The Pro Trick: Making Airtac 4V210-08 "Normally Open"

May 3, 2026

Fail-Safe Pneumatics: Configuring Airtac 4V210-08 for "Normally Open" Logic

In critical automation sequences, the "default" state of a valve can be the difference between a safe stop and a mechanical crash. The Airtac 4V210-08 is a 5/2-way single solenoid valve, meaning it inherently relies on an internal mechanical spring to return the spool to a "Home" position during power loss. By strategically managing your plumbing, you can define whether this state is Fail-Safe Closed or Fail-Safe Open.

1. The Port Swapping Technique: Achieving "Normally Open" Logic

By industry standard, the 4V210-08 connects the pressure port (P) to port B when the solenoid is de-energized. To reverse this logic and ensure your actuator extends without electrical power:

The Default (Normally Closed): "Extend" line on Port A, "Retract" line on Port B. The cylinder retracts on power loss.
The Fail-Safe Open Hack: Simply connect your cylinder's "Extend" port to Port B and the "Retract" port to Port A.
The Result: In the event of a PLC failure or E-stop, the internal spring return of the 4V210-08 will automatically divert air to Port B, ensuring your machine arm moves to its extended safety position instantaneously.

2. Why the 4V210-08 Mechanical Spring is Critical

Not all 5/2-way valves are created equal. The Airtac 4V210-08 utilizes a high-cycle fatigue-resistant spring.

Reliability: Unlike "Air Return" valves that require pilot pressure to reset, the 4V210-08’s mechanical spring ensures a reset even if system pressure drops significantly (above the 0.15MPa minimum).
Application Fit: This is a vital design strategy for safety gates, fire dampers, or clamping jigs where the "unpowered" state must remain engaged to protect the operator or the workpiece.

3. Labeling for Maintenance Safety

When using "Normally Open" logic, always label your machine cabinet. A field engineer might expect the cylinder to retract when the valve is de-energized. Clear labeling prevents "Ghost Movement" accidents during manual maintenance of the 1/4" air lines.

Design Your Logic with Precision

The flexibility of the Airtac 4V210-08 makes it the go-to choice for complex pneumatic logic. Whether you need standard replacement valves, manifold kits, or technical guidance on fail-safe design, visit Airtac-Shop.com to ensure your automation is built on a foundation of safety and efficiency.