JPH1089942A - Method for measuring elongation of turbine stacking bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which the elongation of a tightened turbine stacking bolt can be measured in a short time. SOLUTION: In a method for measuring elongation of turbine stacking bolt, the relation between the difference between measured size values of bolts from an ultrasonic thickness indicator 3 and a micrometer 2 and the elongation of the bolts is calculated in advance and the size of a relevant tightened bolt 1 is measured by using the thickness indicator 23 and micrometer 2, and then, the difference between the measured values of the size from the thickness indicator 3 and micrometer 2 is calculated. Then the elongation of the bolt 1 is measured based on the relation between the difference between the measured size values of bolts from the thickness indicator 3 and micrometer 2 and the elongation of the bolts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a bolt elongation of a stacking bolt of a compressor rotor and a turbine rotor having a stacking structure of a gas turbine for industrial use, aeronautics, etc., and more particularly to a method of applying stress to the stacking bolt. The present invention relates to a method of measuring the amount of elongation of a bolt using an ultrasonic thickness gauge by applying a characteristic that a velocity of an ultrasonic wave passing through a stacking bolt material is different between when a stress is applied and when a stress is not applied. .

[0002]

2. Description of the Related Art In order to measure the elongation of a conventional bolt, a micrometer or an ultrasonic thickness gauge is used before and after tightening a gas turbine rotor with a stacking bolt, that is, before and after the bolt elongates. The dimensions of the bolt before and after tightening were measured, and the amount of elongation of the bolt was calculated from the dimensional difference before and after tightening.

[0003]

In the prior art, the length of the bolt must be measured both before and after the bolt is tightened. However, if the bolts are tightened after running the turbine for a long period of time, etc., and it is necessary to confirm that there is no loosening, the turbine must be re-disassembled. However, bolt elongation measurement was practically impossible. Therefore, a method of measuring the amount of elongation of the bolt in a short time has been desired.

[0004]

The present invention utilizes the principle of the sonic elasticity effect that when a bolt is tightened, a tensile stress is generated inside the bolt, and when the tensile stress is generated, the speed of sound is reduced. In addition, when an ultrasonic wave is caused to flow through a substance, a characteristic is used in which a longitudinal wave and a transverse wave of the ultrasonic wave are transmitted at different speeds in the substance.

When measuring the elongation of a bolt based on the relationship between the elongation of the bolt and the difference between the dimension of the bolt measured by an ultrasonic thickness gauge and the actual dimension of the bolt measured by a micrometer, the turbine rotor is currently tightened, Prepare a bolt of the same dimensions and the same material as the stacking bolt whose elongation is to be measured, and perform a mock-up test. The length of the bolt when the bolt is gradually tightened is measured with both an ultrasonic thickness gauge and a micro gauge, and the elongation of the bolt is measured at the same time. Next, the relationship between the dimension measurement difference between the ultrasonic thickness gauge and the micro gauge and the amount of elongation of the bolt is related by a graph or the like on which a characteristic curve is drawn.

[0006] Subsequently, for a stacking bolt of an actual machine in which the turbine rotor is currently tightened and the amount of elongation of the bolt is to be measured from now on, the same method as in the mock-up test, that is, both the ultrasonic thickness gauge and the micrometer are used. Measure the length of the bolt, and calculate the dimensional difference between the two.

[0007] The data of the dimensional difference is fitted to a graph showing the relationship between the dimensional measurement difference between the ultrasonic thickness gauge and the micrometer and the amount of bolt elongation obtained in the mock-up test. Ask for.

When measuring the amount of elongation of a bolt based on the relationship between the amount of elongation of the bolt and the difference between the reading of the longitudinal wave and the transverse wave of the ultrasonic thickness gauge, the same dimensions and the same material as the stacking bolt whose elongation is to be measured are used. Prepare a bolt and perform a mock-up test. The length dimension of the bolt when the bolt is gradually tightened is measured with an ultrasonic thickness gauge in both longitudinal and transverse waves, and simultaneously the elongation of the bolt is measured. Next, the relationship between the dimensional measurement difference between the longitudinal wave and the transverse wave measured by the ultrasonic thickness gauge and the amount of elongation of the bolt is related by a graph or the like in which a characteristic curve is drawn.

Next, for a stacking bolt of an actual machine for which the turbine rotor is currently tightened and the amount of elongation of the bolt is to be measured, a longitudinal wave and a transverse wave are measured in the same manner as in the mock-up test, that is, using an ultrasonic thickness gauge. The length of the bolt is measured in both cases, and the dimensional difference between the two is calculated.

The data of this dimensional difference was fitted to a graph showing the relationship between the dimensional measurement difference of both longitudinal and transverse waves measured by an ultrasonic thickness gauge, obtained in a mock-up test, and the amount of elongation of the bolt, Obtain the bolt elongation.

In this method, since only the ultrasonic thickness gauge is used, it is not necessary to measure the actual dimensions of the bolt with a micrometer or the like. The elongation amount can be measured, and the measurement time can be greatly reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

When measuring the amount of elongation of a bolt based on the relationship between the amount of elongation of the bolt and the difference between the size of the bolt measured by an ultrasonic thickness gauge and the actual size of the bolt measured by a micrometer, first, the gas turbine rotor is mounted on the turbine rotor. In
A bolt 1 having the same dimensions and the same material as the stacking bolt whose elongation is to be measured is manufactured, and a mock-up test is performed.
While gradually tightening the bolt, the length of the bolt is measured by each method using the micrometer 2 and the ultrasonic thickness gauge 3. At the same time, measure the elongation of the bolt. FIG. 2 is a graph showing the relationship between the difference between the lengths measured by the micrometer 2 and the ultrasonic thickness meter 3 and the elongation of the bolt.

Subsequently, the measurement is carried out with the stacking bolts of the actual machine in which the turbine rotor is currently tightened and the amount of elongation of the bolts is to be measured. In the turbine rotor portion of the gas turbine, the 2-3 stage spacer 4, the third stage wheel 5, and the rear stub shaft 6 are connected by stacking bolts 7. With the bolt tightened, the length of the stacking bolt is measured by a micrometer 8 having a special shape. The length of the same bolt is measured by the ultrasonic thickness gauge 3. The difference between the dimension measured by the micrometer 8 and the length dimension measured by the ultrasonic thickness gauge 3 is calculated.

Subsequently, the dimensional difference obtained from the lengths of the micrometer and the ultrasonic thickness gauge in the actual machine is compared with a graph shown in FIG. 2 created by a mock-up test, and the amount of elongation of the bolt is calculated from the graph.

When measuring the amount of elongation of the bolt from the relationship of the amount of elongation of the bolt with respect to the difference between the reading of the longitudinal wave and the transverse wave of the ultrasonic thickness gauge, the same as in the above-described embodiment, the same as the stacking bolt whose elongation is to be measured. A bolt 1 of the same dimensions and the same material is manufactured, and a mock-up test is performed. In this case, instead of using the micrometer 2, instead of using the micrometer 2, the length of the bolt is measured using both the longitudinal wave and the transverse wave using the ultrasonic thickness gauge 3, and the elongation of the bolt is measured at the same time. FIG. 3 is a graph showing the relationship between the reading difference obtained from the measurement results of the longitudinal wave and the transverse wave measured by the ultrasonic thickness gauge 3 and the amount of elongation of the bolt. Subsequently, similarly to the above-described embodiment, the measurement is performed using the stacking bolts of the actual machine in which the turbine rotor is currently tightened and the elongation of the bolts is to be measured. Then, the reading difference obtained from the measurement results of the longitudinal wave and the transverse wave of the ultrasonic thickness gauge in the actual machine was compared with the graph of FIG. 3 created by the mock-up test,
The bolt elongation is calculated from the graph.

[0017]

According to the present invention, the amount of elongation of a bolt can be calculated in a short time without loosening the bolt.
As a result, the elongation of the bolt can be managed over time, and the operation and management of the bolt elongation can be performed without sacrificing economic efficiency.

[Brief description of the drawings]

FIG. 1 is a procedure for measuring a bolt length based on the results of a micrometer and an ultrasonic thickness meter in a mock-up test according to one embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a difference between lengths measured by a micrometer and an ultrasonic thickness gauge and an elongation amount of a bolt.

FIG. 3 is a graph showing a relationship between a difference between lengths of longitudinal waves and transverse waves measured by an ultrasonic thickness gauge and an elongation amount of a bolt.

FIG. 4 shows a measurement procedure using a micrometer in an actual machine in a turbine rotor portion of a gas turbine.

FIG. 5 is a turbine rotor part of a gas turbine.

FIG. 6 is an enlarged view of a stacking bolt section in FIG. 5;

[Explanation of symbols]

1: Mock-up test bolt, 2: Micrometer,
3 ... Ultrasonic thickness gauge, 4 ... 2-3 step spacer, 5 ... 3 step wheel, 6 ... rear stub shaft, 7 ... stacking bolt, 8 ... micrometer with special shape.

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[Procedure amendment]

[Submission date] December 2, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsuguaki Koga 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Yoshihiro Tsukahara 3-chome, Sachimachi, Hitachi-shi, Ibaraki No. 1 Inside Hitachi, Ltd. Hitachi Plant

Claims (2)

[Claims] In a gas turbine rotor having a stacking structure, the speed of ultrasonic waves passing through a stacking bolt material differs between when a stress is applied to a stacking bolt and when no stress is applied. Based on the relationship between the bolt's elongation and the difference between the bolt's dimensions measured by an ultrasonic thickness gauge and the micrometer's actual dimensions including the effects of internal stress when gradually tightening the bolts, A method for measuring the amount of elongation of a turbine stacking bolt, wherein a method of calculating the amount of elongation by measuring the dimensions of a stacking bolt in a tightened state. 2. In the measurement by the ultrasonic thickness gauge,
Applying the characteristic that the speed of longitudinal wave and shear wave of ultrasonic wave passing through the bolt material is different, tightened state based on the relationship between the difference of reading of longitudinal wave and shear wave of ultrasonic thickness gauge and the amount of elongation of bolt A method for measuring the amount of elongation of a turbine stacking bolt, which comprises calculating the amount of elongation by measuring the size of the stacking bolt.