The method of fixing tubes

 

The invention relates to the processing of metals by pressure and can be used when attaching the tubes of heat exchangers using the effect of localized directional plastic deformation of the pipe material. The ends of the tube profiles with the formation of the tip containing the loaded and supporting sectors as well as the transition area between them. One of the ends is installed in the pipe hole, combined with an annular groove, combining groove of rectangular and triangular cross-sections. While the small base ring of the transition section ends have a front edge of the ring grooves with a rectangular cross-section. Then the pipe is fixed on the possible move and fix in the pipe bore by application of compressive efforts on the inner surface of the loaded area. The result is obtaining permanent connection with high utility features. 5 Il.

The invention relates to the field of metal forming, and in particular to the process of fixing the tubes of heat exchangers using the effect is the accumulation of tubes, including installation one end of the tubes in the tube hole, fixing it from possible move, welded pipe end to the face of the tube with the subsequent fastening of the pipe in the hole in the tube by the application of compressive efforts on its inner surface (see P. Doroshenko A. manufacturing Technology marine steam generators and heat exchangers. Leningrad: Sudostroenie, 1972, 143).

To the main disadvantage of this method of fixing tubes should be attributed to the increased cost of production of the combined compounds. In addition, the latter have a certain restriction on the use, as not all of the material, forming a pair of connected elements are welded., There is also known a method of fixing tubes, including the profiling of the pipe ends with the formation of the tip containing the load bearing sections and conical transition sections between them, one of the ends in the tube hole having an annular groove with a triangular cross-section, fixing the pipes from the possible movement and its subsequent consolidation in the tube hole by application of compressive gain is a remnant of the known method is that, what if its implementation is not ensured transverse shift of the transitional conical section with respect to the outer edge of the annular groove. The latter is a provision in the formation of elevated service characteristics of the longitudinally-pressing fixing tubes.

Object of the invention is to provide such a method of fixing tubes, which would allow permanent connection, providing a transverse shift of the transitional conical section with respect to the outer edge of the annular groove.

The technical result is achieved in that in the method of fixing tubes, including the profiling of the pipe ends with the formation of edge lines containing loaded, the reference sections and conical transition section between them, one of the ends in the tube hole having an annular groove with a triangular cross-section, fixing the pipes from the possible movement and its subsequent consolidation in the tube hole by application of compressive efforts on the inner surface of the loading plot ending, according to the invention in a tube hole perform a combined annular groove, combining the ditch annular transition section ends have a front edge of the ring grooves with a rectangular cross-section.

Implementation of the proposed method of fixing tubes allows permanent connection with high utility features.

This is because fixing the pipe in the pipe hole is longitudinally-pressing method, when performing the conical distributing pipes, produce transverse shear blade relative to the edges of the tube holes with fixing the pipe on the front surface of the tube and the simultaneous filling of the volume of the annular groove non-contact deformation of the pipe material. The median surface of the tapered transition section is in contact with the outer edge of the annular groove. Then move the conical mandrel relative to the tube causes the deformation of the conical transition section transverse shift of the material with respect to the outer edge of the annular groove.

Smoothing action of the tool on the pipe surface allows you to build in the inner surface layers of the pipe favorable compressive residual stresses of the first kind.

The invention is illustrated by drawings, where Fig.1 shows a heat exchanger tube with a profiled tip located is; is a of Fig.2 - stage operation has finished hand loading section ending in a cone in terms of the realization of non-contact deformation of the pipe material when filling the annular groove before fixing the pipes on the walls of the tube holes; Fig.3 - the stage of fixing the pipe on the pipe walls of the hole, followed by radial deformation of the length of the conical transition section located before the outer edge of the annular groove; Fig. 4 - stage fixing the pipe in the hole in the tube, followed by axial irreversible deformation of the blade ends and the transverse shift of the transitional conical section with respect to the outer edge of the annular groove; Fig.5 is a high - quality one-piece connection of the tubes and tube sheets.

Variant implementation of the invention consists in the following.

Heat transfer pipe 1 (Fig.1) perform operations with the aim of preparing the outer surface of its ends to the profile: edit pipe, cut it length and Stripping the outer surface of the ends to the metal layer.

Then on each of the ends of the pipes form a known distribution operations and crimping profiled ends, containing a reference plot with wny the diameter of the hole, and conical transition section between them (marked by dots).

The pipe is placed in the hole of the tube 2, having a combined annular groove of rectangular cross-section, transitioning into a triangular cross-section, and fix it from the possible movement (represented by arrows).

In this case, the small base of the conical transition section ends are placed in front of the annular groove, for example, by dividing the height of the conical transition section into two equal parts (Fig.1).

Check for correct installation of the pipe is carried out by measuring its rearward end on the front surface of the tube.

In the hole ending set conical mandrel 3.

Applying the mandrel axial force (represented by arrows) to the inner surface of the loading plot ending, reach pressures, causing cone distributing ending, followed by non-contact deformation of the supporting pipe section with a partial filling of the volume of the annular groove and the formation of a plastic hinge at the inner edge of the ring groove (Fig.2).

Thus, to produce restriction hearth plastic deformation in the axial direction.

the material of the ends of the length from its end surface to the front surface of the tube with the formation of the influx and the formation of the first ring density between the joined elements.

Further axial movement of the mandrel causes the fixing pipe on the pipe walls of the hole by a transverse displacement of the blade relative to the edges of the tube holes and the simultaneous deformation of the length of the conical transition area in front of the edge of the groove in the radial direction (Fig.3).

At one point during this movement of the mandrel in the axial direction will be full contact length of the conical transition section with the surface of the pipe hole (outside ring grooves).

Further axial movement of the mandrel causes the original to axial movement of the transition section in the direction of the ring grooves with subsequent cross his shift with respect to the outer edge of the ring groove (Fig. 4). Thus, the second ring is formed on account of the density between the joined elements.

The process of fastening the pipe in the pipe hole ends with a stop tapered mandrel in position, when will pan across the canvas of the pipe relative to the back surface (the third ring density between the joined elements).

The removal of deforming the connecting elements of the effort makes practical the internal stresses in the inner layer of the pipe, what determines the obtaining permanent connections specified corrosion characteristics.

Pilot, validation of the developed method was pinned steel (20) of the pipe-shaped outer ends in the tube sheets of steel 16GS. Initial geometrical dimensions of the tube were: outer diameter - 25 mm, wall thickness - 2.5 mm Outer surface of the pipe ends have been calibrated for a length of 33 mm up to a diameter equal to 25.7 mm ends of the pipe profiled radial crimping technology to snap diameters: minimum of 24.3 mm and a maximum of 25.3 mm

Profiling the ends of the pipes was carried out in the technological snap-on horizontal hydraulic press, double action with the effort of not more than 0.2 MN.

Pipe holes were produced with diameters equal to 25,35+0,05mm Combined annular groove had: in a rectangular part of cross section depth of 0.3 mm, width of 1 mm; in the triangular part of the cross sectional length - 4 mm

Annular projections on the fixed tubes in the tube holes had a cross-section with dimensions corresponding to the dimensions of the combined ring grooves.

When installation is relatively outer edge of the ring groove.

Technological equipment for production of pipes with outer circular edge lines and its fastening in the tube holes were made from tool steel WA with hardness after quenching HRC of not less than 56 units and precision of the Executive sizes 9-th degree of accuracy.

The fixing of the tubes was carried out on a special stand with pump station firm "Indresco" and through the conical mandrel, using the extractor.

It is established that the profile of the external surface of the pipe end in combination with fixing pipes on the walls of the pipe openings through the transverse displacement of the blade relative to the front surface of the tube and the outer edges of the annular grooves allow you to perform high-quality permanent connection with high utility features.

Tests for pulling tubes from the tube confirmed enhanced mechanical strength of the obtained compounds.

The density of connections (hydraulic test) provided 100% of their suitability to the requirements of production.

The invention is applicable in the manufacture of the tube bundles of heat exchangers oil refining, Neftchi the property securing tubes, includes profiling of the pipe ends with the formation of the tip containing the loaded and supporting sectors as well as conical transition section between them, one of the ends into the tube hole is made with an annular groove, fixing the pipes from the possible movement and its subsequent consolidation in the tube hole by application of compressive efforts on the inner surface of the loading plot ends, characterized in that an annular groove in the tube hole perform combined in the combination of annular grooves of rectangular and triangular cross-sections, and when you install the tail pipe in the pipe hole of the small base of the conical transition section ends have a front edge of the ring grooves with a rectangular cross-section.

 

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