The valve opening at the site does not match that in the control room
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I often hear people say things like the locator is broken during meetings – what’s going on?
A positioner receives signals from the control system and controls the control valve to adjust to the opening degree specified by the control system. If the valve’s opening degree does not match what is specified, it could be a problem with the positioner; however, it is not necessarily the case that the positioner is damaged. There are various reasons for this, such as sticking inside components of the control valve, damage to the actuator (electrical or pneumatic) resulting in limited mobility. In the case of pneumatic actuators, the pressure of the air supply can also affect the accuracy of the valve’s opening degree. Another point is whether the signal from the control unit meets the requirements of the actuator; generally, smart valve actuators require a signal of 4–20 mA, and poor quality signals can also cause failures.
Great, our company also faces such problems. Let’s talk about how to distinguish between prevention and resolution
There are two types of on-site valve opening position signals: one is the mechanical scale indication on the valve stem linkage, and the other is the indication from the valve positioner. I don’t know which one you are referring to. If the indication from the valve spool linkage does not match that in the control room, you can try resetting the positioner; it’s possible that the initialization data of the positioner is incorrect, and resetting it might resolve the issue ； Or check whether the connecting rods in the mechanical part are loose, which may cause the opening signal sent to the positioner to be inaccurate. If the indication from the locator does not match that in the control room, it is usually a problem with the locator; it might be faulty, as both signals are provided by the locator. It’s also possible that the locator is not set correctly. For example, if the \"signal rise\" and \"signal fall\" settings of Siemens’ smart positioners do not match, it is possible that the on-site display shows 0% while the central control system shows 100%, or when the on-site display indicates full open, the central control system shows 0% opening.