Dear,

Beyond the terminal points indicated in equipment (boiler & steam turbine in your case) vendor documents, piping stress analyst's engineering jurisdiction ceases to exist. Imposed displacements & allowable force/moment at these terminal point isolate equipment design from piping design.

Where such isolation is not possible, structural simulation of the equipment is included in piping model.

Thus, when boiler vendor is happy to isolate at some terminal point, why do you worry!

regards,

sam