ZA200608521B - Device for diverting a gas flow through a single-blade flag valve - Google Patents

Description

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DEVICE FOR DIVERTING A GASEOUS FLOW VIA A SINGLE VALVE

ELEMENT FLAG DAMPER

The invention relates to a diversion device with single valve element flag damper, for the diversion of a gaseous flow, where necessary hot and/or filled with dust and/or containing at least a dangerous even toxic component, between a primary aeraulic circuit and a secondary aeraulic circuit.

Thus, the device according to the invention is used to orient a gaseous flow which, in a first configuration, called the normal configuration, is directed towards the primary aeraulic circuit, and which, in a second configuration is diverted towards the secondary aeraulic circuit, independent and isolated from the primary circuit, that is to say essentially sealed from this primary circuit.

The diversion device of the invention is specifically intended to find a particularly advantageous application in the aeraulic circuits that require a good isolation (seal) of primary and secondary circuits one relative to the other, and this even in the presence of different pressures in these two circuits.

Furthermore, and as already mentioned hereinabove, the gases of the oriented flow may, where appropriate, contain dangerous, even toxic, constituents, be also filled with dust, possibly harmful, and be hot, for example at a temperature greater than 200°C.

In normal operation, such a diversion device directs the gaseous flow towards the primary circuit, which is open, whereas access into the secondary circuit is closed, the flag damper occupying, in this case, a position called open. On the cther hand, in the second configuration, which corresponds for example to the

[L) implementation of a particular process, access to the primary circuit is closed whereas the gaseous flow is directed towards the secondary circuit which is open, the flag damper then occupying a position called closed.

Many different types of devices for diverting gaseous flows are known providing diversion or orientation functions as defined hereinabove. But, by design, these known devices usually have the disadvantage of inadequate sealing at the diversion valve element or elements. In the embodiment with separate valve elements, comprising at least one valve element mounted in a primary duct and at least another valve element mounted in a secondary duct, the mixture of gas resulting from a leakage flow from one of these two ducts to the other is certainly limited, but however this limitation is still inadequate to avoid disrupting the smooth operation of a plant fitted with such devices for diverting gaseous flows between two aeraulic circuits requiring a good isolation (seal) of one relative to the other.

Furthermore, when the automated closure/opening valve elements are duplicated, the diversion devices have the disadvantage of being too costly to produce and maintain.

Also known are diversion devices with a single damper common to the primary and secondary ducts, which are less costly, but which have the disadvantage of less of a seal.

The purpose of the invention is to propose a diversion device with single valve element flag damper, of a generally known type, and which is better suited to the various requirements of the practice, in particular in that it procures a considerable improvement of the

- - 3 = seal, while reducing the gas mixtures between the two primary and secondary aeraulic circuits in the common damper.

Specifically, the invention proposes a diversion device with single valve element flag damper of the type presented above and comprising: - a section of primary duct, rectilinear and tubular of quadrangular cross-section, whose entrance and exit are intended to be connected to the primary aeraulic circuit, - a section of secondary duct, also rectilinear, tubular and of quadrangular cross-section, whose entrance opens into one of the four walls of the section of primary duct, and whose exit is intended to be connected to the secondary aeraulic circuit, - a valve element, of quadrangular shape, mounted pivotingly, substantially along the length of one of its edges, in the section of primary duct, about a geometric axis transverse to the said wall into which the section of secondary duct opens and downstream of the latter, between two positions, a first of which is a position of opening towards the primary aeraulic circuit in which the valve element closes the entrance of the section of secondary duct, and the second of which is a position of closure of the primary aeraulic circuit, in which the valve element is moved away from the entrance of the section of secondary duct and pivoted so as to prevent the gaseous flow from discharging through the exit of the section of primary duct and that the gaseous flow entering via the entrance of the section of primary duct 1s diverted towards the section of secondary duct, and - a link arm assembly, connected to the valve element in order to operate it by pivoting from one to the other of the said two positions, and which is characterized in that the valve element has, on its w face turned towards the section of secondary duct in its first position, a machined quadrangular annular bearing surface to press in sealed manner against a seat formed by machining of the upstream end of the section of secondary duct, delimiting the entrance of the latter in the section of primary duct, the valve element being mounted pivotingly with a limited radial clearance relative to the geometric pivot axis, and in that, in the second position of the valve element, its free edge opposite its pivoting edge 1s resting against the wall of the section of primary duct which is opposite the wall into which the section of secondary duct opens, the two edges of the valve element which are perpendicular to its pivoting edge having, with the facing walls of the section of primary duct, a limited clearance so as not to block the pivoting actions of the valve element between its two positions.

In such a device, the sections of primary and secondary ducts are therefore of rectangular or square section in the zone of action of the valve element, which is most frequently rectangular, and this cross-section of the sections of duct is such that the particles and dust conveyed cannot settle or accumulate in the zone of action of the single, pivoting valve element, which closes the secondary circuit in "open" position and the primary circuit in "closed" position. The limited radial clearance of the pivoting valve element relative to the geometric axis of rotation ensures, in the "cpen" position, an excellent placement of the valve element, via its machined quadrangular annular bearing surface, against the machined seat on the upstream end of the section of secondary duct, so as to cbtain a good sealed pressure of the valve element in the "cpen" position, that 1s to say in normal operation, in which the damper is open towards the primary circuit, making it possible to obtain a minimum of 99% of the flow

" - 5 = which is directed towards the primary circuit and a maximum of 1% of the flow which may be diverted towards the secondary circuit, which is at a different pressure, and because of small leaks around the closed valve element. In "closed" position, that is to say when the damper is closed towards the primary circuit and open towards the secondary circuit, the device of the invention makes it possible to obtain that, at the minimum, 98% of the flow entering into the secondary circuit originates from upstream of the diversion device, and, at the maximum, 2% of this flow may return from downstream of the primary circuit (downstream of the valve element) into the secondary circuit, because of leaks around the valve element in this position.

In an advantageously simple embodiment, to obtain the aforementioned limited radial clearance, the valve element is mounted pivotingly by an edge folded preferably substantially at right angles to the rest of the valve element and secured, at its lateral ends, to two coaxial cylindrical trunnions with circular cross- section, each pivoting with some radial clearance in one respectively of two coaxial bearings secured to one at least of the said sections of primary and secondary duct.

In this case, and in a practical embodiment of the bearings, at least one of the two bearings, and preferably each of them, is formed by a lateral side plate secured to at least cne of the said two sections of duct and having a round or oblong opening in which is engaged, with radial clearance, respectively one of the two trunnions.

According to an economical embodiment, while further improving the seal, at least cne of the two bearings, and preferably each cf them, is formed by a lateral, U- shaped side plate, open in the downstream direction of

. the section of primary duct, in a housing directly adjacent to the downstream edge of the entrance of the section of secondary duct, downstream of this downstream edge, and open in the wall of the section of primary duct in which the entrance of the section of secondary duct is made.

Also for the purpose of further improving the seal in the zone of the edge of the valve element by which the latter is pivotingly mounted, the device also advantageously comprises an elastically deformable metallic sealing flap, preferably made of flat spring steel, of substantially quadrangular form, connected along one of its marginal portions to the wall of the section of primary duct into which the entrance of the section of secondary duct opens, downstream of this entrance, or to the pivoting valve element, and the opposite marginal portion of which is elastically pressing slidingly against the valve element, or against the said wall of the section of primary duct into which the section of secondary duct opens, downstream of the pivoting articulation of the valve element.

According to the design and installation constraints, if a is called the angle between the axes of the two primary and secondary sections of duct oriented from upstream to downstream, this angle o may preferably vary between 30° and 120° and more preferably between 30° and 90°, in order not to increase by too much the loss of pressure created by the gaseous flow diversion "elbow". According to the invention, the valve element in its second position is advantageously pivoted from its first position through a maximum angle 3 limited to 85° or to the angle «a, depending on whether the angle qo is greater than 85° and less than 120° or lying between 30° and 85°, and, in the latter case, the minimum angle

B 1s advantageously equal to 0.35 «.

According to installation requirements, for a given angle «a, chosen in an angular range extending preferably from 30° to 120°, and more preferably from 30° to 90°, the angle PB is advantageously chosen such that the pressure losses in the diverted gaseous flow, when the valve is in the second position, are minimal.

In order that the pressure losses resulting from the presence of the link arm assembly in the device are limited, and, furthermore, that this link arm assembly is subjected for as short a period as possible to the effects of the gaseous, possible corrosive, flow, the link arm assembly advantageously comprising a link arm- handle mechanism, is preferably mounted substantially in the central portion of the section of secondary duct and exerts its action substantially on the centre of gravity of the valve element. Thus, this link arm assembly 1s subjected to the gases only while the flicw is diverted towards the secondary circuit, and, during the operation towards the primary circuit, this link arm assembly experiences only the very limited action of the leakage flow towards the secondary circuit.

Furthermore, a point of action of the link arm assembly substantially in the centre of gravity of the valve element makes it possible to require less force to operate the valve element and keep it in tension on its seat, in "open" position. To facilitate the operation, which may be manual, of the link arm-handle mechanism of the link arm assembly, the latter is advantageously driven by rotating on itself a transverse shaft, traversing the section of secondary duct, and parallel to the pivot axis of the valve element.

But, preferably, the link arm assembly is actuated by an overlength travel actuator, preferably a rotary cylinder, which, in the first position of the valve element, holds the valve element pressed with force by

- its machined bearing surface against the machined seat of the section of secondary duct.

In this case, advantageously, the actuator is a rotary cylinder rotating on itself the drive shaft of the link arm assembly and is mounted laterally cutside the section of secondary duct, which shelters the actuator from the possibly corrosive gaseous flow on the one hand, and, on the other hand, makes it easier to protect, where appropriate, from an ambient magnetic field, for example by a Faraday cage for protecting an electrovalve for controlling a rotary cylinder with operating fluid, when, for example, the device is used close to aluminium electrolysis tanks in which electrodes are supplied with electric current of a very high voltage.

In order, all at the same time, to facilitate the linking of the link arm assembly and the valve element, and to stiffen the latter, the valve element 1s advantageously stiffened by at least two ribs parallel with one another, and between which is articulated a link arm of the link arm assembly for operating the valve element, in which case the sealed bearing surface of the valve element is machined after the ribs are welded onto the valve element and, where necessary, after the trunnions or a pivot shaft are welded onto the bent edge of the valve element.

Other features and advantages of the invention will emerge from the description given below of a non- limiting, exemplary embodiment described with reference to the appended drawings in which: - Figure 1 is a plan view of a gaseous flow diversion device with single valve element flag damper according to the invention, - Figure 2 1s a view in cross-section along II-III of

Figure 1, and

- Figure 3 is a view in longitudinal mid-plane section along III-III of Figure 1.

The gaseous flow diversion device according to Figures 1 to 3 comprises a section of primary duct 1, which is rectilinear and tubular of quadrangular and constant cross-section from its entrance 2 to its exit 3 (respectively on the right and on the left of Figures 1 and 3) delimited by peripheral attachment flanges 4 and 5, projecting outwards perpendicular to the longitudinal and central axis AA of the section of primary duct 1, for the sealed connection of the entrance 2 and exit 3 respectively to the upstream and downstream portions of a primary aeraulic circuit (not shown) for circulation of a gaseous flow which may be hot, dusty and/or contain dangerous even toxic elements.

In this example, the section of primary duct 1 is a horizontal section of square cross-section of which two sides are oriented vertically along the height and the two other sides horizontally along the width of the section of primary duct 1.

The diversion device also comprises a section of secondary duct 6 which is also rectilinear and tubular of quadrangular cross-section, also square in this example, and whose exit 8 is intended to be connected in sealed manner to a secondary aeraulic circuit, via a peripheral exit flange 9 projecting outwards from the section 6 perpendicular to its longitudinal and central axis BB.

In this example, this section of secondary duct 6 has its longitudinal axis BB oriented vertically and its entrance 7 opens into the flat top wall 10 of the section of primary duct 1.

In practical manner, the entrance 7 of the section of secondary duct 6 1s delimited by the upstream edges (the bottom edges on Figures 2 and 3) of the four flat walls of this section 6, that is to say the upstream wall 11 and downstream wall 12 of the section 6, relative to the direction of discharge of the gaseous flows in the section of primary duct 1, from its entrance 2 to its exit 3, and the two side walls 13 and 14 of the section 6, the assembly being thus arranged so that the upstream end portions of these four walls 11, 12, 13 and 14 protrude inside a vertical shallow compartment 15, arranged to project above the top wall 10 of the section of primary duct 1, as shown in

Figures 2 and 3. This compartment 15 is delimited by an upstream wall 16 and a downstream wall 17 which are portions of the top wall 10 bent vertically upwards, and by the top end portions 18 and 19 of the flat side walls 20 and 21 of the section of primary duct 1.

The dimensions of the compartment 15 and of the section of secondary duct 6 are such that the walls 11 and 12 of the section 6 are spaced respectively downstream and upstream of the walls respectively upstream 16 and downstream 17 of the compartment 15, while the side walls 13 and 14 of the section 6 are nested inside the side walls 18 and 19 of the compartment 15 and in contact with the latter, the engagement of the section 6 along its axis BB in the compartment 15 being such that the entrance 7 of this section 6 1s an opening delimited by the upstream edges of the four walls 11, 12, 13 and 14 of the section 6, and situated in the plane of the top wall 10 of the secticn 1. The sections of duct 1 and 6 are secured in this position by a peripheral flange 22, projecting outwards around the secticn 6 and bolted, with interposition of a seal, for example made of silicon, on the flaps 23, 24, 25 and 26 respectively of the walls 16, 17, 18 and 19 of the compartment 15, these flaps being bent outwards.

RR I

The diversion device further comprises a valve element 27, or flag damper, of rectangular shape, whose short sides are oriented horizontally and transversely and define the width of the valve element 27, which is slightly less than the distance between the side walls 20 and 21 of the section of primary duct 1, while the length of the valve element 27 is greater than the distance separating the walls 11 and 12 of the section of secondary duct 6, and this valve element 27 is mounted pivotingly in the section of primary duct 1, about a horizontal and transversal geometric axis XX, by one of its edges 28, extending along the width, and substantially bent at right angles to the rest of the valve element 27. This valve element is, for example, a simple flat metal plate such as a piece of metal sheet.

Along the free end of its bent edge 28, the valve element 27 1s secured to a pivot shaft 29, whose two ends, each turned towards one respectively of the two side walls 18 and 19 of the compartment 15, constitute the cylindrical trunnions 30 of circular section and coaxial about the geometric pivot axis XX, each of which is mounted pivotingly, with a slight radial clearance relative to the geometric axis XX, in one respectively of two bearings 31 coaxial and secured to the section of secondary duct 6, downstream (relative to the direction of discharge of the gaseous flows in the section of primary duct 1) of the downstream wall 12 of this section 6.

In this example, each of the two bearings 31 consists of a lateral side plate secured to the downstream face of the bottom end portion of the downstream wall 12 of the section 6, so as to project into the housing, delimited immediately downstream of the wall 12 of the section 6, between this wall 12 and the downstream wall 17 of the compartment and beneath the flange 22, as is clearly shown in Figure 3. In this housing, each of the side plates 31 extends substantially parallel to the side walls 18 and 19 of this housing, and has an oblong opening 32 into which one respectively of the two trunnions 30 is engaged with some radial clearance.

In this example, the oblong opening 32 of each bearing side plate 31 is delimited by the two branches of a U- shaped side plate 31 on its side pointing downstream of the section of primary duct 1, therefore open towards the downstream wall 17 of the compartment 15 and of the housing that receives the pivot articulation of the valve element 27.

Thus, the valve element 27 is mounted pivotingly, in the section of primary duct 1, substantially with sealing between its edges perpendicular to its pivot shaft 29 and the side walls 20 and 21 facing the section of duct 1, due to the limited clearance between these edges and these walls so as not to block the pivoting of the valve element 27, which pivots between two extreme positions, a first of which, wherein the valve element 27 is represented in section (and therefore hatched} in Figures 2 and 3 is a so-called normal position or "open" towards the primary aeraulic circuit, in which the valve element 27 is pressed against the upstream edges, delimiting the entrance opening 7 of the section of secondary duct 6, of the walls 11, 12, 13 and 14 of this section 6, so as to close this entrance 7 in order that the gaseous flow discharges from the entrance 2 to the exit 3 of the section of primary duct 1. The second position of the valve element 27 is a position of closure of the primary aeraulic circuit, in which the valve element, identified by the reference number 27a in Figure 3, is moved away from the entrance 7 of the section of secondary duct 6 and pivoted until its free transverse edge 33, opposite its curved pivoting edge 28, is pressing, as indicated at 33a in Figure 3, against the bottom wall 34 of the section of primary duct 1, in substantially sealed manner, such that the gaseous flow entering via the entrance 2 of the section of primary duct 1 is diverted by the valve element in its position 27a towards the entrance 7 of the section of the secondary duct 6.

Because of the rectangular shape of the valve element 27 and of its length relative to the height of the section of primary duct 1, in the position of closure of the primary aeraulic circuit, the valve element 27a (see Figure 3) 1s inclined at an angle BB relative to its "open" position, in which the valve element 27 closes the entrance 7 of the section of secondary duct 6, and its free edge 33a, pressing against the bottom wall 34, 1s axially upstream, in the section 1, of the pivot shaft 29 and of the trunnions 30 of the other bent transverse edge 28 of this valve element 27.

To ensure, in the "open" position, a practically sealed closure of the entrance 7 of the section of secondary duct 6, the valve element 27 has, on its face (top face in Figure 3) which is turned towards the section of secondary duct 6, a square and machined annular bearing surface 35, for a sealed pressure against a seat 6a formed by machining of the upstream edges (bottom edges in Figures 2 and 3) of the walls 11, 12, 13 and 14 of the section 6 against which the valve element 27 presses in its position of closure of the entrance 7 of this section 6. A good sealed pressure of the valve element 27 via its square and machined bearing surface against the machined seat 6a at the upstream end of the section of secondary duct 6 is possible thanks to 35 the limited radial clearance with which the trunnions 30 cf the curved edge 28 of the valve element 27 are each mounted in the oblong opening 32 of the corresponding U-shaped bearing side plate 31.

Figure 3 shows schematically at 35 the two transverse sides of the machined annular and square bearing surface on the valve element 27, this bearing surface 35 being able to be machined on an annular and square boss projecting on the face of the valve element 27 turned towards the section of secondary duct 6, or, on the contrary, machined on the bottom of a square annular spot facing made in this face of the valve element 27.

Thanks to the interaction of the pivot shaft 30 mounted swivelling with radial clearance in the two bearings 31 and the machined bearing surface 35 for the valve element 27 to press against the machined seat 6a on the upstream end of the section of secondary duct 6, (relative to a diverted discharge along the axis BB of this section 6), in normal position, that is to say when the valve element 27 closes the opening 7 for entrance of the section of secondary duct 6, it can be defined that at the minimum 99% of the gaseous flow passing through the entrance 2 of the section of primary duct 1 is directed to its exit 3, towards the primary aeraulic circuit, and at the maximum 1% of this flow may be diverted via the secondary aeraulic circuit, through the section of secondary duct 6, due to residual leaks around the valve element 27, and due to the fact that the secondary aeraulic circuit may be at a different pressure from that of the primary aeraulic circuit. In the so-called "closed" position, that 1s toc say in the position 27a of the valve element, at the minimum 98% of the gaseous flow exiting via the exit 8 of the section of secondary circuit 6 originates from upstream of the entrance 2 of the section of primary circuit 1 py diversicn in the device, and at the maximum 2% cf this flow may return from downstream of the primary aeraulic circuit, via the exit 3 of the section of primary duct 1, and discharge into the section of secondary duct 6 due to leaks around the valve element 27.

In the "closed" position, in which the valve element 27 in position 27a closes the access of the gaseous flow to the primary circuit, a relatively significant discharge of gas coming from downstream of the primary circuit, under the effect of the pressure difference between the secondary and primary circuits, may occur at the bent edge 28 and the pivot shaft 30 of the valve element 27. This discharge of gas is eliminated by the installation of a metal sealing flap 36, elastically deformable, also called foil, which is preferably made with the aid of a flat rectangular piece of spring steel, attached along one of its transverse marginal portions 37 against the bottom face of the top wall 10 of the section of primary duct 1, downstream of the housing in which the bent edge 28 of the valve element 27 1s mounted pivotingly, while the other, opposite marginal portion 38 is elastically pressing slidingly against the valve element 27, irrespective of the angle

B taken by the valve element 27 in closure position.

As a variant, and depending on the pivot angle B of the valve element 27, it is possible to attach the flap 36 by its margin portion 38 onto the valve element 27, and the flap 36 presses elastically and slidingly by its opposite marginal end 37 against the internal face of the top wall 10 of the section of the primary duct 1.

To operate the movements of the valve element 27 from one position to the other, the diversion device also comprises an operating link arm assembly 39 comprising an assembly with link arm 40 and handle 41, able to be operated manually, but preferably driven by an actuator 42, such as a rctary cylinder, providing an overlength travel in order to keep the valve element 27 pressed with force against its machined seat 6a at the upstream end of the section of secondary duct 6 projecting into the compartment 15 and delimiting the entrance 7 of this section 6.

The rotary cylinder 42 is attached, as can be seen in

Figures 1 and 2, laterally on the outside of the side wall 13 of the secondary section 6, and, by means of its output shaft 43, it rotates on itself a transmission shaft 44, parallel to the pivot axis XX of the valve element 27, and which traverses the section of secondary duct 6, in the two side walls 13 and 14 of which this transverse shaft 44 is mounted pivotingly.

Substantially in the middle of the transverse shaft 44, the latter is secured in rotation with one end of the handle 41, whose other end is articulated pivotingly about a shaft 46 substantially parallel to the shaft 44 and to the shaft XX for pivoting the valve element 27, on one end of the link arm 40, whose other end is articulated on the valve element 27.

Thus, the shaft 44, rotated by the rotary cylinder 42, itself rotates the handle 41, which moves the link arm 40 so as to operate the valve element 27 from one to the other of its two extreme positions of movement. For this purpose, the rotary cylinder 42 is reversible.

In this configuration, the link arm assembly 39 and the drive shaft 44 are mounted in the section of secondary duct 6, the link arm assembly 39 occupying even substantially the central portion of this section 6, so as to exert its action substantially in the centre of gravity of the valve element 27 in order to further improve the sealing pressure of the valve element 27 against its seat 6a. For this, the link arm 40 is articulated on the valve element 27 while being mounted pivotingly, about a transverse shaft 47, parallel to the pivot axis XX of the valve element 27 and tc the axes of the transverse shaft 44 and of the articulation

46 of the link arm 40 on the handle 41, between two ribs 45 parallel with one another and welded to the face of the valve element 27 which is turned towards the section of secondary duct 6, in order to stiffen the valve element 27. As shown in Figure 2, the two ribs 45 may consist of two flanges of a length of U- section welded onto the valve element 27.

In this embodiment, the welding of the ribs 45 and of the trunnions 30 and/or of the pivot shaft 29 on the valve element 27, made out of metal sheet, must occur before the machining of the annular and quadrangular bearing surface 35 for pressing this valve element 27 sealingly against the sealed seat 6a machined at the upstream end of the four walls 11, 12, 13 and 14 of the section of secondary duct 6.

Concerning the link arm assembly 39, note that it is preferable that the point of action of the transverse drive shaft 44 on the handle 41 is situated, in the direction along the axis XX of the section of primary duct 1, between the pivot axis XX of the valve element 27 and the point of action of the link arm 40 on the valve element 27, substantially on the shaft 47 of articulation of the handle 40 on the ribs 45, while in the axial direction along the axis BB of the section of secondary duct 6, the point of action of the rotary shaft 44 on the handle 41 is shifted downstream, in the section of secondary duct 6, relative to the point of action of the link arm 40 on the valve element 27 in the position of closure of the secticn of secondary duct e.

This configuration has numercus advantages. in particular, the link arm assembly 39 and the drive shaft 44 are sccured by the gaseous flow only in the "closed" position of the valve element 27a, in which the gasecus flow is diverted towards the secondary aeraulic «circuit, a situation which occurs, in the applications envisaged, less frequently and for less time than the situation in which the valve element 27 is in the "open" position, in which it closes the section of secondary duct 6. Furthermore, all of the link arm assembly 39, 1ts drive shaft 44 and the actuator 42, plus the assembly of the valve element 27 and its pivot articulation are, in this example, mounted on the section of secondary duct 6, which, thus equipped, is merely partially engaged and attached thereafter in and on the section of primary duct 1. The tricky operations of assembly, welding and machining are thus combined on elements which are all mounted on the section of secondary duct 6, which considerably simplifies the production of the section of primary duct 1, and makes it possible to reduce the production and maintenance costs of the diversion device.

Furthermore, the cross-section of the two sections 1 and 6 of the device is such that the particles and dust conveyed cannot accumulate or settle in the zone of action of the valve element 27.

It is understood that the positioning of the link arm assembly 39 may be optimized as a function of the length of the valve element 27 and of its angle of rotation B between its twd extreme positions. However, the use of this link arm assembly 39 and its positioning substantially mid-way along the length of the valve element 27 make it possible to ensure a better placement of the valve element 27 against its seat, in the position of closure of the section of secondary duct 6, and less force for the operation and maintenance in tension of the valve element against its seat is required.

According to the design and installation constraints, the angle « between the sections of primary duct 1 and

) dd secondary duct 6, therefore the angle between the axes

AA and BB of these two sections, oriented from upstream to downstream, and therefore also the angle of the corresponding gaseous flows, may preferably vary between 30° and 120°, and more preferably between 30° and 90°, the latter value of the angle oa being that which corresponds to the embodiment in Figures 1 to 3.

This angular range is preferred in order not to increase in too great a degree the loss of pressure created by the gaseous flow diversion "elbow".

Consequently, when the angle a lies between approximately 85° and approximately 120°, the maximum angle B, in which the valve element is in the position 27a blocking off the section of primary duct 1, is preferably 85°, while for an angle o lying between approximately 30° and approximately 85°, the angle {§ of the valve element 27 may be chosen at the maximum to be equal to the angle a and at the minimum to be equal to 0.35 «. In cther words, when ao lies between 20° and 85°, the angle B lies between a and 0.35 «, whereas when o lies between 85° and 120° the angle B is at the maximum of 85°.

More generally, for a given angle «o chosen in an angular range extending from 30° to 120°, and preferably from 30° to 90°, the angle fp is advantageously chosen so that the pressure losses in the diverted gaseous flow, when the valve 1s in position 27a blocking the section of primary duct 1, are minimal. If they are not the lowest, and according to the installation constraints, the angle f may be chosen so that the pressure losses are as close as possible to their minimum value.

Relative to the axis AA of the section cof primary duct 1, the section cf secondary duct 6 may be oriented 3€0° about the axis AA, according to the constraints created by the surrounding installation. However, the seal and mobility of the valve element 27 are greatly influenced and helped if the axis XX of rotation of the valve element 27 is horizontal, as shown in Figures 1 to 3.

In a particular exemplary embodiment, the diversion device according to the invention may be used in aluminium electrolysis workshops, or in similar applications, producing hot gases that have to be discharged for filtration and/or neutralization processes in order to scrub them. Specifically, these gases may, where appropriate, contain dangerous, even toxic, constituents and/or be filled with harmful dust, so that they cannot be placed in the atmosphere without a prior scrubbing treatment. Furthermore, the temperature of these gases may exceed 200°C. It is therefore necessary to confine these gases and ensure that they are discharged into a centralized treatment system. For this, the tanks in which these gases are generated are covered in sealed manner and fitted with conventional intake pipes. The intake «circuits of several tanks are combined as a function of the vclumes of gas to be extracted, volumes which are conveyed towards a treatment and scrubbing/cooling assembly, at the outlet of which the gases are discharged into the atmosphere. Conventionally, in aluminium electrolysis workshops, gas flows of more than one million m’/h are extracted and treated by filtration and scrubbing.

Since these workshops operate continuously, there is no question of waiting or totally shutting down the plant to carry out certain periodic maintenance or service operations, or yet when there are incidents. To carry out these operations, the sealed cover for confining one or more tanks must be opened, which considerably changes the intake conditions on this or these tanks, and may equally lead to disruption of the intake conditions of the other tanks connected to the same intake and treatment system such that, overall, conditions of discharging into the atmosphere may be

Created which are outside the normative limits or those set for the plant in question.

Accordingly, "double intake" or "on intake" plants have already been provided that make use of a second, additional intake system acting on each of the tanks.

In the event of a service or maintenance operation on a given tank, the intake of the gases of this tank is diverted to the "on intake" system, and the main intake pipework is isolated from this tank by a flow diversion device, of the type according to the present invention, in order not to disrupt the intake conditions on the other tanks, in operation, belonging to the same treatment and scrubbing circuit.

Thus, although, in the normal or primary circuit, intake 1s carried out by one or more pumping-out fans placed downstream of the treatment system, in the “on- intake” circuit, intake is carried out by a fan (also called a booster) which creates a forced intake and into which go untreated gases which are then reinjected into the normal circuit just before the gas scrubbing treatment unit.

Thus, thanks to the use of gaseous flow diversion devices of the type according to the present invention, it is possible to isolate a tank under maintenance or for a particular service operation without unbalancing the main aeraulic circuit, while maintaining an effective intake on that tank via the secondary aeraulic circuit.

Furthermore, the two aeraulic circuits (primary and secondary or auxiliary) do not leak from one to the other, which 1s extremely important. Specifically, since the tanks are installed in parallel and where necessary 1n large numbers (possibly reaching 350 tanks), if the valve element of each of the gaseous flow diversion devices used allows a leakage of a few percent, in "open" position, then the secondary aeraulic circuit must absorb the total of these leakages, which may represent a considerable flow, taking into account the number of tanks. On the other hand, in "closed" position and even if the sealing remains an important criterion in the valve element, a leak from the primary aeraulic circuit to the secondary aeraulic circuit is less inconvenient, since only a few tanks are simultaneously connected to the secondary aeraulic circuit (because of undergoing service or maintenance operations), so that the total of any leaks to be absorbed by the secondary aeraulic circuit is much smaller.

It is evident that the gaseous flow diversion device according to the invention is particularly suitable for such uses.

Claims (16)

- 23 = CLAIMS

1. Diversion device with single valve element flag damper for diverting a gaseous flow, where necessary hot and/or filled with dust and/or containing at least a dangerous even toxic component, between a primary aeraulic circuit and a secondary aeraulic circuit, of the type comprising: - a section of primary duct, rectilinear and tubular of quadrangular cross-section, whose entrance and exit are intended to be connected to the primary aeraulic circuit, - a section of secondary duct, also rectilinear, tubular and of quadrangular cross-section, whose entrance opens into one of the four walls of the section of primary duct, and whose exit is intended to be connected to the secondary aeraulic circuit, - a valve element, of quadrangular shape, mounted pivotingly, substantially along the length of one of its edges, in the section of primary duct, about a geometric axis transverse to the said wall into which the section of secondary duct opens and downstream of the latter, between two positions, a first of which is a position of opening towards the primary aeraulic circuit in which the valve element closes the entrance of the section of secondary duct, and the second of which 1s a position of closure of the primary aeraulic circuit, in which the valve element is moved away from the entrance of the section of secondary duct and pivoted so as to prevent the gaseous flow from discharging through the exit of the section of primary duct and that the gaseous flow entering via the entrance of the section of primary duct is diverted towards the section of secondary duct, and Amended 24 June 2008

- a link arm assembly, connected to the valve element in order to operate it by pivoting from one to the other of the said two positions, characterized in that the valve element has, on its face turned towards the section of secondary duct in its first position, a machined quadrangular annular bearing surface to press in sealed manner against a seat formed by machining of the upstream end of the section of secondary duct, delimiting the entrance of the latter in the section of primary duct, the valve element being mounted pivotingly with a limited radial clearance relative to the geometric pivot axis, and in that, in the second position of the valve element, its free edge opposite its pivoting edge 1s resting against the wall of the section of primary duct which is opposite the wall into which the section of secondary duct opens, the two edges of the valve element which are perpendicular to its pivoting edge having, with the facing walls of the section of primary duct, a limited clearance so as not to block the pivoting actions of the valve element between its two positions.

2. Diversion device according to Claim 1, characterized in that the valve element is mounted pivotingly by an edge folded with respect to the rest of the valve element and secured, at its lateral ends, to two coaxial cylindrical trunnions of circular cross-section, each pivoting with some radial clearance in one respectively of two coaxlal bearings secured to one at least of the said sections of primary and secondary ducts.

3. Diversion device according to claim 2, characterized in that said folded edge valve element 1s folded substantially at right angle to the rest of the valve element. Amended 24 June 2008

4, Diversion device according to Claim 2 or 3, characterized in that at least one of the two bearings is formed by a lateral side plate secured to at least one of the said two sections of duct and having a round or oblong opening in which is engaged, with radial clearance, respectively one of the two trunnions.

5. Diversion device according to Claim 4, characterized in that at least one of the two bearings is formed by a lateral, U-shaped side plate, open in the downstream direction of the section of primary duct, in a housing directly adjacent to the downstream edge of the entrance of the section of secondary duct, downstream of this downstream edge, and open 1in the wall of the section of primary duct in which the entrance of the section of secondary duct is made.

6. Diversion device according to any one of Claims 1 to 5, characterized in that it also comprises an elastically deformable metal sealing flap, of substantially quadrangular form, connected along one of its marginal portions to the wall of the section of primary duct into which the entrance of the section of secondary duct opens, downstream of this entrance, or to the pivoting valve element, and the opposite marginal portion of which is elastically pressing slidingly against the valve element, or against the said wall of the section of primary duct into which the section of secondary duct opens, downstream of the pivoting articulation of the valve element.

7. Diversion device according to claim 6, characterized in that said metal sealing flap is made of flat spring steel. Amended 24 June 2008

8. Diversion device according to any one of Claims 1 to 7, characterized in that, if o 1s the angle between the axes of the two sections of primary and secondary ducts oriented from upstream to downstream, the valve element in its second position is pivoted, from the first position, through a maximum angle B limited to 85° or to the angle «, depending on whether the angle «o 1is greater than 85° and less than 120° or lying between 30° and 85°, and, in the latter case, the minimum angle B is equal to 0.35 a.

9. Diversion device according to any one of Claims 1 to 8, characterized in that, for a given angle qa, between the axes of the two sections of duct oriented from upstream to downstream, and chosen in an angular range extending from 30° to 120°, the angle B of pivot of the valve element from its first to its second position is chosen such that the pressure losses in the diverted gaseous flow, when the valve element is in second position, are minimal.

10. Diversion device according to claim 9, characterized in that the angle ao is chosen in an angular range extending from 30° to 90°.

11. Diversion device according to any one of Claims 1 to 10, characterized in that the link arm assembly, comprising a link arm-handle mechanism, is mounted substantially in the central portion of the section of secondary duct and exerts its action substantially on the centre of gravity of the valve element.

12. Diversion device according to Claim 11, characterized in that the link arm assembly is Amended 24 June 2008 driven by rotating on itself a transverse shaft, traversing the section of secondary duct, and parallel to the pivot axis of the valve element.

13. Diversion device according to any one of Claims 1 to 12, characterized in that the link arm assembly is actuated by an overlength travel actuator, which, in the first position of the valve element, holds the valve element pressed with force by its machined bearing surface against the machined seat of the section of secondary duct.

14. Diversion device according to claim 13, characterized in that the overlength travel actuator is a rotary cylinder.

15. Diversion device according to Claim 13 or 14, as attached to Claim 12, characterized in that the actuator is a rotary cylinder rotating on itself the drive shaft of the link arm assembly and is mounted laterally outside the section of secondary duct.

16. Diversion device according to any one of Claims 1 to 15, characterized in that the valve element is stiffened by at least two ribs parallel with one another, and between which a link arm of the link arm assembly for operating the valve element is articulated. Amended 24 June 2008