Normally when a steam supply valve to a turbine fails open, the turbine begins to over-speed. The Over-speed Limiter generally will operate to shut the turbine down to preclude any damage. However, when the limiter fails, damage usually occurs within the turbine.
The picture above shows the last stage of a steam turbine which went into over-speed and the limiter failed. The blades impacted the casing and began to disintegrate causing severe internal damage to the turbine.
BC Engineering and Design engineers were tasked with measuring the blade sockets to determine distortion from the nominal 3D model.