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Flowserve Positioner PMV D20 Series - D20DNU-S23PVA-Z5X0X

The PMV D20 digital positioner uses a digital control algorithm to precisely position a valve by using a piezo-driven valve and hall sensor. The positioner receives a control signal (\(4-20mA\)) and compares it to the actual valve position, which is detected by a hall sensor, and then sends a signal to a piezo-driven poppet to control the air supply to the actuator, moving the valve to the desired position. Its process is characterized by an auto-calibration feature and built-in diagnostics for reliable and precise control.

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Working principle

Input and Feedback: The positioner receives a \(4-20mA\) input signal, which tells it the desired valve position. A hall sensor detects the current position of the valve and sends this information back to the positioner's internal processor.
Digital Processing: The processor uses a digital control algorithm to compare the desired position signal with the actual position feedback signal.
Air Control: Based on the difference between the two signals, the processor sends a precise signal to a piezo-driven poppet. This poppet controls the flow of pneumatic air to the actuator, moving it to the required position.
Auto-Calibration: The D20 can perform a rapid auto-calibration with a single button press to quickly tune itself to the valve's characteristics.
Diagnostics: The positioner includes self-diagnostics to monitor its performance and alert the user to potential issues before they cause a proble.

Key features

High Precision: Offers precise control, even on the smallest valves.
Modularity: Can be equipped with optional modules for limit switches and position feedback (\(4-20mA\)).
Communication: Available with various communication protocols, including HART, Profibus PA, and Foundation Fieldbus, for advanced diagnostics and integration into control systems.
Diagnostics: Features ValveSight DTM predictive diagnostics to monitor valve health and provide alerts.

Key operating components

Electronic controller: A plant's distributed control system (DCS) or other controller sends a variable input signal, typically 4–20 mA, to the D20. This signal represents the desired valve position (e.g., 50% open).
Proportional solenoid: The D20's internal solenoid receives the variable current signal. The strength of the solenoid's electromagnetic field is directly proportional to the strength of the input signal.
Pneumatic relay and actuator: The solenoid's force adjusts the pneumatic relay, which then regulates the air pressure sent to the valve's actuator. This causes the actuator to move the valve's stem to the commanded position.
Feedback loop: To ensure extreme accuracy, the D20 measures the valve's actual position via a mechanical linkage to the valve stem. This feedback is constantly compared against the initial command signal. If there is any discrepancy, the D20 adjusts the air pressure to the actuator until the valve is in the correct position.

Operating principle step-by-step

Signal reception: The PMV D20 receives a continuous electronic control signal (e.g., 12 mA) from a central control system, indicating a precise valve position is needed.
Solenoid action: The proportional solenoid inside the D20 uses the 12 mA signal to generate a specific magnetic force.
Pressure modulation: This force modulates the pneumatic relay, causing it to increase or decrease the air pressure flowing from the air supply to the actuator.
Actuator movement: The change in air pressure moves the actuator, which, in turn, moves the valve's stem to a new position.
Position feedback: The D20's mechanical linkage tracks the movement of the valve stem and provides a real-time position reading.
Correction for precision: The digital processor inside the D20 compares the real-time position with the desired position from the original 12 mA signal. If there is any error, the D20 makes instant, minor adjustments to the air pressure to correct it, achieving very high control precision.