Abstract: A pneumatic actuator system is provided which includes one or more piston-cylinder type actuators (14) intended for crust breaking operations at electrolytic alumina reduction baths. Each actuator (14) includes a working piston (21), and a piston rod (22) carrying a crust breaking working implement (17). A control circuit having a directional valve (24) is arranged to operate the actuator piston (21) in alternative directions. The control circuit includes air feed flow restrictions (26, 27), end position sensors (28, 29) and air feed shut-off valves (30, 31) for minimizing the pressure air volume needed for accomplishing complete working strokes of the actuator piston (21) at varying crust layer thickness.

Abstract: A pneumatic actuator system including one or more piston-cylinder type actuators (14) intended for crust breaking operations at electrolytic alumina reduction baths, each actuator (14) having a working piston (21), and a piston rod (22) carrying a crust breaking working implement (17), and a control circuit including a directional valve (24) is arranged to operate the actuator piston (21) in alternative directions, wherein the control circuit comprises air feed flow restrictions (26, 27), end position sensors (28, 29) and air feed shut-off valves (30, 31) for minimising the pressure air volume needed for accomplishing complete working strokes of the actuator piston (21) at varying crust layer thickness.