What is axial clearance on a steam turbine primarily considered to be?

The correct answer is that axial clearance on a steam turbine is primarily considered to be preset. This is because axial clearance refers to the distance between the rotor and the stationary components of the turbine in the axial direction. It is important for maintaining the efficiency and performance of the steam turbine.

This clearance is typically predetermined during the initial assembly of the turbine, taking into account factors such as thermal expansion, operational conditions, and manufacturer specifications. A preset clearance ensures that there is an optimal gap that minimizes friction and wear while allowing for necessary thermal expansion during operation.

In terms of practicality, once the turbine has been assembled and put into operation, this clearance is not something that is regularly adjusted. Instead, it is set during manufacturing and installation, aligning with the operational design parameters necessary to ensure the turbine functions effectively and reliably.