Valve Positioner
Product Overview
The DVP-Series valve positioner is a microprocessor-based electro-pneumatic control instrument engineered for linear and rotary pneumatic actuators in industrial process loops. It processes standard 4-20 mA control commands from distributed control systems (DCS) and dynamically modulates pneumatic pressure to actuator diaphragms or pistons. Incorporating a non-contact magnetic position sensor and a high-speed piezoelectric pilot valve, the unit eliminates mechanical feedback linkage wear, ensuring precise stem positioning under continuous heavy industrial vibration and variable process loads.
Working Principle & Configuration
The DVP-Series relies on a closed-loop digital control architecture:
Signal Comparison
The embedded 32-bit CPU continuously compares the 4-20 mA / HART setpoint against actual valve travel measured by the magnetic position sensor.
Dynamic Modulation
Control deviation generates a pulse-width modulated (PWM) electrical signal to the piezoelectric pilot stage, instantly regulating airflow into the actuator chambers.
Automated Setup
Local pushbuttons or HART communication execute automated zero and span calibration, mapping travel endpoints without manual mechanical adjustments.
Workflow Sequence
- DCS / Controller sends 4-20mA / HART signal to the microprocessor and control algorithm.
- Microprocessor receives feedback from the non-contact magnetic position sensor.
- Microprocessor triggers the piezoelectric pilot valve and pneumatic relay.
- Modulated air supply is delivered to the pneumatic actuator and control valve.
Key Features
Non-Contact Feedback: Utilizes magnetic position sensing, removing mechanical feedback arms, linkage backlash, and wear points exposed to plant vibration up to 2g @ 500 Hz.
Low Air Consumption: Steady-state air consumption stays below 0.015 scfm (under 0.02 Nm3/h at 1.4 bar supply), lowering compressor utility loads across large instrument air headers.
Corrosion-Resistant Housing: Copper-free die-cast aluminum enclosures feature an epoxy-polyester powder coat, withstanding 1,000-hour salt-spray exposure per ASTM B117.
On-Board Diagnostics: Real-time tracking of travel deviation, cycle counts, operating hours, and valve friction trends facilitates proactive maintenance scheduling.
Universal Mechanical Interfaces: NAMUR VDI/VDE 3845 (rotary) and IEC 60534-6-1 (linear) direct-mounting patterns eliminate custom mounting bracket fabrication.
Technical Specifications
|
Parameter |
Specification Details |
|
Input Signal |
4-20 mA DC, 2-wire; Load voltage <= 8.5 VDC (425 ohms at 20 mA) |
|
Communication Protocol |
HART compatible (optional FOUNDATION Fieldbus / Profibus PA) |
|
Air Supply Pressure |
1.4 to 7.0 bar (20 to 100 psi), instrument air filtered to ISO 8573-1 Class 3.4.3 |
|
Air Delivery Rate |
130 L/min (4.6 scfm) at 1.4 bar supply; 300 L/min (10.6 scfm) at 6.0 bar supply |
|
Linear Travel Range |
10 mm to 150 mm |
|
Rotary Travel Range |
0 degrees to 90 degrees (up to 120 degrees configurable) |
|
Control Performance |
Linearity: <= plus or minus 0.5 percent FS Hysteresis: <= 0.3 percent FS Repeatability: <= 0.2 percent FS |
|
Explosion-Proof Ratings |
Flameproof (Ex db IIC T6 to T4) and Intrinsically Safe (Ex ia IIC T6 to T4) |
|
Enclosure Protection |
IP66 / NEMA 4X |
|
Ambient Temperature |
-40 degrees C to +85 degrees C (LCD operational down to -30 degrees C) |
|
Pneumatic Connections |
Supply/Output: 1/4 in. NPT (or G 1/4); Gauge ports: 1/8 in. NPT |
|
Electrical Conduit Entry |
M20 x 1.5 or 1/2 in. NPT |
Oil & Gas Pipelines: Pig launcher valving, emergency shutdown (ESD) bypass lines, and compressor fuel gas skids.
Petrochemical Refining: High-temperature catalyst feed control, reactor pressure relief loops, and acid washing skids.
Power Generation: Boiler feedwater regulation, main steam pressure reduction stations, and flue gas desulfurization (FGD) slurry control.
Water Treatment: High-capacity municipal raw water intake valves and chemical dosing packages.
Manufacturing & Quality Control
Machining Tolerances: Housing components are CNC-machined from precision ADC12 aluminum die-castings on automated transfer lines, holding positional tolerances within plus or minus 0.02 mm.
Pressure Decay Testing: Every assembled spool valve block undergoes a 100 percent automated nitrogen pressure decay test at 8.0 bar for 120 seconds prior to electronic integration.
Thermal Burn-in & Calibration: Units endure a 24-hour thermal cycle test (-20 degrees C to +70 degrees C active operation), followed by automated calibration mapping on test benches traceable to national metrology standards.
Traceability Package: Shipments include individual factory calibration test reports, material certificates upon request, and compliance documentation.
DVP (Digital Valve Positioner)
Action Type: L (Linear) or R (Rotary)
Communication: H (HART) or P (Profibus)
Explosion-Proof: EXD (Flameproof) or EXI (Intrinsically Safe)
Pneumatic Port: N (1/4 in. NPT) or G (G 1/4)
Ordering Code Example: DVP-R-H-EXD-N
DVP: Digital Valve Positioner
R: Rotary Action (NAMUR standard mount)
H: 4-20 mA with HART Protocol
EXD: Flameproof Enclosure
N: 1/4 in. NPT Pneumatic Connections
FAQ
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