A turbine assembly having a bladed turbine wheel and a turbine casing (1000), extending axially of the turbine assembly, radially outwardly surrounding the tips of the blades of the turbine wheel, the casing having at least one radially outwardly extending dummy flange (2100, 2200) off which, in axial direction, one or more cooling manifolds (1100, 1200, 1300), wrapping radially outwardly around the casing, are mounted, the or each cooling manifold being adapted to receive cooling air and to discharge the cooling air radially inwardly towards the casing, for cooling the casing.