The piston actuator has been designed for valves (globe and gate valves) with a linear stem movement. A special technical feature of the new actuator is a double piston in tandem arrangement used for a variant designed for high actuating forces. This means that two pistons are operated along one rod in separate pneumatic chambers.
The combination of a 500 mm diameter piston and a control pressure of 7 bar in a double-acting actuator design allows actuating forces of more than 250,000 N to be achieved. The pistons are fitted with a disc with single-lip profile joint each. This configuration ensures smooth, low-friction movement. The piston rod is sealed by a U-ring and a scraper ring.
The air is routed internally so external tubing between the solenoid valve and the cylinder chamber is not necessary. The solenoid valve is connected to the actuator via a Namur interface. The actuators are also available with spring assemblies which move the valves to the defined fail-safe position in the event of a compressed air failure.
Fitted with two pistons arranged in tandem, the SISTO-LAP-500 actuators achieve actuating forces of more than 250,000 N. (source: KSB)