Sealing element fastening system for a pressure vessel, in particular a reactor pressure vessel

The invention relates to a sealing element fastening system for at least one sealing element of a pressure vessel, which has at least one opening and a sealing part, in particular a cover, provided for the opening. In the operating state of the pressure vessel each sealing element is at least partially inserted in an accommodating groove in the sealing part and corresponding sealing element fastening devices are positioned in each case in an indentation in the sealing part. The indentations are in each case sealed by a fill element in the operating state of the pressure vessel.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority, under 35 U.S.C. §119, of German application DE 10 2010 024 501.1-12, filed Jun. 21, 2010; the prior application is herewith incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a system for the fastening of sealing elements for a pressure vessel, which has at least one opening and a sealing part provided for the opening. In this case, this can be both a mobile pressure vessel, for example a transport container or a hydraulic reservoir, and a stationary pressure vessel, for example a process control pressure vessel or a reactor pressure vessel. In the case of such pressure vessels, in each case at least one sealing element is introduced in the operating state between the contact surfaces of the pressure vessel in the region of the respective opening and the contact surfaces of the corresponding sealing parts. In some cases, the sealing elements are fastened with the aid of a sealing element fastening system either to the pressure vessel or to the sealing part in order to simplify, among other things, the opening and sealing of the pressure vessel.

Published, Korean patent application No. 1020010038819 A makes known a sealing element fastening system, by way of which O-ring seals are fastened to a pressure vessel sealing part in the operating state of the pressure vessel. To this end, the O-ring seals are inserted at least partially in an accommodating groove in the pressure vessel sealing part. Cap screws, which are screw-connected to the pressure vessel sealing part, are arranged in a countersunk manner in a plurality of indentations that connect directly in each case to the accommodating groove. The cap screws fix, in each case, a holding element that is shaped in the manner of an angle bracket, the portion of which remote from the respective cap screw abutting against the corresponding O-ring seal in such a manner that, on the one hand, the O-ring seal is held in the accommodating groove and, on the other hand, the holding element is positioned in a countersunk manner in the pressure vessel sealing part.

In the case of the sealing element fastening system, in each case a free space remains in the region of the respective indentation and the accommodating groove adjacent thereto. These free spaces result in free contact surfaces at the corresponding O-ring seals. In the operating state of the pressure vessel, a substance kept in the pressure vessel spreads out into those free spaces as far as the contact surfaces. The contact between the substance and the O-ring seal can then lead to unwanted reaction processes, where the O-ring seal is damaged and the substance contaminated.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a sealing element fastening system for a pressure vessel which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which the spreading out of the substance into the free spaces is prevented.

With the foregoing and other objects in view there is provided, in accordance with the invention a sealing element fastening system for sealing elements of a pressure vessel. The sealing element fastening system contains a sealing part having an accommodating groove and an indentation. The sealing part is provided for covering an opening of the pressure vessel. In an operating state of the pressure vessel each sealing element is at least partially inserted in the accommodating groove in the sealing part. Corresponding sealing element fastening devices are disposed in each case in one of the indentations in the sealing part. Filling elements are provided, the indentations in each case sealed by one of the fill elements in the operating state of the pressure vessel.

A sealing element fastening system is provided for at least one sealing element of a pressure vessel, which has at least one opening and a complementary sealing part. Corresponding to the teaching of the invention, in the operating state of the pressure vessel, each sealing element is inserted at least partially in an accommodating groove in the sealing part and corresponding sealing element fastening devices are positioned, in each case, in an indentation, sealed by a fill element, in the sealing part. Through the sealing of the indentations, the spreading of the substance into the free spaces, and as a consequence the interaction between sealing elements and the substance kept in the pressure vessel, is prohibited as extensively as possible. Although in particular in the case of process control pressure vessels, high priority is given to the avoiding of contamination of the substances kept in the pressure vessel, in the case of this invention, proceeding from the fact that the substances can also be hazardous substances, the most important objective is deemed, above all, to be the protection of the sealing elements and consequently the assurance of the tightness of the pressure vessel.

According to a preferred embodiment, each sealing element fastening device includes a ring-shaped holding element with an integrally molded holding arm, which is fixed to the sealing part in the operating state of the pressure vessel. A screw, for example, can be provided for the fixing process. A fastening variant that is technically very simple is realized in this manner.

In this conjunction, it is deemed to be advantageous when, in the operating state of the pressure vessel, each holding arm engages into a recess on the respective sealing element and consequently holds the sealing element on the sealing part. In this case, the engagement of each holding arm in a corresponding recess can be realized in both a detachable and non-detachable manner. Detachable versions, such as, for example, plug-in connections, are to be preferred in particular when simple exchangeability of the sealing elements is desired.

A particularly expedient variant of the sealing element fastening system is characterized in that threaded bolts with two separate threaded portions are used. Whereas the first threaded portion of each threaded bolt passes through a holding element in the operating state of the pressure vessel and is screw-connected into a complementary counter thread in the sealing part, the second threaded portion of each threaded bolt passes through a fill element together with a bolt nut, which serves for fastening the fill element to each second threaded portion. In this case this is a variant with an upgrade character and is conceived, in particular, for already available sealing element fastening systems without a fill element, where the sealing elements are fixed by cap screws.

In an advantageous further development of this variant, a ring-shaped projection is integrally molded in each case between the two threaded portions, as a stop member for the fill element, on the one hand, and for the holding element, on the other. This means that it is possible to perform the fastening of the respective holding element to the sealing part and the fixing of the respective fill element to the threaded bolt by two operating steps that are separate from each other. Such a separation of this type can be helpful, for example, when one individual fill element has to be exchanged on account of damage.

In this context, an embodiment with a number of recesses on each ring-shaped projection as a point of application for a tool is preferred. The tool provided for this is, on the one hand, to simplify the handling of the threaded bolts and, on the other hand, to open up the possibility of predetermining an exact torque at which the threaded bolts are screw-connected into the respective counter thread in the sealing part.

Over and above this, it is particularly advantageous to provide recesses also on each bolt nut, the recesses matching those on the ring-shaped projection in form and relative position to each other. This means that the complete assembly of each unit of the sealing element fastening system is able to be performed with the aid of only one tool. The corresponding tool is preferably provided with a variable torque preset. Different torque values can be predetermined in this way for the tightening of each bolt nut when fastening the corresponding fill element and for the screw-connecting of each threaded bolt into the respective counter thread.

In an alternative variant with an upgrade character, a clamping bush is provided for each unit of the sealing element fastening system, the clamping bush in each case fastening a holding element in a rotatable manner on the corresponding fill element. During the pre-assembly of the respective unit, the clamping bush, passing through the holding element, is pressed for this purpose into a central opening in the fill element. Finally, in the operating state of the pressure vessel, each system module of the sealing element fastening devices is preassembled in such a manner and is preferably fixed on the sealing part by way of a cap screw that passes through the fill element, the holding element and the clamping bush. The rotatability of the holding elements, implemented in this manner, in relation to the fill elements allows, for example, greater tolerance ranges when aligning the sealing elements in the assembly process of the sealing element fastening system.

Although the invention is illustrated and described herein as embodied in a sealing element fastening system for a pressure vessel, in particular a reactor pressure vessel, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

DETAILED DESCRIPTION OF THE INVENTION

In all the figures parts that correspond to each other are provided with the identical references.

Referring now to the figures of the drawing in detail and first, particularly, toFIG. 1thereof, there is shown a sealing element fastening system for ring-shaped sealing elements1of a reactor pressure vessel of a nuclear power station.

FIG. 1shows a top view of an O-ring seal of this type. A plurality of accommodating openings2are positioned circumferentially on the inside of the seal as a type of equipartitioning, recesses connecting to the accommodating openings radially outward. A cross section of the O-ring seal represented inFIG. 2discloses that the sealing element1used is a hollow body. Accordingly, each recess also serves as an access channel to a hollow space3of the tubular sealing element1. The base area4of such an access channel is shown inFIG. 3. It is realized in the shape of a slot in a circumferential direction5of the O-ring seal and can essentially be reduced to a basic rectangular shape, where the two opposite shorter sides have been replaced in each case by an outwardly curved segment.

The reactor pressure vessel looked at in this exemplary embodiment can be regarded in a first approximation as having two parts. In this case the first part, designated below as a reactor pressure vessel or simply only as pressure vessel6, functions as a container that is open at one end. The container can be supplemented by the second part, a sealing part7, for which the term cover is also used below, to form a serviceable pressure vessel6(seeFIG. 16).

Two ring-shaped sealing elements1, which are fastened to the cover of the pressure vessel6, are provided for the reactor pressure vessel. To this end, the two O-ring seals, in the operating state of the pressure vessel6, are inserted at least partially in two concentric and equally ring-shaped accommodating grooves8in the cover of the pressure vessel6. A top view of the accommodating grooves8is shown in detail inFIG. 4. The concentric arrangement of the two sealing elements1creates a double seal-barrier in a radial direction9. The accommodating groove8, partially visible on the right-hand side in the figure, is a component of the inner seal and the adjacent left-hand accommodating groove8is part of the outer seal. A number of indentations10corresponding to the number of accommodating openings2are provided on the inside of the respective ring-shaped seal in the sealing part7with a U-shaped base surface, into which indentations in each case a unit11of the sealing element fastening system can be inserted. A bore12, placed approximately centrally, connects to the bottom of each indentation10in the direction of the cover of the pressure vessel6. The bore12is provided with a counter thread13for accommodating a screw or a threaded bolt14. The profile of each indentation10, just as the profile of the two accommodating grooves8, is rectangular. This is illustrated by a cross section of the sealing part7, represented inFIG. 5, centrally through an indentation10, selected as an example, and through the accommodating groove8connected thereto.

FIG. 6shows a unit11of a variant of the sealing element fastening system. A ring-shaped body16, on which a cuboidal-shaped holding arm17is integrally molded, serves as a holding element15. In the operating state of the pressure container6, each holding arm17engages in a correspondingly positioned access channel on the sealing element1. The corresponding state is documented inFIG. 7. The ring-shaped periphery of the holding element15and the two side faces of the holding arm17connected thereto have been provided at the edge with chamfers18, which are to make an assembly or insertion easier.

On a threaded bolt14with two separate threaded portions20,21, a thread-free region with a reduced outside diameter is provided between the threaded portions20,21, the thread-free region bearing a ring-shaped projection19in the center. In the operating state of the pressure vessel6, the first threaded portion passes through the holding element15associated therewith and is screw-connected into a counter thread13in the cover of the pressure vessel6. The top side of the ring-shaped projection19facing the first threaded portion20serves, in this case, as a stop member for the ring-shaped body16of the holding element15, such that this latter is clamped quasi between the ring-shaped projection19and the bottom of the indentation10in the sealing part7.

The underside of the ring-shaped projection19facing the second threaded portion21functions, in contrast, as a stop member for a fill element22, which, in its turn, in the operating state of the pressure vessel6, is clamped between the underside of the ring-shaped projection19and a cylindrical bolt nut23screw-connected onto the second threaded portion21.

The fill element22, which is to seal the corresponding indentation10in the operating state of the pressure vessel6, has a basic shape similar to a U supplementing the indentation10. A cylindrical opening24that is positioned approximately centrally in the fill element22is subdivided into three regions which differ with regard to the diameter of the opening and the measurement in the direction of the order of assembly25. The first opening portion facing the threaded bolt14is provided with an inside diameter that is slightly greater than the outside diameter of the ring-shaped projection19on the threaded bolt14. For the second opening portion an inside diameter has been selected that, on the one hand, is smaller than the outside diameter of the ring-shaped projection19and of the bolt nut23and, on the other hand, is greater than the outside diameter of the threaded bolt14. The third opening portion finally has an inside diameter that is somewhat greater than the outside diameter of the bolt nut23. The measurements of the opening portions in the order of assembly25are selected such that the ring-shaped projection19, on the one hand, and the bolt nut23, on the other hand, in the operating state of the pressure vessel6, are arranged countersunk in the fill element22closed off in a flush manner.

The wording used in this context, such as, for example, “somewhat greater”, is to be understood in this description to the effect that no precisely complementary shapes are provided for the components placed opposite each other in each case. Instead of which, the assembling of the components is to be made easier with a little play. In particular in the case of the reactor pressure vessel, the important point is the fit as the assembly of the units11can only be performed in protective clothing including appropriate gloves. Accordingly, a deviation in this regard is implemented even for the shapes of fill element22and indentation10that in principle complement each other.

Three cylinder-like recesses26, admitted on the periphery of the ring-shaped projection19and being a type of equipartitioning, serve as a point of application for a tool27, by which the threaded bolt14is screw-connected into the counter thread13in the sealing part7. On the cylindrical bolt nut23associated therewith are also situated three recesses26, which in form and relative position to each other match those on the ring-shaped projection19to such an extent that the identical tool27is able to be used for both elements.

By using a threaded bolt14with a ring-shaped projection19in place of a simple screw, it is possible to perform the assembly of the units11of the sealing element fastening system, as shown in the diagrams inFIGS. 8 to 10, in two part steps. In the first step, the holding element15is positioned in the corresponding indentation10and the holding arm17is introduced into the access channel. To pre-fix the holding element15, the first threaded portion20, passing through the holding element15, is screw-connected into a counter thread13on the cover of the pressure vessel6until the holding element15is fastened to the cover, but is still able to be rotated about a central longitudinal axis28of the threaded bolt14. The degree of freedom of movement consequently remaining serves for compensating inaccuracies in the production of the access channels and for creating a large tolerance range when inserting the O-ring seal into the accommodating groove8provided for this purpose. Once the arm positions of all the holding elements15used have been adjusted, the threaded bolt14is screwed down. In the second assembly step, the fill element22is inverted over the second threaded portion21and fixed with the bolt nut23. The achievement by separating holding element fastening and fill element fastening is that the fill element22does not obstruct the view when the holding arm17is being aligned.

FIGS. 11 to 13show a tool27constructed for a two-stage assembly. In this case this is a rigid body with a tool grip29, a tool shaft30and a tool head31. Three pin-like grip elements33, which can engage in the complementary recesses26on the bolt nuts23or on the threaded bolt projections19, are integrally molded on the end face32of the hollow-cylindrical tool head31. The pin length, in this case, is matched precisely to the recesses26on the bolt nuts23. The inside diameter of the tool head31, formed in the manner of a hollow cylinder, is greater than the outside diameter of the threaded bolt14and smaller than the outside diameter of the ring-shaped projection19. This means that the tool head31can be inverted so far over the second threaded portion21until its pin-like gripping elements33engage in the recesses26on the ring-shaped projection19.

A unit11of the sealing element fastening system of an alternative variant can be seen inFIG. 14. The holding element15is also ring-shaped in this version and has a cuboidal integral molding as holding arm17. However, contrary to the previous version, the edge-face edges are not chamfered. In a pre-assembly, the holding element15is fastened so as to be rotatable on the fill element22by a clamping bush34, which is pressable into a central opening on the fill element22by way of the opening24that connects thereto. The rotatability of the holding arms17makes it possible, even in the case of the alternative variant of the sealing element fastening system, to undertake adaptations with regard to the relative position of the access channels. It is accepted here that during the final assembly vision is at least partially restricted by the fill element22. On the other hand, the ability to pre-assemble the individual components of a unit11of the sealing element fastening system device that the time spent at the final assembly is reduced. This is of great importance, above all in the case of reactor pressure vessels, as the time a fitter is allowed to remain in the near range of the pressure vessel6has to be restricted on account of increased radioactive radiation. Within the pre-assembly process, the hollow-cylindrical part of the clamping bush34, passing through the holding element15, is pushed into the opening24in the fill element22. To realize a frictional connection, the outside diameter of the cylindrical part of the clamping bush34is slightly greater than the inside diameter of the equally cylindrical opening24on the fill element22. As the outside diameter of the cylindrical part of the clamping bush34is smaller than the inside diameter of the ring-shaped holding element15and as a conical part with an increasing outside diameter connects to the cylindrical part of the clamping bush34, it is ensured, on the one hand, that the holding element15is fastened to the fill element22and, on the other hand, the holding arm17is rotatably mounted. In the final assembly, the pre-assembled unit11shown inFIG. 15is inserted into the indentation10in the sealing part7and fastened to the cover of the pressure vessel6by way of a cap screw35that passes through the pre-assembled unit. In the operating state of the pressure vessel6, the cap35or fastening screw is then screw-connected far enough into the counter thread13in the sealing part7so that the head of the screw is positioned countersunk in the fill element22.