Flowserve Positioner LOGIX 3400 Series - 3420MD-01-D6-E-04-40-KS-00

The LOGIX 3400 Series positioner works by using a digital algorithm to control an actuator based on a FOUNDATION Fieldbus (FF) or other control signal. It receives a command signal, uses a two-stage process with a stem-positioning algorithm and a piezo valve to precisely position the actuator stem, and uses sensors to provide feedback on the actual stem position to the control system.

Core components and process

• Signal reception: The positioner receives a digital command signal, typically through a two-wire FF connection, which powers the device as well.
• Digital control algorithm: A 32-bit microprocessor runs a two-stage algorithm to determine the necessary output.

• It calculates the deviation between the desired position and the actual stem position, measured by a Hall effect sensor.
• The algorithm uses a two-stage positioning approach, with the first stage providing a rapid response and the second stage providing precise, fine-tuned positioning.It calculates the deviation between the desired position and the actual stem position, measured by a Hall effect sensor. 

• Piezo valve: The digital algorithm controls a piezo valve (or a similar electronic relay), which precisely directs pneumatic pressure to move the actuator and valve stem.  
• Stem-positioning algorithm: The algorithm converts the command signal into a percentage and then uses the two-stage process to achieve the desired valve position. It continues to make adjustments until the deviation from the target position is zero.
• Feedback: A Hall effect sensor provides real-time feedback on the actual stem position back to the control algorithm, ensuring accuracy

Configuration and tuning:

• Digital Characterization: Instead of mechanical cams, the positioner uses software to map the input signal to the desired output, allowing for linear, equal percent, or custom 21-point curves to be configured digitally via software or a handheld communicator.
• Auto-tune: An automatic tuning feature helps select the correct gain settings for optimal performance by cycling the actuator and analyzing its response.
• HART communication: The positioner uses the HART protocol for two-way communication, enabling remote configuration and diagnostic data retrieval through devices like handheld communicators or software like ValveSight.
• Power and signal: The positioner is a two-wire device that is completely powered by the 4-20 mA input signal.

Key features

• Two-wire FOUNDATION Fieldbus (FF): The device is powered by and communicates through the same two-wire FF signal.
• Configuration: Configuration can be done via the local interface (buttons) or remotely using a handheld device or host software.
• Calibration: The device has an auto-tune feature that allows it to automatically select custom tuning parameters for optimal performance.
• Diagnostics: The 3400MD series includes a suite of diagnostics to alert users to potential problems in the valve, actuator, or positioner.

Core working principle

The process can be broken down into four main steps:

1. Command input: The positioner receives a FOUNDATION Fieldbus™ digital signal from a central control system. This signal specifies the desired valve position as a percentage, for example, 75% open.
2. Position sensing: An internal sensor, such as a Hall effect sensor, constantly monitors and measures the actual position of the valve's stem.
3. Deviation calculation: The positioner's digital algorithm calculates the "deviation," or the difference, between the command input and the actual stem position.
   Position correction:

• If a positive deviation is detected (e.g., command is 75%, actual is 50%), the algorithm sends a signal to move the actuator. It does this by driving a piezo valve to adjust the pressure on the actuator's piston.
• The piezo valve directs supply air to one side of the actuator and exhausts air from the other, causing the actuator to move the valve stem.
• As the stem moves toward the commanded position, the deviation decreases. The algorithm constantly adjusts the piezo valve until the deviation is zero and the valve is at the correct position.

Key technologies

• Piezo technology: This is the core technology used to operate the internal control valve that manages airflow to the actuator. Piezoelectric material expands and contracts when voltage is applied, providing highly precise and rapid control of the air pressure.
• FOUNDATION Fieldbus™: The LOGIX 3400 series uses this all-digital, two-way communication protocol to receive commands and send diagnostic information to the host control system.
• Predictive diagnostics (ValveSight): The device continuously monitors its own performance and that of the valve and actuator. This allows it to identify developing problems, such as excessive friction or failing components, and alert operators before a failure occurs.
• Auto-tuning: During setup, the positioner can automatically configure the zero, span, and gain for most valves in less than a minute, simplifying calibration and commissioning.
• Local interface: While remote communication is possible, the unit also features local controls, including buttons and LEDs, that allow for manual calibration, configuration, and troubleshooting without a handheld device.

 Full Datasheet

Positioner Transmitter Feature  

• Manufacturer: LOGIX 3400
• Product No. :  3420MD-01-D6-E-04-40-KS-00
• 3420 MD - Protocol FOUNDATION Fieldbus, Diagnostics Standard, Material Aluminum (Automax), Design Version Q
• Certifications: 10 - Explosion proof Class I, Div 1, Groups B,C,D Intrinsically Safe Class I, Div 1,
• Shaft: D6 - DD 316 Stainless Steel Shaft (Valtek Standard)
• Conduit Connections: E - 1/2 in. NPT
• Action: 04 - Four-way (Double-Acting)
• Temperature: 40 - Low Temperature (refer to certification table)
• Gauges: KS -  SS with SS internals, psi (kg/cm2)
• Special Options: 00 - No special options

There are several Model of positioner, for more details read the PDF below 

Basic Ordering Information