Selecting the Right Spring for Single-Acting Pneumatic Actuators
Choosing the optimal spring ensures reliable fail-safe operation and longevity. Key factors to consider:
1. Spring Force (Preload & Rate)
- Preload: Must overcome valve seating friction (e.g., 20–30% higher than valve torque)
- Rate: Determines return speed; stiffer springs provide faster reset but require higher air pressure to compress
2. Material & Environment
- Stainless Steel (302/316): Standard for corrosion resistance in humid/chemical environments
- Inconel: For extreme temps (-200°C to 400°C) or H₂S exposure (oil/gas)
- Coated Springs: Zinc or epoxy coatings enhance durability in abrasive conditions
3. Cycle Life Requirements
- General Use: 500,000+ cycles (music wire springs)
- High-Cycle Apps: 1M+ cycles (shot-peened or cryo-treated springs)
4. Size Constraints
- Diameter/Length: Must fit actuator housing without binding; custom springs may be needed for compact designs
5. Compliance Standards
- ISO 10243: Specifies spring dimensions/tolerances
- NORSOK M-650: For offshore/oilfield harsh environments
Testing Tip
Validate spring performance under max operating pressure and temperature before deployment.
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