Instrumentation: [Question of the Week] Week 49, 2011: What considerations should be taken when calibrating control valves after maintenance?

1. First, check the installation position of the actuator or the location of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is at 50% open, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. 2. Depending on whether the valve operates on air open or air close principle, adjust the feedback lever, baffle, or cam of the positioner so that the positioner and the control valve form a negative feedback system. Then send a standard signal to adjust the zero point and range until the requirements are met.

Make sure to follow the standard operating procedures. Minimize abnormal operations. Debug and test according to the usage method defined in the product manual. After verification, the pipes must be flushed promptly to remove potential hazards in operation.

This post was last edited by denghl on 2012-12-12 at 21:30. Reply to 1# Baghdad: ① First, check the installation location of the actuator or the position of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is open by 50%, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. ②Depending on whether the valve operates on air opening or air closing principle, the feedback lever, baffle, or cam of the positioner is adjusted so that the positioner and the control valve form a negative feedback system. Then, a standard signal is used to adjust the zero point and range until the requirements are met.

This post was last edited by denghl on 2012-12-12 at 21:31. 1. First, check the installation location of the actuator or the position of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is open at 50%, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. 2. Depending on whether the valve operates on air open or air close principle, adjust the feedback lever, baffle, or cam of the positioner so that the positioner and the control valve form a negative feedback system. Then send a standard signal to adjust the zero point and range until the requirements are met.

Reply to 1# Baghdad: ① First, check the installation location of the actuator or the position of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is at 50% open, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. ②Depending on whether the valve operates on air opening or air closing principle, the feedback lever, baffle, or cam of the positioner is adjusted so that the positioner and the control valve form a negative feedback system. Then, a standard signal is used to adjust the zero point and range until the requirements are met.

This post was last edited by denghl on 2012-12-12 at 21:31. ①First, check the installation location of the actuator or the position of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is open by 50%, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. ②Depending on whether the valve operates on air opening or air closing principle, the feedback lever, baffle, or cam of the positioner is adjusted so that the positioner and the control valve form a negative feedback system. Then, a standard signal is used to adjust the zero point and range until the requirements are met.

Reply to 1# Baghdad. ①First, check the installation location of the actuator or the position of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is at 50% open, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. ②Depending on whether the valve operates on air opening or air closing principle, the feedback lever, baffle, or cam of the positioner is adjusted so that the positioner and the control valve form a negative feedback system. Then, a standard signal is used to adjust the zero point and range until the requirements are met.

1. First, check the installation position of the actuator or the location of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is at 50% open, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal corresponding to 50% opening can be sent directly to the diaphragm element; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, after which the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. 2. Depending on whether the valve operates on air opening or air closing principle, the feedback lever, baffle, or cam of the locator must be adjusted so that the locator and the control valve form a negative feedback system. Then, standard signals are used to adjust the zero point and range until the requirements are met. 3. After the system is put into operation, it is necessary to check whether it operates normally in manual and automatic mode; if there are any issues, further investigation is required to identify the cause.

1. Make sure to follow the standard operating procedures. Minimize abnormal operations. 2. Debug and test according to the usage method defined in the product manual. 3. After verification, the pipes must be flushed promptly to eliminate potential hazards during operation.

This post was last edited by denghl on 2012-12-12 at 21:31. First, check the installation location of the actuator or the position of the bolts connecting the actuator’s feedback rod, to ensure that when the valve is open at 50%, the actuator’s feedback rod is in a horizontal position. For control valves equipped with a handwheel mechanism, the handwheel can be used to set the valve opening to 50% first. For control valves without a handwheel, a signal indicating an opening of 50% can be sent to the diaphragm element separately; after keeping the feedback rod in a horizontal position, the locator or the bolts connecting the feedback rod can be fixed, and then the handwheel can be used to fully open the valve or the signal to the diaphragm element can be removed. Next, depending on whether the valve operates on air opening or air closing principle, the feedback lever, baffle, or cam of the positioner is adjusted so that the positioner and the control valve form a negative feedback system. Then, a standard signal is used to adjust the zero point and range until the requirements are met.