Abstract: A valve actuator for an automatic fluid control valve actuator which fits an Ames Company predetermined size valve housing and which is also suitable for use in a Cla-Val automatic fluid control valve housing of the same predetermined size and which valve actuator is interchangeable with the actuator of each respective manufacturer. The valve actuators range from 4 inches up to 12 inches and can be used as the original actuator of a set size within the range in either manufacturer's housing. The actuator includes a main body disposed on a shaft with a diaphragm and a diaphragm disk plate adjacent the main body on the shaft, all of which are retained by nuts threadedly engaged to the shaft.