FR2536822A1 - Device of the magnetically-controlled valve type comprising a roller screw. - Google Patents

Abstract

The present invention relates to a valve capable of being used especially in the field of radioactive fluid circuits for nuclear power stations. The valve comprises a body 10 into which emerge two conduits 11, 12 capable of communicating and a cap 20 which houses a shut-off 30 and members for controlling the latter. Permanent magnets 40 are arranged on a mild steel cylindrical element 50 securely fastened to a nut 60 of a roller screw. This nut 60 interacts with a stem 70 at the end of which a valve shut-off 30 is fixed.

Description

 The present invention relates to an apparatus or tap, capable of fulfilling the functions of sectioning and sealing on fluid circuits, in particular radioactive fluids used in the context of nuclear power plants.

More specifically, the present invention relates to a tap of the type comprising a body into which open two conduits capable of communicating with each other, as well as a cap made of non-magnetic material tightly fixed on the body to define a chamber which houses a shutter intended to interrupt the communication between said conduits, as well as shutter movement control members which comprise at least one permanent magnet capable of being rotated by an external part adapted to generate a magnetic field of rotary appearance
Such devices are described in particular in the United States of America patents No. 2,289,574, No. 3,347,262 (GIBSON), No. 3,355,140 (ANDERSEN1 No. 3,908,959 (FICHTNER), and No. 4,232 695 (THE GARRETT CORPORATION) as well as in French patents and patent applications No. 1,200,372 (COTTON DE BENNETOT), No. 2,373,729 (AUTOCLAVE-ENGINNERS) and No. 2,456,892 (AUTOCLAVE
ENGINNERS), to which we will refer for a good understanding of the present invention.

 All these valves must meet an imperative condition, which is that of waterproofing to the outside.

 It is understood in particular that this imperative must be respected, in the context of nuclear power plants, when handling radioactive fluids.

 On the other hand, said fluids are brought to very high pressures, which can exceed 20 M pa (200 bars), and to temperatures varying between, for example, 20 to 340 ° C.

 In practice, it has been found that all of the taps previously proposed, can not give full satisfaction, in the sense that when the fluid pressures exceed a given threshold, the torques applied to the control members of the shutter, thanks to the coupling ma The gnetics produced between the internal permanent magnets and the external part are insufficient to move the shutter and bring the valve to the open position.

 In particular, as described in patent application No. 2 456 892, and as shown in particular in FIGS. 1 and 3, it has proved essential, with the devices hitherto proposed, to provide a mechanical part connected to the shutter control members, and accessible outside the tap after having passed through the wall of the body.

By mechanical intervention on this part, the movement of the shutter can easily be controlled. This said part therefore makes it possible to compensate for the defects of the drive system comprising at least one permanent magnet. The seal between the part and the body is achieved by O-rings. However, it is easily understood that such an arrangement cannot in any way produce a perfectly reliable seal. In other words, such an arrangement, that it has proved essential to use so far, when the fluids to be handled reach very high pressures, eliminates all the advantages linked to the permanent magnet control which made it possible to obtain a perfect seal with respect to the 'exterior and therefore has the drawbacks of conventional taps or valves, such as those described in United States Patent Nos. 969803 and 3,269,698.

It has also been proposed to equip the shutters with bellows, in order to solve the sealing problems, as described in particular in the patents of the United States of America No. 2,642,890 (SXEWIS), No. 4,166,607 (WEBB ) and 4,232,695 (THE
GARRETT CORPORATION). However, such valves do not have satisfactory reliability and therefore cannot be used with fluids for which permanent sealing is a primary imperative.

 There is therefore a need on the market to have taps of the aforementioned type, which are at the same time simple, robust, reliable and economical, which can be used with fluids, such as radioactive fluids, reaching very high pressures. high of the order of 20 M Pa, and temperatures of the order of 3500C while presenting a perfect seal vis-a-vis from the outside, and this requiring quite limited maneuvering effort. Preferably, such taps should furthermore require reduced maintenance, and, as far as possible, present a certain safety, allowing the tap to be handled only by a few given individuals.

 The present invention comes on this point to provide a solution to the problem previously posed, and proposes a new tap of the aforementioned type in which the shutter displacement control members also include a screw / nut system, one of the elements of which is integral permanent magnets driven in rotation to transform the rotational movement of these into translation, and in which more precisely said permanent magnets are arranged at the periphery of a cylindrical element of mild steel which channels the magnetic field, while it are surrounded by a thin envelope of non-magnetic steel, by the fact that the screw / nut system is of the roller type, the nut being linked in rotation and in translation relative to the permanent magnets, and the screw being immobilized in rotation, but free of translation in the body, and provided with a valve at its end, and by the fact that a heat exchanger is provided on the body and / or the cap.

 As will appear on reading the detailed description which follows, the present invention makes it possible to obtain perfectly tight taps while requiring reduced operating torques.

 Preferably, the wall of the cap enveloping the permanent magnets is made of non-magnetic steel doped with boron.

 According to a particular embodiment, the cap consists of two generally cylindrical parts assembled by thread, and the cap is itself assembled by thread on the body.

 According to an important characteristic of the present invention, there are provided elastic washers playing the role of support for the screw / nut system and allowing axial compensation for differential expansions.

 According to another important feature of the present invention, the permanent magnets are cobalt and rare earth metal magnets, and preferably the permanent magnets are cobalt and sanarium magnets.

 According to an advantageous embodiment, the seal between the cap and the body is ensured by welding lips-seals.

 Preferably, said external part adapted to generate a magnetic field of rotary appearance consists of a set of permanent magnets, mounted on the cap and capable of rotation around the axis of the screw / nut system.

 Said set of permanent magnets can be removable and fitted with a torque limiter.

 Other characteristics and advantages of the present invention will appear on reading the detailed description which follows, and with reference to the appended drawing, given by way of nonlimiting example, in which the single figure represents an axial section view of 'A device according to the present invention.

 I1 clearly emerges from an examination of the said appended figure, that numerous geometric shapes of the parts making up a valve in accordance with the present invention must imperatively be observed so as to allow correct cooperation of these said parts. For these reasons, it will be considered, in the following, that said appended figure is integrated into the present description, by the reference made to it here, so that this figure clearly defines the geometric shape ~, and the arrangement of the pieces d 'a tap according to an embodiment of the present invention.

 In the figure, O-O has been referenced the longitudinal axis of the valve through which the cutting plane passes, and which corresponds to the direction of movement of the shutter.

 As shown in the attached single figure, the valve according to the present invention comprises a body 10 into which two conduits 11, 12 capable of communicating with each other open, and a cap 20, made of non-magnetic material, and fixed so sealed on the body 10, to define a chamber 21 which houses a shutter 30 intended to interrupt the communication between said conduits 11 and 12, as well as displacement members of one shutter.

 More specifically, as shown in the figure, the body 10 delimits a valve seat 13, of generally circular shape, equipped where appropriate with a body seat ring (not shown in the figure). The median plane of the seat 13 (referenced A in the figure) is substantially perpendicular to the above-mentioned axis O-O which corresponds to the direction of movement of the shutter 30.

 More precisely, one of the conduits 11, of generally circular cross-section, opens into a blind bore 14 coaxial with the abovementioned axis O-O, and which opens at the bottom of the seat 13.

The conduit 11, as shown in the figure is itself slightly inclined relative to the median plane of the seat.

 Similarly, the second conduit 12, of circular cross section, itself inclined with respect to the abovementioned plane AA, opens into a generally cylindrical chamber 15, of axis OO, leading to the upper part of the seat 13, to the 'opposite of the aforementioned bore 14.

 More specifically, as shown, the two cylindrical conduits 11 and 12, with respective axes 16 and 17, are substantially parallel.

 At their end opening onto the outside of the body 10, the conduits 11 and 12 are provided with any suitable conventional means capable of allowing their connection to the fluid circuit of an installation.

 In the figure, such connection means have been schematically represented and referenced respectively in 18 and 19.

 As shown in the single appended figure, the cap 20 consists of two parts 22, 23 of generally cylindrical shape assembled by thread at 24. The intermediate piece 23, which is open at its two ends, is also assembled by thread on the body 10, as shown in 25. The part 22, opposite the body 10 with respect to the intermediate part 23, is open at its end adjacent to the intermediate part 23, but closed at its opposite end by a shaped wall general hemispherical, 26.said wall of hemispherical form.generality 26 must of course .be connected in leaktight manner to the part 22. Such a watertight assembly can be produced for example by welding at 27.

According to an alternative embodiment, the cap 20 can also be in one piece,
More specifically, the part 22 is screwed onto the outside of the intermediate part 23, until radial bearing surfaces provided respectively on these two parts come into abutment. In this position, annular lips 27a, 28a, provided on the one hand on the outer periphery of the intermediate piece 23, on the other hand at the end of the piece 22, are adjacent. The seal between the two parts 22 and 23 is then ensured by welding lips-seals schematically referenced 29a.

 Similarly, and as always shown in the single appended figure, the intermediate piece 23 is screwed inside the body 10, at 25, until radial bearing surfaces provided respectively on the piece intermediate 23 and on the body 10 abut.

In this position, annular lips 27b, 28b provided on the outer periphery, on the one hand of the intermediate piece 23, on the other hand of the body 10, are brought into contact. The seal between the intermediate piece 23 and the body 10 is then ensured by a weld of lips-seals schematically referenced 29b.

 According to a characteristic of the present invention, the part 22 of the cap 20 is made of non-magnetic steel doped with boron, which makes it possible to produce a thin enclosure resistant to the pressure of the fluid. This arrangement proves to be particularly advantageous, insofar as this part 22 envelopes permanent magnets 40 of the members controlling the movement of the shutter 30 and allows negligible magnetic leaks in the air gap formed by the wall of the cap 20.

 More specifically, said permanent magnets 40, of generally elongated shape, parallel to the axis OO of the assembly, are housed in the chamber 21, on the periphery of a cylindrical element 50, made of mild steel, which channels the magnetic field .

 More specifically, as shown in the figure, the permanent magnets 40 and the mild steel cylindrical element 50 are arranged in a corresponding annular housing provided on the outer periphery of a part 52 of generally cylindrical shape, of OO axis whose role will be explained in more detail in the remainder of this description. Thus, as shown in the figure, the permanent magnets 40 and the mild steel cylindrical element 50 are immobilized in translation relative to said part 52. On the other hand, the permanent magnets 40 and the cylindrical steel element soft 50 are immobilized in rotation relative to this part 52 thanks to a key 53 engaged in corresponding housings provided both in the part 52 and in the cylindrical element in mild steel 50.

 The permanent magnets 40, which are substantially adjacent to the wall of the part 22 of the cap 20, are protected from ambient fluid by a thin envelope 51 of non-magnetic steel, which surrounds them and is applied against the surfaces of the wall of the adjacent part 52. to the aforementioned housing containing the permanent magnets 40 and the mild steel cylindrical element 50.

 According to an important feature of the present invention, the permanent magnets 40 are cobalt and rare earth metal magnets.

 Preferably, said permanent magnets 40 are cobalt and sanarium magnets.

 As also shown in the figure, the part 52 is threaded onto an element 60, of generally cylindrical shape, of the nut type.

 More specifically, this nut 60 cooperates with a screw or rod 70, coaxial with the axis O-O to form a high-efficiency roller screw. This rolling screw has been schematically shown in the figure. Such roller screws are well known in elies-inêmes, therefore this screw will not be described in more detail in the remainder of this description.

 The nut 60 of the rolling screw 8 is introduced into the part 52 until it abuts against an annular radial support surface 54 presented by the part 52, at its end opposite to the body 10, and directed towards the latter. . In this position, a socket 55 is assembled by thread in the part 52 on the body side 10. The nut 60 of the rolling screw is thus immobilized in translation relative to the part 52, and consequently relative to the permanent magnets 40 and l cylindrical element in mild steel 50 carrying these. On the other hand, the nut 60 is immobilized in rotation relative to the part 52 by means of a key 61 parallel to the axis OO which is engaged in a corresponding recess formed in the nut 60, on the periphery thereof, and enters a rectilinear groove 56, provided on the internal periphery of the part 52, parallel to the axis OO.

 The aforementioned rod or screw 70, of axis OO which crosses the entire cap 20, and extends in the chamber 15 of the body 10, is itself immobilized in rotation relative to the body 10 and to the cap 20 thanks to a key 71, parallel to the axis OO, which is engaged in a corresponding recess formed in the rod 70, on the periphery thereof, and enters a rectilinear groove 72, provided on the internal periphery of the intermediate part 23 of the cap 20, parallel to the axis OO.

 Thus, it is understood that any stress on rotation of the permanent magnets 40, and therefore of the nut 60, tends to move the rod 70, in translation, in the body 10 and the cap 20.

 As shown in the figure, the end of the rod 70 opposite the body 10 is introduced into a blind bore provided in the hemispherical wall 26, of the part 22 of the cap 20. More precisely, the rod 70 is guided to this end by a guide ring 73 of generally cylindrical shape, engaged on the rod 70, and in the abovementioned blind bore formed in the hemispherical wall 26.

Similarly, a cylindrical guide ring 74 is threaded on the rod 70, body side 10, and retained in a corresponding cylindrical housing provided at the end of the intermediate portion 23 of the cap 20, adjacent to the body 100
These guide rings 7, 74 can be made of any suitable resistant material. According to an advantageous embodiment, these rings 73, 74 can be made based on an alloy of cobalt, chromium and tungsten. These rings 73 and 74 can be produced for example from material sold under the registered trademark "STELLITE".

 Of course, the guide rings 73 and 74 also ensure the rotation guide of the permanent magnet assembly 40, nut 60. On the other hand, the rotation of this assembly is guided by support rings 57, 58, constituted by the aforementioned parts 55 and 52, on either side of the nut 60.

 These support rings 57, 58 carry the first washer 82, 83 of respective thrust bearings 80, 81, the second washer, 84, 85 of which is supported by generally cylindrical counterplates 91 and 92 threaded on the rod 70, on the 'outside of the aforementioned ball bearings 80 and 81.

 Even more specifically, as shown in the figure, the counterplates 91 and 92 are held axially in the chamber 21- by a plurality of elastic washers 94, 93, which rest respectively on the internal annular radial surface of the hemispherical wall 26 , and on an annular radial surface presented by the intermediate part of the cap 20, and directed opposite the body 10.

 The purpose of the elastic washers 93 and 94 is to compensate for differential thermal expansion.

 A shutter valve 30 is immobilized on the end of the rod 70, body side 10.

 More precisely, this shutter valve 30 is immobilized on the rod 70 by means of a pin 31, or similar member, passing through a radial bore provided in the rod 70 and engaged in the shutter valve 30.

 The shutter valve 30 is thus secured to the end of the rod 70, and guided in translation in the chamber 15 of the body 10, when the permanent magnets 40 are rotated.

 Of course, the end of the shutter valve 30 adjacent to the seat 13 may take any suitable form. If necessary, the shutter valve 30 may be provided with a valve seat ring.

It is the same for the body 13 which may be provided with a body seat ring.

 It is easily understood that the shape and dimensions of the shutter 30 must be determined so that it is applied tightly against the seat 13, so as to seal it tightly and thus interrupt the fluid communication between conduits 11 and 12.

 The assembly further comprises a heat exchanger 100 disposed on the outside of the intermediate piece 23, and in close contact with the latter.

The purpose of such a heat exchanger 100 is to evacuate the calories induced by the fluid and thus limit the temperature of the interior assembly to the chamber 21.

 Preferably, the heat exchangers 100 are provided with internal fins, not shown.

In addition, the cooling can be achieved by a conventional heat pipe mounted on the heat exchanger 100. The particular structure of this heat exchanger 100 will not be described in more detail in the remainder of this description, and reference will usefully be made to the attached figure to determine the particular structure adopted according to an embodiment according to the present invention. ~
The external part 110 adapted to generate a magnetic field of rotary appearance capable of driving the permanent magnets in rotation 40 consists of a set of permanent magnets 111, of generally elongated shape, which extend parallel to the axis
OO and are supported on the internal periphery of a cylindrical element 112, preferably made of mild steel, which channels the magnetic field. This cylindrical element 112 is itself supported in a generally cylindrical housing 113 secured to a handwheel 114 As shown in the figure, the latter rests on the outer surface of the hemispherical wall of the cap 20 More precisely, the part 110 is threaded on a cylindrical support 115 of axis OO welded at 116 on the hemispherical wall 26, and is guided on this support by a ring 117. The part 110 is thus temporarily immobilized by means of a screw 118 engaged in the support 115 and passing through, until it comes to bear against, a socket 119 resting on the upper surface of the steering wheel 114 which makes it possible to make the external part 110 removable by removing the screw 118. The external part 110 can thus be used on several taps.

The permanent magnets 111 and the mild steel cylindrical element 112 carrying these are
immobilized in rotation with respect to the cy housing
lindrique 113 with a screw 120.

Of course, the external part 110 may
take all appropriate forms, and will therefore only
not described in more detail hereinafter
description. The bottom line is that this outdoor piece
be adapted to generate a magnetic field
rotational around the axis OO, so
that by magnetic coupling, it drives in rotation
the permanent magnets 40 of the system. In this case,
such an outer part 110 provided with magnets per
manents 111 can be rotated either
manually, either by any motorization
not shown
Again, the permanent magnets 111 will
preferably cobalt and metal magnets
rare earths, such as from the sanarium.

The external part 110 is preferably
removable. So the tap has security,
since it is necessary to have such a set
110 permanent magnets for ordering
of it.

Preferably, the external part 110
is fitted with a torque limiter
The advantages of the tap
in accordance with the present invention with regard to the availability
There are many previously existing people.

As an example we can cite
- system ensuring tightness towards
the perfect exterior, and exceptional reliability,
since the body 10 and the cap 20 define a
chamber perfectly sealed from the outside thanks to the magnetic coupling produced between the magnets
permanent 40 and permanent magnets 111,
very high efficiency of the torque-force transformation assembly, of the order of 50%, allowing low operating forces on the external part 110, whatever the level of pressure of the fluid applied to the shutter 30,
- consequently reduced operating torque,
security presented by the system, impossibility of opening or closing the tap without said external part 110 capable of achieving magnetic coupling between the permanent magnets 40 and the permanent magnets 111,
robustness resulting from the absence of bellows at the level of the shutter 30, whereas such bellows were commonly used in the prior art, as described in particular in the United States patent No. 4,232 695,
- absence of seals which leads to a particularly reduced maintenance, as well as to the elimination of attack by corrosion of the valve stem,
- bidirectional sealing on sectioning,
- excellent reliability due to the simple screw / nut drive mechanism.

Tests carried out on a valve in accordance with the present invention have made it possible to demonstrate that such a valve allows opening under a differential pressure at the valve equal to 22.2 M Pa at a fluid temperature of 500C.
Tests in the general conditions of service were carried out with the scales of variations of the parameters of state of the fluid as follows
- pressure: 0 to 18 M Pa,
- differential pressure: 0 to 18 M Pa,
- temperature: 20 to 340 "C.

Such tests have shown that
the tightness of the tap, when shut off, and the
maneuverability gave full satisfaction.

Of course the present invention ngest
not limited to the embodiment which has just been
describes from which we can consider many
variant embodiments conforming to the spirit of
the invention.

Of course, the air gap existing on the one hand
between the outer piece and the hat, on the other hand
between the internal permanent magnets 40 and the cap
20 must be reduced as much as possible The same applies to the thickness of the wall of the cap 22

Claims (10)

 1. A valve of the type comprising a body (10) into which open two conduits (ll, 12) capable of communicating with each other, and a cap (20) fixed in leaktight manner to the body so as to define a chamber which houses a shutter (30) intended to interrupt the communication between said conduits, as well as shutter movement control members which include permanent magnets (40) capable of being rotated by an external part (110) adapted to generate a rotary-looking magnetic field, and a screw / nut system, one of the elements of which is integral with the permanent magnets to transform the rotational movement of the latter into translation, characterized in that the said permanent magnets (40) are arranged at the periphery of a cylindrical element (50) of mild steel which channels the magnetic field, while they are surrounded by a thin envelope (51) of non-magnetic steel, by the fact that the system * screw (70) / Nut (60) is t roller type, the nut (60) being linked in rotation and in translation relative to the permanent magnets (40), and the screw (70) being immobilized in rotation, but free to translate in the body (10), and provided a valve (30) at its end, and by the fact that a heat exchanger (100) is provided on the body (10) and / or the cap (20).  2. Tap according to claim 1, characterized in that the wall (22) of the cap (20) enveloping the permanent magnets (40) is made of non-magnetic steel doped with boron.  3. Tap according to one of claims 1 and 2, characterized in that the cap (20) consists of two parts (22, 23) of generally cylindrical shape assembled by thread (24), and in that the cap (20) is itself assembled by thread (25) on the body (10).  4. Tap according to one of claims 1 to 3, characterized in that there are provided elastic washers (93,94) acting as a support for the screw (70) / nut (60) system and allowing compensation axial of differential expansions.  5. Tap according to one of claims 1 to 4, characterized in that the permanent magnets (40) are cobalt magnets and a rare earth metal.  6. Tap according to claim 5, charac terized in that the permanent magnets are cobalt and sanarium magnets.  7. Tap according to one of claims 1 to 6, characterized in that the seal between the cap (20) and the body (10) is ensured by welding lip-seals (296).  8. Tap according to one of claims 1 to 7, characterized in that said outer part (110) adapted to generate a magnetic field of rotary appearance consists of a set of permanent magnets (III), mounted on the cap (20) and capable of rotation about the axis (OO) of the screw (70) / nut (60) system.  9. Tap according to one of claims 1 to 8, characterized in that said set of permanent magnets (111) is removable.  10. Tap according to one of claims 1 to 8, characterized in that said set of permanent magnets (111) is equipped with a torque limiter.