A gas turbine device includes an inlet casing and a stator diaphragm provided inside the inlet casing. The stator diaphragm has an integral inner stator shroud and an outer stator shroud and a plurality of stator vanes provided in a circumferential arrangement between the inner stator shroud and the outer stator shroud. A plurality of key slots is provided in a circumferential arrangement on the stator diaphragm and a corresponding plurality of key slots is provided in a circumferential arrangement on the inlet casing. The key slots provided on the stator diaphragm are aligned with the plurality of key slots provided on the inlet casing. A key is inserted into each of the plurality of key slots provided to prevent rotation of the stator diaphragm with respect to the inlet casing. The stator diaphragm is secured in an axial direction by a stator shear ring.