Partial Stroke Testing (PST) and Smart Valve Positioners

NordenFlow’s Partial Stroke Testing (PST) and Positioner solutions bridge the gap between process productivity and Functional Safety (IEC 61511). By automating valve diagnostics, our systems allow plant operators to extend mandatory Full Proof Test intervals—reducing maintenance costs while maintaining a verified SIL 3 capable safety loop. Designed for high-integrity ESD applications, our technology ensures your safety valves are ‘ready to close’ without ever risking an accidental plant trip.
Our PST and positioner technologies are integrated into actuator assemblies, control panels, or complete skid packages to support continuous safety assurance and process accuracy.

Partial Stroke Test (PST) Overview
PST systems Verify ESD valve readiness without production loss. Our PST systems identify 70% of dangerous undetected failure modes—including stiction, stem shear, and actuator seal degradation—while maintaining your safety loop online. They provide controlled partial movement of the valve (typically 10–20% of stroke), enabling verification of torque, movement, and mechanical integrity — essential for functional safety and minimizing unplanned downtime.

Partial Stroke Testing (PST) Modules ICO4-PST

  • Periodic proof testing of ESD valves without full closure
  • Adjustable stroke range (5–25%) for flexible configuration
  • Test initiation: local push-button or remote signal
  • Automatic reset after test completion
  • Continuous position feedback (4–20 mA or digital)
  • Compatible with pneumatic, hydraulic, and electro-hydraulic actuators
  • Functional Safety: SIL 2/3 Capable (IEC 61511 / IEC 61508)
  • Local visual indication and LED status
  • Manual override and fail-safe protection
  • Hazardous Areas: Options for FM, CSA, and ATEX/IECEx certifications.
Partial Stroke Testing (PST)

Technical Advantage

SIL 3 Enhancement: Integrated PST logic reduces the Probability of Failure on Demand (PFDavg), allowing systems to meet or maintain SIL 3 ratings.
Extended Proof-Test Intervals (PTI): By implementing regular automated PST, operators can safely extend the time between mandatory full-stroke tests and plant turnarounds.
Dual Technology Support: We offer both Positioner-based PST (for ramp/step diagnostics) and Solenoid-based PST (for high-speed safety loop verification).
Diagnostic Data: Capture ‘Valve Signatures’—monitoring torque, friction trends, and air supply pressure to predict maintenance needs before a failure occurs.
Standards Compliance: Fully compliant with IEC 61508 and IEC 61511 functional safety standards.

Every PST cycle generates a Digital Valve Signature. Compare current performance against baseline ‘Birth Certificate’ data to predict maintenance needs months before a failure occurs.

Smart Valve Positioners: High-Precision Control by IMI

NordenFlow provides high-performance IMI Smart Positioners designed for precise modulating control and advanced valve diagnostics. These units serve as the ‘intelligence’ of the valve assembly, offering high-resolution positioning and seamless integration with HART, Foundation Fieldbus, or Profibus protocols. Engineered for stability in high-vibration and harsh industrial environments, our positioners ensure optimal loop performance for both control and safety-critical valves

  • Dynamic Performance Monitoring: Real-time tracking of hysteresis, linearity, and dead-band to ensure control loop precision.
  • Air Consumption Optimization: Low steady-state air bleed technology to reduce plant energy costs.
  • Auto-Tuning Logic: Intelligent calibration that automatically optimizes PID parameters based on actuator size and friction.
  • Predictive Maintenance Data: Integrated counters for total stroke and cycle changes to predict packing wear before it happens.

Positioner Features

  • Signal input: 4–20 mA, HART, Profibus, Modbus
  • Output signal: pneumatic 0.2–1.0 bar
  • Types: analog, digital, electro-pneumatic, or smart positioner
  • Feedback options: potentiometer or encoder
  • Housing materials: aluminum or SS316 (Ex d / Ex ia) IP66/NEMA 4X
  • Mounting: Namur or IEC 60534 standard brackets
  • Auto-calibration and self-diagnostics
  • Optional local LCD for configuration and status monitoring
Smart pneumatic and electro-pneumatic valve positioners for industrial valve control

Why Choose IMI Positioners via NordenFlow?

  • Rugged Construction: Available in Stainless Steel 316 for offshore, marine, and corrosive chemical environments.
  • Global Certifications: Fully rated for hazardous areas including ATEX, IECEx, and North American Class I, Div 1 (FM/CSA).
  • System Compatibility: Optimized for use with IMI Maxseal solenoids and IMI Norgren air prep, creating a unified, high-reliability control assembly

NordenFlow combines PST systems and smart positioners into engineered automation packages for:

  • Refinery ESD valve assemblies
  • Power plant safety loops
  • Oil & gas processing lines
  • Chemical shutdown and control valve systems
  • Industrial modulating control services

NordenFlow is the authorized distributor and technical partner for IMI Industrial Automation and Instrumentation solutions.

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