BLEEDER VALVE FOR PRESSURIZED FURNACE

Abstract

 A bleeder valve (300) for controlling a gas outflow from the interior of a pressurized container (302) to an ambient atmosphere through an exhaust conduit (303) comprises: a valve seat (309) associated with said exhaust conduit (303), a movable lid (311) having a central closure portion (313) and a peripheral sealing surface (315) cooperating with said valve seat (309), and an actuating mechanism (316) connected to said lid (311) for moving said lid between a closed position on said valve seat and an open position distant from said valve seat. The lid comprises a deflection portion (317) at the periphery of said sealing surface. The deflection portion comprises a deflection surface (318) inclined relative to a tangent (Tsl) to said sealing surface (315) by an included angle (α) less than 180 degrees for imparting to a gas outflow passing between said valve seat (309) and said lid (311) a velocity component which is perpendicular or opposite to the initial opening movement of said lid. The central closure portion (313) is recessed with respect to said sealing surface (315).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to bleeder valves for controlling a gas outflow from the interior of a pressurized container, in particular a pressurised furnace, to an ambient atmosphere through an exhaust conduit.

BACKGROUND

[0002] When operating pressurized containers, bleeder valves, also referred as pressure relief valves or explosion prevention valves, may be used to control an interior pressure to an acceptable level by venting gases from the interior of the container to the ambient atmosphere.

[0003] Bleeder valves may be operated by active control, wherein the interior pressure is monitored and the valve is opened in controlled manner using an actuating mechanism when the interior pressure exceeds a predetermined level. In a safety-arrangement the actuating system may comprise a safety mechanism providing a biasing force to maintain the valve closed but allowing opening of the valve when the interior pressure exceeds a predetermined level against the biasing force. In such case the valve should reliably open under the influence of the lifting force derived from the interior pressure against the biasing force.

[0004] The shape of the valve affects its operation. In particular, WO 2007/090747 proposes for a bleeder valve of the above referenced type a closure member comprising a recurved deflection portion at the periphery of the peripheral sealing surface, the recurved deflection portion comprising a deflection surface inclined against the convex surface by an angle in the range of 30° to 70° for imparting to a gas outflow passing between the valve seat and the closure member a velocity component which is opposite to the initial opening movement of the closure member.

[0005] However, further improvements in bleeder valves are desired, in particular in relation to safety and/or reliability and longevity.

SUMMARY

[0006] In view of the above, herewith bleeder valves are provided according to the following.

[0007] An aspect comprises a bleeder valve for controlling a gas outflow from the interior of a pressurized container, in particular a pressurised furnace, to an ambient atmosphere through an exhaust conduit, comprising: a valve seat associated with said exhaust conduit; a movable lid having a central closure portion and a peripheral sealing surface cooperating with said valve seat, and an actuating mechanism which is connected to said lid for moving said lid between a closed position on said valve seat and an open position distant from said valve seat. Said lid comprises a deflection portion at the periphery of said sealing surface. Said deflection portion comprises a deflection surface inclined relative to a tangent to said sealing surface by an included angle less than 180 degrees for imparting to a gas outflow passing between said valve seat and said lid a velocity component which is perpendicular to or opposite to the initial opening movement of said lid. The central closure portion, at least in proximity to said sealing surface, is recessed with respect to said sealing surface.

[0008] With such valve, chattering of the valve and associated damage may be prevented and accurate dimensioning of a biasing force may be facilitated. A reason for this is that the recessed central closure portion provides for balancing opening and closing forces on the lid, in particular in initial stages of opening of the valve.

[0009] The valve is in particular suited as a bleeder valve for containers operating at pressures of several tenths of a bar to a few bars (1 bar = 100 kPa) relative to the ambient atmosphere surrounding the container and/or as a bleeder valve for controlling a gas outflow of such pressures and/or such fluxes that the outflowing gas is a supersonic regime for the particular gas. E.g. the container may be a pressurized blast furnace or a steel making vessel with a customary operating overpressure relative to the environment at the top of the container, e.g. of 0.1 - 4 bar (g) top pressure (the pressure above the blast furnace charge or, respectively, the steel making charge).

[0010] The included angle may depend on dimensions of one or more of the conduit, the valve seat, the sealing surface and the deflection portion.

[0011] At or near the seat, the conduit may extend along a central axis, and in the closed position relative to the axis seen from an interior side of the valve to an exhaust side of the valve, the seat surface may be convex, i.e. flaring outward. This facilitates a gas outflow. The sealing surface may also correspondingly be generally convex. Such combination of correspondingly convex surfaces may provide a self-centring effect facilitating closing of the valve.

[0012] In an embodiment, at or near the seat, the conduit extends along a central axis, and in the closed position relative to the axis seen from an interior side of the container and the valve to an exhaust side of the valve, the sealing surface is convex and the deflection surface is radially plane or concave. Such valve may facilitate imparting on the outflowing gas a velocity component which is perpendicular to or opposite to the initial opening movement of said lid. This provides an improved lifting force on the lid.

[0013] In an embodiment, the central closure portion of the lid is concave, as seen in the closed position relative to the axis seen from an interior side of the container and the valve to an exhaust side of the valve. Such valve may render design and calculation easier. It also may enable weight reduction of the valve member. In particular, the central closure portion of the lid may be concave from a portion of the sealing surface on one side to a portion of the sealing surface on an opposite side of the lid, such as being concave in diametrical cross section.

[0014] In an embodiment at or near the seat, the conduit extends along a central axis, and in the closed position an extension in axial direction of the recessed portion of the lid is more than an extension in axial direction of the sealing surface. Thus, the recessed portion is deeper than the sealing surface. Such valve may facilitate establishment of a homogeneous pressure distribution across a gap between the seat and the sealing surface, as seen in the axial direction. Thus, a smooth outflow may be achieved and pressure differences on the lid may be prevented.

[0015] In an embodiment at or near the seat (309), the conduit (303) extends along a central axis (H"), and the seat and the conduit at or near the seat are defined at least in part by an interior wall surface, and at least part of the recessed portion of the lid is defined by a recess surface, and in the closed position said interior wall surface and the recess surface register with each other. Thus, the conduit at or near the seat defines a lumen and the lumen continues substantially continuously into the lid. Such valve enables a gas flow into the gap from opposite directions, as seen in axial direction of the valve. This facilitates establishment of a homogeneous pressure distribution over the surfaces of the interior wall surface and the recess surface. When a gap is formed between the seat and the sealing surface due to opening of the bleeder valve, the homogeneous pressure difference may substantially be retained across the opening width of the gap as seen along the surfaces, such that the pressures on the interior wall surface and the recess surface on opposite sides of the gap may be substantially equal, which benefits a gas outflow pressure distribution and a gas flow distribution through the gap.

[0016] In an embodiment, the deflection portion extends along the entire periphery of the lid. Thus, the effect of the deflection portion may be achieved around the lid. Depending on, e.g. details of the movement of the lid from the closed position to the open position, details of positions and/or shapes of portions of the valve and/or of objects near the valve, the deflection portion may have different shapes in different sections around the lid, e.g. to affect a local lifting force on the lid which could reduce mechanical moments on associated portions.

[0017] In an embodiment, the seat and the lid have a cylindrical symmetry. Thus, a symmetric behaviour of the valve may be facilitated, e.g. improving predictability and robustness of the valve.

[0018] In an embodiment in at least part of the valve, the conduit extends along a central axis, one of the seat surface and the sealing surface is a frusto-conical surface and the other one of the seat surface and the sealing surface is part of a spherical or toroidal surface. A toroidal surface is formed if the sealing surface has a first radius of curvature about the central axis and a second radius of curvature in a direction perpendicular to the first radius of curvature being (significantly) smaller than the first radius of curvature.

[0019] This facilitates formation of a line contact, providing a relatively high closing pressure, rather than a flat surface contact which may reduce effective contact pressure. Also, tolerances with respect to parallelism may be reduced. Also, a self-centring arrangement may be provided. Any and each of such effects provides for a relatively robust valve.

[0020] In an embodiment, the valve seat comprises a seat surface cooperating with the peripheral sealing surface of the lid and the seat is provided with a soft seal element. The soft seal element may be a resilient seal element, e.g. an O-ring. The soft seal element may be embedded into said seat or into the lid within the seat surface or the sealing surface, respectively. Thus, part of the seal may deform and thus it may cushion a return of the lid onto the valve seat. Further, the soft seal member may conform to (the sealing surface of) the lid and improve tightness of the seal. Embedding of the soft seal into the seat surface or the sealing surface facilitates localisation of the seal, improving its reliability. An O-ring ensures sealing around the valve.

[0021] In an embodiment between the sealing surface and the deflection surface a transition area is located, comprising a surface oriented in another angle than the sealing surface and the deflection surface. The angle may be in between the sealing surface and the deflection surface, more in particular providing a smooth transition from the sealing surface to the deflection surface. The transition zone, which may take the form of a smoothly curved surface, e.g. having a continuously varying tangent, may facilitate manufacturing of the lid. Also, the transition zone may facilitate outflow of gas by preventing obstructions such as sudden bends. Preventing obstructions may also prevent deposition of particles from the gas flow, which could lead to (wear) damage and/or to leakage.

[0022] In an embodiment, at or near the seat, the conduit extends along a central axis, and wherein in the closed position of the valve the deflection surface extends at an angle between 90 and 110 with respect to the axis, being outwardly directed away from an exhaust side of the valve, for imparting to a gas outflow passing between said valve seat and said lid a velocity component which is perpendicular to or opposite to the initial opening movement of said lid.

[0023] In an embodiment said included angle (α) is in a range of 140 degrees to 180 degrees, in particular in a range of 150 degrees to 170 degrees, more in particular in a range of 155 degrees to 165 degrees. The valve seat (309) may have a width (Wv) in the direction of gas flow in a range of 45 mm to 65 mm, in particular in a range of 49 mm to 61 mm, more in particular in a range of 52 mm to 58 mm. The sealing surface (315) may have a width in the direction of gas flow in a range of 37 mm to 56 mm, in particular in a range of 40 mm to 53 mm, more in particular in a range of 43 mm to 50 mm. The deflection surface (318) may have a width in the direction of gas flow in a range of 55 mm to 75 mm, in particular in a range of 59 mm to 71 mm, more in particular in a range of 62 mm to 68 mm. Such values, in particular in combination, are considered to provide, results with, respectively, progressively better results from the widest to the narrowest range specified.

[0024] In an aspect, a container is provided comprising a bleeder valve as provided herein. The container may be a pressurized furnace, such as a blast furnace. Such pressurized container, and in particular such furnace, may be particularly robust and reliable. Operation safety of such container, in particular of such a (blast) furnace may be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above-described aspects will hereafter be further explained with more details and benefits, with reference to the drawings, in which:

Fig. 1 shows a traditional bleeder valve;

Fig. 2 indicates a relation between an uplift force and the amount of opening in a valve according to Fig. 1;

Fig. 3 indicates a relation between an uplift force and a closing force and the amount of opening in a valve according to Fig. 1;

Fig. 4 shows a bleeder valve according to WO 2007/090747;

Fig. 5 indicates a relation between an uplift force and a closing force and the amount of opening in a valve according to Fig. 4;

Figs. 6-7 indicate components of the uplift force in a valve according to Figs. 4 and 5;

Fig. 8 shows a bleeder valve according to the present principles;

Fig. 9 is a detail of a valve according to Fig. 8;

Fig. 10 shows another embodiment of a bleeder valve according to the present principles;

Fig. 11 indicates a relation between an uplift force and a closing force and the amount of opening in a valve according to Fig. 8;

Figs. 12-13 indicate components of the uplift force in a valve according to Figs. 8 and 11;

Fig. 14 shows a comparison between Figs. 5 and 11.

DETAILED DESCRIPTION OF EMBODIMENTS

[0026] It is noted that the drawings show aspects and embodiments by way of example only. The drawings are schematic, not necessarily to scale and details that are not required for understanding the present explanation may have been omitted. The terms "upward", "downward", "below", "above", and the like relate to objects as oriented in the drawings, unless otherwise specified. Further, elements that are at least substantially identical or that perform an at least substantially identical function are denoted by the same numeral, where helpful individualised with alphabetic suffixes, primes and/or in particular by increasing reference numbers by one or more hundreds.

[0027] Referring to Fig. 1, consider a traditional bleeding valve 100 for controlling a gas outflow from the interior of a pressurized container 102, in particular a pressurised furnace, to an ambient atmosphere through an exhaust conduit 103, the exhaust channel 103 extending along a central axis H from an interior side 105 of the valve 100, towards the container 102, to an exhaust side 107, away from the container 102. The valve 100 comprises: a valve seat 109 associated with said exhaust conduit 103; a movable lid 111 having a central closure portion 113 and a peripheral sealing surface 115 cooperating with said valve seat 109 having a seat surface 110; and an actuating mechanism (not shown) which is connected to said lid 111 for moving said lid 111 between a closed position on said valve seat 109 (as shown in Fig. 1) and an open position distant from said valve seat 109 (not shown). Herein, the central closure portion 113 is the portion of the lid 111 radially inside of the valve seat 109 in a closed position of the valve 100 being exposed to the container pressure.

[0028] When closed (Fig. 1), the lid 111 and the exhaust conduit 103 may be cylindrically symmetrical about the central axis H. In the shown embodiment, the central closure portion 113 and the peripheral sealing surface 115 are integrated in a single conically shaped surface.

[0029] In the valve 100, and in general in a bleeder valve, the valve lid 111 is subject to two forces acting in opposite directions: a closing force F_d and an uplift force F_u. Note that we consider the strengths of the forces F_d, F_u only; the forces are (assumed to be) directed parallel to each other. Figs. 2 and 3 schematically show the general behaviour of these forces F_u and, respectively, F_d, in a valve 100 according to Fig. 1 in dependency of valve stroke v_s.

[0030] The uplift force F_u has two components; a static force F_s resulting from the internal container pressure acting on the central closure portion 113 and a gas velocity induced force (also called "wind force") F_w caused by gas flowing between the valve lid and the valve seat:

[0031] The traditional valve design shown in Fig. 1 exhibits a negative relationship between the uplift force F_u and the amount of opening of the valve or "valve stroke" v_s of the lid 111 relative to the seat 109. This behaviour is shown in Fig. 2 and is determined by the following facts:

F_s reduces with valve stroke, i.e. F_s keeps reducing as the valve opening increases;

F_w is absent or negligible, i.e. F_w = 0.

[0032] The valve stroke-dependent behaviour of the uplift force F_u(v_s) may be essentially independent from the interior pressure in the container 102, which mainly determines the absolute value of the force F_u.

[0033] Since bleeder valves are generally oriented substantially vertical, the closing force F_d is generally downward and caused at least in part by the sum of the effective gravitational force on the lid 111 and associated valve portions (parts of the actuation mechanism, handles, etc., that may be attached to the lid 111), and as an optional part forces of a spring and/or other resilient portion of the actuating mechanism that keeps the valve closed. In such case, F_d is generally dependent on the valve stroke s_v:

[0034] However, the dependency need not be proportional; in an actual valve the relation between F_d and s_v will depend on particularities of the system considered. For a system having a spring with spring constant c, Eq. 2 may result in:

wherein F₀ is a possible offset, e.g. due to weight factors, e.g. see point A in Fig. 3. In an embodiment, the closing force F_d may be derived solely on gravity, e.g. based on the weight of the lid and possibly one or more additional weights and/or counterweights.

[0035] In any case for a bleeder valve, if the uplift force F_u is smaller than the closing force F_d, F_u < F_d, the valve will tend to remain closed or to close when opened, and in an opposite situation, when F_u > F_d, the valve will tend to open or open further when opened. An equilibrium position is reached where both forces are equal, F_u = F_d.

[0036] In Fig. 3 can be discerned that F_s keeps decreasing as the valve opening increases whereas F_d increases approximately linearly with increasing valve stroke v_s. In the somewhat simplified model considered, for and during opening a closed valve 100, several stages may be discerned:

a- the pressure on an inside of the valve 100 needs to create an uplift force F_u higher than a closing force F_u > F_d up to a (downward) offset force F = A for initialling opening the valve (Fig. 3);

b- when the valve 100 opens (i.e. v_s small but > 0) the uplift force F_u reduces, while the closing force F_d increases;

c- as long as F_u > F_d, the valve 100 will continue opening (increasing valve stroke v_s) up to the equilibrium valve stroke v_s = D, where the uplift and closing forces are equal at F_u = F_d = C;

d- due to its inertia of the movement, the lid 111 will overshoot the equilibrium position D up to a larger valve stroke v_s = E > D where F_u < F_d and the net closing force (difference between F_d and F_u) is sufficient to stop the movement and

e- impose a return movement of the lid 111 towards an equilibrium position at v_s = D;

f- however, due to its inertia of the movement, the lid 111 will again overshoot the equilibrium position D down to a smaller valve stroke v_s = F < D, where F_u > F_d and the net uplift force (difference between F_u and F_d) is sufficient to stop the movement and

g- force an opposite return movement of the lid towards equilibrium position v_s = D; this is a repetition of stage c above.

[0037] Thus, the lid, subject to the valve stroke v_s-dependent forces F_u and F_d will perform an oscillatory movement (repeating stages c-g), which, dependent on damping in the system reducing the oscillation amplitude E-F, eventually ends in a stable situation at the equilibrium valve stroke D.

[0038] Note that the valve stroke dependent behaviour of the uplift force F_u(v_s) and the of closing force F_d(v_s) F_u are a characteristic of a given valve 100 and that the exact values of F_u = F_d = C and v_s = D may depend on the internal pressure in the container 102 determining a force offset to F_u (e.g. up to F_u = B). Note further that in the above model description it is assumed that, at least for the duration of consideration, the interior gas pressure in the container 102 is substantially constant and unaffected by opening of the bleeder valve 100 and any gas outflow from the container 102.

[0039] Since the valve stroke equilibrium position v_s = D is determined by the relation of the uplift force F_u and the closing force F_d, in actual valves according to Fig. 1, the above-described oscillation effect can occur close to the closed position of the valve 100 where the lid 111 of the valve 100 may hit the valve seat 109 repeatedly, e.g. in every oscillation cycle. This is well known as "chattering" and may cause damage to (surfaces of) the valve seat 109 and/or (of) the lid 111.

[0040] Fig. 4 schematically shows a valve 200 according to WO 2007/090747. Figs. 5-7 show some effects of the valve design according to Fig. 4, cf. Figs. 2-3 relative to the valve design of Fig. 1.

[0041] In the valve 200, relative to a transitional valve 100 according to Fig. 1, the lid comprises a recurved deflection portion 217 at the periphery of the sealing surface 215. The deflection portion 217 imparts to an initial gas outflow passing between the valve seat 209 and the lid 211 (i.e. at small apertures) a substantial velocity component in the direction opposite to the initial opening movement of the lid 211 without compromising gas throughput especially at small apertures. Thus, the design of the valve 200 aims to provide an increased lifting force transmitted to the lid 211 by the gas flowing out of the exhaust conduit 203 and along the lid 211.

[0042] Thus, the uplift force F_u (Fig. 5) is a sum of the static force F_s (Fig. 6) and the nonzero gas velocity induced force F_w (Fig. 7) caused by the recurved deflection portion 217.

[0043] The static force F_s (Fig. 6) in the valve 200 according to Fig. 4 is equal to that in a traditional valve 100 according to Fig. 1, for a given valve diameter.

[0044] When well-optimized, a valve 200 according to Fig. 4 may provide that, different from a traditional valve 100 according to Fig. 1, F_w is nonzero and increases with the opening of the valve 200; see Fig. 7. As such, a decrease of F_s (Fig. 6) is compensated for by increasing F_w (Fig. 7). The resulting uplift force F_u = F_s + F_w (Eq. 1) may then have positive relationship to the valve opening, F_u increasing with valve stroke v_s, see Fig. 5.

[0045] Therefore, the valve 200 may be designed to provide a closing biasing force F_d such that F_u > F_d for all (practical) valve strokes v_s as indicated in Fig. 5. Thus, an equilibrium position of the lid 200 which results from equality of the uplift force and the closing force F_u = F_d is absent and chattering of the valve 200 may be prevented.

[0046] However, the present inventors have realised that also the valve 200 still has significant shortcomings. E.g. the decrease of the static force F_s (Fig. 6) in the initial phases of opening of the valve cannot be compensated by the gas velocity induced force F_w (Fig. 7), so that, just as in the traditional valve 100, the uplift force F_u shows a steep decrease for small valve strokes v_s; see Fig. 5. As a consequence, the minimum value G of the uplift force F_u may readily become equal to or lower than the closing force F_d for small valve strokes v_s, causing chattering at small openings. Thus, to prevent such chattering, valves 200 must be designed to provide an uplift force F_u and a closing force F_d such that an initial opening moment of the valve 200 requires a significantly higher uplift force F_u = B >> A than would be optimum for a safe operation.

[0047] Therefore, a further improved valve is provided herewith. Figs. 8-12 show an embodiment of the further improved valve 300 and a number of its characteristics. The presently provided bleeder valve 300 comprises: an exhaust conduit 303, a valve seat 309 associated with exhaust conduit 303; a movable lid 311 having a central closure portion 313 and a peripheral sealing surface 315 cooperating with said valve seat 309, and an actuating mechanism 316 which is connected to said lid 311 for moving said lid 311 between a closed position on said valve seat 309 and an open position distant from said valve seat 309. The lid 311 further comprises a deflection portion 317 providing a deflection surface 318.

[0048] The lid 311 and the seat 309, here also the conduit 303, have a cylindrical symmetry about the axis H", with the deflection portion 317 extending along the entire periphery of the lid 311 and the recess 319 extending along the entire sealing portion 321. However, such symmetry is not required. For opening of the valve 300, the lid 311 is movable with respect to the valve seat 309 essentially along the axis H", at least for small openings. Suitable actuating mechanisms provide opening of the valve 300 from the closed position to the open position by a movement that is substantially perpendicular to the valve seat 309, at least in initial stages of opening, e.g. a translation along the axis H" and/or a rotation along a path to which the axis H" is tangential. A preferred mechanism comprises the lid 311 being pivotal to a distant pivoting axis by a long arm arranged between the two, but other constructions may also be provided. The actuating mechanism should preferably allow opening of the valve 300 at least up to a separation between the valve seat 309 and the lid 311 sufficient to provide an opening with a cross sectional area for gas flow through it equal to the cross-sectional area of the conduit 303, to reduce flow resistance of the valve 300.

[0049] In a typical example, initial opening of the valve 300 comprises translation of the lid 311 without rotation, or only a small tilt of the lid 311 in the range of 1 - 5 degrees tilting angle relative to the closed position. In such range, and up to a gap height in axial direction along H" of about 10% of the conduit inner diameter, e.g. about 5 cm at a conduit diameter of 50 cm, the outflow of the gas will be substantially unaffected by the tilting. At larger tilting angles, typically > 5 degrees, the gas distribution may become distorted.

[0050] The actuating mechanism 316 should preferably provide as little inertia as possible to the valve. Hydraulic, pneumatic or electrical or other type of actuating mechanism can be used. A powered actuating mechanism 316 should preferably have a power back-up system.

[0051] The valve 300 comprises, compared to the valve 200, predominantly that the central closure portion 313 is recessed with respect to said sealing surface 315, at least in proximity to the sealing surface 315. As will be appreciated from Fig. 8, the lid 311 thus comprises a peripheral sealing portion 321 providing the sealing surface 315 protruding from the adjacent central closure portion 313. This is in contrast the valves 100 and 200, wherein a convex portion of the lid 111, 211, protrudes from the respective lid 111, 211, into the respective conduit 103, 203.

[0052] In the shown valve 300, the recess 319 extends substantially from a portion of the sealing surface 315 on one side of the lid 311 to a portion of the sealing surface 315 on the opposite side of the lid 311, relative to the central axis H", so that the recess 319 spans across the entire lid 311 inside the sealing portion 321 and a dome-like lid 311 is provided.

[0053] In the valve 300, the conduit 303 defines a lumen 327 at least at or near the seat 309, and the lumen 327 continues into (the recess 319 of) the lid 311. Best seen in Fig. 9, the seat 309 and the conduit 303 at or near the seat 309 are defined at least in part by an interior wall surface 323, and at least part of the recessed portion 319 of the lid 311 is defined by a recess surface 325. In the closed position of the valve 300 said interior wall surface 323 and the recess surface 325 register with each other. Thus, here, the lumen 327 continues into (the recess 319 of) the lid 311 substantially continuously and unchanged in shape.

[0054] In the embodiment of Figs. 8-10, at least at or near the seat 309, the conduit 303 extends along the central axis H". The valve seat surface 310 has a width Ws relative to the axis H" and a tangent Tss to the seat surface 301 extends at a seat surface angle φss to the axis H". The extension Dr of the recessed portion 319 of the lid 311 in axial direction along H", or: the depth Dr of the recessed portion 319, is more than said width Ws of the seat surface 310 times the cosinus of said seat surface angle φss, although it may also be equal to that:

[0055] The same holds, mutatis mutandis, for the extension Dr relative to the sealing surface 315. In other words, in the closed position an extension Dr in axial direction of the recessed portion 319 of the lid 311 is more than at least one of (a) an extension S in axial direction of the sealing surface 315 of the lid 311 and (b) an extension V in axial direction of the seat surface 310, i.e. in axial direction H", the recessed portion 319 is recessed deeper into the central portion 313 of the lid 311 than the height of the sealing surface 315 and/or the seat surface 310.

[0056] Relative to the axis H" seen from an interior side 305 of the valve 300 to an exhaust side 307 of the valve 300, the sealing surface 315 is convex and the deflection surface 318 is concave, so that a self-seeking effect is provided during closing of the valve 300. Note that the lid 311 may, after opening return to a slightly different geometry in a closed position than before; however, small (e.g. < 3 % of the seat width Ws) may be acceptable. In particular, in at least part of the valve 300, preferably in all of the valve 300, the seat surface 310 is a frusto-conical surface and the sealing surface 315 is portion of a spherical surface or of a toroidal surface, or the other way around. The frusto-conical surface preferably is tangential to the spherical or, respectively, toroidal surface portion at or near the location of contact between the seat surface 310 and sealing surface 315, forming a line contact. The latter condition of tangentiality preferably also applies along all portions of a non-circular conduit such that along such non-circular seal also a line contact is reliably formed.

[0057] The shown valve seat 309 comprises an optional soft seal element 327, which may be a more or less resilient seal element, e.g. an O-ring of a rubber and/or of any other suitable natural and/or synthetic material, or a relatively soft and deformable material relative to the valve surface and the sealing surface materials. Here, the soft seal element 327 is embedded into said seat surface 310. Alternatively, and/or additionally, a soft seal element (not shown) may be provided in the lid, e.g. embedded into the sealing surface 315, in the latter case the two soft seal elements are preferably radially offset from each other with respect to the axis H". The shown lid 311 is provided, here by embedding, with an optional sealing element 329 providing a sealing surface 315 of a suitable material, which may differ from one or more other portions of the lid 311. One or more of the valve seat 309, the soft seal element 327 and/or the sealing element 329 may be replaceable, e.g. for maintenance or repair.

[0058] In the lid 311 the tangent Tsl to the sealing surface 315 and the tangent Tdl to the deflection surface 318 relative to the axis H" are at an included angle α to each other. Between the sealing surface 315 and the deflection surface 318 an optional transition area 331 is located, comprising a surface 333 with a width Wt in radial direction relative to axis H" and being oriented in another angle than the sealing surface 315 and the deflection surface 318, in particular being curved and transitioning uninterruptedly with a continuously varying tangent to, respectively, both the sealing surface 315 and the deflection surface 318. The transition area 331 thus may provide a smooth aerodynamic transition from the sealing surface 315 to the deflection surface 318, preventing gas turbulence there.

[0059] In embodiments, said included angle α is in a range of 140 degrees to 180 degrees, in particular in a range of 150 degrees to 170 degrees, more perpendicular in a range of 155 degrees to 165 degrees.

[0060] In the closed position of the valve 300 the deflection surface 318 extends at an angle between 90 and 110 degrees with respect to the axis H", i.e. at an angle β between 0 and 10 relative to a radial direction about the axis H".

[0061] Thus, the deflection surface 318 is outwardly directed away from an exhaust side of the valve 300, for imparting to a gas outflow passing between the valve seat 309 and the lid 311 a velocity component which is perpendicular to or opposite to the initial opening movement of said lid 311.

[0062] Further, the valve seat 309, or at least the valve seat surface 310, may have a width Wv along its surface radial to the axis H", the direction of gas flow when flowing out of the conduit 303, in a range of 46 mm to 64 mm, in particular in a range of 49 mm to 61 mm, more in particular in a range of 52 mm to 58 mm.

[0063] The sealing surface 315 may have a width Ws along its surface radial to the axis H", the direction of gas flow when flowing out of the conduit 303, in a range of 37 mm to 56 mm, in particular in a range of 40 mm to 53 mm, more in particular in a range of 43 mm to 50 mm.

[0064] The widths Wv and Ws may differ, but they may also, preferably, be substantially the same, e.g. the width Wv being bigger than Ws by some 20% down to being equal.

[0065] The deflection surface 318 has a width Wd in the direction of gas flow in a range of 56 mm to 74 mm, in particular in a range of 59 mm to 71 mm, more in particular in a range of 62 mm to 68 mm.

[0066] Thus, the deflection portion 317 and the optional transition area 331 are, in a closed state of the valve 300, arranged outside of the valve seat 309 and in particular outside the ring type joint of the conduit 311, so that a protruding wing providing the deflection portion 317 extends to a total width Ww of Ww ≥ Wd + Wt.

[0067] Thus, best seen in Fig. 10, when considering a valve 300 with cylindrical symmetry about the central axis H", the conduit 303 has an inner diameter D_i, the walls 304 of the conduit 303 have a radial thickness E, providing an outer diameter of D_c = D₁ + 2E, the lid has an outer diameter Do and an inner diameter D_dome of the recessed portion or "dome". Thus, the lid 311 has an inner surface area A1 and an outer surface area A2, which here applying that A1 is equal to the cross-sectional area of the conduit A_cond = 1/4 π D_i², and the outer surface area A2 being equal to 1/4 n (D_o² - D_c²).

[0068] As a result of the recess 319, the static force Fs due to the interior pressure of the container 302 onto the central portion 313 of the lid 311 is largely unaffected by opening of the valve 300: see Fig. 12. Thus, local pressure drops due to opening of the valve 300 may be prevented and a stable pressure onto the lid 311 within the valve 300 is provided. Figs. 15-16 indicate pressure levels and, respectively, a gas stream in a valve 200; Figs. 17-18 show pressure levels and, respectively, a gas stream in a valve 300, according to a finite-element- model of the respective valves as shown. From a comparison between Figs. 15-16 and, respectively, Figs. 17-18, but without wishing to be bound to any particular theory, one may consider that the present valve 300 (Figs. 17-18) provides more of a lateral opening and a lateral gas flow component inside of the conduit 303 of the present valve 300, than an axial opening imparting an axial gas flow component inside of the conduit 303 as is the case in the known valve 200. Thus, in the present valve 300 the upward force on the lid 311 within the conduit 303 acts on a larger effective diameter than in the known valve 200. Further, in the present valve 300 a local pressure maximum is formed at or near the transition area 331, further radially outward than in the known valve 200. Note that the upward force may be equal for all container pressures for which the gas flow escaping through the valve 300 is supersonic; a pressure correction of the downward pressure F_d may be obviated. Further, the deflection portion 317 may be designed to provide a deflection surface 318 at a smaller angle α than in the known valve 200 providing a flatter increase of the gas velocity induced force F_w versus the valve stroke v_s (see Fig. 13).

[0069] Since in the initial phases of opening of the valve 300, the uplift force F_u = F_s + F_w (Eq. 1) is mainly determined by the static pressure F_s and in the present valve 300 the static pressure F_s is largely or actually constant, a significant pressure drop and decrease in the uplift force F_u in the initial phases of opening may be prevented.

[0070] Fig. 14 shows a comparison between the uplift force F_u200 of a valve 200 according to WO 2007/090747 (Fig. 5) and the uplift force F_u300 of a valve 300 according to the present teachings (Fig. 11), both valves having equal sizes and masses. Clearly, the decrease in uplift force in F_u300 is less than that in F_u200. Thus, a difference between F_u300 and F_d may be less than that for F_u200 without risking provision of an equilibrium valve stroke v_s where both opposing forces (F_u300 and F_d) are equal (but directed opposite each other) so that chattering may occur. Also, since the uplift force F_u300 increases less with increasing valve stroke v_s compared to the valve 200 a more constant force difference (F_u - F_d) and/or smaller spring constant may be provided for the closing force F_d providing a more linear behaviour of the valve 300.

[0071] Further, removal of the conical central portion 213 of the central portion of the known lid 200, as is done in (the lid 311 of) the presently provided valve 300 reduces weight of the lid 311 compared to a known lid 211 having a convex conical shape. Note that for forming a deflection portion 217, 317 laterally protruding outwards with respect to the lid 211, 311 and the conduit 203, 303, additional material may have to be added to the lid, relative to (the lid 111 of) the traditional valve 100, so that (the lid 211 of) the known valve 200 may be heavier than (the lid 111 of) a traditional valve 100 for a given valve size. The lid 311 of the presently provided valve, providing a recess thus being concave rather than convex, may be designed lighter than the lid 111, 211 of either of both known valves (100 and 200) for a given valve size. This reduces material consumption, and it may enable a lighter structure of the valve as a whole. Further, inertia of the lid of the presently provided valve may thus be reduced relative to the known valves so that a chattering amplitude (see valve stroke range F-E in Fig. 3) and associated damage risks to the lid and/or the valve seat may be reduced.

[0072] The disclosure is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims.

[0073] Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise.

Claims

1. A bleeder valve (300) for controlling a gas outflow from the interior of a pressurized container (302), in particular a pressurised furnace, to an ambient atmosphere through an exhaust conduit (303), comprising:

a valve seat (309) associated with said exhaust conduit (303);

a movable lid (311) having a central closure portion (313) and a peripheral sealing surface (315) cooperating with said valve seat (309),

and an actuating mechanism (316) which is connected to said lid (311) for moving said lid (311) between a closed position on said valve seat (309) and an open position distant from said valve seat (309);

wherein said lid (311) comprises a deflection portion (317) at the periphery of said sealing surface (315),

wherein said deflection portion (317) comprises a deflection surface (318) inclined relative to a tangent (Tsl) to said sealing surface (315) by an included angle (α) less than 180 degrees for imparting to a gas outflow passing between said valve seat (309) and said lid (311) a velocity component which is perpendicular to or opposite to the initial opening movement of said lid (311),

wherein the central closure portion (313), at least in proximity to said sealing surface (315), is recessed with respect to said sealing surface (315).

2. The bleeder valve (300) according to claim 1, wherein at or near the seat (309), the conduit (303) extends along a central axis (H"), and wherein in the closed position relative to the axis (H") seen from an interior side (305) of the container (302) and the valve (300) to an exhaust side (307) of the valve (300), the sealing surface (315) is convex and the deflection surface (318) is radially plane or concave.

3. The bleeder valve (300) according to claim 1, wherein the central closure portion (313) of the lid (311) is concave, in particular being concave from a portion of the sealing surface on one side to a portion of the sealing surface on an opposite side of the lid (311).

4. The bleeder valve (300) according to any preceding claim, wherein at or near the seat (309), the conduit (303) extends along a central axis (H"), and wherein in the closed position an extension in axial direction of the recessed portion (313) of the lid (311) is more than an extension in axial direction of the sealing surface (315).

5. The bleeder valve (300) according to any preceding claim, wherein at or near the seat (309), the conduit (303) extends along a central axis (H"),
wherein the seat (309) and the conduit (303) at or near the seat (309) are defined at least in part by an interior wall surface (323), and at least part of the recessed central closure portion (313) of the lid (311) is defined by a recess surface (325), and
wherein in the closed position said interior wall surface (323) and the recess surface (325) register with each other.

6. The bleeder valve (300) according to any preceding claim, wherein the deflection portion (317) extends along the entire periphery of the lid (311).

7. The bleeder valve (300) according to any preceding claim, wherein the seat (309) and the lid (311) have a cylindrical symmetry.

8. The bleeder valve (300) according to any preceding claim, wherein in at least part of the valve, one of the seat surface (310) and the sealing surface (315) is a frusto-conical surface and the other one of the seat surface (310) and the sealing surface (315) is part of a spherical or toroidal surface.

9. The bleeder valve (300) according to any preceding claim, wherein the valve seat (309) comprises a seat surface (310) cooperating with the peripheral sealing surface (315) of the lid (311) and wherein the seat (309) is provided with a soft seal element (327), in particular a resilient seal element, e.g. an O-ring, wherein preferably the soft seal element (327) is embedded into said seat (310) or into the lid (311) within the seat surface (310) or the sealing surface (315), respectively.

10. The bleeder valve (300) according to any preceding claim, wherein between the sealing surface (315) and the deflection surface (318) a transition area (331) is located, comprising a surface (333) oriented in another angle than the sealing surface (315) and the deflection surface (318), in particular an angle in between the sealing surface (315) and the deflection surface (318), more in particular providing a smooth transition from the sealing surface to the deflection surface.

11. The bleeder valve (300) according to any preceding claim, wherein at or near the seat (309), the conduit (303) extends along a central axis (H"), and wherein in the closed position of the valve (300) the deflection surface (318) extends at an angle (β) between 90 and 110 with respect to the axis (H"), being outwardly directed away from an exhaust side (307) of the valve (300), for imparting to a gas outflow passing between said valve seat (309) and said lid (311) a velocity component which is perpendicular to or opposite to the initial opening movement of said lid (311).

12. The bleeder valve (300) according to any preceding claim, wherein said included angle (α) is in a range of 140 degrees to 180 degrees, in particular in a range of 150 degrees to 170 degrees, more in particular in a range of 155 degrees to 165 degrees,
and wherein the valve seat (309) has a width (Wv) in the direction of gas flow in a range of 45 mm to 65 mm, in particular in a range of 49 mm to 61 mm, more in particular in a range of 52 mm to 58 mm,
and wherein the sealing surface (315) has a width in the direction of gas flow in a range of 37 mm to 56 mm, in particular in a range of 40 mm to 53 mm, more in particular in a range of 43 mm to 50 mm,
and wherein the deflection surface (318) has a width in the direction of gas flow in a range of 55 mm to 75 mm, in particular in a range of 59 mm to 71 mm, more in particular in a range of 62 mm to 68 mm.

13. A container (302) comprising a bleeder valve (300) according to any preceding claim.

14. The container (302) according to claim 13 wherein the container (302) is a pressurized furnace, such as a blast furnace.

Drawing