JP2013076339A - Steam turbine casing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine casing which can prevent steam leak from a flange part of a casing without enhancing a material specification of a bolt or the casing, nor increasing a bolt size even if a steam condition is increased in pressure and temperature.SOLUTION: The steam turbine casing 5 is a steam turbine casing of a divided sturcture. The steam turbine casing includes: the flange part attached to the casing; the bolt penetrated into a hole provided in the flange part; a seal ring attached to an inner surface of the hole provided in the flange part to be matched with a matching surface of the casing; and a nut attached to both ends of the bolt. Moreover, the bolt and the nut fasten the seal ring.

Description

  Embodiments of the invention relate to a steam turbine casing.

  In order to improve the plant efficiency from the viewpoints of environment and economy, studies have been made to increase the main steam pressure to 25 MPa or higher and the temperature to 600 ° C. or higher. In recent years, plants that have dramatically improved pressure and temperature. Study and development are also underway.

  Here, the steam turbine casing has a role of sealing high-temperature and high-pressure steam to the inside, and if the sealing performance is impaired, the internal steam leaks to the outside, reducing the amount of work performed by the rotor blades attached to the rotor, and turbine performance Becomes worse and disadvantageous in terms of economy. In addition, if high-temperature and high-pressure steam leaks to the atmosphere, it may lead to the danger of workers, so a design that does not cause steam leakage in the casing is required. Furthermore, since higher stress is generated in the casing due to high pressure and high temperature, the strength of the structure tends to become more severe with a decrease in material strength due to high temperature.

  Steam turbine casings are generally high-pressure and high-temperature inside, and the casing has a force from the inside to the outside (the combined stress of hoop stress and thermal stress), which exceeds the tightening force of bolts and nuts at the casing flange. When the outward force is applied, the phenomenon that the flange surface does not contact occurs. This is called chamfering, which is one of the causes of leakage of steam from the inside of the casing to the outside.

  In order to suppress the surface opening of the casing flange surface, measures to increase the bolt tightening force are taken. Specifically, there is a method of increasing the initial tightening allowance of the bolt or increasing the bolt size. However, the former uses stricter bolt strength, and if the design does not have strength, a higher strength material is used. In the latter case, the casing flange increases with the bolt size increase, which leads to an increase in casing weight, both of which increase the cost.

  Furthermore, along with the high pressure and high temperature of the steam conditions, the material unit price of the material used is increasing. Moreover, since workability also deteriorates, costs tend to increase in production. Therefore, high-pressure and high-temperature steam conditions are proportional to the increase in overall cost. Moreover, in research that has made steam temperatures higher than 700 ° C. in recent years, the materials used are said to be 5 to 10 times that of conventional materials, and the relationship between material costs and overall plant costs is accounted for by material costs. The proportion becomes very large.

JP 59-58265 A JP 2002-349208 A

  The problem to be solved by the present invention is to prevent steam leakage from the flange portion of the casing without increasing the performance of the bolt or casing material or increasing the bolt size even if the steam conditions are increased to high pressure and high temperature. It is to provide a steam turbine casing that can be prevented.

  The steam turbine casing of the embodiment is a steam turbine casing having a split structure, and is provided with a flange portion attached to the casing, a bolt passed through a hole provided in the flange portion, and the flange portion. And a seal ring attached to the inner surface of the hole with the mating surface of the casing, and nuts attached to both ends of the bolt. Further, the seal ring is tightened with the bolt and the nut.

Schematic of the steam turbine casing of the first embodiment. Sectional drawing which cut | disconnected the rotor central axis of the steam turbine casing of embodiment of FIG. 1 to the vertical direction. Sectional drawing of the penetration type seal ring of the steam turbine casing of 1st Embodiment. Sectional drawing which shows the structure which escapes the extension of the axial direction of the seal ring of the steam turbine casing of 1st Embodiment. Sectional drawing of the one side penetration type | mold seal ring of the steam turbine casing of 2nd Embodiment. Sectional drawing of the internal insertion type seal ring of the steam turbine casing of 3rd Embodiment. Sectional drawing of the multilayer structure seal ring of the steam turbine casing of 4th Embodiment. Sectional drawing which provided the fluid flow path in the intermediate | middle layer of the multilayer structure seal ring of the steam turbine casing of 4th Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
Hereinafter, the steam turbine casing of the first embodiment will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  First, the outline of the steam turbine casing of the first embodiment will be described. FIG. 1 is a schematic view of a steam turbine casing of the first embodiment, FIG. 2 is a cross-sectional view of the steam turbine casing of the embodiment of FIG. 1 taken along the longitudinal axis of the rotor, and FIG. It is sectional drawing of the penetration type seal ring of the steam turbine casing of embodiment. FIG. 4 is a cross-sectional view showing a structure for escaping the axial extension of the seal ring of the steam turbine casing of the first embodiment.

  Here, as shown in FIGS. 1 and 2, in the steam turbine casing 5 of the first embodiment, blades that receive a force from steam are attached to a rotating rotor 22, covering the rotor 22 and sealing the steam inside. It has an internal casing 20 for it. The inner casing 20 is directly or indirectly attached with a nozzle for introducing steam to the blades. Further, an outer casing 21 is provided outside the inner casing 20 to cover the whole. The inner casing 20 and the outer casing 21 have a divided structure. In order to form a sealed container, as shown in FIG. 1, the casing flange 1 attached to the casing body is tightened with bolts and nuts. It is integrated.

  As shown in FIG. 1, the casing 5 is divided into upper and lower parts in the radial direction of the steam turbine and includes a mating surface for combining the casings 5. As shown in FIG. 3, the casing 5 is formed by aligning the casing 5 divided by the aforementioned mating surfaces, and then tightening the bolts 2 and the nuts 3 with the casing flange 1, thereby Prevents leakage. The casing flange 1 is integrated with the casing 5. The casing 5 may be divided in the axial direction of the steam turbine.

  Here, as shown in FIG. 3, the casing flange 1 is provided with a bolt hole for passing the bolt 2, and a cylindrical penetrating seal ring 4 is attached so as to be in close contact with the inner surface of the bolt hole. It has been. Here, the one-side through-type seal ring 7 is a through-type seal ring that penetrates to both sides of the casing flange 1. Further, since the internal steam of the casing 5 leaks outward from the chamfered portion of the mating surface of the casing flange 1, the penetrating seal ring 4 is attached within a range that covers the mating surface of the casing flange 1.

  Furthermore, as shown in FIG. 4, a space 6 is provided in the upper part of the penetrating seal ring 4 in the axial direction. By providing the space 6, the penetrating seal ring 4 can freely move in the axial direction, so that it does not receive the axial compressive stress from the casing flange 1. The space 6 may be provided in either the casing flange 1 or the nut 3.

  Further, when the temperature of the casing flange 1 and the penetrating seal ring 4 is increased by setting the material of the penetrating seal ring 4 to a material larger than the linear expansion coefficient of the casing flange 1 at the target use temperature, the penetrating mold is used. The seal ring 4 is pressed against the inner surface of the bolt hole of the casing flange 1 due to a difference in linear expansion from the casing flange 1. Therefore, the sealing performance against leakage of internal steam in the casing 5 is further improved from the surface opening portion of the casing flange 1.

  Furthermore, by making the material of the through-type seal ring 4 smaller than the thermal conductivity of the casing flange 1 at the intended use temperature, the material is transmitted through the casing flange 1 when the through-type seal ring 4 is not used. The amount of heat transferred from the through-type seal ring 4 to the internal steam in the bolt hole of the casing flange 1 can be less than the amount of heat transferred to the internal steam in the bolt hole. Thereby, it is possible to suppress the thermal elongation, relaxation, material degradation, and the like of the bolt 2, and the sealing performance against leakage of internal steam of the casing 5 is further improved from the surface opening portion of the casing flange 1.

  Further, by making the material of the through-type seal ring 4 smaller than the emissivity of the casing flange 1 at the intended use temperature, the material is transmitted through the casing flange 1 when the through-type seal ring 4 is not used. The amount of heat transferred from the through-type seal ring 4 to the internal steam in the bolt hole of the casing flange 1 can be less than the amount of heat transferred to the internal steam in the bolt hole. Thereby, it is possible to suppress the thermal elongation, relaxation, material degradation, and the like of the bolt 2, and the sealing performance against leakage of internal steam of the casing 5 is further improved from the surface opening portion of the casing flange 1.

  Further, by reducing the heat transfer coefficient of the surface of the penetrating seal ring 4 in contact with the surrounding fluid at the target operating temperature lower than that of the casing flange 1, the casing flange can be used when the penetrating seal ring 4 is not used. The amount of heat transferred from the through-type seal ring 4 to the internal steam in the bolt hole of the casing flange 1 can be made smaller than the amount of heat transferred through 1 to the internal steam in the bolt hole. Thereby, it is possible to suppress the thermal elongation, relaxation, material degradation, and the like of the bolt 2, and the sealing performance against leakage of internal steam of the casing 5 is further improved from the surface opening portion of the casing flange 1.

  In the first embodiment, the through-type seal ring 4 has a circular shape like a bolt hole. However, the present invention is not limited to this, and the cross-section of the through-type seal ring 4 is a polygon or a free cross-section. It is good also as such various cross-sectional shapes.

(Second Embodiment)
Hereinafter, the steam turbine casing of 2nd Embodiment is demonstrated using drawing. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  The second embodiment is different from the first embodiment in that the one-side penetrating seal ring 7 is used instead of the penetrating seal ring 4, and the first embodiment other than the notation of the penetrating seal ring 7 is the first one. Since it is the same as that of embodiment, the same part is attached | subjected to the same code | symbol and detailed description is abbreviate | omitted.

  FIG. 5 is a cross-sectional view of the one-side through seal ring of the steam turbine casing of the second embodiment.

  As shown in FIG. 5, in the steam turbine casing of the second embodiment, a one-side penetrating seal ring 7 is used instead of the penetrating seal ring 4 in FIG. The one-side penetrating seal ring 7 is a one-side penetrating seal ring that penetrates only to one side of the casing flange 1. By using the one-side penetrating seal ring 7, when assembling or disassembling the casing 5, the work of holding the one-side penetrating seal ring 7 can be made unnecessary.

  In addition, since the internal steam of the casing 5 leaks outward from the surface opening portion of the mating surface of the casing flange 1, the one-side through seal ring 7 is attached within a range that covers the mating surface of the casing flange 1.

  The steam turbine casing according to the second embodiment has a sealing performance equivalent to that of the first embodiment, and the seal ring can be made lighter than the first embodiment.

(Third embodiment)
Hereinafter, the steam turbine casing of the third embodiment will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  The third embodiment is different from the first embodiment in that an internal insertion type seal ring 8 is used in place of the penetration type seal ring 4. Since it is the same as that of embodiment, the same part is attached | subjected to the same code | symbol and detailed description is abbreviate | omitted.

  FIG. 6 is a cross-sectional view of the internal insertion type seal ring of the steam turbine casing of the third embodiment.

  As shown in FIG. 6, in the steam turbine casing of the third embodiment, an internal insertion type seal ring 8 is used instead of the penetration type seal ring 4 in FIG. The internal insertion type seal ring 8 is an internal insertion type seal ring embedded in the casing flange 1. By using the internal insertion type seal ring 8, the grounding surface between the nut 3 and the casing flange 1 is made larger than that in the first embodiment, and the fastening force of the casing flange 1 by the bolt 2 and the nut 3 is increased. It becomes possible.

  Furthermore, since the internal steam of the casing 5 leaks outward from the surface opening portion of the mating surface of the casing flange 1, the internal insertion type seal ring 8 is attached within a range that covers the mating surface of the casing flange 1. The steam turbine casing of the third embodiment has a sealing performance equivalent to that of the first embodiment and the second embodiment, and is lighter in the seal ring than the first embodiment and the second embodiment. Is possible.

(Fourth embodiment)
Hereinafter, the steam turbine casing of 4th Embodiment is demonstrated using drawing. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  The fourth embodiment is different from the first embodiment in that a multilayer structure seal ring 9 is used instead of the through-type seal ring 4, and the first embodiment except for the notation of the multilayer structure seal ring 9 is used. Therefore, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  FIG. 7 is a cross-sectional view of the multilayer seal ring of the steam turbine casing of the fourth embodiment, and FIG. 8 shows a fluid flow path in the intermediate layer of the multilayer seal ring of the steam turbine casing of the fourth embodiment. It is sectional drawing provided.

  As shown in FIG. 7, in the steam turbine casing of the fourth embodiment, a multilayer seal ring 9 is used in place of the through-type seal ring 4 in FIG. The multilayer seal ring 9 is a seal ring having a multilayer structure composed of a plurality of layers having the same thickness or different thicknesses. By using the multilayer seal ring 9, it becomes possible to combine different materials having various characteristics, and it is possible to have a function that cannot be achieved with only one kind of material.

  It is also possible to combine materials having a larger linear expansion coefficient than that of the casing flange 1 as the multilayer structure seal ring 9 at the intended use temperature. As shown in FIG. 8, the multilayer structure seal ring 9 includes an intermediate layer 10. Here, the material of the intermediate layer 10 has a larger linear expansion coefficient than the casing flange 1.

  Here, when the temperature of the casing flange 1 and the multilayer structure seal ring 9 rises, the multilayer structure seal ring 9 is pressed against the inner surface of the bolt hole due to the difference in linear expansion between the intermediate layer 10 and the casing flange 1. Therefore, the sealing performance against steam leakage from the face opening portion of the casing flange 1 is improved. Even if a part of the intermediate layer 10 is smaller than the linear expansion coefficient of the casing flange 1, the same function is exhibited as long as the macroscopic linear expansion coefficient in the entire intermediate layer 10 is larger than that of the casing flange 1. .

  Moreover, it is also possible to combine the multilayer structure seal ring 9 with a material whose thermal conductivity is smaller than that of the casing flange at the intended use temperature. As shown in FIG. 8, the multilayer structure seal ring 9 includes an intermediate layer 10. Here, the material of the intermediate layer 10 has a smaller thermal conductivity than the casing flange 1.

  Therefore, when the multilayer seal ring 9 is not used, the amount of heat transferred from the multilayer seal ring 9 to the internal steam of the bolt hole is less than the amount of heat transferred through the casing flange 1 to the internal steam of the bolt hole. can do. Thereby, it becomes possible to suppress the thermal elongation, relaxation, material deterioration, etc. of the bolt 2, and the overall macroscopic thermal conductivity is lower than that of the casing flange 1, not each layer. Even if a part of the intermediate layer 10 is larger than the thermal conductivity of the casing flange 1, if the macroscopic thermal conductivity of the entire multilayer structure seal ring 9 is smaller than the thermal conductivity of the casing flange 1, the same Function is demonstrated.

  Furthermore, the multilayer structure seal ring 9 has a lower emissivity of the innermost layer of the multilayer structure seal ring facing the bolt as the multilayer structure seal ring 9 at a target use temperature. When 9 is not used, the amount of heat transferred from the multilayer seal ring 9 to the internal steam of the bolt hole can be made smaller than the amount of heat transferred through the casing flange 1 to the internal steam of the bolt hole. Thereby, it is possible to suppress the thermal elongation, relaxation, material degradation, and the like of the bolt 2, and the sealing performance against leakage of internal steam of the casing 5 is further improved from the surface opening portion of the casing flange 1.

  In addition, when the multilayer structure seal ring 9 is not used, the casing flange 1 can be obtained by making the heat transfer coefficient of the surface that contacts the surrounding fluid of the multilayer structure seal ring 9 lower than the material of the casing flange 1 at the target use temperature. The amount of heat transferred from the multilayer structure seal ring 9 to the internal steam of the bolt hole can be made smaller than the amount of heat transferred to the internal steam of the bolt hole. As a result, it is possible to suppress the thermal elongation, relaxation, material deterioration, and the like of the bolt 2.

  Here, as shown in FIG. 8, when the fluid passage 11 is cut and the fluid is passed through the intermediate layer 10, the intermediate layer 10 is made of a material having a smaller heat transfer coefficient than the casing flange 1. The function of can be demonstrated.

  According to the steam turbine casing of at least one embodiment described above, without increasing the material specifications of the bolt 2 and the casing 5 or increasing the size of the bolt 2 even if the steam conditions are increased to high pressure and high temperature. Steam leakage from the casing flange 1 can be prevented. Further, by reducing the amount of heat transfer from the casing flange 1 to the bolt 2, the temperature rise of the bolt 2 can be suppressed, the strength of the bolt 2 can be prevented from lowering, and the amount of thermal energy that can be thrown away outside without work. By reducing this, plant efficiency can be expected to improve.

  Needless to say, the present invention is not limited to the above-described embodiments and can be implemented with various modifications.

  In short, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Moreover, various forms can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Casing flange 2 ... Bolt 3 ... Nut 4 ... Through-type seal ring 5 ... Casing 6 ... Space 7 ... One-side through-type seal ring 8 ... Internal insertion type seal ring 9 ... Multilayer structure seal ring 10 ... Middle layer 11 ... Fluid flow Path 20 ... inner casing 21 ... outer casing 22 ... rotor

Claims (15)

A steam turbine casing having a split structure,
A flange attached to the casing;
A bolt passed through a hole provided in the flange portion;
A seal ring attached to the inner surface of the hole provided in the flange portion so as to match the mating surface of the casing;
And nuts attached to both ends of the bolt,
A steam turbine casing for fastening the seal ring with the bolt and the nut.   The steam turbine casing according to claim 1, wherein the seal ring is a penetrating seal ring that penetrates to both sides of the flange portion.   The steam casing according to claim 2, further comprising a spacer on an axially upper portion of the penetrating seal ring.   The steam turbine casing according to claim 1, wherein the seal ring is a one-side-through seal ring that penetrates only to one side of the flange portion.   The steam turbine casing according to claim 1, wherein the seal ring is an internally inserted seal ring embedded in the flange portion.   The steam turbine casing according to any one of claims 1 to 5, wherein a material of the seal ring is a material larger than a linear expansion coefficient of the flange portion.   The steam turbine casing according to any one of claims 1 to 5, wherein a material of the seal ring is smaller than a thermal conductivity of the flange portion.   The steam turbine casing according to any one of claims 1 to 5, wherein a material of the seal ring is a material smaller than an emissivity of the flange portion.   The steam turbine casing according to any one of claims 1 to 5, wherein a thermal conductivity of a surface of the seal ring that comes into contact with a surrounding fluid is smaller than a thermal conductivity of a material of the flange portion.   2. The steam turbine casing according to claim 1, wherein the seal ring is a multi-layer seal ring having a multi-layer structure including a plurality of layers having the same or different thickness.   The steam turbine casing according to claim 10, wherein the seal ring further includes an intermediate layer made of a material larger than a linear expansion coefficient of a material of the flange portion.   The steam turbine casing according to claim 10, wherein the seal ring further includes an intermediate layer made of a material smaller than a thermal conductivity of the material of the flange portion.   The steam turbine casing according to claim 12, wherein the intermediate layer of the seal ring further includes a fluid flow path through which fluid flows.   The steam turbine casing according to claim 10, wherein an emissivity of an innermost layer of the seal ring is a material smaller than an emissivity of a material of the flange portion.   The steam turbine casing according to claim 1, wherein the casing includes an inner casing and an outer casing.

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