WO2021080485A1 - A bypass valve for a steam turbine being part of a power plant and a replacement kit for a steam turbine bypass valve - Google Patents

A bypass valve for a steam turbine being part of a power plant and a replacement kit for a steam turbine bypass valve Download PDF

Info

Publication number
WO2021080485A1
WO2021080485A1 PCT/SE2020/051004 SE2020051004W WO2021080485A1 WO 2021080485 A1 WO2021080485 A1 WO 2021080485A1 SE 2020051004 W SE2020051004 W SE 2020051004W WO 2021080485 A1 WO2021080485 A1 WO 2021080485A1
Authority
WO
WIPO (PCT)
Prior art keywords
valve
seat
bypass valve
valve body
gasket
Prior art date
Application number
PCT/SE2020/051004
Other languages
French (fr)
Inventor
Peter STÅLHAMMAR
Original Assignee
Bvt Sweden Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bvt Sweden Ab filed Critical Bvt Sweden Ab
Publication of WO2021080485A1 publication Critical patent/WO2021080485A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K1/00—Lift valves or globe valves, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces
    • F16K1/32—Details
    • F16K1/34—Cutting-off parts, e.g. valve members, seats
    • F16K1/42—Valve seats
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K1/00—Lift valves or globe valves, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces
    • F16K1/32—Details
    • F16K1/34—Cutting-off parts, e.g. valve members, seats
    • F16K1/42—Valve seats
    • F16K1/427—Attachment of the seat to the housing by one or more additional fixing elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D17/00—Regulating or controlling by varying flow
    • F01D17/10—Final actuators
    • F01D17/12—Final actuators arranged in stator parts
    • F01D17/14—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits
    • F01D17/141—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of shiftable members or valves obturating part of the flow path
    • F01D17/145—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of shiftable members or valves obturating part of the flow path by means of valves, e.g. for steam turbines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K1/00—Lift valves or globe valves, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces
    • F16K1/32—Details
    • F16K1/34—Cutting-off parts, e.g. valve members, seats
    • F16K1/46—Attachment of sealing rings
    • F16K1/465—Attachment of sealing rings to the valve seats
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K25/00—Details relating to contact between valve members and seats
    • F16K25/005—Particular materials for seats or closure elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K47/00—Means in valves for absorbing fluid energy
    • F16K47/08—Means in valves for absorbing fluid energy for decreasing pressure or noise level and having a throttling member separate from the closure member, e.g. screens, slots, labyrinths
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K47/00—Means in valves for absorbing fluid energy
    • F16K47/08—Means in valves for absorbing fluid energy for decreasing pressure or noise level and having a throttling member separate from the closure member, e.g. screens, slots, labyrinths
    • F16K47/14—Means in valves for absorbing fluid energy for decreasing pressure or noise level and having a throttling member separate from the closure member, e.g. screens, slots, labyrinths the throttling member being a perforated membrane
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22G—SUPERHEATING OF STEAM
    • F22G5/00—Controlling superheat temperature
    • F22G5/12—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays
    • F22G5/123—Water injection apparatus
    • F22G5/126—Water injection apparatus in combination with steam-pressure reducing valves

Definitions

  • the invention concerns a bypass valve for use in a power plant comprising a steam turbine.
  • a bypass valve typically routes the working medium around the steam turbine.
  • Working medium of such plants is normally superheated steam, i.e. a high-temperature, high-pressure vapor generated by further heating of the steam obtained by boiling water.
  • the turbine bypass valve When in operation, the turbine bypass valve must reduce pressure as well as temperature of the superheated steam.
  • steam pressure at the valve inlet is about 200 bar and its temperature may be up to 600°C.
  • Pressure reduction is normally accomplished by a multi-stage trim in the interior of a valve body. If desired, temperature reduction may be achieved through a subsequent controlled injection of water into the steam flow - a process called desuperheating.
  • a turbine bypass valve permits operation of the plant boiler independently from the steam turbine during start-up, commissioning and shut down. Accordingly, these valves are required to handle severe process conditions.
  • bypass valves are very useful in cycling power plants.
  • valve components are typically exposed to significant stress cycles several times a day.
  • plant cycling may be defined as changing the output of a power plant, for instance during ramp-up or ramp-down.
  • harsh operating conditions combined with frequent plant cycling entail that it is difficult to provide bypass valve components that are reliable over the long-term.
  • valve seat a ring-shaped part of a valve body against which a sealing element, typically a moving valve plug, rests when the valve is closed.
  • a sealing element typically a moving valve plug
  • the valve seat is traditionally joined to the rest of the valve body by means of welding.
  • the valve seat is typically made in a more resistant steel alloy than the rest of the valve body.
  • a welding process that joins two rather different steel alloys normally presents numerous challenges.
  • heat generated during the welding process could structurally damage either steel alloy and cause reduced mechanical stability and/or degraded heat resistance of the entire bypass valve.
  • valve trim Furthermore, exposure to wet steam and residual particles typically leads to erosion of parts of the valve trim. If erosion takes place at a sealing surface of the valve trim, such as valve seat and valve plug, it might result in undesirable steam leakage. This is particularly common in the context of supercritical pressure drop, i.e. when the steam and the residual particles it carries have very high velocity, and/or when the valve is operating with a small opening of the valve plug.
  • CN110345264A discloses a steam emptying valve having a detachable valve seat (2) and a sealing ring (21). Said ring is snuggly fitted into an annular groove made in the valve seat. Moreover, the sealing ring is non-deformable as its shape is supposed to be congruent with the shape of said groove. This is necessary in order to ensure that the sealing effect is maintained.
  • valve design employed in CN110345264A inherently has a very low tolerance for manufacturing mistakes. Furthermore, the design of the valve seat at hand doesn't provide any means to compensate for dimensional deviations of the surrounding valve components. At least for this reason, the valve seat disclosed in CN110345264A lends itself poorly for replacement of an existing valve seat. Still with reference to the inherent design properties of the valve of CN110345264A, when the interior of the valve is pressurized due to steam inflowing via the valve inlet, spring washers (54) will push adjoining elements (53) upwards thereby enabling undesirable steam flow across the sealing ring (21). In the same context and as visible in Fig. 2 of CN 110345264A, the positioning of the sealing ring (21) of D1 entails that it will not expand in radial direction when subject to axial pressure. In consequence, its sealing performance is rather limited.
  • one objective of the invention at hand is to at least alleviate above-identified and other drawbacks associated with the current art.
  • bypass valve which includes the features defined in the independent claim 1. Particular embodiments of the bypass valve are defined in the dependent claims 2 to 9.
  • the invention further encompasses a replacement kit for a steam turbine bypass valve in accordance with claim 10.
  • valve seat replacement may be carried out as soon as a valve leakage is detected.
  • bypass valve in accordance with the present invention obviates the need for welding when installing a bypass valve in a steam-driven power plant. As discussed above, this entails significant benefits, e.g. preserved structural and thermal properties of the used steel alloys.
  • the plant owner may consider successive valve seat replacements as it becomes economically viable to repeatedly replace the valve seat and thereto associated components instead of exchanging the entire bypass valve. Obviously, this results in significant positive impact on the economy of the power plant.
  • the claimed replacement kit further reduces costs and down-time as it only requires replacement of certain components of the bypass valve.
  • Fig. 1 shows a perspective view of a bypass valve according to one embodiment of the present invention. A portion of a valve body is removed so that a valve trim can appear in greater detail.
  • Fig. 2 is a longitudinal, cross-sectional view of the bypass valve shown in Fig. 1.
  • Fig. 3 is an exploded view of the bypass valve shown in Fig. 1.
  • Fig. 4 illustrates use of a coating of wear resistant material provided on a valve seat respectively on a valve plug.
  • Fig. 1 shows a perspective view of a bypass valve 10 according to one embodiment of the present invention.
  • a portion of a valve body 16 is removed so that a valve trim can appear in greater detail.
  • a substantially axially extending valve body 16 is shown.
  • the valve body 16 is substantially cylindrically-shaped and provided with a steam inlet 12 used for connection to a steam supply (not shown) and a steam outlet 14.
  • a perforated, cylindrical cage 18 is arranged in vicinity of the steam inlet 12.
  • a valve plug (not visible in Fig. 1) is enclosed by the cage 18.
  • One of the purposes of the cage 18 is to hold the plug in place.
  • Avalve seat 34 is sandwiched between the cage 18 and a seat gasket 35.
  • the bypass valve further comprises spray nozzles (not shown) for injecting cooling water into the steam downstream of the steam outlet.
  • spray nozzles not shown
  • Fig. 2 is a longitudinal cross-sectional view of the bypass valve 10 shown in Fig. 1.
  • a plug 28 reciprocally movable in the interior of the valve body 16, is also shown.
  • the bypass valve 10 is closed since the plug 28 abuts against a valve seat 34.
  • the valve body 16 and the plug 28 are typically manufactured in hardened stainless steel.
  • the plug 28 is firmly coupled to a valve stem 29.
  • the valve stem 29 moves the plug 28.
  • the movement of the valve stem 29 is controlled by the actuator (not shown) that may be either hydraulic, pneumatic or electric.
  • Fig. 3 is an exploded view of the assembled bypass valve 10 shown in Figs. 1 and 2.
  • a compression ring 22 typically made in steel, is arranged so that it rests against an internal lip 24 provided in the valve body 16.
  • An annular seat gasket 35 made in compressible material is arranged between the compression ring 22 and a valve seat 34.
  • the gasket 35 prevents steam leakage.
  • the substantially annular valve seat 34 is detachable.
  • the seat 34 is normally made in hardened stainless steel. It is further shown a cylindrical cage 18 provided with a plurality of perforations for allowing steam to enter the interior of the valve body 16.
  • the valve seat 34 is rendered immobile between the cylindrical cage 18 and the seat gasket 35 when the bypass valve 10 is assembled.
  • the immobilization of the valve seat 34 is achieved by a clamping force exerted by the cage 18.
  • the seat gasket material is graphite.
  • the graphite gasket 35 and the compression ring 22 are compressed. In the compressed state, the graphite density doesn't exceed 1,5 g/cubic cm.
  • the height of the graphite gasket 35 is reduced by 1,5 mm due to compression forces and the pressure on the gasket side facing the cage is 40 MPa.
  • the bypass valve 10 in accordance with the present invention obviates the need for welding during installation. This entails significant benefits, e.g. preserved structural and thermal properties of the used steel alloys.
  • the valve further comprises a bonnet 20 and thereto associated bonnet gaskets 21.
  • the bonnet 20 is attached to the valve body 16 by means of bolts 23.
  • a spacing element 39 is also shown.
  • a segment ring 25 that keeps the components located below biased and in place may be seen.
  • a cover plate 33 is also shown.
  • the bypass valve 10 further comprises a stem guide 41 for guiding the valve stem (not shown in Fig. 3) and stem packing rings 19.
  • Agland 27 prevents water leakage.
  • the gland 27 is kept in compression by means of agland yoke 29 and stud bolts31.
  • a lowermost section of the cage is devoid of perforations. Accordingly, a deadband is provided and initial opening of the valve plug doesn't result in steam flow. Consequently, the plug is already significantly open when the steam passes across the cage via the perforations. As a result, the steam entering the interior of the valve body has reduced velocity and may cause less damage to the valve trim.
  • a replacement kit for a bypass valve comprises a substantially axially extending valve body 16, a cylindrical cage 18 enclosed by the valve body 16 and provided with a plurality of perforations for allowing steam to enter the interior of the valve body 16, a plug 28, reciprocally movable within the interior of the valve body, a detachable, substantially annular valve seat 34, a compression ring 22 being arranged so that it rests against an internal lip 24 provided in the valve body 10, and an annular seat gasket 35 made in compressible material and being arranged between the valve seat 34 and the compression ring 22, wherein, in the assembled state of the bypass valve (10), the compression ring (22) and the seat gasket (35) are axially compressed and the valve seat 34 is rendered immobile between the cylindrical cage 18 and the seat gasket 35.
  • the plug 28 is at least partially hollow and its outer wall is provided with a plurality of perforations along at least 30 % of its height H.
  • the pressure drop is also taken at the perforated plug, i.e. at a distance with respect to the interface of the valve seat and the valve plug.
  • the sealing surfaces are protected from prohibitively high steam pressures.
  • Fig. 4 illustrates use of a coating of wear resistant material provided on a valve seat 34 respectively on a valve plug 28.
  • the plug 28 is at least partially hollow and its outer wall is provided with a plurality of perforations.
  • a first coating 13 of wear resistant material is arranged on the valve plug 28.
  • a second coating 15 of wear resistant material is arranged on the valve seat 34 enclosed by a valve body 16.
  • the wear resistant material is a cobalt-based alloy.
  • the coating contributes in improving the resistance of the valve seat to particulate and water drops carried by the steam.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Lift Valve (AREA)

Abstract

The invention relates to a bypass valve (10) for a steam turbine with an axially extending valve body (16) having a steam inlet (12) and a steam outlet (14), and a cage (18) with perforations for allowing steam to enter the valve body (16). A plug (28) is reciprocally movable in the interior of the valve body (16). The valve further comprises a detachable, substantially annular valve seat (34), a compression ring (22) arranged so that it rests against an internal lip (24) provided in the valve body (16) and an annular seat gasket (35) made in compressible material. In the assembled state of the bypass valve (10), the compression ring (22) and the seat gasket (35) are axially compressed and the valve seat (34) is rendered immobile between the cylindrical cage (18) and the seat gasket (35). The invention also relates to a replacement kit for a bypass valve.

Description

A BYPASS VALVE FOR A STEAM TURBINE BEING PART OF A POWER PLANT AND A REPLACEMENT KIT FOR A STEAM
TURBINE BYPASS VALVE FIELD OF THE INVENTION
On a general level, the invention concerns a bypass valve for use in a power plant comprising a steam turbine. BACKGROUND OF THE INVENTION
In a steam-based power plant, a bypass valve typically routes the working medium around the steam turbine. Working medium of such plants is normally superheated steam, i.e. a high-temperature, high-pressure vapor generated by further heating of the steam obtained by boiling water.
When in operation, the turbine bypass valve must reduce pressure as well as temperature of the superheated steam.
Typically, steam pressure at the valve inlet is about 200 bar and its temperature may be up to 600°C. Pressure reduction is normally accomplished by a multi-stage trim in the interior of a valve body. If desired, temperature reduction may be achieved through a subsequent controlled injection of water into the steam flow - a process called desuperheating.
A turbine bypass valve permits operation of the plant boiler independently from the steam turbine during start-up, commissioning and shut down. Accordingly, these valves are required to handle severe process conditions.
In a related context, bypass valves are very useful in cycling power plants. In these, valve components are typically exposed to significant stress cycles several times a day. Here, plant cycling may be defined as changing the output of a power plant, for instance during ramp-up or ramp-down. The harsh operating conditions combined with frequent plant cycling entail that it is difficult to provide bypass valve components that are reliable over the long-term.
One such component is a valve seat - a ring-shaped part of a valve body against which a sealing element, typically a moving valve plug, rests when the valve is closed. When assembling the valve, the valve seat is traditionally joined to the rest of the valve body by means of welding. Here, the valve seat is typically made in a more resistant steel alloy than the rest of the valve body. As is known in the art, a welding process that joins two rather different steel alloys normally presents numerous challenges.
Moreover, heat generated during the welding process could structurally damage either steel alloy and cause reduced mechanical stability and/or degraded heat resistance of the entire bypass valve.
In a related context, welding of these advanced steel alloys is subject to rigorous standards. The compliance with welding procedure according to any such standard entails a more complex production process and results in reduced production rate.
Furthermore, exposure to wet steam and residual particles typically leads to erosion of parts of the valve trim. If erosion takes place at a sealing surface of the valve trim, such as valve seat and valve plug, it might result in undesirable steam leakage. This is particularly common in the context of supercritical pressure drop, i.e. when the steam and the residual particles it carries have very high velocity, and/or when the valve is operating with a small opening of the valve plug.
On the account of above-discussed severe conditions in the valve interior, steam leakage frequently occurs at the valve seat of the turbine bypass valve such that the steam passes across the valve seat although the valve plug is in closed position. Once this leakage becomes substantial it becomes necessary to replace the valve seat.
The valve seat replacement is a complex and time-consuming process that involves use of dedicated cutting tools in order to detach the valve seat from the rest of the valve body. CN110345264A discloses a steam emptying valve having a detachable valve seat (2) and a sealing ring (21). Said ring is snuggly fitted into an annular groove made in the valve seat. Moreover, the sealing ring is non-deformable as its shape is supposed to be congruent with the shape of said groove. This is necessary in order to ensure that the sealing effect is maintained.
The valve design employed in CN110345264A inherently has a very low tolerance for manufacturing mistakes. Furthermore, the design of the valve seat at hand doesn't provide any means to compensate for dimensional deviations of the surrounding valve components. At least for this reason, the valve seat disclosed in CN110345264A lends itself poorly for replacement of an existing valve seat. Still with reference to the inherent design properties of the valve of CN110345264A, when the interior of the valve is pressurized due to steam inflowing via the valve inlet, spring washers (54) will push adjoining elements (53) upwards thereby enabling undesirable steam flow across the sealing ring (21). In the same context and as visible in Fig. 2 of CN 110345264A, the positioning of the sealing ring (21) of D1 entails that it will not expand in radial direction when subject to axial pressure. In consequence, its sealing performance is rather limited.
On the above background, one objective of the invention at hand is to at least alleviate above-identified and other drawbacks associated with the current art.
SUMMARY OFTHE INVENTION
The above stated objective is achieved by means of a bypass valve which includes the features defined in the independent claim 1. Particular embodiments of the bypass valve are defined in the dependent claims 2 to 9. The invention further encompasses a replacement kit for a steam turbine bypass valve in accordance with claim 10.
By providing an easily detachable valve seat, it becomes possible to execute a rapid and simplified valve seat replacement. Accordingly, the down-time of the bypass valve is greatly reduced. In a related context, the valve seat replacement may be carried out as soon as a valve leakage is detected.
Further, the bypass valve in accordance with the present invention obviates the need for welding when installing a bypass valve in a steam-driven power plant. As discussed above, this entails significant benefits, e.g. preserved structural and thermal properties of the used steel alloys.
Finally, for any individual bypass valve, the plant owner may consider successive valve seat replacements as it becomes economically viable to repeatedly replace the valve seat and thereto associated components instead of exchanging the entire bypass valve. Obviously, this results in significant positive impact on the economy of the power plant. The claimed replacement kit further reduces costs and down-time as it only requires replacement of certain components of the bypass valve.
BRIEF DESCRIPTION OF THE DRAWINGS The objects, advantages and features of the invention will appear more clearly in the following description made with reference to the non limiting embodiments, illustrated by the drawings, in which:
Fig. 1 shows a perspective view of a bypass valve according to one embodiment of the present invention. A portion of a valve body is removed so that a valve trim can appear in greater detail.
Fig. 2 is a longitudinal, cross-sectional view of the bypass valve shown in Fig. 1.
Fig. 3 is an exploded view of the bypass valve shown in Fig. 1.
Fig. 4 illustrates use of a coating of wear resistant material provided on a valve seat respectively on a valve plug.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like reference signs refer to like elements.
For the purposes of this application, terms like "axial", "radial" and "longitudinal" are in reference to the different directions of the valve body.
Fig. 1 shows a perspective view of a bypass valve 10 according to one embodiment of the present invention. A portion of a valve body 16 is removed so that a valve trim can appear in greater detail. A substantially axially extending valve body 16 is shown. The valve body 16 is substantially cylindrically-shaped and provided with a steam inlet 12 used for connection to a steam supply (not shown) and a steam outlet 14. A perforated, cylindrical cage 18 is arranged in vicinity of the steam inlet 12. A valve plug (not visible in Fig. 1) is enclosed by the cage 18. One of the purposes of the cage 18 is to hold the plug in place. Avalve seat 34 is sandwiched between the cage 18 and a seat gasket 35. When the valve 10 is open, i.e. steam is flowing through the valve trim, the valve plug isn't abutting the valve seat 34. Steam pressure reduction takes place across the perforated cage 18. Accordingly, the steam having reduced pressure passes across the valve seat 34 and exits the valve 10 via the steam outlet 14. A hereby conferred benefit is that a significant pressure drop is taken at a distance with respect to the sealing surfaces of the valve seat. Accordingly, the sealing surfaces are protected from prohibitively high steam pressures.
In certain embodiments, the bypass valve further comprises spray nozzles (not shown) for injecting cooling water into the steam downstream of the steam outlet. The further components and operation of the bypass valve 10 will be discussed in greater detail in connection with Figs. 2 and 3.
Fig. 2 is a longitudinal cross-sectional view of the bypass valve 10 shown in Fig. 1. With reference to Fig. 2, a plug 28, reciprocally movable in the interior of the valve body 16, is also shown. The bypass valve 10 is closed since the plug 28 abuts against a valve seat 34. The valve body 16 and the plug 28 are typically manufactured in hardened stainless steel. The plug 28 is firmly coupled to a valve stem 29. The valve stem 29 moves the plug 28. The movement of the valve stem 29 is controlled by the actuator (not shown) that may be either hydraulic, pneumatic or electric.
Fig. 3 is an exploded view of the assembled bypass valve 10 shown in Figs. 1 and 2. In a lower portion of Fig. 3, a compression ring 22, typically made in steel, is arranged so that it rests against an internal lip 24 provided in the valve body 16. An annular seat gasket 35 made in compressible material is arranged between the compression ring 22 and a valve seat 34. The gasket 35 prevents steam leakage. The substantially annular valve seat 34 is detachable. The seat 34 is normally made in hardened stainless steel. It is further shown a cylindrical cage 18 provided with a plurality of perforations for allowing steam to enter the interior of the valve body 16. The valve seat 34 is rendered immobile between the cylindrical cage 18 and the seat gasket 35 when the bypass valve 10 is assembled. The immobilization of the valve seat 34 is achieved by a clamping force exerted by the cage 18. In one embodiment, the seat gasket material is graphite. In consequence of the clamping force, the graphite gasket 35 and the compression ring 22 are compressed. In the compressed state, the graphite density doesn't exceed 1,5 g/cubic cm. In the same context, the height of the graphite gasket 35 is reduced by 1,5 mm due to compression forces and the pressure on the gasket side facing the cage is 40 MPa.
By providing an easily detachable valve seat 34, it becomes possible to execute a rapid and simplified valve seat replacement. Accordingly, the down-time of the bypass valve 10 is greatly reduced.
Further, the bypass valve 10 in accordance with the present invention obviates the need for welding during installation. This entails significant benefits, e.g. preserved structural and thermal properties of the used steel alloys. The valve further comprises a bonnet 20 and thereto associated bonnet gaskets 21. The bonnet 20 is attached to the valve body 16 by means of bolts 23. A spacing element 39 is also shown. Furthermore, a segment ring 25 that keeps the components located below biased and in place may be seen. A cover plate 33 is also shown. The bypass valve 10 further comprises a stem guide 41 for guiding the valve stem (not shown in Fig. 3) and stem packing rings 19. Agland 27 prevents water leakage. The gland 27 is kept in compression by means of agland yoke 29 and stud bolts31.
In an embodiment (not shown), a lowermost section of the cage is devoid of perforations. Accordingly, a deadband is provided and initial opening of the valve plug doesn't result in steam flow. Consequently, the plug is already significantly open when the steam passes across the cage via the perforations. As a result, the steam entering the interior of the valve body has reduced velocity and may cause less damage to the valve trim.
In another embodiment of the present invention, a replacement kit for a bypass valve is disclosed. The replacement kit comprises a substantially axially extending valve body 16, a cylindrical cage 18 enclosed by the valve body 16 and provided with a plurality of perforations for allowing steam to enter the interior of the valve body 16, a plug 28, reciprocally movable within the interior of the valve body, a detachable, substantially annular valve seat 34, a compression ring 22 being arranged so that it rests against an internal lip 24 provided in the valve body 10, and an annular seat gasket 35 made in compressible material and being arranged between the valve seat 34 and the compression ring 22, wherein, in the assembled state of the bypass valve (10), the compression ring (22) and the seat gasket (35) are axially compressed and the valve seat 34 is rendered immobile between the cylindrical cage 18 and the seat gasket 35.
In another embodiment of the present invention, having only a few structural differences compared to the bypass valve shown in Figs. 1-3, the plug 28 is at least partially hollow and its outer wall is provided with a plurality of perforations along at least 30 % of its height H. In this embodiment, the pressure drop is also taken at the perforated plug, i.e. at a distance with respect to the interface of the valve seat and the valve plug. Advantageously, the sealing surfaces are protected from prohibitively high steam pressures.
Fig. 4 illustrates use of a coating of wear resistant material provided on a valve seat 34 respectively on a valve plug 28. Here, the plug 28 is at least partially hollow and its outer wall is provided with a plurality of perforations. A first coating 13 of wear resistant material is arranged on the valve plug 28. A second coating 15 of wear resistant material is arranged on the valve seat 34 enclosed by a valve body 16. When the plug 28 abuts against the valve seat 34, the valve is closed and the first and the second coatings are in contact. By way of example, the wear resistant material is a cobalt-based alloy. The coating contributes in improving the resistance of the valve seat to particulate and water drops carried by the steam. In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

CLAIMS 1. A bypass valve (10) for a steam turbine, the bypass valve
(10) comprising: a substantially axially extending valve body (16) having asteam inlet (12) and asteam outlet (14), a cylindrical cage (18) enclosed by the valve body and provided with a plurality of perforations for allowing steam to enter the interior of the valve body (16), a plug (28), reciprocally movable in the interior of the valve body (16), a detachable, substantially annular valve seat (34), a compression ring (22) being arranged so that it rests against an internal lip (24) provided in the interior of the valve body (16), an annular seat gasket (35) made in compressible material, the gasket (35) being arranged between the valve seat (34) and the compression ring (22), wherein in the assembled state of the bypass valve (10), the valve seat (34), the compression ring (22) and the seat gasket (35) are axially compressed and the valve seat (34) is rendered immobile between the cylindrical cage (18) and the seat gasket (35).
2. A bypass valve (10) according to claim 1, wherein the seat gasket (35) material is graphite.
3. A bypass valve (10) according to claim 2, wherein, in the assembled state of the bypass valve (10), the graphite of the seat gasket (35) is compressed so that its density doesn't exceed 1,5 g/cubic cm.
4. A bypass valve (10) according to any of the preceding claims, wherein the immobilization of the valve seat (34) is achieved by a clamping force exerted by the cage (18).
5. A bypass valve (10) according to any of the preceding claims, wherein afirst coating (13) of wear resistant material is arranged on the valve plug (28) and asecond coating (15) of wear resistant material is arranged on the valve seat (34) and, when the plug (28) abuts against the valve seat (34), the first and the second (15) coatings are in contact.
6. A bypass valve (10) according to claim 5, wherein any one of the first (13) and the second (15) wear resistant materials is a cobalt-based alloy.
7. A bypass valve (10) according to any of the preceding claims, wherein a lowermost section of the cage (18) is devoid of perforations.
8. A bypass valve (10) according to any of the preceding claims, wherein the plug (28) is at least partially hollow and its outer wall is provided with a plurality of perforations along at least 30 % of its height.
9. A bypass valve (10) according to any of the claims 2-8, wherein, in the assembled state of the bypass valve (10), the height of the annular seat gasket (35) is reduced by 1,5 mm due to compression forces.
10. A replacement kit for a bypass valve (10), the replacement kit comprising: - a substantially axially extending valve body (16), a cylindrical cage (18) enclosed by the valve body and provided with a plurality of perforations for allowing steam to enter the interior of the valve body (16), a plug (28), reciprocally movable within the interior of the valve body (16), adetachable, substantially annular valve seat (34), a compression ring (22) being arranged so that it rests against an internal lip (24) provided in the interior of the valve body (16), - an annular seat gasket (35) made in compressible material and being arranged between the valve seat (34) and the compression ring (22), wherein in the assembled state of the bypass valve (10), the compression ring (22) and the seat gasket (35) are axially compressed and the valve seat (34) is rendered immobile between the cylindrical cage (18) and the seat gasket (35).
PCT/SE2020/051004 2019-10-20 2020-10-20 A bypass valve for a steam turbine being part of a power plant and a replacement kit for a steam turbine bypass valve WO2021080485A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE1930340A SE1930340A1 (en) 2019-10-20 2019-10-20 A bypass valve for a steam turbine being part of a power plant and a replacement kit for a steam turbine bypass valve
SE1930340-3 2019-10-20

Publications (1)

Publication Number Publication Date
WO2021080485A1 true WO2021080485A1 (en) 2021-04-29

Family

ID=73452254

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE2020/051004 WO2021080485A1 (en) 2019-10-20 2020-10-20 A bypass valve for a steam turbine being part of a power plant and a replacement kit for a steam turbine bypass valve

Country Status (2)

Country Link
SE (1) SE1930340A1 (en)
WO (1) WO2021080485A1 (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4773442A (en) * 1984-09-26 1988-09-27 Sereg S.A. Globe valve having a dismountable seat for rapid maintenance
US5156181A (en) * 1991-07-22 1992-10-20 Allied-Signal Inc. Removable seats for a dual poppet valve
US20090218536A1 (en) * 2008-03-03 2009-09-03 Wears William E High Temperature Valve
US20190024803A1 (en) * 2017-07-19 2019-01-24 Samson Aktiengesellschaft Valve component arrangement and a control valve with a valve component arrangement
US10344757B1 (en) * 2018-01-19 2019-07-09 Kennametal Inc. Valve seats and valve assemblies for fluid end applications
CN110345264A (en) 2019-08-09 2019-10-18 无锡市亚迪流体控制技术有限公司 Heavy caliber superhigh pressure difference steam evacuation valve

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT256891B (en) * 1965-02-15 1967-09-11 Schaeffer & Budenberg Gmbh Valve for converting the pressure and temperature of superheated steam
US5288054A (en) * 1993-06-28 1994-02-22 M&Fc Holding Company, Inc. Globe valve and method for making same
DE202015104151U1 (en) * 2015-08-07 2015-10-08 Samson Ag Control valve

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4773442A (en) * 1984-09-26 1988-09-27 Sereg S.A. Globe valve having a dismountable seat for rapid maintenance
US5156181A (en) * 1991-07-22 1992-10-20 Allied-Signal Inc. Removable seats for a dual poppet valve
US20090218536A1 (en) * 2008-03-03 2009-09-03 Wears William E High Temperature Valve
US20190024803A1 (en) * 2017-07-19 2019-01-24 Samson Aktiengesellschaft Valve component arrangement and a control valve with a valve component arrangement
US10344757B1 (en) * 2018-01-19 2019-07-09 Kennametal Inc. Valve seats and valve assemblies for fluid end applications
CN110345264A (en) 2019-08-09 2019-10-18 无锡市亚迪流体控制技术有限公司 Heavy caliber superhigh pressure difference steam evacuation valve

Also Published As

Publication number Publication date
SE1930340A1 (en) 2021-04-21

Similar Documents

Publication Publication Date Title
US8356622B2 (en) Fluid valves having dynamic valve trim joints
EP1869351B1 (en) Fluid flow control device
JP6457819B2 (en) Steam turbomachinery valve having a valve member and a seal assembly
CA2833481C (en) Pressure balanced spring loaded overtravel sealing apparatus
JP7227845B2 (en) Steam valve drive system, steam valve system and steam turbine plant
US8844288B2 (en) Steam turbine facility
US6772993B1 (en) Plug and seal assembly
CA2915408C (en) Seal assemblies for use with fluid valves
US4802679A (en) Bell seal of improved stability for high pressure turbines
US4812105A (en) Bell seal and retaining nut for high pressure turbines
WO2021080485A1 (en) A bypass valve for a steam turbine being part of a power plant and a replacement kit for a steam turbine bypass valve
CN109555863A (en) It adjusts for the overtravel in double furcation plugs used in valve module
US20160208930A1 (en) Valve for shutting off and/or controlling the flow rate of fluid flows, and a method for the post-production of such a valve
JP6266076B2 (en) Fixing method of valve body and valve stem
US11685528B2 (en) Solenoid valve with non-sliding plunger assembly
US11920683B2 (en) Valve arrangement and fluid flow control element
JPH07139638A (en) Globe valve and its manufacture
CN104455499A (en) Combined sealing stop valve
JP7398805B2 (en) Valve device with automatic cleaning function and pressure reducing valve equipped with it
RU149554U1 (en) NUTRITION PUMP RECIRCULATION VALVE
CN206786328U (en) A kind of quick service drain valve
KR200188809Y1 (en) Disc with piston-ring and disc-cage attached glove valve
RU2206015C1 (en) Shut-off throttling valve and its body
JP2007315603A (en) Method and apparatus for covering pressure vessel
WO2017069925A1 (en) Ball trip valve for a steam turbine

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20807916

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20807916

Country of ref document: EP

Kind code of ref document: A1