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How the motorized control valve converting the (4 —20 ma) control signal to the movement representing open / close?

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تم إضافة السؤال من قبل Bashar Musa , Instrumentation and Control Maintenace Engineer , Sudanese Thermal Power Generating Company.Ltd
تاريخ النشر: 2013/10/07
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The operation of a control valve involves positioning its movable part (the plug, ball or vane) relative to the stationary seat of the valve. The purpose of the valve actuator is to accurately locate the valve plug in a position dictated by the control signal. The actuator accepts a signal from the control system and, in response, moves the valve to a fully-open or fully-closed position, or a more open or a more closed position (depending on whether 'on / off' or 'continuous' control action is used

Ahmed Emad
من قبل Ahmed Emad , Instrumentation - Projects and Maintenance Section Head , ESHPETCO

the motorized control valve doesn't convert4-20 ma control signal it only represent its status using this protocol (4-20 ma )

and the PLC send a signal to a relay to connect the current to the Actuator of the valve to open or close the valve depending on the status of the valve sent before to the PLC

sohail zaman
من قبل sohail zaman , Engineer - Instrumentation and Automation , National Petroleum Services Co.

actually the process value is a reference (feedback) which can be set for a specific flow or result.

when the assigned value lower then the set parameter the valve will open more to bring it on the set point similarly when it cross the higher limit the valve get the command to close .in different applications ,the behavior of the valve can be assigned as per requirements    you can use it as floating and level based with logic (depend on your application ) also can be used as low and high level switching (tanks for example).also it can act as servo with mid and last feedback.

Nazurudin Ahamed
من قبل Nazurudin Ahamed , Instrumentation Engineer , Abunayyan Holding

The MOV has an actuator which controls the movement of the stem. Usually the Basic ON/OFF MOV has5 DO &3 DI. The MOV has an optional4 to20 mA current output to indicate the continuous position feedback. It's the PLC which sends a signal to MOV of the required valve position

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