Steam valve and steam turbine system

Abstract

Steam valve (10), comprising: a valve stem (30); a first valve body (32) which is arranged at a distal end side of the valve stem (30) and is designed to be driven via the valve stem (30); a first valve seat (42) on which the first valve body (32) can be attached; an auxiliary seat surface (98A) extending along a direction transverse to an axial direction of the valve stem (30); an auxiliary seat section (33A, 33B) which is arranged at a proximal end side of the valve stem (30) with respect to the first valve body (32) and is designed to bear against the auxiliary seat surface (98a, 98b) when the first valve body (32) is closed; a preload element (62A, 62B) capable of generating a preload force along the axial direction of the valve stem (30); and a valve housing (22) having a space (46) through which the valve stem (30) passes, and which is designed to be able to introduce steam from a steam flow path (18) which is opened and closed by the steam valve (10), wherein the auxiliary seat surface (98A, 98B) and the auxiliary seat section (33A, 33B) are arranged in the axial direction with respect to the space (46) on opposite sides of the first valve body (32), and wherein either the first valve body (32) or the auxiliary seat section (33A, 33B) is displaceable in the axial direction relative to the valve stem (30) and is preloaded by the preloading element (62A, 62B) to a corresponding position of the first valve seat (42) or the auxiliary seat surface (98a, 98b).

Description

TECHNICAL AREA

[0001] The present disclosure relates to a steam valve and a steam turbine plant comprising this. STATE OF THE ART

[0002] Conventionally, many attempts have been made to prevent fluid leakage when a valve is closed.

[0003] For example, patent document 1 discloses a steam valve for use in a steam turbine. In this steam valve, when the valve is closed, a seat surface of a valve body rests on a valve seat to shut off steam flow, and a back seat, arranged on a section with an enlarged diameter of a valve stem, abuts a valve head to prevent leakage of steam flowing between the valve stem connected to the valve body and the valve head into which the valve stem is inserted. Citation list for patent literature

[0004] Patent document 1: JP 2012- 21 568 A

[0005] Further prior art that is helpful for understanding the present invention can be found in the following documents: US 2 733 041 A and US 2008 / 0 308 761 A1 concern steam valves. DE 515 502 A relates to a through-flow valve that can allow flow in both directions. JP 2012- 21 568 A concerns a horizontal valve. DE 10 2006 027 712 A1 concerns a hydrogen valve with pressure equalization. US 7 954 511 B2 concerns a two-stage valve for controlling fluids. PRESENTATION OF THE INVENTION Problems to be solved

[0006] The steam valve disclosed in patent document 1 is seated simultaneously on two seat sections, namely the seat surface of the valve body and the rear seat of the valve stem, in order to block leakage and steam flow when the valve is closed. However, at this point, the valve is often seated on only one of the two seat sections. In this case, both seat sections are not reliably sealed, and steam leakage cannot be reduced.

[0007] In this context, patent document 1 does not specifically describe any measure against seat failure on the two seat parts.

[0008] In light of the above, it is an object of at least one embodiment of the present invention to provide a valve and a steam turbine system, which makes it possible to reduce the leakage of a fluid. Solution to the problems

[0009] The present invention is defined by the independent claims. The dependent claims define preferred embodiments of the present invention. (1) A valve according to at least one embodiment of the invention comprises: a valve stem; a first valve body arranged at a distal end of the valve stem and configured to be driven via the valve stem; a first valve seat on which the first valve body can be mounted; an auxiliary seat surface extending along a direction transverse to an axial direction of the valve stem; an auxiliary seat section arranged at a proximal end of the valve stem with respect to the first valve body and configured to bear against the auxiliary seat surface when the first valve body is closed; and a preload element capable of generating a preload force along the axial direction of the valve stem;and a valve body having a chamber through which the valve stem passes, and which is designed to introduce steam from a steam flow path (18) which is opened and closed by the steam valve (10), wherein the auxiliary seat surface (98A, 98B) and the auxiliary seat section (33A, 33B) are arranged in the axial direction with respect to the chamber (46) on opposite sides of the first valve body (32), and wherein either the first valve body or the auxiliary seat section is displaceable in the axial direction relative to the valve stem and is preloaded by the preloading element to a corresponding position of the first valve seat or the auxiliary seat surface.

[0010] In the configuration above (1), either the first valve body or the auxiliary seat section is axially displaceable relative to the valve stem and is biased by the biasing element towards a corresponding position of the first valve seat or auxiliary seat surface. When the first valve body is closed in this configuration, the other part of the first valve body or auxiliary seat section rests against or is in contact with the other part of the first valve seat or auxiliary seat surface, while the other part of the first valve body or auxiliary seat section is pressed by the biasing element towards the corresponding position of the first valve seat or auxiliary seat surface. Thus, a seal is ensured at both the first valve body and the auxiliary seat section. Consequently, it is possible to reduce fluid leakage from the valve.

[0011] (2) In some embodiments of the above configuration (1), the first valve body is displaceable in the axial direction relative to the valve stem and is biased towards the first valve seat by the biasing element which is arranged between the first valve body and the valve stem.

[0012] In the configuration above (2), the first valve body is axially displaceable relative to the valve stem and is biased towards the first valve seat by the biasing element. When the first valve body is closed in this configuration, the auxiliary seat section rests against the auxiliary seat surface, while the first valve body is pressed against the first valve seat by the biasing element. This ensures a seal at both the first valve body and the auxiliary seat section. Consequently, it reduces fluid leakage from the valve.

[0013] (3) In some embodiments of the above configuration (2), the valve stem has a valve stem-side engagement section having a projection or recess that extends or is recessed in a radial direction of the valve stem at the distal end, wherein the first valve body has a valve body-side engagement section having a recess or projection that extends or is recessed in the radial direction to engage in the valve stem-side engagement section, and wherein the valve stem-side engagement section is loosely fitted with the valve body-side engagement section so that the first valve body is displaceable in the axial direction relative to the valve stem.

[0014] In the configuration above (3), the valve stem-side engagement section is loosely fitted to the valve body-side engagement section. That is, a gap is formed between the valve stem-side engagement section and the valve body-side engagement section in the axial direction of the valve stem. This gap allows the first valve body to be displaced axially relative to the valve stem, so that the first valve body can be pressed against the first valve seat by the preload force of the preload element in a suitable manner. Thus, it is possible to ensure a seal at both the first valve body and the auxiliary seat section.

[0015] (4) In some embodiments of the above configuration (3), the valve stem has a projection which is the valve stem-side engagement section projecting outwards in the radial direction, wherein the projection which serves as the valve stem-side engagement section comprises: a first surface which is directed towards a valve opening side in the axial direction of the valve stem and is facing the first valve body; and a second surface which is directed towards a valve closing side in the axial direction of the valve stem and is facing the first valve body, and wherein a gap is provided in at least one of a section between the first surface and the first valve body or a section between the second surface and the first valve body.

[0016] In the configuration above (4), a gap is provided in at least one section between the first valve body and the first surface, or in a section between the first valve body and the second surface of the projection, which is the valve stem-side engagement section. That is, a gap is formed between the projection, as the valve stem-side engagement section, and the first valve body in the axial direction of the valve stem. This gap allows the first valve body to be displaced axially relative to the valve stem, so that the first valve body can be pressed against the first valve seat by the preload force of the preload element. Thus, it is possible to ensure a seal at both the first valve body and the auxiliary seat section.

[0017] (5) In some embodiments of the above configuration (4), when the first valve body is seated on the first valve seat, a gap is provided in each of the section between the first surface and the first valve body and the section between the second surface and the first valve body.

[0018] In the above configuration (5), when the first valve body is closed, a gap (first gap) is formed between the first valve body and the first surface, which is directed towards the valve opening side of the projection as the valve stem engagement section, and a gap (second gap) is formed between the first valve body and the second surface, which is directed towards the valve closing side of the projection as the valve stem engagement section.

[0019] The first gap, formed on the valve opening side of the valve stem engagement section (projection) when the first valve body is closed, prevents the first valve body from being lifted by the valve stem if the valve stem shrinks due to a decrease in temperature in response to the cessation of fluid flow (e.g., steam) into the valve. Furthermore, the alignment of the first valve body can be maintained.

[0020] On the other hand, the second gap, formed on the valve closing side of the valve stem engagement section (projection), allows both the first valve body and the auxiliary seat section to seal well when the first valve body is closed, even if the first valve body and the auxiliary seat section cannot seat simultaneously. Furthermore, the second gap can absorb any thermal expansion differential between different components, including the valve stem and the first valve body.

[0021] (6) In some embodiments in one of the above configurations (2) to (5) the valve stem has a valve stem hole extending in the axial direction at the distal end side and opening to a distal end face of the valve stem, and the preload element is a spring arranged in the valve stem hole.

[0022] In the configuration above (6), the spring, which passes through the valve stem hole extending in the axial direction of the valve stem, can exert a preload force in the axial direction on the first valve body. This makes it possible to press the first valve body onto the first valve seat in a suitable manner by the preload element, and it is possible to ensure a seal on both the first valve body and the auxiliary seat section.

[0023] (7) In some embodiments of the above configuration (6) the valve further comprises a preload force receiving section which is arranged between the first valve body and the preload element to transmit the preload force to the first valve body, wherein the preload force receiving section engages with the valve stem hole and is designed to be guided through the valve stem hole in the axial direction.

[0024] With the above configuration (7), a preload force is exerted along the axial direction on the first valve body via the preload force receiving section, which is designed to be guided through the valve stem hole in the axial direction, thus making it possible to press the first valve body more appropriately onto the first valve seat. This ensures a seal of the valve at both the first valve body and the auxiliary seat section.

[0025] (8) In some embodiments of the above configuration (6) or (7) the preload force receiving section has at least a partial spherical section adjacent to the first valve body and the spherical section is designed to come into contact with the first valve body.

[0026] Since, with the configuration above (8), the preload force absorption section is brought into contact with the first valve body at the spherical section, it is possible to reduce stress concentration compared to a case where a corner section comes into contact with the first valve body. Thus, it is possible to improve the service life of the preload force absorption section or the first valve body.

[0027] (9) In some embodiments in the above configurations (6) to (8) the preload force receiving section has a projection which engages with a groove formed in the first valve body, such that it is recessed in the axial direction of the valve stem.

[0028] With the configuration above (9), the projection engaging with the groove formed in the first valve body, recessed in the axial direction of the valve stem, ensures that the preload force receiving section is reliably centered on the central axis. This allows a preload force to be reliably applied to the first valve body along the axial direction, and the first valve body can be more reliably pressed against the valve seat. Thus, it is possible to ensure a seal of the valve at both the first valve body and the auxiliary seat section.

[0029] (10) In some embodiments in any of the above configurations (1) to (9), the valve further comprises: a second valve body with an inner wall surface forming the first valve seat and an interior space defined by the inner wall surface, the interior space accommodating the first valve body; and a valve casing with a second valve seat onto which the second valve body can be placed, wherein, when the second valve body is in an open position away from the second valve seat, either the valve stem or the first valve body is biased in a valve opening direction of the first valve body with respect to the second valve body.

[0030] In the configuration above (10), when the valve is to be closed and the second valve body (primary valve) is in an open position, the valve stem or the first valve body (secondary valve) is biased in the valve opening direction of the first valve body relative to the second valve body. Thus, when the second valve body moves from an open position to a closed position, the first valve body moves along with the second valve body in the valve closing direction of the second valve body, while the first valve body is held in the interior of the second valve body on the valve opening side of the first valve body. Then, after the second valve body is seated on the second valve seat, the first valve body is seated onto the first valve body formed by the inner wall surface of the second valve body.Thus, with the above configuration (10), since the second valve body and the first valve body are seated sequentially when the valve is closed, the mass of the valve body colliding with the valve seat is reduced compared to a case where the second and first valve bodies are seated together (for example, a case where the second valve body is seated on the second valve seat while the first valve body is seated on the second valve body). This reduces the impact force generated on the valve body and the valve seat by collision between the valve body and the valve seat. Therefore, it is possible to reduce damage to the seat section.

[0031] (11) In some embodiments of the above configuration (10), the second valve body has a first bushing positioned on a radially outer side of the valve stem to guide the valve stem in the axial direction of the valve stem, and when the second valve body is in the open position, a first chamber formed between the first bushing and the valve stem has a lower pressure than the pressure of the interior of the second valve body that accommodates the first valve body.

[0032] In the configuration above (11), when the second valve body is in the open position, the pressure in the first chamber, formed between the first bushing and the valve stem, is lower than the pressure in the interior of the second valve body due to the communication channel. Consequently, a preload force acts on the valve stem in the opening direction of the secondary valve, based on the pressure difference between the first chamber and the interior of the second valve body. Since, in the configuration above (11), the second and first valve bodies are set stepwise by the preload force based on the pressure difference when the valve is closed, the mass of the valve body colliding with the valve seat is reduced compared to a case where the second and first valve bodies are set simultaneously.This reduces the impact force exerted on the valve body and valve seat by collisions between the valve body and the valve seat. This, in turn, reduces damage to the seat area.

[0033] (12) In some embodiments of the above configuration (11), the first chamber is a lifting gap which allows the valve stem and the first valve body to be raised relative to the second valve body.

[0034] With the above configuration (12), by using the lift gap to raise the valve stem and the first valve body relative to the second valve body, it is possible to create a lower pressure in the first chamber than in the interior of the second valve body. This reduces the impact force generated on the valve body and valve seat by collision between the valve body and the valve seat. Thus, it is possible to reduce damage to the seat section.

[0035] (13) In some embodiments of the above configuration (11) or (12), the valve stem has a communication channel extending in the axial direction in the valve stem, the valve being designed such that when the second valve body is in the open position, the first chamber communicates with a second chamber via the communication channel, the second chamber having a lower pressure than the first chamber, and when the second valve body is in a closed position, the first chamber does not communicate with the second chamber.

[0036] In the configuration above (13), when the second valve body is in the open position, the first chamber communicates with the second chamber via the communication channel. This reduces the pressure in the first chamber and generates a preload force in the valve opening direction of the first valve body based on the pressure difference between the first chamber and the interior of the second chamber.

[0037] On the other hand, if in the above configuration (13) the second valve body is in the closed position, the first chamber does not communicate with the second chamber, thus preventing any leakage of fluid from the first chamber to the second chamber. This makes it possible to reduce the leakage of fluid from the interior of the second valve body through a gap between the valve stem and the first bushing.

[0038] (14) In some embodiments of the above configuration (13), the valve body has the auxiliary seat surface extending along the direction transverse to the axial direction of the valve stem, the valve stem has the auxiliary seat section which can be applied to the auxiliary seat surface when the second valve body is in the closed position, and when the second valve body is in the closed position, the communication channel from the second chamber is separated by an application section between the auxiliary seat section and the auxiliary seat surface.

[0039] In the configuration above (14), when the second valve body is in the closed position, the section of the system that separates the communication channel from the second chamber reliably blocks the flow of fluid from the first chamber to the second chamber. This makes it possible to reduce fluid leakage from the interior of the second valve body through a gap between the valve stem and the first bushing.

[0040] (15) A steam turbine plant according to at least one embodiment of the present invention comprises: the valve described in paragraphs (1) to (14) above; and a steam turbine arranged downstream of the valve.

[0041] In the configuration above (15), either the first valve body or the auxiliary seat section is axially displaceable relative to the valve stem and is biased by the biasing element towards a corresponding position of the first valve seat or auxiliary seat surface. When the first valve body is closed in this configuration, the other part of the first valve body or auxiliary seat section rests against or is in contact with the other part of the first valve seat or auxiliary seat surface, while the other part of the first valve body or auxiliary seat section is pressed by the biasing element towards the corresponding position of the first valve seat or auxiliary seat surface. Thus, it is possible to ensure a seal at both the first valve body and the auxiliary seat section. Consequently, it is possible to reduce fluid leakage in the valve. Beneficial effects

[0042] According to at least one embodiment of the present invention, a valve and a steam turbine system are provided, which makes it possible to reduce the leakage of a fluid. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic configuration diagram of a steam turbine plant that uses a valve according to one embodiment. Fig. Figure 2 is a schematic configuration diagram of an entire valve according to some embodiments. Fig. Figure 3 is a configuration diagram of a main part of a valve according to one embodiment. Fig. Figure 4 is a configuration diagram of a main part of a valve according to one embodiment. Fig. 5 is a diagram that shows a Fig. The valve shown in Figure 3 is fully open. Fig. 6 is a diagram that shows a Fig. Figure 3 shows a valve moving from an open position to a closed position. DETAILED DESCRIPTION

[0043] Embodiments of the present invention are now described in detail with reference to the accompanying drawings. However, unless specifically indicated, it is intended that dimensions, materials, shapes, relative positions, and the like of components described in the embodiments are to be interpreted as illustrative only and are not intended to limit the scope of protection of the present invention.

[0044] The following example is described in connection with a case in which a valve, according to some embodiments, is used as a steam valve in a steam turbine plant. However, according to some embodiments, the valve can be used for any purpose other than the steam turbine plant; for example, it can be used to control a fluid other than steam.

[0045] First, a steam turbine plant is described that uses a valve according to one embodiment. Fig. Figure 1 is a schematic configuration diagram of the steam turbine system that uses the valve according to one embodiment.

[0046] As in Fig. As shown in Figure 1, the steam turbine plant 1 comprises a steam boiler 2 for generating steam, a steam turbine 4 that converts the pressure of the steam from the steam boiler 2 into rotational energy, and a generator 8 that is driven by the rotation of the steam turbine 4. In the Fig. In the embodiment shown in Figure 1, the steam turbine 4 comprises a high-pressure steam turbine 5, an intermediate-pressure steam turbine 6, and a low-pressure steam turbine 7, and an intermediate superheater 9 is arranged between the high-pressure steam turbine 5 and the intermediate-pressure steam turbine 6. The steam discharged from the high-pressure steam turbine 5 is reheated by the intermediate superheater 9 and fed to the intermediate-pressure steam turbine 6. Furthermore, the steam discharged from the intermediate-pressure steam turbine 6 is fed to the low-pressure steam turbine 7.

[0047] The steam boiler 2 and the high-pressure steam turbine 5 are connected by a main steam supply line 3. The main steam supply line 3 is equipped with a steam valve 10, which has a shut-off valve 11 and a control valve 12. The flow of steam supplied from the steam boiler 2 to the high-pressure steam turbine 5 can be stopped by closing the shut-off valve 11. Furthermore, the flow rate of the steam supplied from the steam boiler 2 to the high-pressure steam turbine 5 can be controlled by adjusting the opening degree of the control valve 12.

[0048] A line connecting the reheater 9 and the intermediate-pressure steam turbine 6 is equipped with a shut-off valve 13 and a control valve 14. The shut-off valve 13 and the control valve 14 can stop the flow of steam supplied to the intermediate-pressure steam turbine or control the steam flow rate. In some embodiments, the shut-off valve 11 is a valve 20, which is described below. In some embodiments, the shut-off valve 13, the control valve 12, or the control valve 14 can be the valve 20 described below.

[0049] Next, with reference to the Fig. 2 and Fig. 6 the valve 20 is described according to some embodiments.

[0050] Fig. Figure 2 is a schematic configuration diagram of the entire valve according to some embodiments. As shown in Fig. As shown in Figure 2, the valve 20, according to some embodiments, is a primary / secondary valve with a valve stem 30, a first valve body (secondary valve) 32 arranged at a distal end of the valve stem 30, a second valve body (primary valve) 34 with an interior 35 that receives the first valve body 32, and a valve housing 22 that receives the first valve body 32 and the second valve body 34.

[0051] The interior 35 of the second valve body 34 is bounded by an inner wall surface 40 of the second valve body 34. The inner wall surface 40 forms a first valve seat (secondary valve seat) 42, onto which the first valve body 32 can be placed.

[0052] The valve housing 22 comprises a housing body 23 and a valve head 24 attached to the housing body 23. The housing body 23 and the valve head 24 together form a steam flow path 18, which connects a steam inlet 21 with a steam outlet 29 and a receiving chamber 25.

[0053] The housing body 23 has a second valve seat (primary valve seat) 26 onto which the second valve body 34 can be placed. The valve head 24 has a through-hole 27. The valve stem 30 is inserted into the through-hole 27.

[0054] The second valve body has a channel 44 that connects the interior 35 of the second valve body 34 with the steam flow path 18 on the side of the steam inlet 21.

[0055] The valve top 24 has a compensating hole 28 that connects a rear surface side space 46 of the second valve body 34 with the steam flow path 18 on the side of the steam inlet 21.

[0056] The valve head 24 has a first collecting line 48 and a second collecting line 50 to collect a fluid that escapes from the valve body (first valve body 32 and second valve body 34) to the atmosphere through a gap between the through-hole 27 and the valve stem 30. The second collecting line 50 is located farther from the first valve body 32 than the first collecting line 48 and is connected to a fluid reservoir (not shown) at a lower pressure than the first collecting line 48.

[0057] The valve stem 30 is connected via a lever 36 to an actuator 38 (e.g., a hydraulic actuator). The valve 20 includes a spring 37 for exerting a preload force in the valve closing direction on the first valve body 32 via the valve stem 30.

[0058] The first valve body 32 and the second valve body 34 are driven via the valve stem 30.

[0059] When the valve 20 is in a closed state, the first valve body 32 and the second valve body 34 are biased by the spring 37 towards the first valve seat 42 and the second valve seat 26 (in the valve closing direction).

[0060] To open the valve 20, the actuator 38 is actuated (for example, by supplying oil to a hydraulic chamber in the case of a hydraulic actuator), so that a driving force is applied to the valve stem 30 via the lever 36 in the opposite direction to the preload force of the spring 37. As soon as the driving force applied by the actuator 38 exceeds the preload force of the spring 37, the first valve body 32 moves together with the valve stem 30 in the valve opening direction, so that the first valve body 32 moves away from the first valve seat 42. At this point, the second valve body 34 is still at rest against the second valve seat 26. Then, a valve stem-side contact surface 72 (see Fig. 3) of the valve stem 30 and a primary valve-side contact surface 74 (see Fig. 3) of the second valve body 34, which are opposite each other in the valve opening / closing direction, are brought into contact, and the second valve body 34 moves together with the first valve body 32 in the valve opening direction, so that the second valve body 34 moves away from the second valve seat 26. In this way, the valve 20 is brought into an open state (see Fig. 5).

[0061] When the valve 20 is opened in this manner, the steam flow path 18 communicates with the rear surface side space 46 of the second valve body 34 via the channel 44 arranged in the second valve body 34 and the compensating hole 28 provided in the valve head 24 when the first valve body 32 moves away from the first valve seat 42 in the valve opening direction, while the second valve body 34 rests against the second valve seat 26. This reduces the pressure difference between the front and rear of the second valve body, thus enabling the second valve body 34 to be opened without requiring a large driving force on the actuator 38 or the like.

[0062] Conversely, to close the valve 20, the actuator 38 is actuated (for example, by releasing oil from a hydraulic chamber in the case of a hydraulic actuator) to reduce the driving force applied to the valve stem by the actuator 38 via the lever 36 in the valve opening direction. Then, the first valve body 32 and the second valve body 34 move towards the first valve seat 42 and the second valve seat 26 by the preload force of the spring 37 or the like, and are seated there. In this way, the valve 20 is brought into a closed state.

[0063] Fig. 3 and Fig. Figure 4 is a configuration diagram of a main part of the valve according to one embodiment. Fig. 3 and Fig. Figure 4 shows the valve that is completely closed (i.e., both the first valve body 32 and the second valve body 34 are in closed positions). Fig. 5 is a diagram that shows the in Fig. The valve shown in Figure 3 is fully open (i.e., both the first valve body 32 and the second valve body 34 are in open positions). Fig. 6 is a diagram that shows the in Fig. Figure 3 shows a valve moving from an open position to a closed position.

[0064] In the Fig. For clarity, the compensating hole is not shown in figures 3 to 6. Furthermore, in Fig. 4 The first collection line 48 and the second collection line 50 are not shown for the sake of clarity.

[0065] In the embodiments described in the Fig. 3 and Fig. As shown in Figure 4, the second valve body 34 has a first bushing 86 positioned on a radially outer side of the valve stem 30 to guide the valve stem 30 in the axial direction. In the examples shown in the Fig. 3 and Fig. As shown in Figure 4, the first bushing 86 is separate from and attached to the second valve body 34. In one embodiment, the first bushing 86 can be formed integrally with the second valve body 34.

[0066] Furthermore, the valve top part 24 (valve housing 22) includes a second bushing 92, which is arranged on a radially outer side of the valve stem 30 to guide the valve stem 30 in the axial direction of the valve stem 30.

[0067] Furthermore, the valve top 24 comprises a sleeve 76, which is arranged on a radially outer side of the second valve body 34 to guide the second valve body 34 in the axial direction (valve opening direction / valve closing direction), and a sleeve 78, which is arranged on a radially outer side of the valve stem 30 to guide the valve stem 30 in the axial direction of the valve stem 30.

[0068] In some embodiments, the valve 20 comprises an auxiliary seat surface 98A, 98B extending along a direction transverse to the axial direction of the valve stem 30, an auxiliary seat section 33A, 33B arranged at a proximal end opposite the distal end where the first valve body 32 is located, and a preload element capable of generating a preload force along the axial direction of the valve stem 30. The auxiliary seat section 33A, 33B is designed to bear against the auxiliary seat surface 98A, 98B when the first valve body 32 is open.

[0069] Furthermore, either the first valve body 32 or the auxiliary seat section 33A, 33B is displaceable in the axial direction of the valve stem 30 relative to the valve stem 30 and is preloaded by the preloading element to a corresponding position of the first valve seat 42 or the auxiliary seat surface 98A, 33B.

[0070] For example, in the Fig. In the illustrative embodiment shown in Figure 3, a proximal end surface of the second bushing 92, which is directed towards the proximal end of the valve stem 30, the auxiliary seat surface 98A and a distal end surface of a part with an enlarged diameter 31, which is provided on a radially outer side of the valve stem 30 so that it moves together with the valve stem 30, forms the auxiliary seat section 33A.

[0071] Furthermore, a spring 62A is arranged as the preload element between the first valve body 32 and the valve stem 30. A valve stem hole 60 is provided at the distal end of the valve stem 30, extending in the axial direction of the valve stem 30 and opening to a distal end surface 70 of the valve stem. The spring 62A is located in the valve stem hole 60.

[0072] The first valve body 32 is displaceable in the axial direction of the valve stem 30 relative to the valve stem 30 and is biased towards the first valve seat 42 by the spring 62A, which is provided between the valve seat 42 and the valve stem 30.

[0073] The part with the enlarged diameter 31 can be formed integrally with the valve stem 30. Alternatively, the part with the enlarged diameter 31 can be separate from the valve stem 30 and attached to a radially outer side of the valve stem 30.

[0074] In the embodiment described in Fig. As shown in Figure 3, the first valve body 32 is displaceable in the axial direction relative to the valve stem 30 and is biased towards the first valve seat 42 by the spring 62A. When the first valve body 32 is closed, the auxiliary seat section 33A rests against the auxiliary seat surface 98A, and the first valve body 32 is pressed against the first valve seat 42 by the spring 62A. This ensures a seal at both the first valve body 32 and the auxiliary seat section 33A, and reduces fluid leakage to the atmosphere through a gap between the through-hole 27 and the valve stem 30.

[0075] Furthermore, for example, the valve head 24 (valve housing 22), which is located in Fig. As shown in Figure 4, an axial hole 85 is provided, which is arranged at the proximal end of the valve stem 30 with respect to the second bushing 92, such that it extends in the axial direction. The axial hole 85 contains a movable segment 82 that can move along the axial direction of the valve stem 30 within the axial hole 85. A recess 83 is provided on a radially inner side of the movable segment 82, extending along the axial direction. The valve stem 30 has a projection 80 that projects radially from the valve stem 30 toward the recess 83. The projection 80 engages with the recess 83 to be displaceable in the axial direction with respect to the movable segment 82.Since the projection 80 is axially displaceable with respect to the movable segment 82 when the first valve body 32 and the second valve body 34 move in the valve opening direction, the projection 80 pushes the movable segment 82 in the axial direction and compresses the spring 62B, thereby releasing the seat on the auxiliary seat section 33B.

[0076] In the Fig. In the embodiment shown in Figure 4, the proximal end surface of the second bushing 92, which is directed towards the proximal end of the valve stem 30, forms the auxiliary seat surface 98B, and a distal end surface of the movable segment 82, which is directed towards the distal end of the valve stem 30, forms the auxiliary seat section 33B.

[0077] Furthermore, a spring 62B is arranged as the preload element in the axial hole 85 at the proximal end of the valve stem 30 in relation to the movable segment 82.

[0078] Furthermore, the auxiliary seat section 33B is displaceable in the axial direction of the valve relative to the valve stem 30 and is preloaded towards the auxiliary seat surface 98B by the spring 62B.

[0079] In the Fig. In the embodiment shown in Figure 4, the auxiliary seat section 33B is displaceable in the axial direction of the valve stem 30 relative to the valve stem 30 and is biased towards the auxiliary seat surface 98B by the spring 62B. When the first valve body 32 is closed, the first valve body 32 rests against the first valve seat 42, and the auxiliary seat section 33B is pressed towards the auxiliary seat surface 98B by the spring 62B. This ensures a seal at both the first valve body 32 and the auxiliary seat section 33B, and reduces fluid leakage to the atmosphere through a gap between the through-hole 27 and the valve stem 30.

[0080] In some embodiments, the valve stem 30 has a valve stem-side engagement section with a projection or recess that protrudes or is recessed in the radial direction of the valve stem 30 at the distal end of the valve stem 30, and the first valve body 32 has a valve body-side engagement section that has a recess or projection that is recessed or protrudes in the radial direction to engage with the valve stem-side engagement section. The valve stem-side engagement section is loosely fitted with the valve body-side engagement section such that the first valve body 32 is displaceable in the axial direction of the valve stem 30 relative to the valve stem 30.

[0081] For example, in the embodiment described in Fig. As shown in Figure 3, the valve stem 30 has a projection 52 (valve stem-side engagement section) that protrudes radially from the distal end of the valve stem 30, and the first valve body 32 has a recess 58 (valve body-side engagement section) that is recessed radially so that it engages with the projection 52. The projection 52 (valve stem-side engagement section) is loosely fitted into the recess 58 (valve body-side engagement section) so that the first valve body 32 is axially displaceable relative to the valve stem 30.

[0082] More precisely, the projection 52 (valve stem-side engagement section) in the embodiment described in Fig. Figure 3 shows a first surface 54, which is directed towards the valve opening side (valve opening direction) in the axial direction of the valve stem 30 and faces the first valve body 32, and a second surface 56, which is directed towards the valve closing side (valve closing direction) in the axial direction of the valve stem 30 and faces the first valve body 32. Furthermore, a gap (55 or 57) is provided in a section between the first surface 54 and the first valve body 32 and / or in a section between the second surface 56 and the first valve body 32.

[0083] In this way, the projection 52 (valve stem-side engagement section) is loosely fitted in the recess 58 (valve body-side engagement section), and a gap is formed between the projection 52 (valve body-side engagement section) and the recess 58 (valve body-side engagement section) in the axial direction of the valve stem 30. This gap allows the first valve body 32 to be displaced axially relative to the valve stem 30. This makes it possible to press the first valve body 32 onto the first valve seat 42 in a suitable manner by the preload force of the spring 62A, which serves as the preload element, and to ensure a seal on both the first valve body 32 and the auxiliary seat section 33A.

[0084] If the first valve body 32 is in the Fig. 3 shown embodiment rests on the first valve seat 42 (i.e., when the valve 20 is in a state which is in Fig. (as shown in Figure 3), a first gap 55 is formed between the first surface 54 and the first valve body 32 and a second gap 57 is formed between the second surface 56 and the first valve body 32.

[0085] In this case, when the first valve body is closed, the first gap 55 is formed between the first valve body 32 and the first surface 54, which is directed towards the valve opening side of the projection (valve stem engagement section), and the second gap 57 is formed between the first valve body 32 and the second surface 56, which is directed towards the valve closing side of the projection (valve stem engagement section).

[0086] The first gap 55, which is formed on the valve opening side of the projection (valve stem engagement section) when the first valve body 32 is closed, prevents the first valve body 32 from being lifted by the valve stem 30 when the valve stem 30 shrinks due to a decrease in the temperature of the valve stem in response to the cessation of the flow of a fluid (e.g. steam) into the valve 20.

[0087] On the other hand, the second gap 57, which is formed on the valve closing side of the projection (valve stem-side engagement section), ensures that both the first valve body 32 and the auxiliary seat section 33A are well sealed when the first valve body 32 is closed, even if the first valve body 32 and the auxiliary seat section 33A cannot be installed simultaneously. Furthermore, the second gap 57 can accommodate differences in thermal expansion between various components, including the valve stem 30 and the first valve body 32.

[0088] As described above, in the Fig. In the embodiment shown in Figure 3, the spring 62A is arranged as the preload element in the valve stem hole 60, which extends in the axial direction of the valve stem 30 and opens to the distal end surface 70 of the valve stem 30.

[0089] In this case, the spring 62A, which is guided through the valve stem hole 60 extending in the axial direction of the valve stem 30, can exert a preload force in the axial direction on the first valve body 32. This makes it possible to press the first valve body 32 onto the first valve seat 42 in a suitable manner by the spring 62A, and it is possible to ensure a seal both on the first valve body 32 and on the auxiliary seat section 33A.

[0090] In the embodiment described in Fig. As shown in Figure 3, the valve 20 further comprises a preload force receiving section 64 between the first valve body 32 and the spring 62A in order to transmit the preload force of the spring 62A to the first valve body 32. The preload force receiving section 64 engages with the valve stem hole 60 and is guided through the valve stem hole 60 in the axial direction of the valve stem 30.

[0091] Thus, the preload force is exerted along the axial direction on the first valve body 32 via the preload force receiving section 64, which is designed so that it can be guided through the valve stem hole 60 in the axial direction, making it possible to press the first valve body 32 onto the first valve seat 42 in a more suitable manner.

[0092] Furthermore, the preload force absorption section 64 has at least a partial spherical section 66 adjacent to the first valve body 32, and the spherical section 66 is designed such that it comes into contact with the first valve body 32.

[0093] In this case, compared to a case where a corner section comes into contact with the first valve body 32, it is possible to reduce stress concentration and to improve the service life of the preload force absorption section 64 or the first valve body 32.

[0094] Furthermore, the preload force receiving section 64 has a projection 68 which engages with a groove 69 formed in the first valve body 32, such that it is recessed in the axial direction of the valve stem 30. Typically, the groove 69 and the projection 68 are designed to extend through the central axis of the valve stem 30.

[0095] When the projection 68 engages with the groove 69 formed in the first valve body 32, such that it is recessed in the axial direction of the valve stem 30, the preload force receiving section 64 can be reliably centered on the central axis of the valve stem. This allows the preload force to be reliably applied to the first valve body 32 along the axial direction, and the first valve body 32 can be more reliably pressed against the first valve seat 42. Thus, it is possible to ensure a seal of the valve 20 both at the first valve body 32 and at the auxiliary seat section 33A.

[0096] In some embodiments, the valve is designed such that when the second valve body 34 is in an open position away from the second valve seat 26, either the valve stem 30 or the first valve body 32 is biased in the valve opening direction of the first valve body 32 with respect to the second valve body 34.

[0097] Here, a state in which the valve body is "in an open position" can mean that the valve body is located at an optional position away from the valve, or it can mean that the valve body is located at a specific position away from the valve seat. That is, the state in which the valve body is "in an open position" means that the valve body is located at least at one of these positions away from the valve seat.

[0098] In the Fig. In the embodiment shown in Figure 3, a first chamber 88, which is formed between the valve stem 30 and the first bushing 86 arranged on the second valve body 34, is designed such that it has a lower pressure than the pressure of the interior 35 of the second valve body 34, which accommodates the first valve body 32, when the second valve body 34 is in the open position (see Figure 3). Fig. 5).

[0099] More precisely, the valve stem 30 has a communication channel 90 that extends axially in the valve stem 30, and when the second valve body 34 is in the open position (see Fig. 5), the first chamber 88 communicates via the communication channel 90 with a second chamber 89, which has a lower pressure than the first chamber 88.

[0100] In the illustrative embodiment shown in Fig. As shown in Figure 3, the second chamber 89 is formed by the first collecting line 48 for collecting a fluid that exits through a gap between the valve stem 30 and the second bushing 92, which is arranged on the valve body 22.

[0101] Furthermore, in the embodiment described in Fig. As shown in Figure 3, the valve stem 30 has a pair of communication holes (94, 96) extending radially along the valve stem 30 and each connected to opposite ends of the communication channel 90. The pair of communication holes comprises a first communication hole 94 located on the side of the first valve body 32 and a second communication hole 96 located on the opposite side (adjacent to the proximal end of the valve stem 30) of the first valve body 32.

[0102] When the second valve body 34 is in the open position (see Fig. 5) The first communication hole 94 of the pair of communication holes (94, 96), which is positioned on the side of the first valve body 32, communicates with the first chamber 88 and the second communication hole 96 of the pair of communication holes (94, 96) communicates with the second chamber 89 (first collector line 48 in the in Fig. 3 examples shown).

[0103] An exemplary procedure for closing valve 20 with the above configuration is described with reference to the Fig. 3, Fig. 5 and Fig. 6 shown.

[0104] First, as in Fig. As shown in Figure 5, when the second valve body 34 is in the open position, which is away from the second valve seat 26, the first communication hole 94 of the communication channel 90, which is located in the valve stem 30, communicates with the first chamber 88 and the second communication hole 96 communicates with the first collector line 48, which is the second chamber 89.

[0105] Thus, the first chamber 88, formed on the rear surface of the first valve body 32, is connected via the communication channel 90 to the first manifold 48, which is the second chamber 89 with a lower pressure than the interior 35, and the pressure of the first chamber 88 is lower than the pressure of the interior 35 of the second valve body 34. Consequently, a preload force acts on the valve stem 30 in the valve opening direction of the first valve body 32 based on the pressure difference between the first chamber 88 and the interior 35 of the second valve body 34. The first communication hole 94 opens to the valve stem 30 on the valve opening side of the valve stem contact surface 72 and communicates with the first chamber 88.

[0106] If the actuator 38 (see Fig. 2) When actuated in this state (for example, by releasing oil from a hydraulic chamber in the case of a hydraulic actuator), the valve stem 30 is moved in the valve closing direction of the first valve. At this point, as described above, since the second valve body 34 is in the open position, the first valve body 32 is biased in the valve opening direction with respect to the second valve body 34. When the second valve body 34 moves from the open position (see Fig. 5) to the closed position (see Fig. 6) When the first valve body 32 moves, it moves together with the second valve body 34 in the valve closing direction of the second valve body 34, while the first valve body 32 is held on the valve opening side of the first valve body 32 in the interior 35 of the second valve body 34 (process of transition from a state of Fig. 5 to a state of Fig. 6).

[0107] Then, after the second valve body 34 is placed on the second valve seat 26, as in Fig. As shown in Figure 6, the valve stem 30 continues to move in the valve closing direction and the first valve body 32 is placed onto the first valve seat 42 (a Fig. 3 (shown state).

[0108] Thus, since the second valve body 34 and the first valve body 32 are seated sequentially when the valve is closed, the mass of the valve body colliding with the valve seat can be reduced compared to a case where the second valve body 34 and the first valve body 32 are seated together (for example, a case where the second valve body 34 is seated on the second valve seat 26 while the first valve body 32 is seated on the second valve body 34). This reduces the impact force generated on the valve body and the valve seat by collision between the valve body and the valve seat. Therefore, it is possible to reduce damage to the seat section.

[0109] In the Fig. In the embodiment shown in Figure 3, the first chamber 88 is a lifting gap that allows the valve stem 30 and the first valve body 32 to be raised relative to the second valve body 34. Part of the lifting gap is defined by the valve stem-side contact surface 72 of the valve stem 30 and the first bushing 86.

[0110] Thus, by using the stroke gap to lift the valve stem 30 and the first valve body 32 relative to the second valve body 34, it is possible to form the first chamber 88 with a lower pressure than the interior of the second valve body 34.

[0111] As in Fig. As shown in Figure 3, when the second valve body 34 is in the closed position, the first chamber 88 does not communicate with the first manifold 48, which is the second chamber 89. That is, the communication channel 90 is separated from the first manifold 48, which is the second chamber 89, by a section of the system where the auxiliary seat section 33A abuts the auxiliary seat surface 98A.

[0112] Thus, since the first chamber 88 does not communicate with the first manifold 48, which is the second chamber 89, when the second valve body is in the closed position, any leakage flow of fluid from the first chamber 88 to the first manifold 48, which is the second chamber, is blocked. This makes it possible to reduce the leakage of fluid from the interior 35 of the second valve body 34 through a gap between the valve stem 30 and the first bushing 86.

[0113] As described above, in the Fig.In the embodiment shown in Figure 3, the second collecting line 50 is arranged in the valve housing 22 at a position that is further away from the first valve body 32 than the first collecting line 48, and the second collecting line 50 is connected to a fluid reservoir (not shown) that has a lower pressure than the first collecting line 48.

[0114] If the valve 20 has a second collecting line 50 in addition to the first collecting line 48, it is possible to collect leakage fluid with the second collecting line 50 without releasing the leakage fluid to the atmosphere, even if the entire leakage fluid cannot be collected with the first collecting line 48 through a gap between the second bushing 92 and the valve stem 30.

[0115] In some embodiments, when the valve is fully closed (i.e., when both the first valve body 32 and the second valve body 34 are in closed positions), as soon as the valve stem 30 is moved in the valve opening direction, the first chamber 88 communicates via the communication channel 90 with the second chamber 89, which has a lower pressure than the first chamber 88, and the pressure of the first chamber 88 becomes lower than the pressure of the interior 35 of the second valve body 34.

[0116] This allows leakage fluid to flow from the interior 35 into a gap between the first bushing 86 and the valve stem 30, thereby improving the sliding performance between the first bushing 86 and the valve stem 30. This makes it possible to move the valve stem 30 with a relatively small driving force. Reference symbol list 1 steam turbine plant 2 steam boilers 3 Main steam supply 4 steam turbine 5 high-pressure steam turbine 6 Medium-pressure steam turbine 7 Low-pressure steam turbine 8 Generator 9 Intermediate superheaters 10 Steam valve 11 Shut-off valve 12 Control valve 13 Shut-off valve 14 Control valve 18 Steam flow path 20 valve 21 Steam inlet 22 Valve housings 23 Housing body 24 Valve top 25 Recording room 26 Second valve seat 27 Through hole 28 Compensation hole 29 Steam outlet 30 Valve stem 31 parts with enlarged diameter 32 First valve body 33A, 33B Auxiliary seat section 34 Second valve body 35 Interior 36 levers 37 spring 38 Actuator 40 interior wall area 42 First valve seat 44-channel 46 Rear surface side space 48 First collection line 50 Second collection line 52 lead 54 First surface 55 First gap 56 Second surface 57 Second gap 58 In-depth study 60 Valve stem holes 62A, 62B spring 64 Preload force absorption section 66 Spherical section 68 lead 69 Nut 70 Distal end surface 72 Valve stem side contact surface 74 Primary valve side contact surface 76 Sleeve 78 Sleeve 80 lead 82 Movable segment 83 In-depth study 85 Axial Hole 86 First socket 88 First Chamber 90 Communication channel 92 Second socket 94 First communication gap 96 Second communication gap 98a, 98b Auxiliary seat

Claims

[1] Steam valve (10), comprising: a valve stem (30); a first valve body (32) which is arranged at a distal end side of the valve stem (30) and is designed to be driven via the valve stem (30); a first valve seat (42) on which the first valve body (32) can be mounted; an auxiliary seat surface (98A) extending along a direction transverse to an axial direction of the valve stem (30); an auxiliary seat section (33A, 33B) which is arranged at a proximal end side of the valve stem (30) with respect to the first valve body (32) and is designed to bear against the auxiliary seat surface (98a, 98b) when the first valve body (32) is closed; a preload element (62A, 62B) capable of generating a preload force along the axial direction of the valve stem (30); and a valve housing (22) having a space (46) through which the valve stem (30) passes, and which is designed to be able to introduce steam from a steam flow path (18) which is opened and closed by the steam valve (10), wherein the auxiliary seat surface (98A, 98B) and the auxiliary seat section (33A, 33B) are arranged in the axial direction with respect to the space (46) on opposite sides of the first valve body (32), and wherein either the first valve body (32) or the auxiliary seat section (33A, 33B) is displaceable in the axial direction relative to the valve stem (30) and is preloaded by the preloading element (62A, 62B) to a corresponding position of the first valve seat (42) or the auxiliary seat surface (98a, 98b). [2] Steam valve (10) according to claim 1, wherein the first valve body (32) is displaceable in the axial direction relative to the valve stem (30) and is preloaded towards the first valve seat (42) by the preloading element (62A, 62B) which is arranged between the first valve body (32) and the valve stem (30). [3] Steam valve (10) according to claim 2, wherein the valve stem (30) has a valve stem-side engagement section (52) which has a projection or recess that protrudes or is recessed in a radial direction of the valve stem (30) at the distal end side, wherein the first valve body (32) has a valve body-side engagement section (58) which has a recess or projection that is recessed or protrudes in the radial direction to engage in the valve stem-side engagement section (52), and wherein the valve stem-side engagement section (52) is loosely fitted with the valve body-side engagement section (58) so that the first valve body (32) is displaceable in the axial direction relative to the valve stem (30). [4] Steam valve (10), comprising: a valve stem (30); a first valve body (32) which is arranged at a distal end side of the valve stem (30) and is designed to be driven via the valve stem (30); a first valve seat (42) on which the first valve body (32) can be mounted; an auxiliary seat surface (98A) extending along a direction transverse to an axial direction of the valve stem (30); an auxiliary seat section (33A, 33B) arranged at a proximal end face of the valve stem (30) with respect to the first valve body (32) and designed to bear against the auxiliary seat surface (98a, 98b) when the first valve body (32) is closed; and a preload element (62A, 62B) that is able to generate a preload force along the axial direction of the valve stem (30), wherein the first valve body (32) is displaceable in the axial direction relative to the valve stem (30) and is preloaded towards the first valve seat (42) by the preloading element (62A, 62B), wherein the valve stem (30) has a valve stem-side engagement section (52) which has a projection that extends in a radial direction of the valve stem (30) at the distal end side, wherein the first valve body (32) has a valve body-side engagement section (58) which has a recess that is deepened in the radial direction to engage in the valve stem-side engagement section (52), and wherein the valve stem-side engagement section (52) is loosely fitted with the valve body-side engagement section (58) so that the first valve body (32) is displaceable in the axial direction relative to the valve stem (30), and wherein the projection, which serves as the valve stem-side engagement section (52), has: a first surface (54) which is directed towards a valve opening side in the axial direction of the valve stem (30) and faces the first valve body (32); and a second surface (56) which is directed towards a valve closing side in the axial direction of the valve stem (30) and faces the first valve body (32), and wherein a gap (55) is provided in at least one of a section between the first surface (54) and the first valve body (32) or a section between the second surface (56) and the first valve body (32). [5] Steam valve (10) according to claim 4, wherein, when the first valve body (32) is seated on the first valve seat (42), a gap is provided in each of the section between the first surface and the first valve body (32) and the section between the second surface and the first valve body (32). [6] Steam valve (10) according to one of claims 2 to 5, wherein the valve stem (30) has a valve stem hole which extends in the axial direction at the distal end side and opens to a distal end surface of the valve stem (30), and wherein the preload element (62A, 62B) is a spring which is arranged in the valve stem hole. [7] Steam valve (10) according to claim 6, further comprising a preload force receiving section which is arranged between the first valve body (32) and the preload element (62A, 62B) to transmit the preload force to the first valve body (32), wherein the preload force receiving section engages with the valve stem hole and is designed to be guided through the valve stem hole in the axial direction. [8] Steam valve (10) according to claim 6 or 7, wherein the preload force receiving section has at least partially a spherical section adjacent to the first valve body (32) and the spherical section is designed such that it comes into contact with the first valve body (32). [9] Steam valve (10) according to one of claims 6 to 8, wherein the preload force receiving section has a projection which engages with a groove which is formed in the first valve body (32) such that it is recessed in the axial direction of the valve stem (30). [10] Steam valve (10) according to one of claims 1 to 9, further comprising: a second valve body (34) with an inner wall surface forming the first valve seat (42) and an interior space defined by the inner wall surface, the interior space accommodating the first valve body (32); and a valve housing with a second valve seat on which the second valve body (34) can be attached, wherein, when the second valve body (34) is in an open position away from the second valve seat, either the valve stem (30) or the first valve body (32) is biased in a valve opening direction of the first valve body (32) with respect to the second valve body (34). [11] Steam valve (10) according to claim 10, wherein the second valve body (34) has a first bushing which is positioned on a radially outer side of the valve stem (30) to guide the valve stem (30) in the axial direction of the valve stem (30), and wherein, when the second valve body (34) is in the open position, a first chamber formed between the first bushing and the valve stem (30) has a lower pressure than the pressure of the interior of the second valve body (34) which accommodates the first valve body (32). [12] Steam valve (10) according to claim 11, wherein the first chamber is a lifting gap which allows the valve stem (30) and the first valve body (32) to be raised relative to the second valve body (34). [13] Steam valve (10), comprising: a valve stem (30); a first valve body (32) which is arranged at a distal end side of the valve stem (30) and is designed to be driven via the valve stem (30); a first valve seat (42) on which the first valve body (32) can be mounted; an auxiliary seat surface (98A) extending along a direction transverse to an axial direction of the valve stem (30); an auxiliary seat section (33A, 33B) arranged at a proximal end face of the valve stem (30) with respect to the first valve body (32) and designed to bear against the auxiliary seat surface (98a, 98b) when the first valve body (32) is closed; and a preload element (62A, 62B) that is able to generate a preload force along the axial direction of the valve stem (30), wherein either the first valve body (32) or the auxiliary seat section (33A, 33B) is displaceable in the axial direction relative to the valve stem (30) and is preloaded by the preloading element (62A, 62B) to a corresponding position of the first valve seat (42) or the auxiliary seat surface (98a, 98b), wherein the steam valve (10) has: a second valve body (34) with an inner wall surface forming the first valve seat (42) and an interior space defined by the inner wall surface, the interior space accommodating the first valve body (32); and a valve housing with a second valve seat on which the second valve body (34) can be attached, wherein, when the second valve body (34) is in an open position away from the second valve seat, either the valve stem (30) or the first valve body (32) is biased in a valve opening direction of the first valve body (32) with respect to the second valve body (34), wherein the second valve body (34) has a first bushing which is positioned on a radially outer side of the valve stem (30) to guide the valve stem (30) in the axial direction of the valve stem (30), and wherein, when the second valve body (34) is in the open position, a first chamber formed between the first bushing and the valve stem (30) has a lower pressure than the pressure of the interior of the second valve body (34) which accommodates the first valve body (32), wherein the valve stem (30) has a communication channel extending in the axial direction in the valve stem (30), wherein the steam valve (10) is designed such that when the second valve body (34) is in the open position, the first chamber communicates with a second chamber via the communication channel, the second chamber having a lower pressure than the first chamber, and when the second valve body (34) is in a closed position, the first chamber does not communicate with the second chamber. [14] Steam valve (10) according to claim 13, wherein the valve housing has the auxiliary seat surface (98a, 98b) which extends along the direction transverse to the axial direction of the valve stem (30); wherein the valve stem (30) has the auxiliary seat section (33A, 33B) which can be applied to the auxiliary seat surface (98a, 98b) when the second valve body (34) is in the closed position, and wherein, when the second valve body (34) is in the closed position, the communication channel is separated from the second chamber by an installation section between the auxiliary seat section (33A, 33B) and the auxiliary seat surface (98a, 98b). [15] Steam turbine system (1), comprising: a steam valve (10) according to any one of claims 1 to 14; and a steam turbine located downstream of the steam valve.

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