JPS59224404A - Steam lead-in pipe of extra high temperature steam turbine - Google Patents

Abstract

PURPOSE:To reduce thermal stress generated by the difference in thermal expansion by connecting a steam lead-in pipe with internal components through L- shaped airtight rings and with the external casing through a U-shaped airtight ring. CONSTITUTION:A steam lead-in pipe 34 is connected with an internal casing 22 and a nozzle box 21 through L-shaped airtight rings 47, 48. The fitting part of cup-shaped flange part 34a of this steam lead-in pipe 34 with the external casing 23 is sealed airtightly with a U-shaped airtight ring 44. Thereby the thermal stress because of difference in the thermal expansion between steam lead-in pipe 34 and casings can be reduced.

Description

[Detailed Description of the Invention] [Technical Field to Which the Invention Pertains] The present invention relates to a steam inlet pipe having a large thermal expansion at a steam inflow portion of an ultra-high temperature steam turbine that connects an inner casing and a nozzle box inside an outer casing, and particularly relates to a steam inlet pipe having a large thermal expansion. A large amount of heat is generated when the main steam and reheat steam introduction pipe of a steam turbine that uses ultra-high-temperature steam is made of austenitic stainless steel, and the connected inner and outer casings are made of martensitic or ferritic steel. This invention relates to a device that further alleviates the occurrence of thermal stress caused by expansion differences.

[Prior art and its problems]

In general, it is desired that the high-pressure part of the casing of a steam turbine, which operates at high temperatures of 500"C or higher, be made as simple as possible, and it is often constructed as a so-called double or triple casing structure. In the case of gauging, an inner casing and a nozzle box are provided within the outer casing, and a steam expansion chamber is formed between the blades of the rotor and the vanes at the inner periphery of the inner casing and nozzle box.

The inner casing and nozzle box expand or contract differently from the outer casing during startup or load fluctuations, and are at different temperature levels.
The hermetic connections between the steam inlet pipe supported by the outer casing and the inner casing, and the steam inlet pipe and the nozzle box, must be thermoelastic, and this tightness is best achieved in the first turbine, where the steam pressure and temperature are greatest. It is most required in the steam inlet pipe support section of the stage.

Generally, it is inevitable to use austenitic stainless steel material for steam introduction pipes through which ultra-high temperature steam exceeding 1050° F. (595° C.) flows. On the other hand, by adopting the above-mentioned multiple cage puffer structure, except for the pressure vessel, such as the nozzle box, which is directly exposed to live steam or reheated steam, components exposed to relatively low-temperature steam after steam expansion, such as through the control stage, The turbine rotor, which comes into contact with steam, and the inner casing placed around its outer periphery are made of stator vane holders, and the outer casing is often made of martensitic or ferritic translational steel due to casting technology and economic efficiency. .

By the way, the problem in this case is that an austenitic stainless steel material with a very high coefficient of thermal expansion is used in the high-temperature part, and a martensitic or ferritic steel material with a lower coefficient of thermal expansion than the austenitic stainless steel material is used in the relatively low-temperature part. In other words, a large difference in thermal expansion occurs between the materials at the support portion of the steam introduction pipe and the external casing, which causes an excessive effect on the support portion as thermal stress.

FIG. 1 is a sectional view of a main part of a steam introduction pipe section showing a conventional example of this type. In the figure, 1 is a steam introduction pipe, 2 is an outer casing, 3 is an inner casing, and 4 is a rotor shaft (not shown). In this structure, an elastic, thin-walled tubular member 1a that releases thermal stress as thermal deformation is placed around the outer periphery of a steam introduction pipe 1, and a similar tubular member 2a protruding from an outer casing 2 is welded. It is generally widely adopted. However, even in this structure, it is technically impossible for large residual strain to occur after welding in the welded joint between the steam introduction pipe 1 made of austenitic stainless steel and the outer casing 2 made of martensitic or ferritic steel. Furthermore, in a welded part where ultra-high temperature steam is passed through and heated, there is a disadvantage that thermal stress generated between the materials cannot be avoided.

Therefore, in order to counteract this excessive thermal stress, the tubular member 2a of the outer casing is made of ferritic steel.
In addition, a structural measure is taken in which a material 2 that has a high strength value even at high temperatures, such as a nickel-chromium Inconel material, is overlaid and a pipe made of the same material is inserted and welded. However, even in this structure, fl,
However, it has the disadvantage that it cannot be used in turbines with a pot-shaped casing structure that requires assembling and disassembling internal components in the axial direction.

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks and improves temperature by the difference in thermal expansion.
[Summary of the Invention] According to the present invention, the above object is to provide a highly safe steam introduction pipe for an ultra-high temperature steam turbine that can alleviate the generated thermal stress and can be assembled and disassembled. A steam inlet pipe with a large coefficient of thermal expansion of the steam inlet door of the ultra-high temperature steam turbine that connects the internal casing and the nozzle box inside the tube, and the steam inlet pipe has a removable ring on the outer circumference and a plurality of outer circumferential surfaces. 7 cup-shaped flange portions formed in steps are provided at intervals, and air-tight rings each having a cross-section are provided on the inner casing and the pipe portion on the nozzle box side, and the cup-shaped flange portion is air-tightly attached to the outer casing. an airtight ring which is fitted into the ring nut and is held between the ring and the flange by both sides of a ring nut which is screwed onto the inner peripheral surface of the outer casing, and in which the inner casing and the nozzle box are connected This is achieved by connecting the pipe portions of the steam introduction pipes through the airtight rings so as to be slidable in the axial direction.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings. Second
4 to 4 show embodiments of the present invention, FIG. 2 is a longitudinal cross-sectional view of the main part of an ultra-high temperature steam turbine, FIG. 3 is a cross-sectional view of the main part of the steam introduction pipe, and FIG. It is a detailed view of the main part of the steam introduction pipe shown in the figure. In the figure, 20 is a rotor, 21 is a nozzle box, 22 is an internal casing, 23 is an external casing, 24 is a steam introduction pipe section, and 34 is a steam introduction pipe of an ultra-high temperature steam inflow section. This structure consists of the outer casing 2
3 is shaped like a pot, and the internal casing 22 and nozzle box 21 are divided into upper and lower halves on a horizontal plane. Ultra-high-temperature steam exceeding 1050°F (595°C) flows through the steam introduction pipe 34, passes through the nozzle port 21a of the nozzle box 21, and flows from the high-pressure stage to the low-pressure stage in the vehicle interior to do work.

The steam introduction pipe 34 of the ultra-high temperature steam inflow section has a ring 42 removably fixed to its outer periphery with a knock pin 41.
and a cup-shaped flange portion 3 with multiple steps formed on the outer circumferential surface.
4a is provided, and the flange portion 34a is fitted to the inner peripheral surface of the outer casing 23. Also, ring 42
and the cup-shaped flange portion 34a are held by both sides of a ring nut 430 that is screwed into the outer casing 23, and the steam introduction pipe 34 is held by a knock pin 4 that fixes the ring 42.
It will not be possible to move in the υ-axis direction unless 1 is removed.

It has become. Reference numeral 44 denotes a G airtight ring having a U-shaped cross section, which is pressed by a ring nut 43 to seal the gap between the fitting portion of the outer casing 23 and the flange portion 34a of the steam introduction pipe. Further, a stepped portion is formed in the inner casing 22 and nozzle box 21 side pipe portion of the steam introduction pipe 34,
Threaded portions are provided on its inner and outer surfaces, and a threaded ring 45° is screwed into the threaded portion on the outer circumferential surface, and a threaded ring 46 is screwed onto the threaded portion on the inner circumferential surface. 47.48 is a cross-sectional airtight ring,
The airtight ring 47 is attached to the end surface '34b of the stepped section of the steam introduction pipe by means of a threaded ring 45, and the airtight ring 48 is attached to the end surface 34c of the stepped section of the steam introduction pipe by means of a threaded ring 46. Internal casing 22 and nozzle box 2
1 have annular grooves 21a into which airtight rings 47 and 48 are tightly fitted, respectively, and in which the pipe portion of the steam introduction pipe 34 can slide in the axial direction due to thermal expansion.

22a is provided, and said rings 47, 48 are inserted into respective annular grooves 21a, 22a.

With the above configuration, the steam inlet pipe 34 and nozzle box 21 of the steam inflow section that directly come into contact with ultra-high temperature steam are made of austenitic stainless steel, and the internal casing 22 expands in the control stage and comes into contact with relatively cooled steam. Tame 12
Thichrome steel is used, and the outer casing is translational steel. As mentioned above, the nozzle box 21 and the internal casing 22 are chambers with different temperature and pressure conditions, and there is an airtight mechanism between them and the steam introduction pipe 34 that connects them, and each heat It is necessary to absorb the difference in expansion, and this is done by the nozzle box 21 and the steam introduction pipe 34.
An L-shaped gas-tight ring 47, 48 is established between the inner nine-part casing 22 and the steam inlet pipe 34, respectively.

Further, airtightness between the atmospheric pressure and the steam inside the vehicle compartment is established by an fcU-shaped airtight ring 44 provided at the fitting portion between the outer casing 23 and the flange portion 34a of the steam introduction pipe. Further, the difference in thermal expansion between the steam introduction pipe 34 and the outer casing 23 is alleviated by the ring 42° ring nut 43 and the cup-shaped flange portion 34a, so that even if a difference in thermal expansion occurs, the difference in thermal expansion between the steam introduction pipe 34 and the outer casing 23 is reduced by the ring 42 and the cup-shaped flange portion 34a. The fitting portion of the cup-shaped flange portion 34a allows thermal movement while maintaining the tube axis.

Therefore, since the steam inlet pipe 34 is not rigidly fixed to the outer casing 23, the stress level at the fixed part is 50% or less compared to a welded joint, increasing the safety of the ultra-high temperature steam inlet part. I can do it.

〔Effect of the invention〕

As described above, the present invention uses an L-shaped airtight ring to connect the steam introduction pipe and the internal components, and the fitting part is made airtight with a U-shaped ring. By sealing, it is possible to provide a steam introduction pipe for an ultra-high temperature steam turbine that can relieve excessive thermal stress that often occurs due to differences in thermal expansion, can be disassembled and reassembled, and is highly safe. Although the above-mentioned embodiments have been described with respect to the main steam introduction pipe of an ultra-high temperature steam turbine, the present invention is not limited to this, but can also be applied to a reheat steam introduction pipe.

[Brief explanation of the drawing]

FIG. 1 shows a conventional embodiment, and is a sectional view of the main part of the steam introduction pipe.
Figures 2 to 4 show embodiments of the present invention, with Figure 2 being a longitudinal cross-sectional view of the main part of an ultra-high temperature steam turbine, Figure 3 being a cross-sectional view of the main part of the steam introduction pipe, and Figure 4 being a cross-sectional view of the main part of the steam introduction pipe. FIG. 4 is a detailed view of the main part of the steam introduction pipe shown in FIG. 3;

Claims (1)

[Scope of Claims] 1) A steam introduction pipe having a large coefficient of thermal expansion at a steam inflow section of an ultra-high temperature steam turbine that connects an inner casing and a nozzle box inside an outer casing, the steam introduction pipe having a large coefficient of thermal expansion. a ring that can be attached and detached from the inner casing and a cup-shaped 7 flange portion whose outer circumferential surface is formed in a plurality of stages are provided at intervals, and airtight rings each having a cross-section shape are provided on the inner casing and the tube portion on the nozzle box side, respectively; A cup-shaped seven flange portion is airtightly fitted into the outer casing, and a portion between the removable ring and the seven ranks is held by both sides of a ring nut screwed onto the inner circumferential surface of the outer casing, and the inner casing is and the nozzle box are each tightly connected to the above-mentioned airtight ring, and the pipe portion of the steam introduction pipe is slidably connected in the axial direction via the airtight ring. Turbine steam introduction pipe. 2. In the steam introduction pipe according to claim 1,
A steam introduction pipe for an ultra-high-temperature steam turbine, characterized in that an airtight ring having a U-shaped cross section and press-welded by a ring nut is disposed at the fitting part between the cup-shaped seven flange part and the external casing.