Technicians working related to control valve should know about the exact position of control valve. For certain valves, an indication of the exact position of the valve is given in the form of position lights indicating whether the valves are open or closed.
Valve position indicators:
Components indicating the position of the remote valve use a position detector that senses the position of the stem and disk or actuator. One sort of position detector is the mechanical limit switch operated by the motion of the valve.
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Another form is magnetic switches or transformers that senses the motion of their magnetic cores that are operated by motion of the valve physically.
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The local position of the valve indicator relates to some visually discernible valve characteristics indicating the position of the valve.
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Rising stem valve position is indicated by the stem position.
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Sometimes non-rising stem valves have tiny mechanical pointers operated concurrently with valve operation by the valve actuator.
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Typically, power actuated valves have a mechanical pointer that gives an indication of the local position of the valve.
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On the other hand, some valves do not have any feature for position indication.