ES2279091T3 - CONTAINER UNDER PRESSURE GIVEN WITH A TUBULAR CONNECTION. - Google Patents

Abstract

The invention relates to a pressurised container (1) comprising at least one tubular connection (2) to an opening in the container wall. According to the invention, the cross-sections of the opening and at least the tubular connection (2) in the vicinity of the opening are oval-shaped, the large axis of the oval shape being aligned with the direction of the first primary stress, which would be generated if the pressurised container (1) were subjected to an internal pressure at the connection point without the opening and the connection (2). This permits both the local and global maximum comparison stress to be advantageously reduced in the component when the latter is subjected to a pressure and/or the stress to be displaced into areas, in which it is not as critical. The invention can be used in a particularly advantageous manner for injection-moulded parts consisting of plastic, as joint lines in many geometrical forms cannot be avoided in precisely those areas where the most stress occurs as a result of the geometry of said parts.

Description

Pressure vessel equipped with a connection tubular.

Technical field

The present invention consists of a vessel under pressure containing at least one tubular connection over an opening of the vessel wall according to the preamble of claim 1 .

If a vessel is fed under pressure, then example with an internal, pneumatic or hydraulic overpressure, Tensions appear on the vessel wall. To reduce to minimum tensions as well as to maximize the ratio of volume on the surface, we build containers under pressure of so that they approach the sphere or the cylinder as much as possible. Whether a connection is applied on said container, the tensions are concentrate on the connection zone, which makes this zone is more strongly pressed and forms a weak point of the vessel under pressure.

In pressure vessels manufactured with a plastic injection molding technique with tubular connections, such as those used for example for water meter boxes, we have link joints, due to the manufacturing, in the sense of spillage of the molding material by injection behind the connections, and thus an area in which tensions are also concentrated. For the piece, this means a noticeable weakening, because a stronger demand precisely it appears there where you must have simultaneously the weaker properties of the material.

Even on T-shaped or similar pieces, in which a pipe is branched from a piece of pipe of approximately identical section, they appear on the inner side of the curvature of the branching with an accumulation of pressure Internal crisp stress concentrations. In the pieces in T manufactured by means of an injection molding technique, we find link junctions again, and because of the concept of emptied, sharp edges appear. The concentration of tensions with the junction joints and the edges leads there, again, to a remarkable weakening of the piece.

Fundamentally similar problems appear in the elbows of tubes. Mathematically, we can describe the tensions for each point of the vessel wall, by tensioners of tension. Three main call tensions, of which one, in the mechanical terminology of tension tensioners, is defined as the first main voltage, they are constants of the tensioners of tension versus coordinate transformations. In the case of a vessel that is under an internal overpressure, the first main tension corresponds to the greatest effort of traction. Likewise, this notion is used below. The we call some main addresses are always attributed to the main tensions

State of the art

To compensate for a weakening of the vessels under pressure by connection integration, we know provide for fortifications of the vessel wall and / or the Connection. It is not possible however to always enter so simple such fortifications, particularly out of time, or  this may cause an additional cost and expense in material.

WO 01/69187 A1 recommends, in as for a vessel under particular useable pressure as water meter box, form its bottom part in ellipse with the In order to reduce tensions. We do not know well in what background part here document WO 01/69187 A1, because the background forms hemispherical or at least those that approach the ellipse (whatever called a patterned background) are naturally known for time in the state of the art and would present properties so less so good. As a complement, the WO document 01/69187 A1 recommends, to remove the tensions from the joints of  welding in the area between two connections and the part of below the box, which is identical to the bottom part, give a elliptical shape to the connections. Figure 2 gives an example. He WO 01/69187 A1 does not give details that would allow understand the claimed displacement of tension, and does not explain neither where tensions would be displaced.

A vessel under pressure of the type mentioned above is known as document US-A-3342209, this document which mainly contemplates vessels under pressure of thick walls, such as those of a reactor with boiling water through nuclear fission, where the tubular connection leaves in the form of an outlet nozzle of a wall area and is thus manufactured from a piece with this wall area. The section of the outlet nozzle thus manufactured widens here inwards to the shape of an oval section. Document US-A33422 also mentions the possibility of fixing a tube having a corresponding profile, produced for example by compression, in an oval through hole mixed in the wall of the vessel under pressure, to improve crack resistance .

Description of the invention

The purpose of the invention is to indicate how to obtain judiciously technical properties of container tension under pressure of the type mentioned above, particularly in the pressure vessels manufactured by a molding technique pressure or by injection with a junction joint.

To solve this problem, the invention recommends a vessel under pressure as characterized in claim 1. In this sense, the invention also makes use of an ovalization of the connection in the connection zone . The section of the opening and that of the tubular connection in this opening are made oval, and with the major axis of the oval shape in the direction of the first main tension that would appear in case of feeding under pressure with an internal overpressure in the Connection place without opening and connection.

The hypothesis of an internal overpressure serves here only as a theoretical model to determine the direction of the first coercion of main tension and as well as the direction of major axis of the oval shape. However the geometry that follows It is also generally valid for external overpressure. For simplify the description, however we will consider below, Essentially, only the case of internal pressure.

We can express the ovality O by the relationship of the length of the major axis (D) with the minor axis (d) of the shape oval, this relationship is, depending on the application and the geometry, approximately in a range between 1.1 and 3.0, preferably in a range between 1.1 and 2.5, and particularly preferably in a range between 1.1 and 1.9.

As a simple example for the direction of the higher main voltage, a low vessel can be contemplated essentially circular cylindrical circular pressure, in which, in In case of accumulation of internal pressure, tensions appear in the vessel wall, being these tensions about two more times important in the circumferential sense than in the sense longitudinal. A tubular sleeve, oval at least in the area of connection should therefore be added to the wall according to the invention of the vessel, with its major axis directed in the direction circumferential.

In purely spherical containers or those they have a relatively important flat wall, the invention does not It has application, because no major main voltage appears, because to geometry.

Under the term oval, you have to understand very generally, within the framework of the invention, a form rounded elongated, whose elliptical shape for example would represent a particular case

The ovalization of the connection towards the main tension mentioned does not only have an influence notable on the decrease of the maximum tensions that appear on the wall of the vessel under pressure. Thanks to her, too we can move the tensions that appear towards other areas, by example where there are no link junctions or edges pronounced, and where, to this extent, they reveal less annoying

This leads to a certain inconvenience, namely the section reduction available for example for a spill, which is linked to ovalization, which has been produced from a form of circular section by flattening said form, respectively by shortening an axis. To get the advantages according to the invention, however, it is sufficient to proceed with the ovalization only immediately in the connection zone, and make it evolve again, on a regular basis, over a distance relatively short, towards a circular tube shape. The length of this transition distance L can be located for example in the order of dimensions of the diameter of the circular shape of the tube connection, or if that is the case, be too short. By a so limited section reduction, we cause only small pressure losses, which in relation to the losses of the whole of a system are most often negligible.

The invention also includes, however, vessels under pressure not covered by a spill, subjected to static pressure The conception of the vessel under pressure and / or of the tubular connection must be understood very generally in The framework of the invention. In addition to the example already indicated, also we must fundamentally contemplate the combinations of vessels under pressure and connections in which the vessel under pressure and the connection present approximately the same section, as is the case for example in what is called the T-pieces as a limit case of a vessel under pressure Cylindrical closed on one side, narrowed in diameter with pipes arranged laterally at the closed end, we can include a tube elbow, and there is no need for a difference between the part that serves as a container under pressure and the part that It serves as a pipe. On the other hand a tube elbow can also be considered as a T-piece with one arm.

In addition, as already mentioned, the concept of vessel under pressure should not be understood in a sense limited, in the sense that it would always be solely pressed by an internal overpressure against, for example, a normal external pressure The principle of the invention and geometry resulting from it remain the same in every situation of pressure difference, and then also in case of overpressure external in relation, for example, to a normal internal pressure, as is the case for example in submarines or the like. We can therefore have applications both as a vessel under pressure internal as a vessel under external pressure.

Brief description of the figures

The invention will be specified below with the help of embodiments in reference to the drawings.

Figure 1 shows in a representation in perspective a cylindrical container containing a nozzle oval tubular;

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Figure 2 shows in a representation in cut, a) the box of a water meter with two pipes connection in the form of opposite tubes, b) a side view and c) a top view of the same box;

Figure 3 shows a) to d) the segments of each quarter of the box corresponding to the one in figure 2, but with connecting pipes of different shapes, the state of tension that it is observed in an accumulation of an internal pressure is every time indicated by gray shades in gradient; shades of white designate here a high tension and the black tones a tension low;

Figure 4 presents in a histogram the local and global maximum comparative stresses for various ovalities of connections with a container of the type of the figure 2;

Figure 5 shows in a view as well as in several cuts an ovalized T-piece according to the invention;

Figure 6 shows an oval tube elbow according to the invention, cut in half in a representation in perspective;

Figure 7 shows a) to d), each time cut in half, the tube elbows corresponding to that of the Figure 6, but with a different ovality, the gray hue gradients each time indicates the state of tension for a internal pressure build-up; Y

Figure 8 shows in a histogram the local and global maximum comparative stresses for various ovalities in a tube elbow corresponding to the one in the figure 6.

Embodiments of the invention

Figure 1 shows, as the first simple example, a vessel under pressure 1 of circular cylindrical section to which a pipe 2 is added, laterally in relation to the surface of the body. If one imagines the connection pipe 2 removed, we can indicate three main tensions in the place of the pipe connection for an accumulation that appears when the vessel under pressure is subject to internal overpressure. Under the place of connection of the pipe, it is necessary to understand here by example the meeting point P of the axis of the pipe A on the vessel wall 1. Given the circular cylindrical shape of the vessel under pressure 1, the tension in the direction circumferential is about twice as important as the tension in the longitudinal direction of the container body. In the extent to which the pipe 2 has an oval shaped section and in which the major axis of the oval shape is directed in the sense of the circumference of the container 1 and therefore in the sense from the first main tension, we get a reduction of tensions as well as a favorable distribution of tensions, about all in the zone of connection of the pipe 2. Thus the minor axis of the Oval shape, because of geometry, is directed perpendicularly to the major axis and therefore in the longitudinal direction of the body of the container.

Figure 2 shows in a), b) and c) a container under pressure 3, as used for example for water meters, according to three views. The vessel under pressure 3 it has an essentially cylindrical main body 4, which in the Present example is closed below by a spherical bowl. We find arranged laterally on the cylindrical piece 4 two connection pipes 5 and 6. Connection pipe 5 is oval in the transition zone L and the cut plane of its point of Connection. The direction of the major axis of the oval shape is, as see in b), oriented in the direction of the circumference of the piece cylindrical In the present example, the major axis corresponds to circular diameter of the connecting tube, as also seen in the view from above c). The maximum comparative tensions that appear in the connection zone are reduced as well and are simultaneously  displaced

In the direction of the free end of the pipe connection 5, the oval section is transformed into a circular section, what makes the pipe can be neatly joined more simple, for example also by means of a connection by screw, with other tubular or similar pipes. The transition length L between the oval shape and the circular shape is chosen here so that it is relatively smooth and not produce supplementary tensions. In the case given as For example, the length of the transition L corresponds approximately half the diameter of the circular shape.

Connection pipe 6 is not ovalized and not It is thus formed according to the invention. Serve here only for give a comparative representation of the state of the art.

Figure 3 shows in a) to d) each time quarter segments 7 of a box corresponding to that of the figure 2, but with connecting pipes of different shapes, 8.1 - 8.4, the shading of the voltage state determined by the calculation during an accumulation of internal pressure it becomes apparent. The connecting pipes are simply formed in a closed state, for reasons of calculation technique. The calculation of the voltage state It rests on a model of finished elements. The state of tension, itself multidimensional, is determined by a size scalar, what is called the comparative or von Mieses tension \ sigma_ {v}, which can be derived from the voltage state of defined and known by specialists. Use is made also on the other hand of this type of characterization of the state of tension within the framework of figures 4, 7 and 8 described later.

First, image a) shows how reference the case that contains a connecting pipe with section circular, where we started, for the calculation of 40 mm of diameter, which corresponds to a usual diameter in pipes, for example water pipes. We can recognize high voltage concentrations in zones I and II (white areas in figure 3a). If the container is manufactured by an injection molding technique, by projection on the center of the spherical bowl (above in figure 3a), we have for example along the cutting edge designated by a 9, in direction to the spill, behind the connecting pipe 8.1, a junction joint resulting from the spill union of two melt streams in the injection molding mold. Since this joint corresponds to the high tension in the area II, two factors of unfavorable influence in terms of strength of the container accumulate here.

Then in images b) - c) and d), we see how tensions are reduced in zones I and II and also how displace. In image b), the ovality is 40: 32, in the image c), of 40: 26, and in the image d), of 40: 22. The second number corresponds here always to the length of the minor axis d in millimeters, while the major axis D has remained at 40 mm mentioned by the circular reference section. The case favorable should be here in the image c), because they are few stress concentrations and tensions are distributed completely regularly at a relatively low level. In the image d), on the other hand, a zone III has been formed again high voltage sector.

The influence of pipeline ovality on the maximum comparative tension is also represented in the figure 4 in the form of a histogram, and we still consider, here, additionally in relation to figure 3, others ovalities We note along the horizontal axis a variation of ovality, which is expressed on the one hand by the D / d ratio of the length D of the long axis with the length d of the short axis, by example always in millimeters. The value of the relationship that Observe for ovality Or always indicated. The height of the striped bars is given in relative unit of \ sigma_ {v} per a part the comparative tension that appears in I or II, is described as local maximum tension, while the height of the bars does not scratched gives the maximum comparative tension that appears, described as global maximum voltage in any place, in image d) by example in place III. While the global maximum is in the points I and II, the maximum local comparative voltage is identical to the global tension We recognize that the maximum comparative tension, both local and global, based on the round section (ovality 40: 40, respectively 1) decreases when ovality increases. Only from the middle of the diagram the comparative tension global maximum increases again, because from there, it starts to a zone of tension is formed in zone III. Instead, the tension Maximum local comparison in zones I and II still decreases. According to the requirements placed on the piece, we confer an ovality appropriate according to the developments of tension that are recognized in the Figure 4, where we have for example an oval located in a range from 1.5 to 1.7. Considering the strength reduced material along the joint junction of the injection molded parts, and when a maximum burst pressure for the part, however, can be also in this case the judicious case of choosing ovality in a zone in which the global maximum comparative tension returns to increase.

In the containers of the type of Figure 2, we can lower the global maximum comparative tension as much as the local in more than 50%.

Completely right in figure 4, it is still represented, as a comparison, the case that would have for a round section without ovality with a diameter of 30.6 mm With this diameter, we have the same section surface that in case we have 24 mm. We recognize according to the height of the bars of this case that by a simple decrease of section Without simultaneous ovalization, we cannot achieve a noticeable effect of tension reduction. Expressing ourselves in reverse, too we could say that the reduction of the maximum comparative tension It is due firstly to ovalization, and only for one small part of the decrease of the free section to shortening of the minor axis to which one proceeds according to figure 4 (variant 40: 24).

As another example of application, Figure 5 shows a piece in T 10 with three oval connections 11, 12 and 13, which are all in the same plane (drawing plane) and that they also have approximately the same section. The major axis of the oval shape of the three connections is always chosen perpendicular to the mentioned plane. Opposite connections 11 and 12 one to another could be assimilated, for example, to container 1 of the Figure 1, and in this case connection 13 would correspond to the pipe 2. Unlike the example in Figure 1, the connections are here the three ovalized, as seen also with the help of the section B-B and C-C represented. Fundamentally, it would also be possible not to ovalize however more that two of the three connections, 11 and 12, or not even ovalize that only one of the connections, for example connection 13. As with  the connection pipe 5 of figure 2, the oval section of the three connections again transforms into its free end, about a relatively short distance, in a round section form, although it could always be added to the tube connections round, for example by means of a screw connection. The Round sections are designated in Figure 5 by A-A, respectively D-D.

If in the application example of figure 5, abandon for example one of the two connections 11 or 12 that are made front, we get a 90 ° tube elbow.

Figure 6 shows a particular case, namely a tube elbow 14 that can be manufactured by a technique of injection molded, cut in half and represented in perspective, in which there are pronounced edges, because of the manufacturing. The two connecting pipes 15 and 16 are both ovalized The major axis of the oval plane shape is, in both connections, chosen perpendicular to the plane of the tube bend. Do not we go here to a transition from a round section in Your free end. This would be possible though, and it is also favorite. Connection 15 is shown again closed, purely for reasons of calculation technique.

Figure 7 shows each time in a) to d) semi-shells of corresponding tube elbows to that of figure 6, but with different ovalities, and that are given by new every time for a shading as it has been presented in the figure 3 the state of tension that results from an accumulation by internal pressure Image a) of Figure 7 shows first place, as a reference, the case we have with a section round, not ovalized. We see in the zone I the concentrations of particularly high comparative voltage (field represented in White).

With the help of the sequence of images b) - d), in which only the minor axis in the drawing plane has been of new shortened by stages with preservation of shaft length major, it is clear that when the ovality of connections 15 and 16 increases, tensions in zone I decrease, but on the other hand however in zones II and III new concentrations of tensions appear, although distributed according to the surface in the images b) and c) in total still at a low level. Only in the image d) comparative tensions in the centers of zones II and III are clearly increased. In image b), the ovality amounts to 20:18, in image c) to 20: 16 and in image d) to 20: 14.

Figure 8 shows the four cases of the figure 7 in a histogram corresponding to figure 4, in the which, as in figure 4, the maximum comparative tensions local and global ones are represented each time again at side of the others. With the help of the diagram, it appears so particularly clear that the optimal effect should be at a ovality interval of approximately 20: 16. In the case of a ovality of 20: 16, the maximum global comparative tension versus the round reference form is reduced by about 47%, and the local maximum comparative tension of the inner side of the curvature it is reduced even about 65%.

The preceding examples show that the ovalization, is realizable on numerous geometries of vessels and connections, the concept of vessel and connection can and should, as already mentioned, be understood in a very general way. The example of the pipe elbow in particular shows that both concepts of container on the one hand and of connection on the other hand describe even in this case the same geometry and can theoretically be changed.

As material for manufacturing by a injection molding technique in the ways described more above, synthetic materials can be used among others thermoplastics, in particular those made with a polymer fiberglass reinforced, polymer advantageously chosen in the group of polyamides and copolyamides and which has a melting point of at least 250 ° C, for example as PA 66 and PA 46. We prefer to use in particular a polymer for which is a partially aromatic copolyamide, partially crystallized having a melting point comprised between 300ºC and 350ºC. Said polymer particularly well suited it is marketed for example under the name of "GRIVORY ® HTV-5H1 "by Ems Chemie AG / Ems-Grivory, Domat / Ems, Switzerland. It's about here of a PA 6T / 61 reinforced with 50% by weight of glass fibers (in relation to total weight) with a melting point of 325 ° C, then of a partially aromatic and partially crystalline copolyamide constituted by the hexamethylene diamine monomer components, terephthalic acid and isophthalic acid. The material suits generally in particular for the manufacture of molded parts by injection extremely rigid, solid, heat resistant and of constant mass, and is also characterized by a resistance Very good to chemicals. The mass temperature in the moment of discharge by injection rises to approximately 345 ° C.

Finally we must mention again that Pressure vessels can be manufactured not only in materials synthetic, but from any appropriate material. The invention is also applicable in particular to the construction of metal containers It is particularly advantageous to use the invention in the pouring under pressure of metals (for example the aluminum).

Legend of the drawings

one

Container under pressure

2

Oval connection pipe over the container under pressure 1

3

Container under pressure

4

Cylindrical main body of the lower container pressure 3

5

Oval connection pipe over the container under pressure 3

6

Round connection pipe over the container under pressure 3

7

Segment quarters of the vessel under pressure 3

8.1-8.4

Connecting pipes over the segment rooms 7

9

Die Edge / Link Joint

10

T-piece

11-13

T-part connections 11

14

Tube elbow

15.16

Tube Elbow Connections

A-A

Cutting plane

TO

Pipe shaft

P

Pipe shaft axis meeting point

I, II, III

Tension zones

L

Transition length

D

Length of the major axis of the oval shape

d

Length of the minor axis of the oval shape

OR

Ovality

\ sigma_ {v}

Comparative voltage (respectively tension maximum comparison)

Claims (11)

1. Container under pressure (1; 3; 10; 14) containing a tubular connection (2; 5; 8.2; 8.4; 11-13; fifteen; 16) in the form of a connection nozzle to an opening of the vessel wall,

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in the which section of the opening and the connection nozzle in this opening is oval, the major axis of the oval shape is oriented following the first main rule that would be generated during the loading of the vessel under pressure by a pressure internal, in the connection zone, in the absence of the opening and the connection, and

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at which section of the connection nozzle (5) is circular in its free end,

characterized by

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that he major axis of the oval shape of the opening and the nozzle of connection (5) in this opening corresponds to the diameter of the section circular connection nozzle at its free end and

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that presents a link junction on the vessel wall extends from the connection nozzle in the direction of the shaft minor of the oval form.

2. A pressure vessel according to claim 1, characterized in that it has an essentially cylindrical main body (4), on the cylindrical part of which two connecting nozzles (5, 6) are preferably fixed opposite each other and having at least partially an oval section, the major axis of the oval shape is oriented in the circumferential direction of the cylindrical main body. 3. Pressure vessel according to claim 1, characterized in that it is constituted by a T-piece (10) with three connecting nozzles (11, 12, 13) located in a plane, between which at least one is partly in section oval, the major axis of the oval shape being oriented perpendicularly to the aforementioned plane. 4. Pressure vessel according to claim 1, characterized in that it is constituted by an elbow (14) with two nozzles (15, 16) located in a plane, substantially of identical shapes, and at least in part of oval section, the major axis of the oval shape being oriented perpendicularly to the aforementioned plane. 5. Pressure vessel according to claim 1, characterized in that the ovalization expressed in relation to the major axis (D) on the minor axis (d) of the oval shape is chosen in the range between 1.1 and 3.0, preferably in the range between 1.1 and 2.5 and even more preferably in the range between 1.1 and 1.9. 6. Pressurized container according to one of claims 1 or 2, characterized in that it is made of thermoplastic synthetic material, in particular of glass fiber reinforced polymer. 7. Pressurized container according to claim 2, characterized in that the cylindrical body (4) is closed on one of its sides by a cap and that the junction joints are present on the wall of the container, being visible from the rear cap of the connection nozzles (5, 6). 8. Container under pressure according to one of claims 6 or 7, characterized in that the polymer is chosen from the group of polyamides and copolyamides and has a melting point of at least 250 ° C. 9. Pressure vessel according to one of claims 6 to 8, characterized in that the polymer is a partially aromatic and partially crystallized copolyamide with a melting point of 300 ° C to 350 ° C. 10. Use of the vessel under pressure according to one of claims 1 to 9 as a low container internal pressure 11. Use of the vessel under pressure according to one of claims 1 to 9 as a low container external pressure