If the clearance between the nozzle diaphragm and the adjacent row of blades on an SSTG turbine is outside prescribed limits, what action should be taken?

In the context of a SSTG (Steam Turbine Generator) turbine, maintaining proper clearance between the nozzle diaphragm and the adjacent row of blades is crucial for efficient operation. If this clearance is outside the prescribed limits, it typically indicates a misalignment or a need for adjustment rather than a component failure.

Adjusting the position of the rotor by changing the filler piece in the thrust bearing is the appropriate action because this adjustment can help reposition the rotor, thereby correcting the clearance issue without the need for component replacement or major overhauls. It allows for fine-tuning of the turbine's alignment relative to the nozzle diaphragm and blades, ensuring optimal performance and preventing issues such as vibration or reduced efficiency.

Other options, like replacing the nozzle diaphragm or recalibrating the turbine, may not directly address the clearance issue, which is primarily related to rotor positioning. Increasing steam pressure may lead to further complications or exacerbate the problem without resolving the underlying clearance issue. Therefore, adjusting the rotor's position is the most direct and effective solution to restore the proper clearance and maintain operational integrity.