Under what circumstances is a handwheel required for a control valve? What factors are considered in process design?
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Under what circumstances is a handwheel required for a control valve? What factors are considered in process design?
Control valves are equipped with a handwheel only when it is not convenient to add front and rear hand valves and bypass lines.
To ensure continuous operation of the process, manual adjustment via a handwheel can be used in case of automatic valve failure.
If no front and rear valves are added, how should isolation between the control valve and its surrounding components be achieved?
The control valve without a bypass and equipped with a first-stage mechanism is designed to allow for manual operation of the control valve in the event of instrument failures. If a fault occurs inside the valve body of the control valve and normal production cannot be maintained, then shutdown is necessary.
As mentioned on the 3rd floor, there are no control valves for the auxiliary lines; once automatic operation fails, the valves can no longer be adjusted and may not even allow the flow of medium. A handwheel is available to adjust the valve opening, enabling the automatic valve to function as a manual valve as well and thus maintaining its usability