JPS61129409A - Supervisory method of steam turbine nozzle blade - Google Patents

Abstract

PURPOSE:To enable the generation of erosion to be easily estimated, by previously catching a condition of steam in the vicinity of a nozzle box in a steam turbine respectively when it is in a sound condition and when the erosion is generated and comparing the condition of steam with the actual condition of steam. CONSTITUTION:A steam turbine, providing a moving blade inlet pressure detecting seat 18 communicating with the downstream side of a nozzle box 4, supervises the pressure P1 in that part. This pressure P1 changes in a different pattern in accordance with an increase of load for when the steam turbine is in a sound condition with no erosion and when an erosion is generated. Hereupon the pressure P1 is set to an alarm value PANN, not causing an obstacle for operation but necessary to take care, and a stopping value Pmax immediately stopping the turbine. And the steam turbine, comparing these control reference values PANN and Pmax with the value of the present moving blade inlet pressure P1, is controlled so as to generate an alarm or stop operation of the turbine in accordance with the compared result.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for monitoring the state of erosion and growth of nozzle blades provided in a nozzle box of a steam turbine.

[Background of the invention]

Recently, the mainstream of newly constructed power plants is large-scale and nuclear power plants. Thermal power plants make full use of the latest technology,
The plant is highly efficient and has good operating characteristics, and the steam turbine nozzle blades are placed under extremely severe conditions in terms of erosion, as they are started and stopped every day and on weekends.

FIG. 10 is a longitudinal cross-sectional view of the vicinity of the high-pressure first stage where the above-mentioned erosion occurs most severely.

2 is the rotor, 2 is the internal casing, and 3 is the main steam inlet. A cross section showing the arrangement of the main steam population 3 is shown in FIG.

Steam flows from the above-mentioned main steam port 3 through the nozzle box 4 shown in FIG. FIG. 12 is an enlarged view of the vicinity of the nozzle box 4 mentioned above. FIG. 13 is an explanatory diagram of the arrangement of the nozzle box 4, in which four steam chambers 1o are provided corresponding to the four nozzle boxes 4, each communicating with the first to fourth control valves 6 to 9. are doing.

Arrows 5 in FIG. 12 indicate steam streamlines. A in Figure 12 of the book
-A cross section is shown in FIG. The steam flow passes through the bridge and nozzle blades 13 shown in FIG. 14, and flows to the rotor blades. Accompanied by this steam flow 5, scale from the boiler flows into the turbine, and at the same time, an adverse effect on the turbine occurs in the form of two α-jones of the nozzle blades.

The nozzle blades 13 arranged as shown in FIG. 14 are adjusted to an appropriate throat S shown in FIG. 15, and serve to effectively supply steam to the rotor blades. As mentioned above, since the steam flow 5 supplied from the boiler contains scale from the boiler, the nozzle blade erosion part 14 shown in FIG. 16 occurs, and an unstable nozzle throat structure is formed. be done.

FIG. 17 is a chart showing changes in steam pressure due to changes in turbine load. The solid line 15 shows the high-pressure first stage rotor blade outlet pressure in an example of a healthy steam turbine, and the inlet pressure (
design value) is indicated by a broken line 16.

When erosion occurs in the nozzle blades of this steam turbine, the rotor blade inlet pressure changes as shown by the chain line 17.

The pressure difference between the exit and entry portions of the rotor blades in the steam turbine of this example will be described next.

For example, the pressure difference at 4'1 atomization with the adjustment valve open for 4 atomization is the design value ΔP0, and the pressure difference when nozzle blade erosion occurs is ΔP1'.The increase rate of nozzle throat S1 When the pressure difference is 40 inches, the pressure difference ratio becomes 2 to 3 times higher, further accelerating nozzle blade erosion. As a result, if only the erosion of the nozzle blades increases, the steam to the rotor blades assembled on the rotor increases, and the shock may cause the worst situation, such as the rotor blades breaking and flying off.

In the prior art, no separate consideration was given to monitoring the state of wear and tear of the nozzle box of the steam turbine described above.

Publicly known literature, Thermal Power Generation Technology Association “Turbine and Generator Course”
P63 also does not address the occurrence and growth of erosion in nozzle blades as a checkpoint. In the above-mentioned known documents, I would say that the first
Although the rotor blade outlet temperature conversion seat 19 and rotor blade inlet pressure detection seat 20 shown in Figure 0 are described, these descriptions are related to operational control such as monitoring thermal stress and are not used to check the wear situation. has not been touched.

In other words, the effect of erosion on the nozzle blade on the high-pressure first stage is a change in metal temperature.

Even if changes in steam pressure are derived, they are used only as changes for operational control, and are not used to monitor wear and tear.

However, it goes without saying that it would be extremely useful for safety management if erosion could be monitored by understanding the relationship between these metal temperature changes, pressure changes, and the nozzle blades.

[Object of the Invention] The present invention was made in view of the above-mentioned circumstances, and it is possible to easily and safely check the occurrence and progress of erosion in the nozzle vanes of the nozzle box of a steam turbine while continuing the operation of the steam turbine. The aim is to provide a method that can be used to monitor

[Summary of the invention]

To briefly explain the basic principle of the method of the present invention created to achieve the above object, the present invention utilizes the fact that the temperature and pressure of steam change due to the occurrence of erosion, as explained with reference to Fig. 17. and the temperature of the steam and
Alternatively, the generation and progress of erosion can be estimated by measuring pressure.

In order to achieve the above objective (monitoring of erosion) based on the above principle, the monitoring method of the present invention monitors the steam conditions near the nozzle box of a steam turbine in a healthy state, and the nozzle box when erosion occurs. The steam conditions in the vicinity are known in advance, the steam conditions near the nozzle box of the steam turbine in operation are detected, and the detection results are compared with the previously known steam conditions to determine the occurrence and growth of erosion. Estimate the state of.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG.

As shown in FIG. 1, a rotor blade outlet pressure detection seat 18 communicating with the lower fi side of the nozzle box 4 is provided to monitor the pressure P1 in this portion. This pressure P1 corresponds to the rotor blade inlet pressure curve 16 shown in FIG. 17 when the steam turbine is healthy and there is no erosion, but as erosion occurs and progresses, the rotor blade inlet pressure at the time of erosion Approaching curve 17.

This pressure is monitored at the control valve steam chamber 6 as shown in Figure 2.
．． By installing it every 7.8.9, more minute monitoring is possible.

An example of a specific management method recommended for monitoring the pressure P works when the present invention is applied will be explained.

Regarding the pressure P1, an alarm value PANN indicating that there is no problem with operation but requires caution, and a stop value Pmax that immediately causes the turbine to stop are set.

These management standard values PANN! When setting PmaX, it may be set based on whether the stress in the rotor blade enters a dangerous range due to an increase in the pressure difference caused by erosion.

FIG. 3 shows a block diagram for controlling the operation by comparing the values of the rotor blade entry pressure P based on the control reference values set as described above. If the rotor blade entry pressure P is larger than the stop value Pmax, the turbine must be stopped and a release inspection performed. If it is less than Pmax, it is compared with the alarm value PANN, and if it is larger than % PANN, an alarm is generated, the inlet pressure change rate is checked, and bank data for future countermeasures is provided.

FIG. 4 shows an embodiment different from the above. A rotor blade outlet temperature variation sensor 19 is provided to detect the rotor blade outlet temperature T2, and this is detected by the sixth
The state of occurrence of erosion is determined by comparing it with the load-temperature curve shown in the figure. In FIG. 6, the solid line 21 is the rotor blade outlet temperature (design value) of a healthy steam turbine, and the broken line 22 is the rotor blade outlet temperature when erosion occurs.

FIG. 6 shows a further different embodiment. A rotor blade outlet pressure detection force is provided to detect the rotor blade outlet pressure P2, and this is compared with the load-pressure curve shown in FIG. 7 to determine the state of occurrence of erosion. In FIG. 7, the solid line 15 is the rotor blade outlet pressure (design value) of a healthy steam turbine, and the broken line 23 is the rotor blade outlet pressure when erosion occurs.

FIGS. 8 and 9 each show further different embodiments,
FIG. 8 shows the temperature T3 of the second shaft packing part being detected by the second shaft packing middle part temperature detection seat 24, and FIG. 9 shows the second shaft packing part pressure P3 being detected by the second shaft packing part pressure detection seat 5. It is detected by The steam in the second shaft packing section is at the same level as the steam after the first stage.
The temperature and pressure before and after the nozzle blade 201 are shown in Figures 5 and 7.
Since the curves are at the same level as those shown in the figure, the state of occurrence of erosion can be estimated by comparing each detected value with these curves in the same manner as in the embodiments shown in FIGS. 4 and 6.

〔Effect of the invention〕

As detailed above, according to the monitoring method of the present invention, the occurrence of erosion in the nozzle blades of the nozzle box can be detected while the steam turbine continues to operate.

It has an excellent practical effect of being able to easily and safely estimate the progress state, and contributes to improving the safety management of steam turbines. It's large.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of the installation position of pressure detection dust for monitoring in one embodiment of the method of the present invention, and FIG. 3 is a diagram of the monitoring system in the above embodiment. 4 and 5 are explanatory diagrams of an embodiment different from the above, and FIG.
7 and 7 are explanatory diagrams of further different embodiments, and FIGS. 8 and 9 are explanatory diagrams of still further different embodiments. Figure 10 is a vertical cross-sectional view showing the vicinity of the high-pressure first stage of the steam turbine, Figure 11 is a cross-sectional view of the same, Figure 1 is an enlarged view of the vicinity of the nozzle box in Figure 1O, and Figure 13 is an explanatory diagram of the arrangement of the nozzle box. , Fig. 14 is a sectional view taken along line A of Fig. n, Fig. 15
The figure is an explanatory diagram of the shape and arrangement of nozzle blades that have not caused erosion, and FIG. 16 is an explanatory diagram of the shape of a nozzle that has experienced erosion. FIG. 17 is a chart showing the relationship between pressure and load in the high-pressure first stage of the steam turbine. DESCRIPTION OF SYMBOLS 1... Rotor, 2... Internal casing, 3... Main steam inlet, 4... Nozzle box, 5... Steam streamline, 6... First regulating valve, 7... Second control valve, 8...
・Third control valve, 9...Fourth control valve, lO...Steam room, 11...Steam room partition, 12...Bridge, 13.
... Nozzle Jil, 14... Nozzle blade erosion part, 15... Moving blade outlet pressure, 16... Moving blade inlet pressure (
Design value), 17... Moving blade inlet pressure during nozzle blade erosion, 18... Moving blade outlet pressure detection seat, 19... Moving blade outlet warm wheel detection seat, addition... Moving blade specific pressure Detection locus, 21
... rotor blade outlet temperature (design value), 22 ... rotor blade outlet temperature at the time of nozzle blade erosion, field ... rotor blade outlet pressure at the time of nozzle blade erosion, for... 2nd shaft 7 top packing section Temperature detection seat, 3...Second shaft gasket pressure detection seat. Agent Tadashi Akimoto Actual Figure 4 Figure 5 □ψ Clause (High) Figure 6 Figure 7 □ Member □ (Mu) Figure 8 Public; S9 Figure 10 Figure 12 Figure 15 Figure S Figure 16 Figure 17 m-Prayer □ (sub.

Claims (1)

[Claims] 1. The steam conditions near the nozzle box of the steam turbine in a healthy state and the steam conditions near the nozzle box when erosion occurs are known in advance, and the nozzle of the steam turbine during operation is determined in advance. A method for monitoring a steam turbine nozzle blade, comprising detecting steam conditions near the box and comparing the detection results with the previously known steam conditions to estimate the state of erosion occurrence and growth. . 2. The steam turbine nozzle blade according to claim 1, wherein the steam condition is at least one of steam temperature and steam pressure at the outlet of the stator blade of the steam turbine. monitoring method. 3. The steam turbine nozzle blade according to claim 1, wherein the steam condition is at least one of steam temperature and steam pressure at the inlet portion of the rotor blade of the steam turbine. monitoring method. 4. The steam turbine nozzle blade according to claim 1, wherein the steam condition is at least one of steam temperature and steam pressure at the outlet of the rotor blade of the steam turbine. monitoring method. 5. Claim 1, wherein the steam condition is at least one of the steam temperature and steam pressure of the second shaft packing portion of the steam turbine.
A method for monitoring a steam turbine nozzle blade as described in .