Ahmed..
Boiler supplier is going to do analysis of internal piping?
As per my understanding, supplier has calculated displacements based on some fixing point of internal piping/nozzles. So you should simply input that displacements at connection node and analyse your part.
Adrian,
What you said is correct that piping shall have relative displacements according to routing and temperature, BUT here, connection is with equipment so there should be some fixed point for nozzle pipe.