METHOD FOR SECURING TUBES TO TUBE PLATES Russian patent published in 2002 - IPC

FIELD: plastic metal working. SUBSTANCE: method comprises steps of preliminarily reducing tube end portion, then forming on its outer surface annular protrusion in the form of two different-size trapeziums. Small base of upper trapezium has sharpened edges mutually spaced by distance equal to interval between apexes of angles of outer annular groove of tube plate opening. Above mentioned annular groove has trapezoidal cross section. Tube is placed in opening of tube plate at matching annular protrusion of tube with outer annular groove of opening. Tube is fixed against possible motion and it is fixed in opening of tube plate due to applying compression effort to inner surface of tube. At first annular protrusion is freely introduced to outer annular groove of tube plate. Said stage is terminated by compacting angular portions of joined members. Then tube is locally expanded for subsequent fixation of annular protrusion in annular groove at plastic yielding of tube material. When local expanding is over tube is finally fixed relative to opening of tube plate due to cross shift of tube material relative to its annular protrusion. It provides enhanced quality of filling cavities of annular grooves. EFFECT: improved operational characteristics of expanded joints. 5 dwg