JPS61231434A - Apparatus for testing stress corrosion cracking of turbine - Google Patents

Abstract

PURPOSE:To make prevention and maintenance certain by enabling the reproduction of the test in an actual environment turbine and quantitatively grasping a crack propagation speed, by arranging a test piece comprising the same material quality as the a part apprehensive of the generation of stress corrosion cracking in the monitoring capsule arranged in the bypass piping arranged in stream extracting piping. CONSTITUTION:Bypass piping 3 is arranged to the steam extraction piping 2 connected to a turbine 1 and a stress corrosion cracking testing apparatus 4 is arranged in piping 3. The testing apparatus 4 is constituted by fixing a monitoring capsule 11 having a plurality of steam passing orifices 11A to the inner wall of the bypass piping 3 by bolts 12. One or plural test pieces among test pieces 13a-13c is received in the capsule 11 and contacted with a steam stream extracted at an arbitrary position to generate a crack which is, in turn, observed and measured. Each of the test pieces 13a-13c is formed of the same material quality as a part apprehensive of stress corrosion cracking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stress corrosion cracking testing device for a turbine for investigating the cause of stress corrosion cracking occurring in a part of the turbine.

[Prior art and problems to be solved by the invention] At present, the cause of stress corrosion cracking (hereinafter referred to as SCC) that occurs in turbines has not been clearly elucidated. That is, SCC occurs due to only three combinations: material, stress, and environment.

these? The material of the two factors can be clarified by observing and measuring the material of the turbine.
Regarding stress, with the recent development of stress analysis methods such as the finite element method, it is now possible to estimate the temperature and pressure of areas where SCC is likely to occur.

However, it has not been possible to clarify this regarding the harmful substances contained in SCCEG. For this reason, there is no choice but to estimate the amount of harmful SCC substances that occur in the turbine environment, and it has been considered impossible to carry out experimental SCC reproduction tests.

Furthermore, it is impossible to measure the propagation speed of cracks that occur in turbines because it is not possible to know the point at which cracks occur, and furthermore, it is not possible to measure the propagation speed of cracks that occur in turbines separately. Furthermore, because the conventional equipment was installed inside the turbine, there was a problem in that observation and measurements could only be made during an overhaul.

The present invention has been made based on the above points, and its purpose is to enable the implementation of SCC reproduction tests in real environment turbines, quantitatively grasp the crack propagation speed, and prevent stress corrosion cracking. An object of the present invention is to provide a stress corrosion cracking testing device for a turbine that can ensure maintenance.

[Means for Solving the Problems] That is, the stress corrosion cracking testing device for a turbine according to the present invention extracts the steam flow of an arbitrary turbine to the outside of the turbine through a steam extraction pipe, and connects a bypass pipe to the steam extraction pipe. A monitoring capsule with a steam passage hole is installed in this bypass piping, and a test piece made of the same material as the material of the part where stress corrosion cracking is concerned is housed in the monitoring capsule. It is characterized by the fact that

[Function] In other words, a monitoring capsule is installed in the bypass pipe installed in the steam extraction pipe, and a test piece is made of the same material as the part of the monitoring capsule where stress corrosion cracking is likely to occur. By installing a test piece, it is possible to take out a test piece at any time and observe and measure it, without being limited to the time of turbine open inspection.

[Effects of the Invention] Therefore, a monitoring capsule having a steam passage hole is installed in the bypass piping from the steam extraction piping that extracts steam from an arbitrary turbine, and a monitoring capsule having a steam passage hole is installed in the monitoring capsule in the area where stress corrosion cracking is concerned. By accommodating test pieces made from the same material as the material, it becomes possible to carry out SCC reproduction tests in the actual turbine environment, and it is possible to quantitatively understand the crack propagation speed and incubation period. Preventive maintenance against stress corrosion cracking can be ensured.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 11. Reference numeral 1 in FIG. 1 indicates a turbine, to which a steam extraction pipe 2 is connected. A bypass pipe 3 is provided in the steam extraction pipe 2. A stress corrosion cracking test device 4 is installed inside the bypass pipe 3. In addition, the reference numeral 5 in the figure is the turbine rotating part, and the reference numeral 6 is the turbine rotating part.
1 and 2 respectively indicate the turbine stopped portions.

Next, the structure of the stress corrosion cracking testing apparatus 4 will be explained. FIG. 2 is an enlarged view showing the installed state of the stress corrosion cracking test device 4, in which the monitoring capsule 11 having a plurality of steam passage holes 11A is fixed to the inner wall of the bypass pipe 3 with bolts 12. Note that instead of fixing with the bolts 12, it may be fixed by welding. Inside the monitoring capsule 11 is a test piece 13a as shown in FIG.
, 13b and 13c.

The test pieces 11a, 11b, and 11C are brought into contact with the extracted steam flow at arbitrary positions, thereby generating cracks, which are observed and measured.

The test pieces 13a, 13b and 13C are made of the same material as the part where SCC is a concern,
FIGS. 4 to 6 each show an enlarged view. and test piece 1
Test pieces 3a and 13b are used to measure crack propagation speed, and test piece 13c is used to observe SCC occurrence. Note that the reference numeral 14 in FIGS. 4 and 5 indicates the generated crack.

Next, the stress intensity factor (
The relationship between K) and crack propagation velocity (da/dt) will be explained with reference to the seventh factor and FIG.

FIGS. 7 and 8 are diagrams showing the relationship between the stress intensity factor (K) on the horizontal axis and the crack propagation velocity (da/dt) on the vertical axis. First, as shown in Fig. 7, the test piece 13a is a type in which the stress intensity factor (K) decreases as the crack progresses (K-variable test piece) (indicated by arrows A and B in the figure). Parts where length measurements can be made frequently,
Alternatively, it is advantageous to use it in areas where the propagation speed of cracks is extremely slow. In addition, as shown in Figure 8, the test piece 13b is a type that maintains a substantially constant stress intensity factor (K) even if a crack develops (K-shaped test piece) (indicated by point C in the figure), and has a long-term The crack propagation velocity (da/dt) in the steam extracted from the steam flow of any turbine 1 in the actual plant shown in FIG. A correlation curve between the stress intensity factor (K) and the stress intensity factor (K) can be obtained.Furthermore, the characteristics shown in Fig. 10 can be obtained using the test piece 13C for observing the occurrence of SCC. , the vertical axis is the peak stress (σ/σy), and it is a diagram showing the change in peak stress over time.From this Figure 10, it is possible to know the stress in the part where stress corrosion cracking is most likely to occur. The occurrence behavior of SCC can be understood by this.

Next, referring to FIG. 11, the monitoring capsule 8
Explain that the installation and removal of the turbine will not affect the turbine system. An on-off valve 21 is inserted into the steam extraction pipe 2, and bypass valves 22A and 22B are inserted into the bypass pipe 3, respectively. In other words, when attaching and detaching the monitoring capsule 8, the procedure shown in Fig. 11 (
As shown in A), the bypass valves 22A and 22B are closed (shown in black in the figure). Therefore, installation and removal work will not affect the turbine system.

In addition, when steam is extracted, the on-off valve 21 and the bypass valves 22A and 22B are operated in FIGS. 11(B) to (D).
), open and close as appropriate.

[Brief explanation of the drawing]

Wow. ♂t□11 figure. *,! 1゜Examples and illustrations. Figure 1 shows the stress corrosion cracking test device installed from the steam extraction pipe that extracts steam from the turbine to the bypass pipe, Figure 2 is a plan view of the stress corrosion cracking test equipment, and Figure 3 is a sectional view taken along ■-■ in Fig. 2, Figs. 4 to 6 are plan views of the test piece, and Figs. 7 to 9 are crack propagation speeds (D
Diagram showing the relationship between A/DT) and stress intensity factor (K), 1st
Figure 0 shows the change in peak stress over time, Figure 11 (A)
FIGS. 3A to 3D are diagrams showing the open and close states of the on-off valve and the bypass valve when attaching and detaching the monitoring capsule. DESCRIPTION OF SYMBOLS 1... Turbine, 2... Steam extraction piping, 3... Bypass piping, 4... Stress corrosion cracking test device, 5...
Turbine rotating part, 6...Turbine stationary part, 11...
... Monitoring capsule, 11A... Steam passage hole, 13a, 13b, 13c... Test piece. Applicant's Sub-Attorney Patent Attorney Takehiko Suzue No. 1 (! )k%m jig
Time 7-rath (A) ((j (D)

Claims (1)

[Claims] The steam flow of any turbine is extracted to the outside of the turbine through a steam extraction piping, a bypass piping is arranged in the steam extraction piping, a monitoring capsule having a steam passage hole is installed in the bypass piping, and a monitoring capsule having a steam passage hole is installed in the bypass piping. A stress corrosion cracking testing device for a turbine, characterized in that a test piece made of the same material as that of a portion where stress corrosion cracking is concerned is housed in a capsule.