Method for prestressing tubes of a heat exchanger with precise tailoring of the prestress

摘要

In order to prestress a tube (4) of a heat exchanger in tension in the axial direction, with precise tailoring of the prestress, at least one of the end parts (4a, 4b) of the tube (4) is expanded diametrally using a hydraulic pressure while the tube (4) is fixed at its ends in the tube plates (3a, 3b). The value of the prestress in each of the tubes (4) of the heat exchanger is tailored by altering the initial radial clearance between the external surface of the end part (4a, 4b) of the tube (4) and the internal surface of the hole (5) passing through the tube plate (3a, 3b) in which hole the end part (4a, 4b) of the tube (4) is engaged before diametrally expanding the end part. The end part (4a, 4b) of the tube which runs substantially over the entire length of the hole (5) passing through the tube plate (3a, 3b) is hydraulically diametrally expanded. The initial radial clearance (6) between the tube (4) and the hole (5) is tailored to obtain longitudinal contraction of the tube (4) and therefore a prestress of a precisely determined value. The invention applies in particular to once-through heat exchangers.