I presume that you are referring to typical plate heat exchnagers in auxilliary cooling water circuits in a power plant.Plate exchanger nozzles are normally mounted on a sheet of the face of the plate exchanger. They are normally mounted on a foundation from the grade.It is better to have the vendor supplied displacements. In the absence of such information, you will have to work out based on the fixities defined on the vendor drawings for an estimate of the movements.