Turbine vane segment and impingement insert configuration for fail-safe impingement insert retention

The present invention relates generally to cooling gas turbines that are used, for example, for electrical power generation and, more particularly, to the impingement insert to nozzle connection in such gas turbines. An impingement insert sleeve is provided that is adapted to be disposed in a coolant cavity defined through a stator vane. The insert has a generally open inlet end and first and second pairs of diametrically opposed side walls, and at least one fail-safe tab defined at a longitudinal end of the insert for limiting radial displacement of the insert with respect to the stator vane.