A turbine assembly includes a basically hollow aerofoil. A wall segment may be arranged at a side of the aerofoil. An insertion aperture in the wall segment provides access to the aerofoil and an impingement tube may be inserted via the insertion aperture into the aerofoil to be located within the aerofoil and extend at least in a span wise direction of the aerofoil. A protrusion section of the impingement tube may extend in a direction basically perpendicular to the span wise direction over an edge of the insertion aperture. The protrusion section may be overlapped by at least a part of the wall segment. Adjacent to the protrusion section, an overlap section of the impingement tube is arranged to abut the edge of the insertion aperture. The protrusion section and the overlap section may be formed integrally with each other in one piece.