Abstract: A gas motor actuator is provided for opening or closing an actuated valve, such as a pipeline valve, using power gas, which is a gas under pressure. The gas motor actuator includes a gas turbine motor, a high-volume shuttle valve coupled to the gas turbine motor, and a pair of control-limit valve assemblies for delivering power gas to the shuttle valve. One control-limit valve assembly is for opening the actuated valve, and the other is for closing the actuated valve. The gas motor actuator can receive a signal to open or close the actuated valve, which allows pilot gas to open a control valve portion of one of the control-limit valve assemblies, allowing power gas to pass through the control portion to the shuttle valve. The power gas passes through the high-volume shuttle valve, through the gas turbine motor, and back to the shuttle valve for discharge as an exhaust. The power gas rotates a shaft in the gas turbine motor, which, through gears, opens or closes the actuated valve.