it is necessary to check whether there is mechanical vibration or abnormal noise in the valve stem and valve seat. 3) Adjustment of the handwheel mechanism: Check whether the handwheel mechanism can rotate and operate properly, and whether the limit and locking devices function correctly. 4) When the deviation exceeds the allowable limit, corresponding adjustments should be made. For example, change the position of the valve position switch, and check for leaks in the wiring or pipelines.

Calibrating a control valve is simple: first, check the signal circuit, then calibrate it in conjunction with the positioner, and adjust the air pressure – generally, perform calibration at 0%, 25%, 50%, 75%, and 100% points, and then calibrate from 100% down to 0%.

General debugging mainly involves adjusting the control circuits and correcting the accuracy of the adjustment positions; it is also necessary to determine the time required for the valve to move from full open to full closed, as well as the time it takes to reach full open status, based on the signals output by the DCS.

For the individual testing of control valves, it can be done simply in this way; however, it is best to test the intermediate positions (25%, 50%, 75%) as well as the full range of movement back and forth.