Masoneilan SVI II Smart Digital Valve Positioner HART 4-20mA Auto Tune for Pneumatic Actuators

Product Overview

The Masoneilan SVI II is a 32-bit microprocessor digital valve positioner with a local interface that controls a pneumatic actuator using a two-wire 4-20mA control signal. It offers bi-directional communication using the HART protocol, supporting HART 5 or 7 over 4-20mA. The universal design allows easy retrofit in place of existing analog positioners on Masoneilan or non-Masoneilan pneumatic actuators, either single-acting or double-acting.

Non-contact position sensing technology reads through the housing — no mechanical moving parts enter the main housing cavity, prolonging service life. The LCD and pushbuttons are operable in all certified hazardous environments, and commissioning is quick and accurate with auto stops and auto tune methods. One design fits both rotary and linear applications, remote or local.

Technical Specifications

Application Industry

The Masoneilan SVI II is used in power generation, refining, petrochemicals, midstream oil and gas, and upstream oil and gas. Key applications include steam turbine generators, condensers, cooling towers, reactor buildings, turbine buildings, heat recovery steam generators, balance of plant, distillation, hydroprocessing reforming, cracking, secondary blending, quenching and fractioning, charge gas compression, separation, pipeline integrity operations, dehydration, refrigeration, liquefaction, loading and shipping, regasification, and compression.

Common Problems

• Autotune doesn't complete: The friction measured is more than 30% of the spring force or the valve is visibly jumping around the setpoint. Run Autotune with Aggressiveness settings of 2 or 4, or proceed to manually tune ensuring the Integral Gain (I) is set to a minimum of 100. Autotune may fail if the valve is too slow — in this case manually tune.

• Position oscillation — Fast: Positioner gain (P) set high. Position overshoots by more than 20% of the step and oscillates more than twice. Decrease the Gain (P) and (Padj) by 50% increments until oscillation ceases. If an external booster is tuned aggressively, adjust the booster's bypass to a 1 1/4" turn from the closed position of the bypass adjustment.

• Position oscillation — Slow: Position gain (P) set low. Increase gain (P) and (Padj) by 5% increments until oscillation has reduced. Reduce the Integral Gain (I) by 25% until the position is flat line. If the oscillation is a square wave, increase the integral by 25% until it is a flat line.

• Valve friction greater than 25% of spring range: Verify using the ValVue Trend that the oscillation resembles a square wave pattern. Increase the integral Gain (I) by 25% until the oscillation stretches out to a flat line. Set DeadZone parameter to 0.25%.

• Loose feedback: For rotary installation, the magnet assembly rotates using hands. For reciprocating bracket, the turnbuckle, rod-end, and take off arm aren't secured. Tighten set screws and lock nuts as necessary.

• SelfCheckError (Hardware failure): Remove power to the device for two minutes and restart. Clear the alarm using ValVue or HART Host. If the failure persists, replace the complete device or electronics module.

• SoftwareError (Hardware failure): Remove power to the device for two minutes and restart. Clear the alarm using ValVue or HART Host. If the failure persists, replace the complete device or electronics module.

• Stops Fail error after calibration: This fault typically occurs when the mandatory Find STOPS function is not performed during standard calibration. This function locates and stores the mechanical travel limits of the valve assembly. Redo calibration and ensure Find STOPS is executed.

• Positioner doesn't power up with 4-20 mA: Check for insufficient voltage. Verify compliance voltage requirements: >11 VDC at 4 mA, >9 VDC at 20 mA.

Replacement Models

The Masoneilan SVI3 AP is the next-generation digital valve positioner from the same product line. It features stainless steel mounting brackets for any valve/actuator combination and is fully backwards compatible to SVI II AP and SVI1000 brackets. For cross-vendor alternatives, verify actuator mounting, travel range, and communication protocol before ordering.