EP0101362B1 - Method for tightly sealing an arrangement of a container and plug by heat shrinking of two conical bearing surfaces and arrangement container-plug designed for carrying out this method - Google Patents

Description

The subject of the present invention is a method of sealing a sealed enclosure-plug assembly by shrinking two conical surfaces and an enclosure-plug assembly for implementing this method.

Is used, in particular in the nuclear industry, enclosures requiring sealing to different fluids under pressure and at a relatively high temperature. This is the case for example of transport containers which are used to transport the irradiated fuel assemblies from the nuclear reactor to the reprocessing plant. The closure of such a container must meet the required safety and operating requirements.

There are known, in the prior art, devices for closing an enclosure which use one or more metal seals to produce a metal-to-metal seal. In a device of this kind, the seal must be strongly compressed without rotation by clamping screws or an equivalent means. In general, after dismantling, the metal seals cannot be reused. In addition, a device of this kind often causes problems of seizing or wear of the clamping devices.

Closure devices are also known in which the metal-metal seal is ensured by a fusible joint. In this case, the seal is good, but the mechanical strength of the seal is low. In addition, fusible metal is entrained when the plug is removed, which is troublesome.

Document EP-AL -0 061400, not published on the priority date of this application, describes a method and a device for sealing and opening a container-stopper assembly, the container being closed by shrinking hot the upper edge of the cylindrical opening of the container on the cylindrical plug and the opening being obtained by rapid heating of the upper edge of the opening of the container followed by the extraction of the plug.

The plug is extracted by producing a new relative expansion between the plug and the opening.

• a) on produit un déséquilibre thermique entre le bouchon et les parois de l'ouverture pour provoquer une dilatation relative de l'ouverture par rapport au bouchon,
• b) on introduit le bouchon dans l'ouverture jusqu'à une position axiale prédéterminée correspondant, après retour à l'équilibre thermique, à un serrage prédéterminé,
• c) on rétablit l'équilibre thermique entre le bouchon et l'ouverture,
• d) l'extraction du bouchon étant obtenue en produisant une nouvelle dilatation relative entre le bouchon et l'ouverture.

The subject of the present invention is a method of sealing and opening a chamber-cap assembly, the chamber comprising an opening, the cap and the opening having the same low conicity of the order of 1 to 2 degrees. , this process comprising the following successive steps:

• a) a thermal imbalance is produced between the plug and the walls of the opening to cause a relative expansion of the opening relative to the plug,
• b) the plug is introduced into the opening to a predetermined axial position corresponding, after return to thermal equilibrium, to a predetermined tightening,
• c) the thermal balance between the plug and the opening is restored,
• d) the extraction of the plug being obtained by producing a new relative expansion between the plug and the opening.

According to another aspect of this process, the axial position of the plug in the opening is predetermined by adjusting an axial stop between the plug and the opening and the adjustment of the stop is carried out by axial machining of a flange.

The subject of the invention is also an enclosure-stopper assembly according to claim 4.

It is necessary that the two cones are made with the same metal or with metals having the same coefficient of expansion in order to ensure an appropriate and lasting tightening during the operation of the enclosure during which the temperature of the closure device varies. It is also necessary that the surfaces of the cones are machined with care, and in particular that they have no longitudinal scratches. Of course, it is necessary that the tightening stresses remain in the range of the elastic limit of the metal used for the expected operating temperature.

The male conical bearing can be produced either on the plug or on the opening, which gives several alternative embodiments of the device of the invention.

In case the length of the span is important relative to the diameter, we can. according to a characteristic of the invention, to split the conical surfaces of the plug and of the opening into a plurality of connected cones of the same conicity. This allows the plug to be inserted and removed without requiring an excessively large expansion of the shell.

• la figure 1 est une vue en coupe d'une première variante de réalisation ;
• la figure 2 représente une deuxième variante de réalisation ;
• les figures 3a et 3b représentent deux autres variantes du dispositif de fermeture de l'invention, dans lesquelles la portée conique femelle a été réalisée dans le bouchon ;
• la figure 4a représente un montage pour l'usinage, à partir d'une virole étalon, de la collerette limitant la pénétration des cônes à la valeur correspondant au serrage désiré.
• la figure 4b représente un montage pour l'usinage de la portée annulaire, à partir d'un tronc de cône étalon, de façon à limiter la pénétration du bouchon à la valeur correspondant au serrage désiré.
• la figure 5 représente un deuxième mode de réalisation de l'invention qui comporte deux bouchons à conicités inversées ;
• la figure 6 représente un troisième mode de réalisation dans lequel les portées coniques ont été fractionnées ;
• la figure 7 représente une variante de réalisation de ce troisième mode de réalisation.

Other characteristics and advantages of the invention will become apparent on reading the following description of several exemplary embodiments given by way of indication and in no way limitative, with reference to the appended drawings, in which:

• Figure 1 is a sectional view of a first embodiment;
• Figure 2 shows a second alternative embodiment;
• Figures 3a and 3b show two other variants of the closure device of the invention, in which the female conical bearing has been produced in the plug;
• FIG. 4a represents an assembly for machining, from a standard ferrule, the flange limiting the penetration of the cones to the value corresponding to the desired tightening.
• FIG. 4b represents an assembly for the machining of the annular seat, from a standard truncated cone, so as to limit the penetration of the plug to the value corresponding to the desired tightening.
• FIG. 5 represents a second embodiment of the invention which comprises two caps with inverted conicities;
• FIG. 6 represents a third embodiment in which the conical bearing surfaces have been split;
• FIG. 7 represents an alternative embodiment of this third embodiment.

In FIG. 1, the reference 2 designates the wall of a sealed enclosure. This sealed enclosure can be fixed or mobile. It may for example be a container placed in a transport castle used to transport the irradiated fuel assemblies from the nuclear reactor to the reprocessing plant.

An enclosure of this type must include a closure device meeting very strict safety and sealing requirements. This device must be capable of withstanding high temperature and pressure.

The closure device of the invention shown in Figure 1 uses the tightening properties of the male-female cones of slight slope. The closure device consists of two parts: a ferrule 4 secured to the wall of the sealed enclosure which delimits an opening 6 which gives access to the interior of the enclosure. The opening 6 is closed by a plug 8 inserted inside the shell 4. Tapered surfaces of low taper are produced on the shell 8 and on the plug. In the variant shown in FIG. 1, a female conical bearing has been produced in the shell, while the plug 8 has a complementary male conical bearing. Of course, other combinations are possible, as will be described later.

The closure of the sealed enclosure by means of the device of the invention shown in Figure 1 is obtained in the following manner. The ferrule 4 is heated, which has the effect of expanding it and increasing the diameter of the female conical bearing 4a to the position 4'a shown in broken lines. It is then possible to introduce the plug 8 without difficulty inside the ferrule 4. The ferrule cools, which has the effect of contracting it and therefore of obtaining the desired tightening effect. This provides a tight seal and having good mechanical strength.

It is also possible, instead of heating the shell 4, to cool the plug 8. This can be obtained by cooling by means of liquefied gas introduced by the pipe 10 inside the cavity 12 formed in the plug 8.

It is also possible, if the dimensions of the stopper so require, to cool the stopper at the same time as the shell 4 expands.

The plug is removed in reverse, either by heating the ferrule 4, or by cooling the plug 8 to contract it by means of liquefied gas or by any other similar means.

The plug 8 has a housing 8b for a gripping head 14 which allows it to be handled conveniently and from a distance.

The positioning of the plug 8 relative to the ferrule 4 can be easily obtained by means of a flange 8c of the plug coming to bear on an annular bearing 4c of the ferrule. When the two parts are in this position when a sufficient relative expansion has been caused, it is ensured that the insertion of the plug is such that there is between the two conical surfaces 4a and 8a an assembly clearance and that the tightening, once the thermal equilibrium of the two parts has been reached, will ensure satisfactory sealing and sufficient resistance to tearing, without exceeding the elastic limit of the metal. This allows the enclosure to be closed without having to worry about precisely controlling the temperature difference between the cap and the shell 4.

In the case where the geometrical conditions do not allow the presence of a flange, the precise positioning, in translation, of the plug can be ensured by the mechanism for positioning the latter using a stop, adjustable or not, coming into contact with the plane surface of the ferrule, or even by precise control of the travel of this mechanism. If necessary, the variation of this stroke makes it possible to ensure closings with tightenings of variable value.

There is shown in Figure 2 an alternative embodiment of the device of Figure 1. In this variant, the shell 4 has a female conical bearing and the plug a male conical bearing. However, the slope of the cone has been reversed. The female conical bearing 4a widens towards the inside of the enclosure. It is obvious that in this case, it is necessary to further dilate the ferrule 4 to introduce the plug, since the smallest diameter of the conical seat 4a must become greater, at the time of the introduction of the plug, at most large diameter of the male conical bearing 8a.

As in the previous case, the plug 8 may include a flange 8c which comes into contact at the time of tightening with an annular surface 4c of the ferrule 4, which makes it possible to obtain a precise tightening without having to worry about precisely controlling the temperature difference between the ferrule and the cap.

There are shown in Figures 3a and 3b two other alternative embodiments of a sealed closure device for an enclosure. In these two variants, it is the plug 8 which has a female conical bearing in which the ferrule is received. In the case of FIG. 3a, the diameter of the female conical bearing tapers towards the bottom of the plug. This embodiment can be compared to that of FIG. 1.

In the case of the embodiment of FIG. 3b, on the contrary, the diameter of the female conical bearing is increasing towards the bottom of the plug. This embodiment can be compared to that of the variant in FIG. 2.

The assembly and disassembly of the plug 8 is carried out in a similar manner to that of the plug of Figures 1 and 2. We also note the presence of an annular bearing 4c which, in these embodiments, is in the form of a shoulder of the ferrule 4. The annular bearing 4c cooperates with the flange 8c of the plug 8 (Figures 3a and 3b) to stop in translation the plug relative to the ferrule and obtain as explained above a suitable tightening of the two parts once the temperature balance obtained.

FIG. 4a shows an assembly for machining a plug 8, and in particular for calibrating the flange 8c which allows the positioning of the plug relative to the shell at the time of assembly. As it is the tightening of the two parts constituting the enclosure closure device which determines the tightness and the mechanical strength of this closure, this is an important parameter. It is therefore desirable that this tightening can be controlled as precisely as possible. Due to the low taper this can be achieved by a usual value tolerance on the penetration dimension of the male and female tapered seats. The machining assembly shown in FIG. 4a makes it possible to obtain the precision required for tightening by machining the flange.

In this figure, the reference 16 designates the jaws of a lathe in which the plug 8 is tightened. A standard ferrule 18 is then presented on the plug 8 and fixed thereon.

A dressing tool 30 comprising a roller, is then brought to bear on the face 10 of the standard ferrule. The tool advance ensures the calibration of the cap flange.

FIG. 4b shows the calibration of the annular bearing surface 4c of the ferrule 4 by the installation of a standard plug 20 having a face 20a for the support of a roller integral with the dressing tool 30.

This way of proceeding, for the calibration of caps and ferrules, using standard parts authorizes the machining of the conical surfaces with fairly wide diametrical tolerances, the calibration ensuring interchangeability and avoiding the pairing cap-ferrule, all ensuring high precision on the tightening value.

FIG. 5 shows a second embodiment of a closure device of the invention. This device comprises two plugs arranged one behind the other. This produces a primary seal by means of the plug 8 'and a secondary seal by means of the plug 8 ". In the variant shown in FIG. 5, the diameter of the conical surface of the plug 8' increases with increasing movement. moves away from the flange 8'c, which ensures a very high resistance of this plug to axial displacement, for example under the effect of shocks coming for example from parts contained inside the enclosure during transport.

FIG. 6 shows a third embodiment of the invention. In this embodiment, the tapered bearings, both male and female, have been split into several tapered bearings 4 ,, 4 ₂ , 4 ₃ etc. for ferrule 4 and 8 ₁ , 8 ₂ , 8 ₃ etc. for plug 8. Two consecutive conical bearing surfaces are separated by a heel. Thus, between the conical surfaces 4, and 4 ₂ , there is the heel 31, and between the conical surfaces 8, and 8 ₂ , there is the heel 32.

This embodiment has the advantage of allowing a large length 1 of the conical bearing surfaces relative to the diameter 34 of the opening. Thus, the plug is easier to set up and remove while ensuring a better seal and better mechanical resistance. In addition, heels 31 and 32 have a safety role. They hold the plug in place in case it comes to move, for example under the effect of a shock coming from inside the enclosure and directed towards the outside.

There is shown in Figure 7 a variant of the embodiment of Figure 6 which also includes tapered bearings which have been divided into several conical bearings. This embodiment corresponds to the case of a reverse cone. It has the same advantages as the embodiment of Figure 6. In addition. in this case of the reverse cone, the fact of reducing the ratio of the length of the spans relative to the diameter of the opening has a greater advantage since, as mentioned above, it is necessary to dilate the flange or further contract the plug to introduce into each other due to the reverse taper.

In the case of the embodiment of FIG. 7, the heels do not play a safety role as is the case in the embodiment of FIG. 6, but it is the conical bearings themselves which play this role because the reverse taper ensures better immobilization in translation of the plug relative to the ferrule.

The advantages of the invention which has just been described are as follows: it allows, particularly in the case of the right cone, easy introduction of the plug into the shell at the time of assembly. It ensures a determined tightening without requiring great precision on the temperature difference between the parts at the time of assembly, thanks to the presence of a flange and an annular bearing which makes it possible to identify the axial position of the two parts. one in relation to the other. This ensures the reproducibility of the tightening without any special requirements as regards the precision of the machining of the conical bearings. For the construction of a series of closing devices, it is not necessary to pair the cones.

Claims (5)

1. Method for sealing and opening a container/stopper assembly, the container having an opening (6), the stopper (8) and the opening (6) both having a slight conicity of the order of 1 to 2 degrees, this method comprising the following successive stages :

a) a thermal disequilibrium is created between the stopper and the walls of the opening so as to cause relative expansion of the opening in relation to the stopper ;

b) the stopper is inserted into the opening until it reaches a predetermined axial position which corresponds, after the thermal equilibrium has been restored, to a predetermined degree of tightness ;

c) the thermal equilibrium is restored between the stopper and the opening ;

d) the stopper is removed by causing renewed relative expansion between the stopper and the opening.

2. Method according to Claim 2, in which the axial position of the stopper (8) inside the opening (6) is determined in advance by adjusting an axial stop between the stopper and the opening.

3. Method according to Claim 2, in which adjustment of the stop is performed by means of axial machining of a flange (8c).

4. Container/stopper assembly, the container having an opening (6), the stopper (8) and the opening (6) both having a slight conicity of the order of 1 to 2 degrees, the stopper (8) having, before being assembled with the container (6), a diameter which is slightly greater than that of the container (6), the stopper (8) and the walls of the opening (6) possessing the component members of an axial stop consisting of a flange (8c) formed on one of the parts and of a matching annular bearing surface (4c) formed on the other part, and the stopper (8) and the walls of the opening (6) being made of materials having substantially the same coefficients of expansion, so as to retain the same tightening effect obtained by means of heat-shrinking performed on the opening (6) of the container and the stopper (8), whatever the temperature of use.

5. Container/stopper assembly according to Claim 4, in which conical bearing surfaces (4a, 8a) of the stopper and of the opening are divided up into a plurality of cones possessing the same degree of conicity.

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