Metal sealing system for triple eccentricity butterfly valve

Abstract

A metal sealing system for a triple eccentricity butterfly valve includes a dynamic metal seal, having a metal core surrounded by an external coating; a metal case with an external surface that has an inclined conical shape, including a first housing inside which the dynamic metal seal is mounted; a metal cover fixed to the metal case to allow it to close by flush fitting of the upper or lower faces of the metal cover and the metal case, the metal case having a second housing into which the metal cover fits, the dynamic metal seal being located between the metal cover and the surface of the metal case defining the first housing.

Claims

1. A metal sealing system for a triple eccentricity butterfly valve comprising: a dynamic metal seal, comprising a metal core surrounded by an external coating; a metal case with an inclined conical external surface, the metal case including a first housing inside which the dynamic metal seal is mounted, and including a second housing formed as a cut-out in an upper or lower surface of the metal case; and a metal cover, attached to the metal case to allow the metal case to close by flush fitting of the upper face or lower face of the metal cover with a respective upper face or lower face of the metal case, wherein the metal cover is positioned within the cut-out of the metal case and extends along a portion of the first housing and is positioned adjacent the metal seal positioned inside the first housing, and wherein the dynamic metal seal is located between the metal cover and the surface of the metal case defining the first housing.

2. The metal sealing system according to claim 1, wherein the metal core is composed of a coil spring with adjacent turns that is closed on itself and that has the shape of a torus when in the rest state.

3. The metal sealing system according to claim 2, wherein the external coating inside which the metal core is inserted, has the shape of a toroidal surface for which the generating circle does not close on itself, when in the rest state.

4. The metal sealing system according to claim 1, wherein the first housing of the metal case comprises a lateral bearing surface with which the dynamic metal seal is positioned in contact, the lateral bearing surface having a non-circular shape, configured to obtain a variable interference around the periphery of the sealing system.

5. The metal sealing system according to claim 4, wherein the lateral bearing surface is elliptical in shape.

6. The metal sealing system according to claim 5, wherein the dynamic metal seal is circular in shape and can be radially compressed to take on an elliptical shape.

7. The metal sealing system according to claim 1, wherein the dynamic metal seal is a “U” shaped seal, with an opening facing the upper or lower face of the case.

8. The metal sealing system according to claim 1, wherein the metal sealing system is configured to be fitted in a disk or in a valve body, of a triple eccentricity butterfly valve comprising a valve body defining a conduit, and comprising an inclined conical part forming a valve seat, a valve stem guided in rotation on each side of the conduit, connected to a control rod of the butterfly valve, and a disk rotating simultaneously with the valve stem, the metal sealing system bearing on a secondary seal, crushing it to make the seal between the metal sealing system and the disk or the valve body, and of which an external or internal inclined conical section respectively provides the seal with the valve seat or the disk respectively, and said case being in contact with the secondary seal.

9. The metal sealing system according to claim 8, wherein the metal sealing system is configured to be installed in a recess in the disk or in a recess in the valve body.

10. The metal sealing system according to claim 8, wherein the metal sealing system is configured to be fitted in the disk, and wherein the metal sealing system and the secondary seal are configured to be compressed axially by a flange, attached to the disk by a network of nuts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood after reading the following detailed description of non-limitative example embodiments of the invention, and an examination of the diagrammatic and partial figures in the appended drawing on which:

(2) FIG. 1 is a perspective sectional view in a plane perpendicular to the axis of the control stem of the disk of a triple-eccentricity butterfly valve, illustrating an example of a metal sealing system conforming with the invention for a triple-eccentricity butterfly valve,

(3) FIG. 2 and FIG. 3 are detailed sectional views in the plane of the valve control rod, illustrating the metal sealing system in FIG. 1 with the butterfly valve closed,

(4) FIG. 4 and FIG. 5 are perspective and front views respectively, illustrating an example of a case of a sealing system conforming with the invention,

(5) FIG. 6 is a perspective sectional view illustrating an example of a sealing system conforming with the invention comprising the metal case, the metal cover and the dynamic metal seal, and

(6) FIG. 7 is a detailed sectional view, illustrating a variant embodiment of the metal sealing system conforming with the invention.

(7) In all these figures, identical references may designate identical or similar elements.

(8) Furthermore, the different parts shown on the figures are not necessarily all at the same scale, to make the figures more easily understandable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

(9) Examples of embodiments of the invention will now be described with reference to FIGS. 1 to 7.

(10) Firstly, a first example of a triple eccentricity butterfly valve 30 comprising a metal sealing system 6 conforming with the invention will be described with reference to FIGS. 1 to 6.

(11) FIG. 1 is thus a sectional view illustrating the butterfly valve 30 in the open position, and the metal sealing system 6 in a plane perpendicular to the axis of the control rod of the disk 3.

(12) FIGS. 2 and 3 are detailed sectional views in the plane of the control rod of the butterfly valve 30 in the closed position.

(13) The triple eccentricity butterfly valve 30 thus comprises a hollow valve body 1, that is hollowed out to define a conduit 4. Furthermore, at its internal periphery delimiting its hollow part, the valve body 1 comprises a conical and inclined internal annular part that forms the valve seat 5, visible for example in FIG. 1. In other words, the valve seat 5 comprises an internal surface 5a with an inclined conical shape.

(14) This internal surface 5a extends between an upstream lateral face 5b and a downstream lateral face 5c of the valve seat 5. It should be noted that the terms “upstream” and “downstream” must be understood as being relative to the normal flow direction of the fluid from upstream to downstream, as represented by the arrow F in FIG. 1.

(15) The upstream lateral surface 5b and the downstream lateral surface 5a are contained in planes perpendicular to the X axis of the conduit 4. Furthermore, if the valve seat 5 is intersected by a plane perpendicular to the X axis of the conduit 4 and is located between the two planes in which the lateral surfaces 5b and 5a are inscribed, the inner edge of valve seat 5 would be elliptical in shape.

(16) The butterfly valve 30 also has a stem passage 2, into which the valve stem (not shown) will fit, that is guided in rotation on each side of the conduit 4, and is connected to a control rod of the butterfly valve 30. The butterfly valve 30 also comprises a disk 3 housed in the conduit 4 and through which the stem 2 passes, and will rotate simultaneously with the valve stem 2 in the direction indicated by the arrow 7 in FIG. 1.

(17) Furthermore, at its periphery, the disk 3 comprises a recess 13 for the integration of a sealing system 6 conforming with the invention as can be seen for example in FIG. 6, at the bottom of which a groove 14 is machined. Alternatively, if the metal sealing system 6 is installed on the valve body 1, the recess would be located on the valve body 1. Similarly, the groove could be formed in the valve body 1 if the metal sealing system 6 is installed in the valve body 1.

(18) A secondary seal 10 is positioned in the groove 14, and the metal sealing system 6 then covers the secondary seal 10. The secondary seal 10 may for example be a spiral seal. It is designed to interrupt the leakage path between the metal sealing system 6 and the disk 3.

(19) The assembly formed by the metal sealing system 6 and the secondary seal 10 is compressed axially by a flange 11, that is itself clamped by a network of nuts 12.

(20) FIG. 2 shows a detailed view at 90° from the valve axis, showing the sealing system 6 on the disk 3 in the closed position.

(21) The sealing system 6 thus comprises a case 15, adapted to be installed in the recess 13 formed in the disk 3. As shown in FIG. 2, there is a clearance J between the inside diameter 17 of the case 15 and the outside diameter 16 of the disk 3, in the recess 13, so that the assembly can position itself during the first closure.

(22) The external surface 18 of the case 15 is has an inclined conical shape, with dimensions such that it is in uniform contact with the valve seat 5 at the end of the closure.

(23) Furthermore, a first housing 19 is formed in the case 15. This first housing 19 comprises a lateral bearing surface 20, preferably parallel to the central axis T of the case 15, shown in FIG. 4. It should be noted that the two surfaces perpendicular to the central axis T of the case 15 are referred to as the “upper face” and the “lower face” of the case 15. By convention, the “upper face” is the surface closest to the top of the cone forming the external surface. Unlike a solid seal according to prior art, the first housing 19 would then be formed by removal of material on the upper surface or on the lower surface. In this case, the first housing 19 is formed on the upper face of the case 15, but it could be formed on the lower face without going outside the framework of the invention.

(24) The first housing 19 is thus opened towards the exterior. If the case 15 is intersected on a plane containing the central axis T, a geometry similar to the geometry of a staircase is observed, intersecting the outer cone. The bottom 19f of the first housing 19 is preferably flat while the lateral bearing surface 20 is preferably parallel to the central axis T.

(25) Furthermore, it should be noted that, as can be seen in FIG. 4, the case 15 incorporates an indexing system 40 so that it can be positioned at a correct angle on the disk 3, for example a notch for a pin on its inside diameter. In fact, the entire internal part of the case 15 is such that it can be positioned on the disk 3.

(26) Thus, the case 15 is indexed in an angular position in the recess 13 by an axial pin fitted in the disk 3 and passing through the notch 40 in the case 15, this arrangement not being fully represented.

(27) FIG. 5 represents a top view of the case 15. It is observed that the lateral bearing surface 20 is elliptical in shape with a major axis 23 and a minor axis 22. The major axis 23 is coincident with the horizontal median axis of the inside diameter 17 of the case 15. The minor axis 22 is parallel to the vertical median axis 24 of the inside diameter 17 of the case 15 with an offset equal to a value e.

(28) Furthermore, a dynamic metal seal 21 is fitted in the first housing 19. It comprises a coil spring 26 and a coating 27. For example, it may be a simple “U” torus seal. It should be noted that the term “C” opening is used when the opening faces the inside or outside diameter of the case. When seen in a sectional view, in this case the opening is oriented towards the upper or lower face such that the term “U” opening is used. In other words, the position is at 90° from a “C” opening. This dynamic seal 21 has smooth parts on its inside and outside diameters, and can therefore make a radial seal when its inside and outside diameters come into contact.

(29) For example, it may be a HELICOFLEX® seal marketed by the French Technetics Group company, the basic principle of which is described in the French patent application FR 2 151 186 A1. It can be noted that the difference in dimensions between the minor axis 22 and the major axis 23 is visually quite small. The seal 21 can be manufactured in circular form, and can then be stretched manually during installation in the first housing 19 to take its elliptical shape, being retained by the lateral bearing surface 20.

(30) Once positioned in its first housing 19, the inner periphery of the dynamic seal 21 is in contact with the lateral bearing surface 20 or the vertical surface of the first housing 19. In a section on a plane containing the central axis T, the section of the outer periphery of the dynamic seal 21 intersects the dummy conical surface prolonging the actual conical surface that forms the outer shape of the case 15. The maximum penetration of the circle arc of the torus of the dynamic seal 21 into the cone, measured perpendicular to the surface of the cone, is referred to as “interference”. When the valve 30 is closed, the sealing system 6 will move into position in contact with the valve seat 5 with an inclined conical shape made so that, at the end of the closing, its surface will be coincident with the inclined conical surface forming the outer shape of the case 15. The case 15 can act as a stop, if there are no stops elsewhere on the valve 30, and the interference will correspond to the effective compression of the dynamic seal 21 on the valve seat 5. As stated in the presentation of prior art, the conical surfaces of the case 15 and the valve seat 5 cannot match perfectly. However, this is not a problem because the seal is made by the interference of the dynamic seal 21 and not by a perfect fit of the two conical surfaces.

(31) The coating 27 has a “U” shape. In the example described, the angle of the opening 28 of the “U” is very slightly offset inwards from its normal position, i.e. parallel to the central axis T of the case 15; therefore, it is certain that the ends of the coating 27 cannot catch the valve seat 5 during movements of the valve 30, which would damage the coating 27. Regardless of the exact position of the opening 28, it is important that it does not intersect the outside and inside diameters of the seal under any circumstances, since the seal will be made at these diameters.

(32) Furthermore, a cover 29 closes the metal sealing system 6 by flush fitting, or with a substantially continuous surface, between the upper surface 29p of the cover 29 and the upper surface 15p of the metal case 15 so that the sealing system 6 can be positioned in contact with the flange 11. This cover 29 is advantageously positioned in a second housing 39 in the case 15, formed in this case by a cut-out 15s in the upper face 15p of the case 15 (but it could also be the lower face). In addition, the cover 29 is held in place by three axial screws 32, visible in FIGS. 1 and 6. These screws 32 must be capable of holding the cover 29 in place during transport and assembly of the sealing system 6. Finally, the assembly is held in place on the valve 30 by the flange 11 and the nuts 12. In other words, the sealing system 6 forms an assembly comprising the seal 21 between the case 15 and the cover 29 that is homogeneous and independent of the flange 11. The presence of the cover 29 in a second housing 39 of the case 15, designed such that the upper face of the sealing system 6 is formed by the cover 29 and a part of the case 15, advantageously facilitates handling of the sealing system 6 and makes the assembly easier. In addition, any maintenance operation, and particularly replacement of the seal 21, is made easier by the use of this cover 29.

(33) The external shape of the cover 29 is inclined and conical. The angle between the cover 29 and the case 15 is indexed. After assembly, the inclined conical area forming the outside of the cover 29 replaces the equivalent inclined conical area of a conventional plain metal seal that was removed from the same location when creating the first housing 19 for the dynamic seal 21.

(34) Furthermore, a clearance J′ is formed between the outside of the cover 29 and the valve seat 5. Furthermore the cover 29 never comes into contact with the valve seat 5. Advantageously, given its small thickness, this avoids the risk of twisting the cover 29 when the valve 30 is closed. When closing, the radial compression of dynamic seal 21 will be made as a result of the interference i between the periphery of the seal 21 and the valve seat 5.

(35) In FIG. 3, that shows a sectional view similar to that in FIG. 2 but in a plane containing the centre line of the valve, not shown, there is also interference i′ of the seal 21. In one preferred embodiment, an expert in the subject will be able to determine the lengths of the major axis 23 and the minor axis 22, and the offset e, so as to create a uniform interference of the dynamic seal 21 with the valve seat 5 around the entire periphery of the sealing system 6 so as to obtain i=i′. However, the length of the minor axis 22 can be reduced so as to obtain i<i′. This may be useful for reducing operating torques and torsion forces on the coating 27 at the stem, and therefore making a consequential limitation of wear of the coating 27. In general, an expert in the subject can modify all or part of the shape of the bearing surface 20 to manage interference locally.

(36) During assembly, the metal sealing system 6 thus defined is positioned on the disk 3 in the same way as a solid metal seal that it replaces. It comes into contact with the secondary seal 10, preventing the leak around itself, and the assembly is compressed by the flange 11.

(37) It should be noted that the inclined conical area of the cover 29 is preferably positioned to be slightly set back from the equivalent inclined conical area of a conventional plain seal. This enables optimum retention of the dynamic seal 21 in the first housing 19, without obtaining contact between the valve seat 5 and the cover 29 when closing. Such contact would not contribute to the seal, but would create mechanical stresses on the cover 29, that could damage it.

(38) Furthermore, the ellipse formed by the lateral bearing surface 20 of the first housing 19 is defined such that the effective interference of the dynamic seal 21 is identical around the entire periphery of the sealing system 6. Specifically, this is achieved by optimising the dimensions of the major and minor axes. The centre of the ellipse is also adjusted in position on the line collinear with its own major axis.

(39) Furthermore, interference around the perimeter of the sealing system 6 can be variable. To achieve this, this lateral bearing surface 20 of the first elliptical housing 19 should be reconsidered, and should also be defined as having an arbitrary shape. It can then be defined as desired to obtain a specific interference of the dynamic seal 21 at each cardinal point of the sealing system 6. This has several advantages: for example, it may be useful to limit interference in areas close to the axis so as to limit the closing torque of the valve 30. These areas are also the areas in which the material of the dynamic seal 21 is stressed in torsion, which reduces its potential life. As explained in the state of prior art, interference will become manifest at the time of closure in these areas close to the control axis and will therefore generate a resistive torque and torsion at the surface of the dynamic seal 21. However, these areas are also the areas in which the dynamic seal 21/valve seat 5 interference is most easily controlled, in terms of the precision of the dimensions and the positioning between the sealing system 6 and the valve seat 5. Therefore it would be possible to reduce it locally in these areas. In this specific case, a bearing surface 20 of the elliptically shaped dynamic seal 21 can be retained, but the minor axis of which is reduced to reduce interference in areas close to the axis. The bearing surface 20 can also be made as follows: an elliptically shaped bearing surface is taken as the base giving interference with uniform compression. This ellipse is then intersected by lines parallel to the major axis. This reduces interference at stem passages.

(40) One improvement may consist of creating a complete spring 26, by welding several free lengths of springs. The turn diameter is the same for all free lengths. However, the diameter of the spring wire and/or the wire material may be different. Therefore the stiffness of each free length will be different, making it possible to have different local mechanical behaviours. Obviously, areas with different stiffnesses should be identified so that each can be positioned at its corresponding location when installing the assembly.

(41) Furthermore, FIG. 7 shows a version of the invention with an “inverted” configuration, in other words the sealing system 6 is mounted in the valve body 1, coming into contact with a valve seat formed by the outer surface of the disk 3. It should be noted that in this case the secondary seal 10 is a spiral seal and not an O-ring. The invention is not restricted to a particular type of secondary seal.

(42) Obviously, the invention is not limited to the example embodiments that have just been described. An expert in the subject can make various modifications to it.