The sealing element is lifted directly via an externally controlled actuator by means of compressed air. A pressure spring is installed in single acting cylinder to ensure a reset to the rest position by drawing off the control air. The standard functions are: ‘Closed by spring force and with the medium flow’ or ‘Closed by spring force and against the medium flow’. Closing valves are used in liquid-bearing pipes for shutting off ‘against the medium flow’, in order to alleviate the water hammer effect.Valves are suitable for controlling gaseous, higher viscous, not too dirty, as well as aggressive mediums. The actuator is separated from the medium.