STI DigitalTrak2 - User Manual

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Overview

DigitalTrak2™ Digital Electro-Pneumatic Valve Positioner

DigitalTrak2™ Digital Electro-Pneumatic Valve Positioner

The DigitalTrak2™ is an intelligent electro-pneumatic valve positioner designed for precise control of pneumatic valves. It operates as a loop-powered instrument, receiving a 4-20mA signal from a control system and converting it into a pneumatic signal to actuate the valve. The positioner utilizes a microprocessor for advanced control and feedback, ensuring accurate valve positioning and rapid response. It is suitable for both linear and rotary actuators and can be used in a wide range of industrial applications, including chemical, electric power, paper, print, and other fields requiring precise valve control.

Function Description

The DigitalTrak2™ positioner receives a 4-20mA input signal from a control system, which represents the desired valve position. This signal is processed by the internal microprocessor, which then generates a pneumatic signal to drive the valve actuator. A feedback signal, typically a 4-20mA signal, is sent back to the control system, indicating the actual valve position. This closed-loop control ensures that the valve accurately reaches and maintains the desired position. The positioner is capable of self-adaptive function, automatically searching for the Zero and Span of the valve, and optimizing the valve's control parameters for improved precision. It supports various configuration functions, including valve characteristics (curve, action mode, dead band, stroke range, shut-off value, and setpoints), self-diagnosis functions (showing setpoint current, travel time, and dead band), and fault mode functions (fail safe or fail freeze). It also supports HART communication protocol and provides valve position feedback (4-20mA DC valve position feedback signal, switch valve feedback signal).

Important Technical Specifications

Pneumatic:

Air supply pressure: 0.14 ÷ 0.7 mMPa
Air consumption in stable state: < 36 L/H
Air supply quality: According to ISO 8573-1, Size and density of particulates: Class 4, Oil concentration: Class 4, Dew point: Class 4 or at least 10K below surrounding environment
Valve leakage (in fail freeze): < 0.6 L/H

Actuator:

Actuator type: Single acting, double acting

Communication:

Protocol: HART

Input / Output:

Input Current: 4 ÷ 20mA DC, minimum input current 3.8 mA, split range start and end point adjustable.
Feedback Output: 4-20 mA DC
Digital Input: One dry contact
Digital Output: Electronic switch: 2 channels
Piezo Valves Switch Time: Average failure free time: >2 billion
Output Characteristic: Linear, 1:30, 30:1, user defined (20 points)
Stroke: Linear actuator 10 ÷ 100mm (10-20mm, 1:8 transmission ratio is optional), Rotary actuator 30 ÷ 105°
Electrical connection: M20x1.5 or NPT1/2
Pneumatic connection: G ¼ or NPT1/4

Display:

LCD: 2x7 digits, dimensions: 22x38 mm
Manual: 3 keys on the front panel

Operate:

Self tuning: Automatic calibrate the zero and span, dead band
Self diagnostic: Show value of input current, travel time, dead band, etc.

Precision:

Dead band: 0.1 ÷ 10% adjustable
Hysteresis: 0.2% F.S.
Linearity: 0.5% F.S.

Environment:

Environmental temperature: -40 ÷ +80°C
Environmental humidity: 5 ÷ 95% RH
Vibration Resistance: 15 ÷ 150 Hz @2g
Enclosure degree of protection: IP65

Appearance:

Weight: 2 kg
Dimension: 170x96x96mm
Shell material: Aluminum Die Casting

Usage Features

The DigitalTrak2™ offers several user-friendly features for configuration, operation, and maintenance. The LCD display provides clear information on the valve position, setpoint, and various parameters. The three front panel buttons (A/M, DOWN, UP) allow for easy navigation through menus and parameter adjustments.

Configuration: The positioner can be configured in normal mode or configuration mode. In normal mode, the display shows the valve position, the second line shows the direction of the valve motion, the state of running, and the setpoint. In configuration mode, the display shows the parameter value, the second line shows the parameter name, and the third line shows the parameter number. Users can choose from four different parameter groups (P1, P2, P3, P4) to adjust various settings.

Calibration: The calibration process includes "Ready to initialize" and "Auto-tuning."

Ready to initialize: This step involves checking the positioner installation and electrical connection, confirming the power supply, and ensuring the valve manually runs from fully open to fully closed. The position sensor angle check mode allows for adjusting the valve movement.
Auto-tuning: This automatic process connects the positioner to the pneumatic actuator and performs a series of steps to determine and set the optimal control parameters. The display shows "n0" during this process.
Manual tuning: If auto-tuning is not sufficient, manual tuning allows for fine-tuning parameters such as zero, span, and dead band.

Diagnosis: The positioner includes a diagnosis mode to identify and troubleshoot issues. It displays various parameters such as input current, travel time up/down, dead band up/down, prediction up/down, impulse length up/down, short step zone up/down, and short step zone down. Specific error messages are provided for conditions like zero point of position sensor too low, span point of position sensor too high, initialization error, measurement span insufficient, user characteristics setting error, feedback over limits, input current out of work range, and actuator error.

Maintenance Features

The DigitalTrak2™ is designed for reliability and ease of maintenance.

Trouble shooting: A comprehensive table outlines common faults, their probable causes, and recommended actions. This includes issues related to air supply, actuator movement, oscillation, valve not fully opened or closed, display problems, exhaust not smooth, no position feedback current, feedback current mismatch, and position display on LCD mismatch.
Maintenance: Regular instrument maintenance is crucial. The air supply of the positioner should be kept dry and clean. Regularly check water and pollution of the regulator connecting the positioner in order to keep the positioner normally. Feedback connection may be loose due to long term work, so check the feedback connection regularly. If loose, tighten the screw and decide whether to initialize or not according to error of zero or span. In order to see whether the positioner is normal, keep the pressure gauge clear.
Warranty: STI S.r.l. guarantees that all items produced, if installed, used, and subject to maintenance, are without material and manufacturing defects, and comply with specifications in force. The period of warranty is one year, starting from the date of shipment to the first user.
Safety notices: The manual includes safety notices with symbols (warning, caution) and explanations to alert users to potential dangers and ensure safe operation.
Transport and storage: The positioner should be stored in a clean, dry, and well-ventilated environment, protected from extreme temperatures (-40 to +80°C) and high humidity (no more than 75%). It should also be protected from harmful and corrosive substances.