WO2004099658A1

WO2004099658A1 - Drive mechanism for a turbine valve

Info

Publication number: WO2004099658A1
Application number: PCT/EP2004/004813
Authority: WO
Inventors: Ralf Steinborn
Original assignee: Firma Siemens Aktiengesellschaft
Priority date: 2003-05-07
Filing date: 2004-05-06
Publication date: 2004-11-18
Also published as: DE112004000191D2; DE112004000191B4

Abstract

The invention concerns a drive mechanism for a turbine valve, in particular a regulating valve and a control valve, and comprising a valve stem provided with a valve cone, actuated by an electric/transmission motor unit and designed to adjust the opening and closing position of the turbine valve, the valve stem of both turbine valves capable of being prestressed by means of a spring-loaded accumulator for a fast closing process. The invention is characterized in that a hydraulic coupling element (9) for transmitting loads and for prestressing the spring-loaded accumulator (10) is located between the electric/transmission motor unit (22) and the valve stem (4). Such a structural shape enables very high adjusting loads to be economically transmitted, in particular to the spring-loaded accumulator, so as to provide fast closure.

Description

Drive for a turbine valve

The invention relates to a drive for a turbine valve, in particular a control valve and a switching valve, with a valve spindle actuated by an electric motor / gear unit and provided with a valve cone for setting the opening and closing position of the turbine valve, the valve spindle of both types of turbine valve using a Spring storage can be preloaded for a quick closing process.

In turbine construction, in particular in steam turbine construction, a large number of valves are required to control and supply the turbine sets of such a system, which are used as double shut-offs in the form of a switching and control valve with a quick-closing function, for example for live steam, trapping steam or bypass steam. The opening position of each of these valves is used to set a respective material or Steam flow, the structure of the valve usually being characterized by a conical valve seat and a corresponding valve cone with a valve spindle connected to it.

To actuate the turbine valve or the valve spindle, a drive is predominantly assigned to each valve. In modern steam turbine systems in particular, high demands are made on the drives with regard to the provision of large adjustment forces and the speed of the adjustment speed. In modern steam turbine systems, for example, actuating forces of up to 350 kN and actuating times of less than 200 milliseconds must be provided by the actuators in question for an actuating path of up to 250 mm until the valve is completely closed.

Various construction solutions for drives have become known in the prior art, with electrical mechanical drives in steam turbine construction have found their way into fire protection aspects in particular.

As an example for the solution of such an electromechanical drive, reference is made to WO 99/49250, in which an electromechanical drive for a valve is disclosed, which has an electric motor / gear unit with which a valve spindle provided with a valve cone can be actuated, whereby the Valve spindle can be preloaded by means of a spring accumulator for a quick closing process.

A special feature of the drive described there is to provide the drive with a transmission device coupled to the electric motor / gear unit, by means of which variable torques can be generated depending on the axial displacement of the push rod. Due to the structural units of the drive described in the document mentioned, the spring accumulator must be tensioned at the same time as, in the event of a quick closing of the associated valve, a rapid separation of the electric motor / gear unit and valve stem must be brought about.

In accordance with the structural design disclosed in WO 99/49250, this object is achieved by an electromagnetically actuated positive coupling.

The drives permitted in this way have proven themselves in principle, but they reach their physical limits, particularly in new steam turbine systems, since greater clamping forces of the associated spring-loaded mechanisms in connection with the required short shutter speeds can no longer be achieved by means of the electromagnetic couplings used.

It is therefore an object of the present invention to further develop a drive of the type described above in such a way that the turbine valves to be designed in future with steam turbine systems with higher steam press controlled easily and if necessary can be closed in a correspondingly short period of time. In addition, the drives should be inexpensive to manufacture from a cost point of view and have small dimensions.

This object is achieved according to the invention by a drive for a turbine valve which, in conjunction with the generic features of claim 1, has the technical teaching disclosed in the characterizing part of the claim.

It is essential to the invention that a hydraulic coupling element for power transmission and for prestressing the spring accumulator is arranged between the electric motor / gear unit and the valve spindle.

The novel use of the hydraulic coupling element enables the reliable transmission of the highest forces, while at the same time the triggering process for the hydraulic coupling element can be implemented sufficiently quickly with the appropriate dimensions.

Special refinements of the subject matter of the invention additionally result from the features listed in the dependent subclaims.

An advantageous constructive realization of the hydraulic coupling element has been shown to be a hydraulic cylinder with a control and supply unit which can be displaced translationally by means of the electric motor / gear unit, in the interior of which a pressure plate coupled to the valve spindle is movably arranged by means of oil pressure. Due to the oil pressure that can be applied within the hydraulic cylinder in connection with the effective surface of the pressure plate, the required clamping forces for the spring-loaded mechanism can be transferred without any problems. The overall volume of the drive according to the invention can be adapted to the often limited environmental conditions in accordance with an advantageous development of the subject matter of the invention in that the spring accumulator is arranged within the hydraulic cylinder and can thereby be preloaded directly against the pressure plate.

In addition, a compact design of the entire drive can be achieved in that the electric motor / gear unit, valve spindle, spring accumulator and hydraulic cylinder with control and supply unit are arranged in a common drive housing.

As already mentioned above, differently high forces can act on the valves to be moved by the drive as a result of the general operating conditions during an opening and closing process. An expedient embodiment therefore provides that at least one auxiliary spring supporting the closing movement of the valve cone acts on the hydraulic cylinder, which acts as a coupling element by means of the electric motor / gear unit, in the closing direction of the turbine valve. According to an advantageous development, this auxiliary spring can be received on the outside of the hydraulic cylinder in a recess provided for this purpose.

If the spring accumulator is accommodated within the hydraulic cylinder, a further advantageous development of the subject matter of the invention provides that the hydraulic cylinder is divided into a spring accumulator space and an oil pressure accumulator space, the oil pressure accumulator space being separated by means of the pressure plate in the prestressed state of the spring accumulator and the pressure oil therein being the hydraulic one Coupling function takes over. The oil pressure storage space is filled or emptied with pressure oil by means of the supply unit, which according to an expedient development can consist of at least one solenoid valve, an oil pressure pump and a hydraulic fluid reservoir. Oil pressure storage space and spring storage space can be separated from one another in a pressure-tight manner by means of gas-filled sealing elements. The gas-filled sealing elements form an advantageous embodiment with regard to the fact that the pressure plate cannot assume its predetermined clamping position exactly for operational reasons.

An alternative embodiment of the supply unit for building up and reducing the oil pressure in the oil pressure storage space can also provide that the control and supply unit has at least two solenoid valves, a hydraulic fluid reservoir and a check valve, one solenoid valve each on a passage in the wall of the interior of the oil pressure storage space and the spring storage space and the check valve is arranged in a bypass between the oil pressure storage space and the spring storage space. This construction of the control and supply unit makes the pressure oil pump unnecessary.

It follows from the aforementioned statements that pressure oil build-up only takes place inside the hydraulic cylinder. As an additional safety measure, the interior of the drive housing can be provided as the hydraulic fluid reservoir. Due to this constructive design, the pressure oil within the hydraulic cylinder is enclosed by an unpressurized oil filling and thus encapsulated. This measure serves to prevent possible fire hazards due to the escape of pressure oil.

Several exemplary embodiments of the subject matter of the invention and its mode of operation are explained in more detail below with the aid of the accompanying drawings.

It shows:

Figure 1 is a sectional view through an inventive

Drive in operating position with spring loaded when the turbine valve is closed, FIG. 2 shows the drive from FIG. 1 with the spring loaded, with an opening degree of 50% of the turbine valve,

FIG. 3 shows the drive of FIGS. 1 and 2 with the spring accumulator tensioned when the turbine valve is fully open,

FIG. 4 shows the drive when the spring accumulator is fully opened after the spring valve has been released as a result of a rapid closing process of the turbine valve,

FIG. 5 shows the drive during the re-tensioning of the spring accumulator after it has been triggered before the associated turbine valve has been completely opened,

FIG. 6 shows the drive according to the invention when closed

Turbine valve and at the same time relaxed spring accumulator,

FIG. 7 shows a different embodiment variant of the drive with regard to the arrangement for the auxiliary spring supporting the closing movement of the turbine valve,

8 shows a further embodiment variant of the drive according to the invention with a modified design of the control and supply unit for the pressure oil in the hydraulic cylinder compared to FIGS. 1 to 7,

9 shows the drive according to the invention corresponding to FIG. 8 after the spring accumulator has been released as a result of a rapid closing process of the turbine valve,

10 shows the drive according to the invention of FIGS. 8 and 9 immediately before the end of the tensioning process for the

Spring, FIG. 11 shows the drive according to the invention after the travel path for tensioning the spring accumulator has ended,

FIGS. 12a, 12b and 12c show an enlarged partial sectional view of the interior of the hydraulic cylinder of a drive according to FIGS. 8 to 11 during various stages of the tensioning process for the spring accumulator,

FIGS. 13a, 13b and 13c are schematic diagrams of the steam actuating forces acting on the valve cone as a function of the turbine valve stroke or the angle of rotation of the crank disk belonging to the electric motor / transmission unit,

Figures 14a, 14b and 14c an enlarged sectional view of a portion of the hydraulic cylinder in the area of the seal between

Pressure plate and partition of the oil pressure storage space and spring storage space during different stages of the clamping process and

FIGS. 15a, 15b and 15c show a schematic representation of the connection area between the hydraulic cylinder and the electric motor / gear unit during different opening positions of the turbine valve.

FIG. 1 shows an overall drive designated 1, which serves to drive a turbine valve consisting of a valve cone 5 and a valve seat 5a. The turbine valve is actuated by the drive 1 via a valve spindle 4, to the lower end of which the valve cone 5 shown in the closed position in FIG. 1 is fastened. The turbine valve is acted upon via an opening 33 with steam, which escapes again through the opening 34 from the turbine valve. The flow through the turbine valve indicated by the arrows Pi and P ₂ is regulated by means of a corresponding stroke of the valve spindle 4 in the opening direction indicated by the arrow P ₃ .

The drive 1 is connected to the turbine valve via a valve flange 3 and has a drive housing 32. Within the drive housing 32, the essential elements of the drive 1 are a hydraulic cylinder 9, a spring accumulator 10 arranged inside the hydraulic cylinder and an electric motor / gear unit 22 serving to translate the hydraulic cylinder 9 in the direction of the longitudinal axis of the valve spindle 4.

The electric motor / gear unit 22 consists of an electric motor with a crank disk 15, to which a connecting rod 17 is connected via a crank pin 16. The connecting rod 17 is in turn connected to a crosshead 18, via which the hydraulic cylinder 9 can be moved. The hydraulic cylinder 9 is mounted within the drive housing by means of the cylinder guides 21. Starting from the valve cone 5, the valve spindle 4 passes through the valve flange 3, the crosshead 18 and the wall of the hydraulic cylinder 9 and is provided with a pressure plate 13 at its end located inside the hydraulic cylinder. Inside the hydraulic cylinder 9 there is an intermediate wall 23 provided with an opening, which divides the interior of the hydraulic cylinder 9 into an oil pressure storage space 12 and a spring storage space 14. The oil pressure accumulator space 12 and the spring accumulator space 14 are separated by means of the pressure plate 13 which, in the operating state of the drive shown in FIG. 1, bears against the intermediate wall 23, a seal in the contact area between the pressure plate 13 and the intermediate wall 23 using an o-ring shaped sealing element 20 takes place. Between the pressure plate 13 and the rear wall of the hydraulic cylinder 9, a spring accumulator 10 consisting of a plurality of disc springs is arranged within the spring storage space 14, the spring accumulator 10 providing the actuating forces that are necessary for a quick closing of the turbine valve, regardless of the position Hydraulic cylinder and thus the valve cone 5 is located straight.

As a result of its design, the drive according to the invention serves both to adjust the valve cone 5 for regulating the steam flow and to tension the spring accumulator for the rapid closing of the turbine valve, necessary, for example, as a result of an unforeseen operating state. The quick shot function of the quick drive has to provide forces which are the maximum steam actuating force on the valve cone 4 plus a corresponding closing safety reserve. It must be ensured under all operating conditions that the turbine valve closes reliably on the valve cone 4 and its direction of force regardless of the respective steam actuating force.

The spring forces acting on the pressure plate 13 through the spring accumulator 10 are balanced on the opposite side of the pressure plate 13 by an oil pressure built up within the oil pressure storage space 12. This oil pressure forms the hydraulic coupling element for actuating the valve spindle 4 during normal operation. In the exemplary embodiment shown in FIG. 1, the oil pressure is maintained by means of an oil pressure pump 6 via a flexible pressure hose 7. The oil pressure pump 6, like a solenoid valve 8, which is connected to a further pressure hose 7a opening into the oil pressure storage space 12, belongs to a supply unit for the oil pressure loading of the oil pressure storage space 12. The entire interior of the drive housing 32 serves as a hydraulic fluid reservoir and thus encapsulates the inside of the Hydraulic cylinder 9 located high pressure area to the outside, so that possible fire hazards due to escaping pressure oil are excluded.

The operation of the drive results from its special design as follows:

To open the turbine valve, the valve spindle 4 is to be moved in the direction of the arrow P ₃ . This is done by actuating the electric motor / gear unit 22, an adjusting force being exerted on the entire hydraulic cylinder 9 via the crank disk 15, the connecting rod 17 and the crosshead 18. This force is transmitted by means of the oil cushion located in the hydraulic cylinder 9 in the oil pressure storage chamber 12 to the pressure plate 13, which moves the valve cone 5 in the direction of arrow P3 via the valve spindle 4.

This is clearly illustrated by comparing the position of the hydraulic cylinder 9 in the closed position in FIG. 1 with an open position of approximately 50% in the representation in FIG. 2. On the one hand, the position of the hydraulic cylinder 9 shifted to the rear, which is caused by the rotation of the Cam 15 in the direction of arrow P _{4 has been} effected. A further rotation of the cam disc 15 in the direction of arrow P causes a further displacement of the hydraulic cylinder 9 up to its end position shown in FIG. 3, in which the actuated turbine valve is completely, ie 100% open.

In Figures 1 to 3 it can also be seen that an auxiliary spring 11 is arranged in a rear wall recess 24 of the drive housing 32, which is designed as a compression spring and is tensioned by the movement of the hydraulic cylinder 9 in the direction of arrow P ₃ . This auxiliary spring serves to support the closing movement of the valve cone 4, on which corresponding steam forces act when the turbine valve is open. The steam actuating forces acting on the valve cone as a function of the auxiliary spring 11 also result from those in FIGS. 13b and 13b 13c shown diagrams, which will be discussed in more detail in a later part of the description.

It is also clear from the diagrams in FIGS. 13a, 13b and 13c that the electric motor / gear unit can provide different adjustment forces due to its special design as a crank mechanism via the angle of rotation. 1 to 3, the direction of rotation of the electric motor / gear unit must be reversed so that the hydraulic cylinder 9 is moved back to a front position with the aid of the spring force F2 of the auxiliary spring 11.

For certain operating conditions, it may be necessary to close the turbine valve suddenly within millisecond ranges in addition to normal control operation. This takes place with the aid of the spring accumulator 10 arranged in the spring accumulator space 14. The sequence of such a quick-closing process from any position of the hydraulic cylinder 9 takes place in the sequence steps described below:

For a quick closing process, the solenoid valve 8 is first opened. The trigger signal for the quick closing process is usually a quiescent current signal, which means that the solenoid valve is closed as long as power is supplied to the associated solenoid valve coil. An interruption of this power supply and thus the signaling for the quick-close release usually takes place in the control system provided to control the turbine system.

The opening of the solenoid valve 8 causes a relatively low pressure oil volume flow through the solenoid valve 8 into the interior of the drive housing, which also serves as a hydraulic fluid reservoir, to be discharged from the oil pressure storage space 12 via the pressure hose 7a. However, the relatively low volume flow causes the oil pressure in the oil pressure storage space 12 to drop instantaneously, which creates a counterforce to the spring force provided by the spring accumulator 10 is no longer present.

The pressure plate 13 is thus moved out of its sealing position into contact with the intermediate wall 23, the pressure oil flowing directly from the oil pressure storage space 12 into the spring storage space 14 via the gap formed between the pressure plate and the intermediate wall. A movement of the pressure plate 13 with the connected valve spindle 4 in the direction of the arrow P ₅ in FIG. 4 is thus possible within an extremely short period of time. In order to prevent the valve cone 5 from hitting the valve seat 5a without being braked, the drive 1 is provided with hydraulic end position damping 2, which is constructed in a conventional manner known from the prior art, so that no further explanation is given here ,

The illustration in FIG. 4 shows the position of the drive 1 after triggering a quick-closing process, starting from the sequence steps described, the drive being fully open immediately before the quick-closing process is triggered, which is indicated by the end position of the hydraulic cylinder on the left in the illustration 9 can be read.

In order for the turbine valve to be able to carry out its normal control function again after a quick-closing process, it is necessary to re-tension the spring accumulator 10 constructed from the disk spring assemblies. This tensioning process is described with reference to FIG. 5, it being assumed in the present exemplary embodiment that the quick-closing process when the hydraulic cylinder 9 is approximately in the end position, i.e. occurred during an almost complete opening of the turbine valve.

To tension the spring accumulator 10, the hydraulic cylinder 9 is moved in the direction of the valve seat 5a, ie in the direction of the arrow P ₆ , with the aid of the electric motor / gear unit 22. Since the valve cone 5 in Supports valve seat 5a, the pressure plate 13 connected to the valve cone 5 via the valve spindle 4 will remain unchanged in its position. At the same time, the spring accumulator 10 is tensioned as a result of the movement of the rear wall of the hydraulic cylinder 9. This tensioning process is accompanied by a reduction in the size of the spring storage space 14, with the oil pressure storage space 12 increasing at the same time in front of the pressure plate 13. The oil displaced from the spring storage space 14 flows past the pressure plate 13 into the oil pressure storage space 12. Since the direction of force of the auxiliary spring 11 points in the same direction as the direction of movement of the hydraulic cylinder 9, the tensioning process is supported by the action of the auxiliary spring 11. The electric motor / gear unit thus only has to compensate for the difference between the spring force of the auxiliary spring 11 and that of the spring accumulator 10.

It can be seen in FIG. 6 that with sufficient movement of the hydraulic cylinder 9 in the direction of the arrow Pe, the deformable sealing element 20 arranged on the intermediate wall 23 comes into contact with the pressure plate 13. As a result, the oil pressure storage chamber 12 is sealed, at the same time the tensioning process for the spring accumulator 10 is ended. A slight further movement of the hydraulic cylinder 9 in the direction of arrow P leads to the deformable sealing element 20 giving way, as a result of which the oil pressure in the oil pressure storage space 12 rises suddenly. The oil pressure necessary for balancing the spring accumulator forces depends both on the dimensioning of the spring accumulator 10 and on the size of the surface of the pressure plate 13. To end the tensioning process, the electric motor / gear unit 22 is switched off and, at the same time, the oil pressure pump 6 is activated. Via a movable pressure hose 7, the oil pressure pump 6, if necessary, pumps oil into the oil pressure storage space 12 and can be designed so that it maintains the oil pressure built up during the tensioning process and any leaks between the oil pressure storage space 12 and the interior of the drive housing 32 as Hydraulic fluid reservoir compensates. The prerequisite is, of course, that the solenoid valve 8 has been closed again after the quick closing process.

After the tensioning process for the spring accumulator 10 is completed by the build-up of the oil pressure in the oil pressure accumulator chamber 12, the preload of the spring accumulator 10 is now retained regardless of the movement of the hydraulic cylinder 9, so that the drive and turbine valve form one unit. The state of the drive is therefore brought about again, as is already shown in FIG. 1.

The state of the drive 1, which can be seen in FIG. 6, corresponds essentially to that of FIG. 1 with the difference that the oil pressure storage space 12 is depressurized in the operating state of FIG. 6 (recognizable by the missing hatching in the oil pressure storage space 12).

This means that a quick-closing process has taken place in the drive shown, although the turbine valve has already been in the completely closed position. For this reason, the valve cone 5 is supported in the valve seat 5a, which leads to an immobility of the pressure plate 13. Thus, the spring accumulator 10 cannot relax in the oil pressure accumulator space 12 despite the absence of an oil back pressure. For this special case, the spring accumulator 10 would have to be re-tensioned by refilling the oil pressure accumulator chamber 12 with pressure oil, if necessary by means of the oil pressure pump 6 after the solenoid valve 8 has been closed.

The illustration in FIG. 7 shows a drive 1 with a connected turbine valve, which essentially corresponds to that drive which has been explained above with reference to FIGS. 1 to 6. Structural differences between the drive variant of FIGS. 1 to 6 and that of FIG. 7 result on the one hand from the positioning of the auxiliary spring 11 and from the structural design of the control and supply unit responsible for the pressure oil assembly.

With regard to the auxiliary spring 11, it can be seen from FIG. 7 that it is received within a recess 25 arranged in the rear wall of the hydraulic cylinder 9. In contrast to the variant in FIGS. 1 to 6, the overall length of the drive 1 can be reduced by this design.

With regard to the supply unit, it can be seen in FIG. 7 that both the oil pressure pump 6 and the solenoid valve 8 are arranged directly on the hydraulic cylinder 9. On the one hand, this has the advantage that the flexible pressure hoses 7 or 7a present in the other embodiment variant can be dispensed with, on the other hand, however, neither the drive motor of the oil pressure pump 6 nor the drive coil of the solenoid valve 8 is now easily accessible from the outside; rather, the corresponding units can be repaired only through appropriate repair openings after draining the hydraulic oil inside the drive housing.

FIGS. 8 to 11 show a drive which, with respect to the control and supply unit responsible for the pressure oil build-up in the oil pressure storage space 12, differs significantly from the design variants discussed so far.

As FIG. 8 shows, the hydraulic cylinder 9 has an oil pressure storage space 12 and a spring storage space 14, which are separated from one another by means of the known pressure plate 13, analogous to the previously discussed exemplary embodiment. The differences in the design variants consist in the fact that the drive of FIGS. 8 to 11 has a solenoid valve 26 and 27, respectively, on a passage in the wall of the interior of the oil pressure storage space 12 and spring storage space 14. About that In addition, in a bypass 28 there is a check valve 29, which is installed in such a way that an oil flow from the spring storage space 14 in the direction of the oil pressure storage space 12 is possible, but the flow is blocked in the opposite direction. Due to the modified structure of the control and supply unit, the oil pressure pump 6 required in the other design variants is no longer required.

The mode of operation of the drive itself with the provision of the quick-closing forces by means of a spring accumulator 10, the arrangement of the auxiliary spring 11 and the provision of the coupling forces by means of the pressure oil contained in the oil pressure accumulator space 12 correspond to those features of the variant described in detail at the outset, so that at this point there is a detailed explanation is omitted.

Due to the changed supply unit, however, a completely different procedure results for the necessary tensioning process of the spring accumulator 10. This process sequence is explained in more detail below with reference to FIGS. 9 to 11 and, in addition, FIGS. 12a, 12b and 12c.

FIG. 8 first shows the drive with the spring accumulator under tension when the associated turbine valve is fully opened. The corresponding pressure oil medium, which is responsible for transmitting the forces from the moving hydraulic cylinder 9 to the pressure plate 13, is located within the oil pressure storage space 12.

In contrast, FIG. 9 shows the drive after a quick closing process has been triggered. For this purpose, the solenoid valve 26 was opened, whereby a pressure oil flow escapes from the oil pressure storage chamber 12 via the solenoid valve 26 into the surrounding interior of the drive housing 32, which acts as a hydraulic fluid reservoir. Due to the escape of part of the pressure oil, the oil pressure in the oil pressure storage space collapses, as a result of which the spring force of the spring accumulator 10 is released. The Spring accumulator presses the pressure plate 13 out of its sealing position in the direction of arrow P, so that the oil can penetrate directly into the spring accumulator chamber 14 from the oil pressure accumulator chamber 12 via the gap that is created. The consequence of this is the sudden movement of the pressure plate 13 with the valve spindle 4 and valve cone 5 connected to it in the corresponding closed position. In order to avoid an unbraked impact of the valve cone 5 in the valve seat 5a, this further embodiment variant also has a hydraulic end position damping 2, which, as can be seen from the drawing, is constructed differently than in FIGS. 1 to 7, but in terms of its function as that of the exemplary embodiments corresponds to Figures 1 to 7.

Due to the different supply unit, there is a different process sequence with regard to the tensioning process for the spring accumulator 10:

If one assumes that the rapid closing process has been triggered when the turbine valve is fully opened, the starting position for the clamping process is the position of the drive according to FIG. 9. The clamping process begins with a displacement of the hydraulic cylinder 9 by means of one in the figures 8 to 11, not shown in detail, but constructed analogously to the first exemplary embodiment in the direction of arrow P _7/8 - by fixing the valve cone 5 within the valve seat 5a, the position of the pressure plate 13 remains unchanged. Both solenoid valves 26 and 27 are closed during the tensioning process. The hydraulic fluid flows through the bypass 28 or the check valve 29 therein into the oil pressure storage space 12 from the shrinking spring storage space 14. Additionally displaced liquid is discharged into the interior of the drive housing 32 via an opening 30 in the front area of the hydraulic cylinder 9 facing the turbine valve , In this context, it should be noted that the structure of the second embodiment variant with respect to the valve spindle 4 differs in that, in addition to the pressure plate 13, a further pressure plate 19 is arranged on the valve spindle 4 in front of the hydraulic cylinder 9. As a result of the movement of the hydraulic cylinder 9, both the intermediate wall 23 of the pressure plate 13 and the front wall of the hydraulic cylinder 9 with the opening 30 of the pressure plate 19 located therein approach both sealing elements 35 on the intermediate wall 23 and on the front of the hydraulic cylinder 9 and 36 arranged. These sealing elements 35 and 36, which are designed as flexible O-rings, come into contact with the pressure plates 13 and 19 when the hydraulic cylinder is advanced appropriately and lead to a seal of both the oil pressure storage space 12 and the spring storage space 14.

The enlarged representation of FIGS. 12a and 12b makes the contact of the sealing elements with the associated pressure plates 13 and 19, which results from the feed movement of the hydraulic cylinder, clear once again. If, according to FIG. 10 or FIG. 12b, contact of the sealing elements 35 or 36 with the pressure plates 13 or 19 is made, a slight further displacement of the hydraulic cylinder 9 leads to a deformation of the flexible sealing elements 35 and 36. This process is carried out in particular 12c clearly, in which the position of the hydraulic cylinder 9 in accordance with FIG.

The slight further movement of the hydraulic cylinder 9 causes, due to the volume changes of the oil pressure storage space 12 and the spring storage space 14 in the oil pressure storage space 12, a slight negative pressure and in the spring storage space 14 a slight excess pressure of the hydraulic fluid therein. The pressure difference is compensated for by briefly opening the check valve 29 in the bypass 28 between the adjacent storage spaces. When designing the hydraulic cylinder with regard to the dimensions, care must be taken to ensure that, after the underpressure and overpressure have been compensated for within the storage spaces, an overall overpressure arises both in the oil pressure storage space 12 and in the spring storage space 14. If the corresponding overpressure has set in both rooms, the spring accumulator 10 has reached its final clamping position. Subsequently, by opening the solenoid valve 27, the excess pressure in the spring accumulator 14 is reduced, which results in a drive situation corresponding to FIG. 8 such that only the oil pressure accumulator 12 is pressurized with the appropriate pressure oil.

Under these general conditions, an adjustment operation can be carried out under normal operating conditions of the drive by moving the hydraulic cylinder 9 with the aid of the electric motor / transmission unit. Furthermore, by opening the solenoid valve 26, as already described with reference to FIG. 8, a quick closing process for the associated turbine valve is provided , For clarification, the situation is shown in FIG. 11 that occurs immediately before opening the solenoid valve 27 to remove the excess pressure in the spring storage space.

In addition, with regard to the configuration variant discussed last, it should be noted that the solenoid valves 26 and 27 are located directly inside the interior of the drive housing 32, so that, as in the exemplary embodiment in FIG. 7, any pressure hoses can be omitted. Thus, the last-mentioned design variant offers significant advantages in terms of operational safety and manufacturing costs, particularly due to the omission of the oil pressure pump.

It should also be noted that the electric motor / gear units 22 shown in FIGS. 1 to 7 are shown off-center for better clarity when the invention is implemented Construction, however, the crank disks 15 should be positioned in the center and the connecting rod 17 should be placed in the middle of the crosshead 18.

As already mentioned above, different diagrams are plotted in FIGS. 13a, 13b and 13c, from which the relationship of the necessary closing forces for the turbine valve is shown schematically as a function of the steam actuating forces acting on the valve cone as well as the valve spring force F1 of the spring accumulator 10 and the drive spring force F2 of the auxiliary spring 11 results. It should be noted that the valve spring force F1 of the spring accumulator 10 must always be designed for the maximum steam actuating force on the valve plug 5 plus a corresponding closing safety reserve, since the steam valve must always close securely regardless of the steam actuating force applied to the valve plug 5 and its direction. The following initial situation can be assumed to explain the diagrams:

The tensioning process of the drive for the spring accumulator 10 is completed. The actuating force of the auxiliary spring 11, which is also preloaded to a certain extent, loads the hydraulic cylinder 9 in the closing direction. If one now considers the steam actuating force on the valve cone 5 in the case of intercepting control valves, it can be seen that a steam actuating force acts on the valve cone in the closing position in the closing position. After a slight opening movement of the valve cone, the direction of force on the valve cone 5 changes in the opening direction. This actuating force then remains relatively constant until shortly before the opening position is reached and then increases relatively quickly to a much larger value in the direction of opening. In contrast to this force curve, there is no change of force direction in so-called live steam control valves (FD quick-action valves) as in interception control valves. In all opening positions, a steam actuating force occurs in the opening direction. In the diagrams of FIGS. 13a, 13b and 13c, the non-linear actuating forces are plotted over the rotation of the crank disk 15 over 180 ° for clarification. The diagrams show an example of what support the auxiliary spring 11 can provide. The actuating force of this auxiliary spring 11 basically acts against the steam actuating force. The spring force F2 of the auxiliary spring 11 can thus be designed such that it covers or exceeds the steam actuating force on the valve cone 5 in the middle stroke range. This means that the direction of force is not reversed for the drive until shortly before the turbine valve is in the open position. In the two end positions, however, the crank mechanism used has a correspondingly high actuating force, whereas in the middle stroke range, where the driving force is lowest, only the force difference between the steam force on the valve cone 5 and the spring force F2 of the auxiliary spring 11 is required. The drive power can thus be reduced accordingly.

In FIGS. 14a, 14b and 14c, a section of the hydraulic cylinder 9 is schematically shown once again to illustrate the mode of operation of the sealing elements 20, 35 and 36 already described in detail.

If the hydraulic cylinder 9 moves during the tensioning process of the spring accumulator 10 in the direction of the arrow Pg, oil initially flows from the spring accumulator space 14 into the oil pressure accumulator space 12. If the sealing elements 20, 35 and 36 designed as deformable O-rings come on the pressure plate 13 or 19 to the system, these seal the oil pressure storage space 12 against the spring storage space 14 or the interior of the drive housing.

A further, albeit slight, movement of the hydraulic cylinder 9 in the direction of the arrow Pg leads to a deformation of the sealing elements 20, 35 and 36, so that the oil pressure in the oil pressure storage space 12 rises suddenly. At this moment the movement of the hydraulic cylinder 9 stops, with which the Tensioning process for the spring accumulator 10 has ended. The oil pressure is then kept constant at least in the first exemplary embodiment discussed via the oil pressure pump 6.

In the construction of the drive according to the invention, it must also be taken into account that a compensation of possible thermal stresses may be necessary for the overall assembly to function properly.

These thermal stresses are expressed in particular in an expansion of the valve spindle. In order to prevent the drive from pressing the valve cone into the valve seat as a result of valve spindle expansions, which would lead to tensions and wear on the drive and on the valve seat, a so-called connection in the area of the connection of the crosshead 18 to the hydraulic cylinder 9 is required under certain general conditions Clearance provided.

The problem is explained with reference to FIGS. 15a, 15b and 15c. In FIG. 15a it can be assumed that the hydraulic cylinder is in the closing end position, i.e. the hydraulic cylinder 9 is blocked by the valve cone 5 engaging in the valve seat 5a. Under these general conditions, it is provided that the drive moves into a neutral closed position, as a result of which the crosshead 18 moves away from the hydraulic cylinder 9. 15a is referred to as the so-called clearance and corresponds at least to the calculated thermal expansion of the valve spindle 4. During the movement of the opening and closing of the turbine valve shown in FIG. 15b, the crosshead 18 and the hydraulic cylinder 9 are below the Prerequisite that the spring force F2 of the auxiliary spring 11 is greater than the opposing acting steam force directly against each other.

In contrast, FIG. 15c illustrates the situation in the open end position of the turbine valve. The position of the crosshead is determined by determines the drive that is in its neutral opening position. The position of the hydraulic cylinder 9 is characterized in that the steam force outweighs the spring force F2 of the auxiliary spring 11, particularly in the case of openings greater than 98%. On the basis of these framework conditions, the hydraulic cylinder in turn moves away from the crosshead, so that, in the opening position shown in FIG. 15a, “open” results.

The hydraulic cylinder 9 forms the overall link between the valve spindle 4 and the electric motor / gear unit 22, the movement of the translationally movable hydraulic cylinder 9 corresponding to that adjustment of the valve spindle 4 for opening and closing the turbine valve. The electric motor / gear unit 22 can advantageously have a crank drive for providing a torque that can be varied over the length of the movement path of the driven hydraulic cylinder. This is particularly advantageous in the case of valves in which the force to be exerted on the valve spindle changes when the valve spindle closes or opens as a function of the stroke of the valve spindle. This occurs, for example, in the case of valves in a steam turbine in which the steam pressure present is on the valve plug and supports it during the closing process or keeps the valve plug closed. With such a valve, a large force must initially be overcome in order to open the valve a small gap. As soon as a certain opening cross-section is given, the pressure is relieved, so that a smaller force is required to displace the valve spindle during the further opening process. Due to the crank mechanism used, the electric motor / gear unit can be designed accordingly, depending on the size, load and requirements on the valve.

However, other drive variants are of course also conceivable LIST OF REFERENCE NUMBERS

1 drive

2 Hydraulic cushioning unit

3 valve flange

4 valve stem

5 valve cones

5a valve seat

10 6 oil pressure pump

7 pressure hose

7a pressure hose

8 solenoid valve

9 hydraulic cylinders

15 10 spring loaded

11 auxiliary spring

12 Oil pressure storage room

13 pressure plate

14 spring storage space

20 15 Motor with crank disc

16 crank pins

17 connecting rod

18 Phillips

19 pressure plate

25 20 sealing element

21 cylinder guide

22 Electric motor / gear unit

23 partition

24 recess

30 25 recess 26 solenoid valve

27 solenoid valve

28 bypass

29 check valve

30 opening

31 opening

32 drive housing

33 opening

34 opening

10 35 sealing element

36 sealing element

Claims

claims

1. Drive for a turbine valve, in particular a control valve and a switching valve, with a valve spindle operated by an electric motor / gear unit and provided with a valve cone for setting the opening and closing position of the turbine valve, the valve spindle of both turbine valves using a spring accumulator for a quick-closing process can be pretensioned, characterized in that a hydraulic coupling element (9) for power transmission and for prestressing the spring accumulator (10) is arranged between the electric motor / gear unit (22) and the valve spindle (4).

2. Drive according to claim 1, characterized in that the coupling element is designed as a translationally displaceable by means of the electric motor / gear unit (22) hydraulic cylinder (9) with a control and supply unit, in the interior of which is coupled to the valve spindle (4) Pressure plate (13) is movably arranged by means of oil pressure.

3. Drive according to claim 2, characterized in that the spring accumulator (10) is arranged within the hydraulic cylinder (9) and can be pretensioned by the pressure plate (13).

4. Drive according to claim 2 or 3, characterized in that

Electric motor / gear unit (22), valve spindle (4), spring mechanism

(10) and hydraulic cylinder (10) with control and supply unit are arranged in a common drive housing (32).

5. Drive according to one of claims 2 to 4, characterized in that the electric motor / gear unit (22) has a crank drive for providing a torque variable over the length of the path of movement of the driven hydraulic cylinder (9).

6. Drive according to one of claims 2 to 5, characterized in that at least one, on the hydraulic cylinder (9) acting, the closing movement of the valve cone (5) supporting auxiliary spring

(11) is provided.

7. Drive according to one of claims 2 to 6, characterized in that the hydraulic cylinder (9) is divided into a spring storage space (14) and an oil pressure storage space (12), the oil pressure storage space (12) by means of at least one pressure plate (13, 19) can be disconnected in the prestressed state of the spring accumulator (10).

8. Drive according to claim 7, characterized in that the oil pressure storage space (12) and the spring storage space (14) by means of gas-filled sealing elements (20, 35, 36) can be separated in a pressure-tight manner.

9. Drive according to one of claims 7 or 8, characterized in that the oil pressure storage space (12) by means of the at least one solenoid valve (8), an oil pressure pump (6) and a hydraulic fluid reservoir, control and supply unit can be filled with pressure oil and emptied is.

10. Drive according to one of claims 7 or 8, characterized in that the control and supply unit has at least two solenoid valves (26, 27) and a hydraulic fluid reservoir and a check valve (29), each with a solenoid valve (26, 27) to a passage in the wall of the interior of the oil pressure storage space (12) and the spring storage space (14) and the check valve (29) in a bypass (28) between the oil pressure storage space (12) and the spring storage space (14).

11. Drive according to claim 6, characterized in that the auxiliary spring (11) is arranged in a recess in the outer wall of the hydraulic cylinder (9).

12. Drive according to one of claims 9 to 11, characterized in that the interior of the drive housing (32) is provided as hydraulic fluid reservoir