EP2140146A1

EP2140146A1 - Variations in valve closing speed obtained by the use of different orifices

Info

Publication number: EP2140146A1
Application number: EP08735786A
Authority: EP
Inventors: Günter Musch; Gerta Zimmer
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2007-05-02
Filing date: 2008-04-03
Publication date: 2010-01-06
Also published as: WO2008135328A1; EP1988296A1

Abstract

The invention relates to a quick action valve (21) that has a valve train (23) located in an upper housing part (22), an opening or orifice (24), which can be integrated into a non-return valve, for a control medium being situated in said upper housing part (22). The valve train (23) has a closure element (26) and an orifice (28, 32) is situated in the upper housing part (22) at a vertical distance to the opening or orifice (24). To prevent leakage flows, the interior of the upper housing part (22) has a guide surface (36) for the closure element (26), at least in the region of at least one series of orifices (28, 32; 29, 31; 32, 34) situated at a vertical distance from the opening or orifice (24), said surface running in a straight line parallel to the central axis (X) of the part and having a closure surface (46) that also runs in a straight line.

Description

description

Variations in valve closing speed by using different apertures

The invention relates to a quick-acting valve, which has a valve drive arranged in an upper housing part, wherein in the upper housing part at least one opening or aperture, which may be integrated in a check valve, is introduced for a control medium, wherein the valve drive has a closure element, and wherein the housing upper part a seen in the vertical direction to the opening spaced aperture is introduced.

Such quick-acting valves are known and are used, for example, in turbomachines, e.g. Steam turbines used for fast closing of connected to the turbomachine pipes or the like lines.

Closing the quick-acting valves with constant

Closing speed produces a non-linear drop, for example, the steam mass flow which can sometimes lead to large pressure surges in the connected pipe. This problem occurs, for example, in steam turbines with e.g. four separate valve lines on.

By failure of a control valve in the closing direction, it can happen that three valves are shut off properly, whereas the fourth valve remains open. This results in a much higher steam mass flow through the remaining valve and thus, when shut off by the corresponding quick-closing valve, a much higher pressure surge in the steam line.

In order to avoid this, it is known to use a quick-acting valve in which the closing speed of the valve drive is successively slowed down by using special gaps in the upper housing part. A known quick-action valve is shown by way of example in FIG. 1 shows a quick-closing valve 1 in a partial cross-section through a housing upper part 2. In the upper housing part 2, a valve rod 3 is guided, which carries a closure element 4. The closure element 4 can also be referred to as a piston. Not shown in Figure 1 is an opening which is incorporated in the upper housing part 2. Through the opening, a control medium, for example hydraulic oil, can flow into the housing upper part 2. Due to the resulting overpressure, the closure element 4 is moved in the direction of the housing head. The closure element 4 takes the valve rod 3 with it. The valve rod 3 protrudes into a spring housing, and carries at least one energy accumulator, for example a spiral spring, which is tensioned in accordance with the movement of the valve rod 3. The quick-closing valve 1 is open when the energy store is tensioned.

To close the quick-closing valve 1, the excess pressure is reduced by diverting the control medium, so that relaxes the energy storage.

On the housing inner wall 6 of the upper housing part 2, a bevel 7 arranged in cross-section is arranged so that the upper housing part 2 conically tapers in this inner wall area from the housing head in the direction of the spring housing. The closure element 4 has on its outer circumference a bevel 7 corresponding to the slope 8. The example shown in Figure 1 results for low-pressure hydraulic (eg 8 bar) a diaphragm flow. In the relaxation of the energy storage so a steadily decreasing gap 9 is created, through which the control medium can flow. In the low pressure range, a diaphragm flow is realized with this configuration. As a result of the gap 9 becoming progressively smaller in the closing direction 11, the closing speed of the quick-closing valve 1 slows down. This embodiment according to FIG. 1 can be used disadvantageously only in the low-pressure range (eg 8 bar). For high pressure hydraulics (eg 160 bar) would be, with the same construction, very small Flow cross sections required so that it would no longer be possible to realize a diaphragm flow.

FIG. 7 shows a further, known quick-closing valve 51 with a combination of the gap flow with a diaphragm flow. For this purpose, a step 54 is arranged in the housing inner wall between an opening 52 (screen) and a panel 53 spaced apart in the vertical direction, which cooperates with a corresponding bevel 56 on the closing element 57, so that the disadvantageous gap flow results. The

Closing element 57 is adapted to the step 54 of the housing inner wall also made stepwise.

As already described, the configuration according to FIG. 1 results in a low-pressure hydraulic system (for example up to 8 bar)

Orifice flow. The higher the pressure in the hydraulic fluid, and thus the dimensions must be smaller, the more the diaphragm flow is in a gap flow. In order to largely prevent this, the design according to FIG. 7 has been developed. The design according to FIG. 7 represents the valve drive executed in high pressure hydraulics. Here a diaphragm combination has been selected in order to realize an end position damping. Here, the outlet of the hydraulic oil through two apertures 52, 53. Shortly before impingement of the drive, the flow is closed to the lower in the drawing plane (larger) aperture 53 by a cone (slope 56). In the region in which the cone (bevel 56) passes by the nose (step 54), there is a gap flow between the nose (step 54) and the cone (bevel 56). During the closing process, two different diaphragm flows result, on the one hand in the upper region of the stroke, where two diaphragms 52, 53 are available, and on the other hand in the lower region of the stroke, in which only one diaphragm 52 with a smaller diameter is available. In this area, the pure diaphragm flow is superimposed by a gap flow through the gap between the step 54 and the slope 56. FIG. 2 shows a linearly extending closing cam 12 with the stroke (Y-axis) of the closing element being plotted over time (X-axis), with FIG. 2 referring to a drive for high-pressure hydraulics (eg 160 bar). Further, Figure 3 shows the course of the mass flow 13 during the closing operation of the quick-closing valve.

A major disadvantage of the known quick-acting valves is that a linear course of the drive results in a convex course of the mass flow curve. To linearize the mass flow curve, the valve closing speed must be successively reduced. This is possible in the low-pressure region (FIG. 1) in that the contour (housing inner wall 6, slope I) ₁ along which the "nose" passes is adapted accordingly Manufacturing tolerances are no longer realized, so that therefore the construction of Figure 7 is used.

Another disadvantage is that the components must be executed with extreme accuracy, which is virtually unrealizable. Even small manufacturing tolerances cause large changes in relation to the flow velocity of the control medium or the hydraulic oil, and thus to the closing speed of the quick-closing valve. In particular, the hydraulic oil changes its viscosity due to temperature. However, if the viscosity of the hydraulic oil changes, this also has a direct influence on its flow speed and thus also on the closing speed. The

Slit flow is disadvantageously temperature dependent, which causes the closing speed to be different for cold and warm oil.

The invention is therefore based on the object to improve a operated with high pressure hydraulic quick-closing valve with simple means to the effect that changed the discharge characteristics of the drive to relieve the steam line is, wherein the closing speed of the quick-closing valve is independent of the temperature of the control medium or the hydraulic oil and piston play or Verschlusselementspielen.

According to the invention the object is achieved in that the upper housing part has in its interior a at least in the range of at least one series of two viewed in the vertical direction to the opening spaced diaphragm parallel to its central axis rectilinear guide surface for the closure element with a correspondingly rectilinear closing surface.

The invention is based on the finding that, due to new power plant plans, there is a need to use valves with a high-pressure hydraulic drive and to adapt the mass flow characteristic to the effect that the resulting characteristic has as shallow a tangent as possible; that is, the requirement is to modify the characteristic shown in FIG. 3 in such a way that a flow path of the steam throughput which is as linear as possible can be realized. The construction according to FIG. 1 makes it possible to adapt the valve closing speed to influence the characteristic of the steam mass flow to be shut off in the area of the low-pressure hydraulic system. However, this is not applicable to the application in high-pressure hydraulics. The drive used so far in the field of high pressure hydraulic (Figure 7) has a largely linear closing characteristic, resulting in a convex mass flow characteristic. Only in the area before the immediate placement of the cone on the seat was a cushioning provided. In the relevant range, this does not affect the mass flow characteristic. In addition, the realization of the end position damping is not a pure diaphragm flow.

In the high-pressure hydraulic range (eg 160 bar), in the case of a gap flow, even small manufacturing tolerances of the interacting components result in major changes on the flow or flow rate of the hydraulic oil and thus on the closing speed of the quick-closing valve. Also, the influence of temperature dependence leads to significant fluctuations in the flow rate (up to 100% difference in cold and warm hydraulic oil). In contrast to the slit flow, the flow through an orifice (orifice flow) depends only on the pressure of the hydraulic oil. The viscosity of the hydraulic oil plays no role in the diaphragm flow. This also largely eliminates the influence of temperature, so that the closing speed is approximately the same for cold and warm hydraulic oil due to the diaphragm flow. Due to the advantageous avoidance of the gap flow, the production cost of the quick-acting valve according to the invention is also considerably simplified, since the originally cooperating bevels and / or steps on the housing inner wall and closure element are omitted. Rather, the housing inner wall or the guide surface and the closing surface of the closure element can be carried out in the simplest manner with a constant inner diameter. The diaphragms are preferably continuous in the

Housing wall introduced and the outside connected to a medium recirculation system or the hydraulic system, which is set to return when closing the quick-closing valve with appropriate reagents.

In the context of the invention, it is favorable if the at least two diaphragms, viewed in longitudinal section, are each arranged diametrically opposite to the central axis. Appropriately, seen in longitudinal section, in each case at least two diaphragms on each side, viewed in the vertical direction each spaced from each other, arranged the upper housing part. It is advantageously provided that the respective diametrically opposite diaphragms are arranged symmetrically at least with their mouth openings.

In a preferred embodiment, the upper housing part, viewed in longitudinal section, has on both sides, in relation to its center axis, on each side three diaphragms or diaphragm pairs, which in vertical direction tion are each arranged one above the other. Of course, the at least two apertures in the housing upper part can also be arranged in a circular angle of less than 180 °. Preferably, at least the orifices of the respective successive successive high aperture are each arranged at the same height. Of course, more than two or three apertures can be provided spaced apart in the vertical direction.

Conveniently, the principle of the circumferential groove is abandoned with an aperture in the oil flow by means of the invention. Rather, two opposite holes connect the interior with the oil return. In these holes, the actual panels are inserted, preferably screwed. As a result, they can be modified comparatively easily. Another advantage is that the gap flow is no longer from one circumferential groove to the next. Now only gap flows with respect to the holes are relevant. However, due to the much smaller cross-section they are almost no longer significant.

The closure element is connected to a valve rod, which protrudes from the upper side of the housing on the head side and leads to the foot side into a spring housing part adjoining the upper housing part. On the foot side, the valve rod has a support element for at least one energy store, e.g. for a plate spring, which is supported opposite to the support element on the head side of the spring housing part.

In an advantageous embodiment, the closure element is designed as a head-side and foot-side closed cylinder, which is adapted with its cylinder wall or its closing surface to the inner diameter of the guide surface, or with little play on this, wherein the guide surface preferably sealed by a sealing device or seal is to avoid a gap flow. The closure element can be designed as a solid cylinder or as a hollow cylinder. Of course it is possible to use the encryption key ment also perform piston-like with a piston head and a piston skirt, wherein the piston head can be arranged oriented either to the foot side or the head side of the valve rod. The piston skirt would then be arranged according to its free end oriented either to the head or to the foot of the valve rod on the piston head. The piston skirt is adapted with its diameter to the inner diameter of the guide surface or lies with its closing surface with little play on this. In a preferred embodiment, the piston skirt is designed as a circumferentially continuous cylinder jacket. Of course, the piston skirt in the circumferential direction but also be interrupted so that each piston skirt webs are arranged corresponding to the position of the mouth openings of the panels or aperture pairs, and can cover these. Of course, too

Cylinder wall of the closure element in the embodiment as a cylinder in the circumferential direction to be interrupted accordingly.

During the closing movement of the quick-closing valve, due to the valve drive according to the invention, the hydraulic oil flows through the sequence of the at least two shutters which are spaced from one another in the vertical direction, one of which is covered one after the other by the closing element closing and thus closed. The valve drive is thus advantageously braked by successive shut-off of superimposed diaphragms. Advantageously, a graduated barrier is thus provided by the apertures which are spaced apart from one another in the vertical direction and subsequently closing, thereby prolonging the closing time, in particular in the lower stroke region of the closure element. When the valve is closed, the stroke has a magnitude of zero, so that the closing element moves in the closing of its upper stroke range toward the lower stroke range. Thus, the stroke decreases steadily when closing or the stroke is smaller. By closing or covering the first aperture relative to the top side of the housing upper part, the effective flow cross-section is reduced, which has a direct effect on the outflow velocity of the hydraulic outlet. liköls and thus on the closing speed of the quick-acting valve. Both speeds become lower. The successive reduction of the closing speed of the valve causes a slowing down of the reduction of the steam mass flow through the quick-closing valve (smaller maximum gradient in the steam mass flow curve) and thus a reduction of the resulting pressure surge in the steam line.

It is advantageous that, depending on how many panels are arranged one above the other, the closing speed of the quick-closing valves can be varied. The more apertures are arranged one above the other or closed or concealed one after the other, the longer the closing speed of the valve and thus the characteristic of the steam mass flow can be influenced. The arrangement of several superposed diaphragms or diaphragm pairs, the characteristic (contour) of the steam mass flow can be influenced. A linear decrease of the valve lift causes a konve ve steam mass flow curve (see prior art Figures 2 and 3). With the invention, however, a concave closing curve for the valve lift is generated by means of a plurality of diaphragms or a plurality of diaphragm pairs. This should ideally cause a linear decrease of the steam mass flow, which, however, can not be realized in the upper closing region or in the upper stroke region, of course, for geometrical reasons. However, in the lower closing region or in the lower stroke region, which is anyway the critical region due to the large gradients, the quick-action valve designed according to the invention has an advantageous effect, which means that a linear decrease of the steam mass flow is effected.

Further advantageous embodiments of the invention are disclosed in the subclaims and the following description of the figures. Show it

4 shows a longitudinal section through a quick-closing valve,

5 shows a course of the closing speed of the quick-closing valve of Figure 4, and

6 shows a course of a steam mass flow in the

Closing movement of the quick-closing valve of Figure 4.

In the different figures, the same parts are always provided with the same reference numerals, which is why these are usually described only once.

FIG. 4 shows a quick-closing valve 21, for example for a steam turbine, which has a valve drive 23 arranged in an upper housing part 22. In the upper housing part 22 at least one opening (aperture) 24 is arranged for a control medium. The control medium is preferably hydraulic oil. The valve drive 23 has a closure element 26.

As seen in the vertical direction (double arrow 27), the upper housing part 22 has a sequence of three pairs of diaphragms 28, 29, 31, and 32, 33, 34, which are introduced one above the other, as well as the diaphragm 24. The successive shutters 28, 29, 31, and 32, 33, 34 are relative to a central axis X of the quick-acting valve 21 diametrically opposite each other, that is arranged symmetrically to each other. This means that in the vertical direction 27, viewed from the diaphragm 24, the lowest diaphragm 28 is arranged on the left-hand drawing plane and the diametrically opposite diaphragm 32 is arranged on the right-hand plane of FIG. The two panels 28 and 32 are thus arranged symmetrically in the circumferential direction of the upper housing part 22, and form an aperture pair. In the following in the vertical direction apertures or aperture pairs 29 and 33 or 31 and 34, the same applies. The aperture 24 is present only once. The diaphragms 28, 29, 31, and 32, 33, 34, in which the diaphragm components are inserted, preferably screwed in, are inserted continuously in the housing upper part 22 and open on the inside into the interior of the housing upper part 22. On the outside, the diaphragms 28, 29 , 31, and 32, 33, 34 connected to a hydraulic system. The panels 28, 29, 31, and 32, 33, 34 are preferably arranged perpendicular to the central axis X extending.

The upper housing part 22 has a cylindrical inner wall 36, which can also be referred to as a guide surface 36 for the closure element 26. The guide surface 36 extends in the illustrated embodiment continuously parallel or straight to the central axis X.

The closure element 26 is connected to a valve rod 37, which protrudes from the upper housing part 22 on the head side and is guided on the foot side into a spring housing part 38. On the foot side, the valve rod 37 has a support element 39 for at least one energy accumulator 41, wherein the energy accumulator 41 is embodied by way of example as a plate spring, which rests on the support element 39 on the foot side and is supported on the spring housing part 38 on the head side.

The closure element 26 is designed as an example of a piston with a piston head 42 and a piston skirt 43. The piston head 42 is arranged oriented to the head side of the valve rod 37, wherein the piston skirt 43 is oriented with its free end 44 in the direction of the foot side of the valve rod 37. In a preferred embodiment, the closure element 26 has an outer diameter, which is adapted to the inner diameter of the guide surface 36, so that the piston skirt 43 or the corresponding portion of the piston crown 42, so the closing surface 46, abuts the guide surface 36 with a small clearance. The closure element 26 or the piston head 42 has a sealing device or seal 58, which causes a seal to the guide surface 36. The opening 24 is a bore into which a diaphragm is integrated. This panel can be integrated in a check valve. In the illustrated embodiment, the quick-closing valve 21 is closed. All diaphragms 28, 29, 31, and 32, 33, 34 are covered or closed by the closing surface 46 of the closure element 26. To open the quick-closing valve 21, the control medium or the hydraulic oil through the aperture 24 or through the disposed in the inlet check valve, in which the aperture 24 may be integrated, passed into the interior of the housing upper part 22. Due to the resulting overpressure in the upper housing part 22, the closure element 26 lifts in the direction of the head side, whereby at the same time the support element 39 is raised. As a result, the energy storage 41 and the diaphragm spring is tensioned. In the cocked position, the quick-closing valve 21 is opened, the hub has its largest amount. The free end 44 of the piston skirt 43 is arranged in the tensioned position above the first aperture 31 and 34 relative to the top side of the housing upper part 22. All seen in the vertical direction and on both sides symmetrically arranged to each other screens 28, 29, 31, and 32, 33, 34 and their mouths are free when the quick-closing valve 21 is open.

To close the quick-closing valve 21, the hydraulic system is set to return. This can be done with suitable reagents. During the closing movement of the quick-closing valve 21, the hydraulic oil flows through the orifices 24; 28, 29, 31, and 32, 33, 34 out of the interior of the housing upper part 22, whereby the overpressure is reduced. For very small orifices, the integration of the lowest in the drawing plane aperture 24 could be provided in a check valve. At the same time, the closure element 26 moves with its piston skirt 43 or its free end 44 in the direction of the foot side. In this downward movement in the plane of the drawing, the piston skirt 43 initially covers the first orifice 31 and 34 simultaneously. One after the other, the following panels 29 and 33 or 28 and 32 are each concealed or closed at the same time. The stroke becomes smaller (lower stroke range), with the stroke having a zero value when the valve is closed.

By the successive closing of the orifices, in each case the effectively free flow cross-section decreases, so that consequently the flow velocity of the hydraulic oil and thus the closing speed of the quick-closing valve

21, in particular in the lower stroke range of the closure element 26 is reduced.

In a preferred embodiment, the quick-acting valve 21 or its valve drive 23 is operated with high-pressure hydraulics (for example 160 bar). The flow in the respective aperture 24; 28, 29, 31, and 32, 33, 34 is only dependent on the pressure in the hydraulic oil. A temperature dependence (change in viscosity) is largely eliminated by means of the use of the diaphragm flow according to the invention, so that the

Quick-closing valve 21 closes almost equally quickly with warm or cold hydraulic oil. Of course, the valve drive can also be operated with low pressure hydraulics.

FIG. 5 shows the closing speed of the quick-action valve 21 provided with the valve drive 23 according to the invention. It can be seen that, in contrast to the prior art, the closing curve 47 does not run linearly but decreases in a hyperbolic manner. As FIG. 5 further shows, only the closing speed in the lower stroke region of the closure element 26 decreases. FIG. 6 shows the course of the mass flow 48 (mass flow characteristic) resulting from the embodiment according to the invention, wherein a tangent to be applied to the mass flow curve 48 is significantly flatter as in the prior art (see Figure 3). A similarly flat course would only be possible for a linearly closing valve drive (FIG. 1) if the total closing time were considerably increased. By the arrangement of a plurality of superposed diaphragms or aperture pairs 24; 28.31; 29.32; 31,34, the characteristic (contour) of the steam mass flow can be influenced. A linear decrease of the vapor mass flow causes a convex vapor mass flow curve whose tangent becomes steeper (Figures 2 and 3). By contrast, with a plurality of diaphragm pairs according to the invention, a concave closing curve for the valve lift is generated (FIG. 5). This should ideally cause a linear decrease in the vapor mass flow. Of course, this can not be achieved in the upper area of the closing area for geometrical reasons, but is very realizable or successfully achievable in the lower area, which is anyway the critical area due to the gradients (FIG. 6, mass flow profile 48).

Claims

claims

1. Quick-action valve which has a valve drive (23) arranged in an upper housing part (22), wherein an opening or aperture (24) for a control medium is introduced in the upper housing part (22), wherein the valve drive (23) has a closure element (26 ), and wherein in the upper housing part (22) arranged in the vertical direction to the opening or aperture (24) spaced diaphragm (28, 32) is arranged, characterized in that the housing upper part (22) in its interior at least in the range of at least one series of two apertures (28, 32, 29, 31, 32, 34) spaced apart from one another in the vertical direction relative to their central axis (X) and extending rectilinearly for the closure element (26). having a correspondingly rectilinear closing surface (46).

2. Quick-acting valve according to claim 1, characterized in that the at least two orifices (28, 32, 29, 31, 32, 34), viewed at least with their mouth openings in longitudinal section, are arranged diametrically opposite diametrically opposite central axis (X).

3. Quick-acting valve according to claim 1 or 2, characterized in that the at least two diaphragms (28, 32, 29, 31, 32, 34) in

Longitudinal section seen on each opposite side of the housing upper part (22) are arranged.

4. Quick-action valve according to one of the preceding claims, characterized in that the closure element (26) is designed as a closed cylinder.

5. Quick-action valve according to one of the preceding claims, characterized in that the closure element (26) is designed as a solid cylinder or as a hollow cylinder.

6. Quick-action valve according to one of the preceding claims, characterized in that the closure element (26) piston-like with a piston head (42) and a piston skirt (43) is executed.

7. Quick-action valve according to one of the preceding claims, characterized in that the closure element (26) with its closing surface (46) with a small clearance on the guide surface (36), wherein the closure element (26) preferably associated with a sealing device (58) is.