Method for producing welded connections and an auxiliary device

An auxiliary device for a method for producing welded connections between inner tubes and a tube support plate of a tube bundle for a product-to-product shell-and-tube heat exchanger, wherein the welded connection is designed such that:

• an inner tube of the inner tubes, with its tube inner bore, is connected to an end face of the tube support plate that faces the inner tubes in a plane perpendicular to an inner tube longitudinal axis, which tube support plate comprises a plate inner bore, and wherein the tube support plate is disk-shaped;
• the tube inner bore and the plate inner bore have inner diameters of equal size and are oriented so as to be aligned with one another,
• in an unwelded starting position, the inner tube and the tube support plate are fixed to one another by means of a first form fit, which is effective both radially and axially and in each case in opposing directions,
• a circumferential round weld is made orbitally, starting from the tube support plate and the tube inner bore, in a single pass and continuously from radially inside to radially outside;
• and
• a weld width of the circumferential round weld covers at least one axial form fit depth of the first form fit, wherein:
• a first holding ring half and a second holding ring half define holding ring halves and together form a closed ring,
• the holding ring halves touch in a parting plane that extends through a center of the auxiliary device, and the holding ring halves form a non-displaceable second form fit in the parting plane,
• the tube support plate establishes a tube layout pattern for arrangement of inner tubes arranged in parallel with one another by defining more than one plate inner bore,
• the tube layout pattern is reproduced in the holding ring halves in such a way that the inner tubes arranged so as to be evenly distributed around a single pitch circle are in each case enclosed at most by one half by the holding ring halves, wherein an opening of relevant enclosing contour faces the center,
• the parting plane additionally extends through at least one inner tube longitudinal axis lying on the single pitch circle,
• holding means engage displaceably in the holding ring halves in each case on a periphery of the holding ring halves and in a star shape oriented towards the center,
• the holding means are in each case tangent on both sides to adjacent inner tubes arranged on the single pitch circle, and
• if necessary, the holding means fix an inner tube of the inner tubes that is arranged in the center by means of their relevant end face facing the center and are in each case detachably fixed in this position themselves.