Method and apparatus for measuring turbine shell clearance

A turbomachine comprising:

• a rotor;
• a stator surrounding the rotor, the stator including a lower stator shell and an upper stator shell,
• a plurality of sensors inserted in the lower stator shell, each of the plurality of sensors being configured to measure:
• a tops-on clearance between a rotor blade tip and an inner surface of the stator, wherein in the tops-on condition, the clearance is measured while the upper stator shell and the lower stator shell are assembled together and the rotor is installed within the assembled stator, and
• a tops-off clearance between the rotor blade tip and the inner surface of the stator while the lower stator shell and the rotor are assembled together, and the upper stator shell is not affixed to the lower stator shell;
• and
• a computing device operably connected to each of the plurality of sensors, the computing device being configured to determine a tops-on/tops-off shift, wherein the tops-on/tops-off shift is equal to a difference between the tops-on clearance and the tops-off clearance;
• wherein the plurality of sensors are spaced such that either:
• one sensor is axially aligned with each of a plurality of stages of rotor blades, or
• one sensor is axially aligned with every other stage of the plurality of stages of rotor blades.