Abstract: Valve actuators are protected by fireproof enclosures capable of withstanding temperatures up to 2300.degree. F. The fireproof enclosures are made up of two or more units, one of which is a center unit rigidly mounted upon the valve actuator itself. The other units are attached to the center unit by means of stepped flanges forming airtight seals therewith. Each unit has a substantially box-shaped frame with expanded metal sides, which frame, exclusive of stepped flanges, is substantially completely encased in a homogeneous body of refractory material, preferably formed by vacuum molding form a slurry of refractory material into a mold surrounding the exterior of the frame and curing the refractory material deposited thereby. The preferred refractory material is a mixture of alumina ceramic fibers and a colloidal silica binder.