Importance

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Abstract

An apparatus for securing straight tubes between two tube sheets in a pressure-tight manner, especially in the manufacture of heat exchangers. Tubes are inserted, with play, in bores of the tube sheets. One end of each tube is hydraulically expanded via a pressure medium to thereby press this one end against the associated tube sheet. The one end is secured to the associated tube sheet, preferably by being welded thereto. Each tube is heated in conformity with a prescribed prestress that is to be produced in secured ones of the tube to take into account subsequent operation conditions to push a portion of the non-secured other end of the tube out of its associated tube sheet until a predetermined difference in length between the cold and heated-up states of the tube is pushed out. That portion of the other end of the tube that is disposed in one of the bores of the tube sheets is hydraulically expanded, whereupon the pushed-out end portion of the tube is secured to its associated tube sheet, preferably by being welded thereto. The expansion resulting from heating the tube is used as a control signal for the hydraulic expansion process. For this purpose, a switch for the valve for supplying pressure medium to the annular chamber is disposed on the expansion mechanism, with this switch being adapted to be activated by the end face of the tube that expands due to heat.

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First Claim