How does a Closed Loop work?

The Closed Loop is a control option to prevent the inlet of outside atmosphere into the actuator pneumatic cylinder. Altough RFS actuator cylinders are designed with internal anti-corrosion properties, the closed loop system enhances our offer and complies with the request of 'clean breath system' often received for applications such as offshore platforms, coastal areas, chemical plants, paper mills, etc. where the atmosphere can be highly saline, caustic or dust laden.

As shown in the image, the accessories making up a closed loop are: a quick exhaust valve (2), a flow regulator (6) and a check valve (3).
When the solenoid valve (1) is energized, the air flows into the pneumatic cylinder, strokes the piston and the spring is compressed; air from the inboard side of the piston is vented to the atmosphere through the check valve (3).
Upon de-energizing of the solenoid valve (1), the spring is released, driving the actuator to the fail-safe position. The presence of the chack valve (3) inhibits the ingress of ambient air into the cylinder and thanks to the quick exhaust valve, the outboard piston volume exhausts into the inboard side. Excess volume is vented through the check valve (3).