FR2863340A1 - Low-pressure liquid containing reservoir, has cylindrical spacer with structure forming incipient crack zone at level of central part of other spacers, where central part of former spacer has diameter less than that of spacers - Google Patents

Abstract

The reservoir has spacers (5, 6) provided as internal walls and extending vertically to connect upper and lower walls (1, 2). A cylindrical spacer has a structure forming an incipient crack zone distant from junction zones and situated at the level of a central part of the spacers (5, 6). The central part of the cylindrical spacer has a diameter less than that of the spacers (5, 6) and reduced thickness.

Description

2863340 1

RESERVOIR FOR PRESSURIZED FLUID

  The invention relates to a tank for pressurized fluid with improved burst performance. The invention more particularly relates to polymorphic reservoirs.

  Different polymorphic reservoirs are described in the document FR-2 766 906.

  In a first embodiment, described with reference to FIG. 1, the reservoir consists of two upper and lower curved outer walls 1 connected by lateral walls 3, 4 in the form of truncated cylinders. These are closed along their length by internal walls 5, 6 welded tightly. The upper and lower walls 1 and 2 are secured to the inner walls 5, 6 to form a reservoir with three compartments C whose ends are closed by plugs not shown. The different walls can be made of sheet steel or aluminum stamped and welded to each other. Or, the tank body can be made of aluminum by an extrusion process and then closed by welded end plugs.

  In another embodiment, shown in Figure 2, the tank is made of sheet steel or aluminum stamped. It is formed of two half-shells 7 and 8 whose side edges are welded together along their length. Each half-shell has three longitudinal cylindrical cavities 9, 10, 11 whose concavity is directed towards the other half-shell to form three compartments C. Cylindrical spacers 12 are force-fitted into corresponding openings 14 formed in the half-shells. shells and flared against the walls of the latter, then sealed welded.

  However, in these reservoirs, bursting tends to occur in the welded zones, and more particularly in the thermally affected zone in which the mechanical properties of the materials in stress at break and in elongation are lower than in the walls. external or in the spacers. Such a burst at the weld zones has the disadvantage of limiting the increase in volume bursting, detrimental to the safety of the tank.

  The invention aims to overcome the disadvantages mentioned above.

  To this end, the object of the invention relates to a pressure tank intended to contain at least one fluid under pressure, comprising at least one spacer joined to two opposite outer walls, in which at least one spacer has a generating structure. a breaking initiation zone, distant from the junction zones, in which the concentration of the stresses is greater than the stress concentrations at the junction zones.

  The beginning of the rupture, namely the plastification of the material, will then occur primarily in the rupture initiation zone during the bursting of the reservoir. The rupture initiation zone is thus produced by modifying the shape of the spacer, without reducing the intrinsic mechanical properties of the material, such as may occur during heat treatment, welding, etc., which makes it possible to conserve a high burst pressure of the tank.

  Advantageously, said initiation zone is situated substantially at the level of the central part of said at least one spacer, in order to optimize burst volume increase and to increase safety. The location of the rupture in the central parts of the tank makes it possible to reduce the mass of the external walls. The burst pressure value of the tank will then be lower overall while remaining acceptable from the point of view of safety.

  In a variant, the reservoir comprising at least one flared cylindrical spacer, said at least one spacer has a section of asymmetrical shape in the rupture initiation zone.

  Such a spacer is for example formed by forming under pressure.

  Advantageously, these sections have the same surface and / or the same traction behavior along their longitudinal direction.

  More particularly, the section of asymmetric shape is an ellipse whose small (b) and large (a) lengths are respectively smaller and greater than the diameter of the circle (d3).

  In the case of an elliptical section, the maximum stress in the plane of the section resulting from the external pressure is greater than in the case of a circular section, so that the beginning of the plasticization, then the beginning of the Failure to burst will occur primarily in the elliptical part.

  In a variant, the reservoir comprising at least one flared cylindrical spacer, said at least one spacer has a smaller cross-section and / or thinned walls in the rupture initiation zone.

  In another variant, the reservoir comprising at least one spacer forming an inner wall, said at least one inner wall has a smaller thickness in the breaking initiation zone. More particularly, the lateral surfaces of said at least one inner wall are concave over substantially their entire height between the two opposite outer walls.

  The local thinning of the spacers allows in particular to slightly reduce their mass, and therefore that of the tank.

  The invention is now described with reference to the accompanying non-limiting drawings, in which: FIG. 1 is an embodiment of a first type of polymorphic reservoir according to the prior art; FIG. 2 is an embodiment of a second type of polymorphic reservoir according to the prior art; - Figure 3 is a partial front view of a tank according to the invention of the type shown in Figure 1; FIG. 4 is an enlargement of an inner wall of the reservoir shown in FIG. 3; FIG. 5 is a longitudinal sectional view of a spacer of a first embodiment of a reservoir according to the invention, of the type of that shown in Figure 2; - Figure 6 is a longitudinal sectional view of a spacer of a second embodiment of a tank according to the invention, of the type shown in Figure 2; - Figures 7a and 7b are cross-sectional views of the spacer shown in Figure 6 along lines A-A and B-B respectively.

  The tanks of the prior art shown in FIGS. 1 and 2 have already been described in the preamble.

  A first embodiment of a reservoir according to the invention is described with reference to FIGS. 3 and 4. This reservoir has a general shape similar to that described with reference to FIG. 1, the identical parts are therefore referenced with the same numbers. and are not detailed again. The tank according to the invention is distinguished from the prior art by the structure of the spacers 5, 6, in the form of internal walls, which extend substantially vertically, connecting the upper and lower walls 1 and 2 closing the truncated cylinders lateral 3, 4.

  In the rest of the text, we define a X, Y, Z trihedron, the X, Y axes defining a horizontal plane, and the Z axis being vertical.

  The longitudinal direction of the reservoir extends in the direction X, the inner walls 5, 6 extending in a substantially vertical plane parallel to the plane XZ.

  Each wall 5, 6 has in section along the YZ plane, as shown in FIG. 4, a variable di-dimension, or thickness, the smallest value of which is situated substantially at the level of the central part of the wall. The zone of smaller dimension forms a breaking initiation zone according to the invention. Preferably, in this zone, the wall has opposite concave lateral surfaces 20, 21, their concavity being directed towards the inside of the reservoir (towards the compartments C). The rupture initiation zone is then distant from the weld zones S, forming the junction between the walls 5, 6 and the upper and lower walls 1 and 2.

  A second embodiment of a reservoir according to the invention is described with reference to FIGS. 5 to 7. In this embodiment, the reservoir has cylindrical spacers 12 whose flared ends 13 are joined to the half-shells 7 and 8 The structure of the reservoir is similar to that of the tank described above with reference to Figure 2, which differs in the shape of the spacers 12. Only these will be detailed with reference to the figures. On the latter, only the upper part of the spacer is shown, the spacer being symmetrical with respect to an XY plane passing substantially in its center.

  A first variant is described with reference to Figure 5. The latter is a sectional view (YZ) of a portion of a spacer 12. The central portion of the spacer 12 has a diameter d2 smaller than the rest of the spacer and a thickness e lesser. In order to obtain these dimensions, traction can be applied to a cylindrical spacer 12 in order to form an elongated and thinned zone at its center. This traction will lengthen the cylinder in its central right part while slightly reducing its thickness. This elongation value can advantageously be controlled in geometry by applying a constant force. This operation is carried out in the plastic field of the material, without approaching the forces or elongation break so as not to deteriorate too much the mechanical characteristics of the spacer. Advantageously, this traction is performed during the flaring of the ends 13 of the spacer. The thinned zone thus forms a rupture initiation zone remote from the junction zones of the spacer with the half-shells of the reservoir.

  In a second variant described with reference to Figures 6 and 7, the central portion of each spacer 12 has a cross section of variable shape along the Z axis to generate an asymmetry of the radial stresses in the XY plane. Such an asymmetry is for example achieved by press-forming the initially cylindrical central part of the spacer into a section of elliptical shape or having an asymmetrical shape along the X and Y axes. In the example, the spacer has a zone Zc cylindrical connected to the flared portion 13, and substantially at its center, a zone Ze whose cross section is elliptical, the two zones Zc, Ze being connected by a transition zone Zt. The ellipse has a small length b and a long length a, the diameter d3 of the cylindrical portion being between these two lengths: b <d3 <a.

  The elliptical (FIG. 7b) and cylindrical (FIG. 7a) sections then have the same surface and the same traction behavior along the Z axis. On the other hand, the maximum stress in the XY plane resulting from the external pressure is greater in the case of an elliptical section only in the case of a circular section. The beginning of the plasticization and then of the burst rupture will thus occur primarily in this elliptical portion which forms a rupture initiation zone, distant from the junction zones with the half-shells 7, 8.

  Although the described examples comprise three compartments C, the invention also relates to tanks having a different number of compartments, and at least one spacer.

2863340 6

Claims (8)

  A pressure vessel for containing at least one pressurized fluid, comprising at least one spacer (5, 6, 12) joined to two opposite outer walls (1, 2), characterized in that at least one spacer (12) ) has a structure generating a breaking initiation zone, distant from the junction zones, in which the concentration of the stresses is greater than the stress concentrations at the junction zones.   2. Tank according to claim 1, characterized in that said primer zone is located substantially at the central portion of said at least one spacer (5, 6, 12).   3. Tank according to claim 1 or 2, comprising at least one flared cylindrical spacer (12), characterized in that said at least one spacer has a section of asymmetrical shape in the breaking initiation zone.   4. Tank according to claim 3, characterized in that said sections have the same surface and / or the same traction behavior along their longitudinal direction.   5. Tank according to claim 3 or 4, characterized in that the asymmetric section has an elliptical shape, the small (b) and large (a) lengths are respectively smaller and greater than the diameter of the circle (d3).   6. Tank according to claim 1 or 2, comprising at least one flared cylindrical spacer (12), characterized in that said at least one spacer has a smaller dimension section and / or thinned walls in the initiation zone of break.   7. Tank according to claim 1, comprising at least one spacer forming an inner wall (5, 6), characterized in that said at least one inner wall (5, 6) has a thickness (dl) lower in the zone d breaking point.   8. Tank according to claim 7, characterized in that the lateral surfaces of said at least one inner wall are concave over substantially their entire height between the two opposite outer walls.