Manufacturer
Spring Return Actuator Manufacturer
Fail-safe spring return pneumatic actuators from a Wenzhou factory: SR-series single acting units that move the valve to a safe position automatically when air supply is lost, with spring-to-close and spring-to-open options, custom spring sets and pre-load adjustment for process safety systems.
Why Buy Direct
Fail-Safe Is Engineered, Not an Option
A spring return actuator is specified for one reason: it must act when everything else fails. That single requirement drives the engineering of the SR series — from spring material selection to the way pre-load is recorded on the test sheet — and the three sections below explain how we build for it.
Fail-Safe by Design
A spring return actuator does one job that a double acting unit cannot: when air pressure is lost, a mechanical spring cartridge drives the valve to its fail position without electricity, control signals or an operator in the loop. The SR series delivers this in spring-to-close (FC) or spring-to-open (FO) configurations, so a process can be specified to shut off a fuel line, open a cooling water path or vent a vessel the moment the air supply drops. The air stroke compresses the springs on the way to the operating position, so the actuator does two jobs in one cycle: position the valve, and store the energy that will move it back. Spring material, wire diameter and the number of coils are selected so the set keeps its rate within specification across the −20°C to +80°C operating band.
Custom Spring Engineering
Valve seating torque varies with size, pressure class and media, so the spring set is treated as a design variable rather than a fixed option. Spring cartridges use 4–12 springs per side, and the number of springs, their rate and the pre-load are selected to match your valve's torque requirement at the fail position. Pre-load remains adjustable after installation, which lets maintenance teams fine-tune seating torque on site without changing parts or removing the actuator from the valve. Because spring torque declines as the valve closes and the spring extends, the fail position torque is verified at the end of the spring stroke — the point where seating force is at its minimum — rather than at the start of travel.
Safety & Compliance Support
Spring return actuators are the moving part of many safety loops, and the documentation matters as much as the hardware. SR-series units are suited to safety-instrumented systems, with ATEX options for hazardous areas and spring torque data provided for each configuration so the fail-safe performance can be verified. For safety system integrators, we supply the spring torque table, fail position and stroke data needed for loop documentation, and ATEX-specified versions carry the same data pack. Distributors can also stock standardized FC and FO units for fast delivery on routine shutdown and relief valve retrofits, while our engineers review valve torque curves and recommend the spring set, fail position and accessories for project orders.
Product Line
SR Series Spring Return Range
| Parameter | SR Series Specification |
|---|---|
| Output Torque | 8 – 1,000+ Nm (air stroke) |
| Spring Torque | Selectable per valve requirement; 4–12 springs per side |
| Fail Position | Spring-to-close (FC) / spring-to-open (FO) |
| Rotation Angle | 90° |
| Supply Pressure | 3 – 8 bar |
| Operating Temperature | −20°C to +80°C |
| Mounting Standards | ISO 5211, NAMUR |
| Typical Valve Sizes | DN15 – DN200 ball, butterfly and plug valves |
* Spring torque is selected per project against the valve seating requirement. Larger fail-safe duties are covered by our AW scotch yoke line in spring return configuration.
Quality & Testing
Spring Performance Verified on the Rig
A spring return actuator is only as trustworthy as its spring set, so spring torque gets measured rather than assumed. Each unit is stroked on a calibrated torque rig in both directions, with output recorded for the air stroke and for the spring stroke at the fail position, then compared with the datasheet curve for the fitted spring configuration. Air leak tests at rated pressure verify the piston seals and port threads, and the fail action itself is exercised to confirm the valve reaches the FC or FO position smoothly when the air supply is vented.
Batch samples are endurance-cycled through repeated air-and-spring strokes while spring torque and leak rate are monitored, since spring fatigue is the failure mode that matters in safety service. Spring pre-load settings are recorded per unit and included in the QC report, along with dimensional checks on ISO 5211 and NAMUR interfaces. Per-lot QC reports accompany every shipment, and material certificates for springs and bodies are available on request.
What We Test
- ✓Air stroke torque measurement on calibrated rig
- ✓Spring stroke torque verification at fail position
- ✓Fail action test — valve reaches FC/FO on air vent
- ✓Air leak test at 3–8 bar rated pressure
- ✓Endurance cycling of air-and-spring strokes on batch samples
- ✓Spring pre-load recorded per unit in QC report
Applications
Fail-Safe Applications We Supply
Spring return actuators protect processes by acting automatically when air is lost. The SR series is used wherever a valve must fail to a known position for safety, environmental or asset-protection reasons.
FAQ
Spring Return Actuator Manufacturer — FAQ
What happens when air supply is lost?
The internal spring cartridge moves the valve to its fail-safe position automatically — closed for spring-to-close (FC) units, open for spring-to-open (FO) units. The action is purely mechanical and requires no electricity or control signal, which is why spring return actuators are specified in safety loops where a valve must reach a known position on loss of air.
How do I choose between FC and FO?
The choice follows the process safety requirement. Fail-closed is common on fuel, chemical and pressure lines where isolating the flow is the safe state; fail-open is used on cooling water, venting and some utility services where maintaining flow prevents damage. Our engineers will review your application and recommend a fail position if you are unsure.
Can spring torque be adjusted after installation?
Yes. Spring pre-load is adjustable, so seating torque can be fine-tuned on site to match the valve requirement without removing the actuator or replacing parts. The number of springs per side can also be changed at the factory when a valve torque curve changes.
When should I choose spring return over double acting?
Choose spring return whenever the valve must fail to a safe position on loss of air — for example in shutdown, relief and fire protection duty. Double acting is suitable where fail-safe positioning is not required, offers higher torque per frame size, and is generally lower in cost. For very large fail-safe duties, our AW scotch yoke line is available in spring return configuration.
Specify Your Fail-Safe Requirement
Valve torque, fail position (FC or FO), supply pressure and volume — we reply with a spring set recommendation and factory-direct pricing within 24 hours.