JPS61132704A - Nozzle box of steam turbine - Google Patents

Abstract

PURPOSE:To facilitate the process of replacing a nozzle plate, by fitting and holding the nozzle plate caught between inner and outer rings of a nozzle diaphragm, into the outlet of a nozzle box body. CONSTITUTION:A nozzle plate 15 is caughted between the inner ring 16 and the outer ring 17 of a nozzle diaphragm. Radially extending annular projections 16a, and 17a are formed on the inner ring 16 and outer ring 17 respectively. Annular grooves 18, and 19 are formed in a nozzle box body 10 the nozzle plate 15 is held by fitting the annular projections 16a and 17a into the annular grooves 18 and 19. Because way of attachment is just is just a process of fitting. the nozzle plate 15 can be easily replaced.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a nozzle box for a steam turbine, and in particular, reliability is improved by mounting the nozzle plate so as not to form an integral groove with the main body container side. Regarding the nozzle box that can be used to improve the steam flow.

(Technical Foreword of the Invention and Problems thereof) The first stage of a steam turbine is exposed to extremely harsh operating conditions. In particular, when the nozzle is closed and controlled, the pressure difference in the low load range is also extremely large. In addition, there is a lot of steam leakage from the gap between the static section and the rotating section, and this has a large effect on turbine performance. Furthermore, the deflection due to thermal expansion and high pressure difference is large, which poses a major obstacle to operation.

Therefore, a nozzle box structure is often used in the first stage of recent steam turbines. As shown in FIG. 6, this nozzle box consists of a sealed main body container 1 having an annular cavity inside, and a nozzle plate 2 for a high-pressure first stage attached to the outlet of this main container 1. It is fixed to the turbine casing side via a key (not shown). Further, the main body container 1 is composed of a nozzle ring 3 that holds a nozzle plate 2, and a nozzle box box 1-5 that has a steam chamber 4 formed from an annular cavity. The nozzle plate 2 and the nozzle ring 3 are integrally connected by welding, and the nozzle ring 3 and the nozzle box 4 are also integrally welded. Furthermore, the nozzle plate 2 has weldability.

In consideration of corrosion resistance, 120r base steel is usually used.

However, even if the material of the nozzle plate is selected in this way,
Erosion can often occur on the nozzle plate due to the impact of solid particles contained in the steam.

In particular, in supercritical pressure units, iron solid particles consisting of iron oxide are found in the seventh layer from flaking on the inner surface of the boiler tube.
As shown by the arrow A in the figure, the deformation and cracks often occur in the nozzle plate 2 due to cutting and collision phenomena, as shown by the dashed line in FIG.

If such erosion of the nozzle plate occurs, as mentioned above, the entire nozzle box is made into a welded integral structure, so by performing reinforcement welding on the nozzle plate, the entire nozzle box will be thermally affected. , the entire nozzle box had to be annealed. When such annealing treatment was performed several times, the strength of the nozzle box deteriorated significantly, and it was necessary to replace it with a new one. As a result, in the past, repair costs were high, and the steam turbine had to be forcibly shut down, resulting in a power outage.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, the present invention provides a steam turbine nozzle box that can overcome the drawbacks of the conventional steam turbine nozzle box as described above and improve the reliability and replaceability of the nozzle plate. With the goal.

[Summary of the invention]

In order to achieve the above object, the nozzle box for a steam turbine according to the present invention has a nozzle plate sandwiched between a nozzle diaphragm outer ring and a nozzle diaphragm inner ring, and these two rings are fitted into an outlet nozzle portion of a main body container. The main body container side and the nozzle plate are not integrally constructed.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIGS. 1 and 2, the nozzle box chest 10 constituting the main container portion of the nozzle box has a steam chamber 11 made of an annular cavity inside, and a plurality of The nozzle bridge 12 extends radially. This nozzle bridge 12 supports the nozzle box chest 10 sufficiently against the differential pressure between the inside and outside.

Roughly speaking, a nozzle plate 13 is attached to the tip nozzle portion constituting the outlet portion of the nozzle box chest 10. This nozzle plate 13 consists of an inlet nozzle plate 14 and an outlet nozzle plate 15 which are arranged in series in the steam flow direction (arrow C). Of these, the inlet nozzle plate 14 is integrally fixed to the inner passage side of the nozzle box chest 10 by welding or the like. On the other hand, the outlet nozzle plate 15 is held between an annular nozzle diaphragm inner ring 16 and a nozzle diaphragm outer ring 17, and is fitted and fixed to the nozzle box chest 10 side via these two rings 16 and 17. That is, the two wheels 16 and 17 are formed with annular protrusions 16a and 17a extending in the radial direction, and the nozzle box chest 10 side is provided with an annular groove that accommodates the annular protrusions 16a and 17a. 18,19/);
It is formed.

As shown in Fig. 3, the two wheels 16 and 17 are installed by inserting them into the upper and lower halves separately as shown by the arrows.
Figure 3 shows the upper half. ), each steam chamber 11 as shown
(Two of the upper half are shown in the figure.) Roughly speaking, both wheels 16 and 17 are fixed in the circumferential direction by one means shown in Fig. . In addition, a key groove 21 extending in the axial direction is recessed in the horizontally divided end faces of the upper half side and the lower 1' side of the nozzle box chest 10, and a key 22 is fitted into this key groove 21 to lock the key. Bolts are tightened at both ends of the nozzle 22 to prevent the entire temporary nozzle from falling off.

In the steam turbine nozzle box having such a configuration, the outlet nozzle plate 15 is not integrated with the main body. Therefore, non-weldable materials can be employed, while the nozzle plate can be removed and replaced at will.

In the embodiment shown in FIG. 5, the nozzle diaphragm outer ring 27 is housed in a wide groove 29 provided on the side of the nozzle box chest 10, and the nozzle diaphragm outer ring 26 is placed on the tip surface of the nozzle box chest 10. Tightening is fixed in the axial direction by bolts 30.

An adjustment key 31 is accommodated in the groove 29 on the front side of the nozzle diaphragm outer ring 27, and this adjustment key 31
Tightening is fixed in the radial direction by bolts 32 on the nozzle box chest 10 side. The adjustment key 31 has a width dimension sufficient to press the nozzle diaphragm outer ring 27 in the axial direction, but is formed with a small thickness so as to form a predetermined maximum gap with the nozzle diaphragm outer ring 27 in the radial direction. It has become. This gap allows the entire nozzle plate to freely expand and contract in the radial direction, and prevents unnecessary stress from being generated on the bolt 30, which is subjected to a strong steam action force in the axial direction.

〔Effect of the invention〕

As described above, according to the present invention, since the nozzle plate is fitted onto the main body side and is not attached integrally by welding or the like, only the nozzle plate can be easily and inexpensively replaced. Furthermore, it is possible to select a material for the nozzle plate that has excellent corrosion resistance, such as Hiramic, but cannot be welded. Hence the durability of the nozzle box.

Reliability can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory longitudinal cross-sectional view of a nozzle box in one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line B-B in FIG. 1, and FIG.
Figures 4 and 4 are front and perspective views showing the assembled state, Figure 5 is a vertical cross-sectional view corresponding to Figure 1 showing another embodiment of the present invention, and Figure 6 is a conventional nozzle box. 7 and 8 are horizontal cross-sectional views showing the state of particle collision and damage to the nozzle plate. 10... Nozzle box chest (main container), 11
...Steam room, 12...Nozzle bridge, 13...
Nozzle plate, 14... Inlet nozzle plate, 15... Outlet nozzle plate, 16.26... Nozzle diaphragm inner ring, 1
7゜27...Nozzle diaphragm outer ring, 16a, 17
a... Annular convex portion, 18.19... Annular groove. Applicant's agent Kiyoshi Inomata Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a steam turbine nozzle box that is used in the high-pressure first stage of a steam turbine and has a number of nozzle plates arranged at the outlet of a main body container; the nozzle plates are sandwiched between a nozzle diaphragm inner ring and a nozzle diaphragm outer ring. Also, a nozzle box for a steam turbine, characterized in that these two wheels are fitted into an outlet portion of a main container to hold a nozzle plate.