The contained block protects the spring chamber of single-acting actuators from corrosion, e.g. by aggressive gases in the atmosphere. The block is to be connected at the NAMUR-connection of the actuator and bears a further connection for NAMUR-solenoid valves resp. a 1/4" air connection.
By A1 influxing pressure air will go to chamber A and moves the pistons against spring force tothe outer side. At disconneting of the pressure air the air content of spring chamber A moves to spring chamber B and additionally into the atmosphere (B1). Intrusion of air from outside into the spring chamber is protected thereforet.