RU2353851C1 - High-pressure cylinder lining tube - Google Patents

Abstract

FIELD: mechanics.

SUBSTANCE: proposed high-cylinder inner sealing thin-wall lining tube made from Ti-containing steel comprises cylindrical shell with shaped all-molded bottoms welded thereto. At least one of the said bottoms has a though opening receiving a pole metal cylindrical union welded to the bottom all along the opening edges. Said bottoms represents the parts of an oblate ellipsoid of revolution with its smaller axis length part making 0.32 to 0.4 of the shell cylindrical part radius and comprises cylindrical sections, ahead of the welded joint zone, with length making 0.15 to 0.2 of the shell cylindrical part that get smoothly conjugated with the part of aforesaid oblate ellipsoid of revolution. Welded seam cast zone on the cylindrical shell features the width exceeding 2 to 4 thicknesses of the walls of the parts being welded together. Aforesaid zone is produced in an inert medium and contains Cr, Ni, Ti in the range of 92 to 99% with respect to the composition of material outside the welding zone. Aforesaid pole metal union has an inner shaped cavity, on the bottom side, that forms a banding belt for the said circular welded seam over the through opening edges. Note that the opening wall thickness equals that, in the welded seam zone, of the bottom material, while the bottom maximum diameter is equal to that of the through opening plus 8 to 10 thicknesses of the material of welded enclosure.

EFFECT: higher reliability.

5 dwg

Description

The present invention relates to pressure vessels, the robust housing of which contains a sealed enclosure inside the liner.

These vessels are intended for storage and transportation of a fluid (liquid or gas) under pressure, and their power casing is made of composite material containing inside a sealed shell - a liner, which, depending on the type and nature of the fluid filling the vessel, is made of aluminum, steel or thermoplastic.

Such vessels, as a rule, are subject to repeated cyclic high pressure loads. In cylinders of this type, in order to avoid leakage of fluid or leakage, special importance is given to the material of the sealing shell - liner.

Known examples of creating composite pressure cylinders using thermoplastics as the main material of the liner (see, for example, patents GB 1023011 A, 16.03.66, F17C 1/16, EP 0300931 A1, F17C 1/16, WO 99/27293, WO 99 / 13263, US 4925044, RU 2150634).

However, in this case, the task of ensuring reliable sealing of the balloon is not completely solved due to the fact that a common drawback of these design decisions and previously known design decisions of the balloon is that the thermoplastics used as the sheath – liner material have high viscoelastic deformability and low compared to metals gas permeability coefficients for almost all technical gases and at high pressures have the main disadvantages - loss of strength during decompression and cracking under prolonged loading.

Numerous examples are known of creating pressure cylinders using a metal liner from various alloys (see, for example, patents: US 5494188, US 5538680, US 5653358, US 5862938, US 5938209, US 5979692, US 6190598, US 6202674, US 6230922, US 2003111473 US 6810567).

However, these designs do not fully provide the solution to the main problems in the design of the container: ensuring reliability with high cyclic loading of its high pressure at the lowest possible weight and manufacturing cost, comparable or lower than that of all-metal cylinders.

Numerous examples are known of creating composite pressure cylinders using thin-walled metal liners from various alloys (see, for example, US Pat. Nos. 3,066,822, 3,446,385, 5,292,027, 5,822,838, 5,918,759, WO 03/029718, RU 2255829, JP 2005133847, WO2005022026 , RU 2149126, RU 2094695, RU 2077682, RU 2001115743, RU 2000123739, RU 2140602, RU 2187746, RU 93049863, RU 2065544, RU 2001115191, RU 2003115384, RU 2002101904, GB1161846, EP 0497687, US 5287988) to solve the problem of ensuring a greater cyclic loading of its high pressure with a weight lower than that of all-metal cylinders.

The closest analogues of the proposed design solution for the implementation of a metal composite cylinder with a thin-walled liner are solutions according to patents RU 2077682, RU 2255829, RU 2140602, RU 2001115743, RU 2000131724, RU 2094695, RU 2000123739, RU 2187746, GB 1161846, EP 0497687.

In designs according to patents RU 2077682, RU 2255829, RU 2140602, the liner is made of steel with a wall thickness of 0.5-0.9 mm, while it is welded and contains a middle cylindrical part and two bottom parts connected to the middle by means of washer rings.

Almost similar solutions are proposed in applications and patents WO 2005220268, WO 2005075880, US 3446385, WO 2005106894.

In the design of the container according to the application RU 2001115743 for a high-pressure metal-plastic container containing a composite shell and a thin-walled metal liner, the problem is solved in that the liner wall thickness and the thickness of the composite shell are selected from the condition that the main supporting element of the cylinder is a composite shell and the material is metallic the liner at operating pressure is in the field of elastic deformation. The disadvantage of this solution is that due to the large difference in the values of the ultimate strain of fracture of the composite (up to 2%) and the strain of elasticity of the metal (0.2%), the weight of the structure and its cost are very high, which makes the cylinder of this design practically competitive with metal counterparts.

Almost a similar solution is proposed by application RU 2000131724.

In the designs of cylinders according to the applications and patent RU 2094695, RU 2000123739, RU 2187746, GB 1161846, EP 0497687, the use of a metal liner made with longitudinal and circular corrugations is proposed. In this case, the outer cavities of the longitudinal corrugations can be filled with elastic material. As an elastic material, an elastomer is used. In addition, the liner can be equipped with additional rings and ring stiffeners installed in the ring corrugations from the outside and the ability to move them around the ring.

The solutions mentioned include the solution according to patent RU 93049863, where it is proposed to use a metal welded liner, and in the zones of the weld seam there is a cavity open on the side of the power shell and filled with elastic material without gaps between the elastic material, the liner and the outer power shell.

A common drawback of these solutions is that a set of longitudinal and annular corrugations increases the overall bending stiffness of the liner, but does not ensure that the conditions for compatibility of deformations in the liner material and the composite shell material are met. In annular corrugations, plastic deformations occur during annular tension, and in axial corrugations during axial tension of the liner during loading of the cylinder with internal pressure. The introduction of various elastic layers and additional rigid rings in the cavity of the corrugations practically does not lead to the solution of the task of creating a highly efficient pressure cylinder.

In the decisions on patents US 6145692, WO 02/30613 and US 6547092 it is proposed to use a thin-walled metal liner with one set of longitudinal or circular corrugations, and lay the reinforcing fibers in the composite sheath in such a way that the deformations of the composite sheath correspond to the deformations of the metal liner. Moreover, the liner corrugations are also filled with elastic material, and the liner itself is separated from the composite shell by a layer made also of elastic material.

The disadvantages of the solutions for these analogues is that under the action of high pressures, the composite shell deforms in a given direction, the material of the elastic layer and the material located in the corrugations are compressed and redistributed. Due to the fact that the corrugated surface of the liner is not an isometric cylindrical surface of the composite shell or the surface concentric to it, the corrugations of the thin-walled liner are deformed arbitrarily and plastic deformations arise in them, which upon repeated cyclic loading lead to the destruction of the liner.

The closest prototypes of the proposed solutions are solutions for applications and patents WO 2005096712, WO 2004096459, US 2005006393, US 2003111473, US 5287988, US 5292027, US 5535912.

The presence of a metal liner in the design of the cylinder requires solving the problem of optimal design of the combined structure, i.e. choosing the optimal ratio of the liner wall thickness to the thickness of the composite, choosing the appropriate composite reinforcement scheme and choosing the appropriate profile shape of the liner bottoms.

The above patents partially solve the first two tasks, i.e. only solutions related to the choice of the design of the middle part of the liner are considered, and, practically, solutions for making the bottom parts and connecting the outlet fitting are not indicated anywhere, which is a common drawback of the mentioned patents.

The objective of the invention is to create such a design of the liner of the cylinder, which would provide highly efficient performance at any level of cyclic loading with high pressure with minimal weight and the cost of its manufacture.

The problem has been solved and the technical result has been achieved due to the fact that the internal sealing thin-walled liner made of stainless Ti-containing steel for the high-pressure cylinder contains a cylindrical shell and integral-shaped profile bottoms welded to it, in at least one of which a through hole is made and it has a pole metal fitting welded to the bottom along the perimeter of the hole, while the new one is that the bottoms are in the form of part of a compressed ellipsoid of revolution, in which part the axis of the minor axis is 0.32-0.4 of the radius of the cylindrical part of the shell, and contain, up to the weld zone, cylindrical sections 0.15-0.2 in diameter of the cylindrical part of the shell smoothly conjugated with part of the compressed rotation ellipsoid, and the cast zone the weld at the weld point on the cylindrical shell has a width exceeding 2-4 wall thicknesses of the parts to be welded, and is made in an inert medium with the content of Cr, Ni, Ti within 92-99% with respect to the composition of the material outside the zone to be welded, the pole metal thing formed with an inner profile cavity from the bottom side to form bandazhiruyuschego waist girth weld along the perimeter of the orifice, the wall thickness at the weld zone is equal to the thickness of the bottom material, and its maximum diameter equal to the diameter of the passage opening plus 8-10 thicknesses welded shell material.

The invention is further explained in detail with a description of exemplary embodiments with reference to the drawings, where:

- figure 1 shows a General view of the liner of the pressure vessel;

- figure 2 shows a General view of the design of the connection node of the fitting;

- figure 3 shows a General view of the possible forms of the profile of the bottom of the liner;

- figure 4 shows a view of the possible forms of stress concentration in the zone of connection of the bottom and shell of the liner;

- figure 5 shows the pattern of voltage changes in the zone of connection of the bottom and the fitting of the liner.

As shown in figure 1, the liner of the pressure vessel contains a cylindrical shell 1, welded to it bottoms 2 and fitting 3, also welded to one of the bottoms 2.

Due to the fact that the main load during the operation of the container is the internal pressure of the medium, when choosing the shape of the profile of the bottom 2, equal tension should be required for both the liner material and the composite. Such a condition is equivalent to fulfilling the requirement of constancy of deformations of cylinder structural elements, i.e.

ε_m=ε_α=ε_β=ε_ν,

ε _m = ε _α = ε _β = ε _ν ,

where ε _m is the deformation of the metal of the liner;

ε _α - meridional deformation of the bottom;

ε _β — tangential deformation of the bottom;

ε _ν - deformation along the reinforcing fibers of the composite.

In the particular case of the design of the container with a thin metal liner and the laying of the composite reinforcing threads along geodesic paths, the shape of the bottom profile for it can be determined from the solution of a differential equation of the following form

,

,

obtained by considering the geometric, static and physical conditions of the construction behavior of the combined metal composite shell.

The following notation is accepted here:

r, y - current coordinates of the profile determining the shape of the shell

y ′, y "- the first and second differential (derivative) of the y coordinate

R is the radius of the cylindrical part of the shell (maximum radius)

r ₀ is the radius of the pole hole in the composite shell

- параметр, учитывающий отношение прочностных характеристик используемого металла и материала армирующих волокон.

- a parameter that takes into account the ratio of the strength characteristics of the metal used and the material of the reinforcing fibers.

Where: σ _m - yield strength of the used liner material

δ _m - thickness of the used liner material

σ _ν - tensile strength of the composite used

δ _R is the thickness of the composite material used on the cylinder.

The solution of the above equation allows you to determine the desired shape of the profile of the bottom of the liner, taking into account the used liner material and composite material. Typical shapes of the profiles of the bottoms obtained by solving this equation are shown in figure 3. An analysis of the obtained profile shapes of thin-walled liners shows that for a wide class of liner and composite materials used, the profile depth is 0.32-0.4 of the radius of the cylindrical part.

As a rule, in the manufacture of the liner, a constant thickness design is used and there are local changes in the curvature of various sections. In such a liner, when it is deformed, local zones of stress concentration are observed. Typical patterns of manifestation of stress concentration zones for a wide class of liner wall thicknesses used are shown in FIG. 3. Analysis of the diagrams shown in Fig. 4 shows that the attenuation of the stress concentration occurs over a length in the range of 0.15-0.2 of the diameter of the cylindrical part. Due to the fact that the bottoms of the liner are welded to the cylindrical part, it is advisable to determine the zones of the welds outside the zones of manifestation of stress concentration, that is, for a length exceeding 0.15-0.2 of the diameter of the cylindrical part, from the point of contact between the bottom profile and the cylinder generatrix.

The essence of the operation of the liner in this design is as follows: when pressure arises in the cavity of the balloon liner, the liner shell 1 is uniformly deformed only due to membrane tensile deformations and in the ultimate state reaches yield stresses σ _m simultaneously over its entire surface. By virtue of the selected shape, the bottoms 2 are also deformed uniformly over the entire surface and, at the same time as the shell 1, achieve fluidity. Moreover, in the zones of the welds, no stress concentration arises leading to their destruction. Thus, the liner is an equally stressed structure. This can significantly reduce its weight and the cost of its manufacture.

As already noted, the bottoms of the liner 2 have pole holes to accommodate the nozzle 3. Due to the fact that the nozzle 3 and the bottom 2 have different stiffnesses, when they are deformed, a local stress concentration arises in the joint zone, leading to premature destruction of the material of the bottom 2. Analysis of the dependences of stress concentration shows that, subject to the condition of equal thickness of the material of the elements being welded along the diameter of the bore and the width of the welded belt in the fitting, which is 8-10 thicknesses of the material, days a 2, localization of the stress concentration in the material of the bottom 2 is almost completely eliminated. Thus, creating an internal profile cavity on the side of the bottom in the fitting with the formation of a retaining band of the ring weld along the perimeter of the bore, the wall thickness of which in the weld zone is equal to the thickness of the bottom 2 , and its maximum diameter is equal to the diameter of the bore, plus 8-10 thicknesses of the material of the welded shell, also provide an almost completely equally stressed liner design but.

As a rule, when welding as a result of heating in the heat-affected zone, the structure and properties of the material change. Figure 5 shows a diagram of characteristic sections of metal in the area of the welded parts. In the zone 4 adjacent to the seam directly, a coarse-grained vidmanshette structure is formed, section 5 corresponds to the complete recrystallization of the metal and differs in its dispersed structure. Zones 6-7 are consistently characterized by a weakening of the temperature factor and structural transformations during welding.

The presence of heterogeneity of material properties in the welded joint leads to the appearance of residual tensile stresses. Despite the structural heterogeneity of the metal of the heat-affected zone, it is believed that its mechanical properties are improved in comparison with the base material, which to a certain extent reduces the probable decrease in the strength of the compound due to residual tensile stresses and stress concentration.

Using the technological method of the formation of compressive stresses, it is possible to reduce the likely decrease in the endurance of the compound. It was experimentally established that for connecting thin-walled plates, the width of the cast zone should exceed 3-4 thicknesses of the welded plates. In this case, sections 4 and 5 expand significantly in the weld zone, which leads to a decrease in the concentration of residual stresses in these zones and the joint as a whole. Thus, by connecting the bottoms 2 of the liner with the shell 1 with the formation of the cast zone of the welded joint of more than 3-4 thicknesses of the parts to be connected, an almost completely uniform structure of the liner shell is ensured.

The functioning of a high-pressure cylinder consists in filling it with a fluid (liquid or gas) to the required pressure level, storing, transporting, emptying, subsequent new filling, and spending the fluid, i.e. in the repetition of actions and operations with multiple cyclic loading. The operation of the device according to the invention was given in the description of embodiments of its design and does not require further special explanation in this case.

With the creation of the proposed device, there was a real opportunity to use pressure vessels of different materials using a thin-walled metal inner shell - liner.

The manufacture and testing of pressure vessels with the proposed liner for their sealing confirmed their high reliability and efficiency.

The invention is not limited to the above-described forms of execution, which are given only to illustrate the invention, and may have changes in the framework of the claims.

Claims (1)

An internal sealing thin-walled liner made of stainless Ti-containing steel for a high-pressure cylinder containing a cylindrical shell and integrally formed profile bottoms welded to it, at least one of which has a through hole and a pole metal fitting welded to the bottom along the perimeter holes, characterized in that the bottoms are in the form of part of a compressed ellipsoid of revolution, in which part of the length of the minor axis is 0.32-0.4 radius of the cylindrical part of the shell, and contain up to For the welded joint, cylindrical sections 0.15-0.2 in diameter of the cylindrical part of the shell smoothly mating with the part of the compressed ellipsoid of revolution, and the cast zone of the weld at the weld point on the cylindrical shell has a width exceeding 2-4 wall thicknesses of the parts to be welded, and made in an inert medium with the maintenance of the content of Cr, Ni, Ti within 92-99% with respect to the composition of the material outside the welded zone, and the pole metal fitting made with an internal profile cavity from the bottom with the formation of a banding its ring weld zone along the perimeter of the bore, the wall thickness of which in the weld zone is equal to the thickness of the bottom material, and its maximum diameter is equal to the diameter of the bore plus 8-10 thicknesses of the material of the welded shell.

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