JPH08219751A - Method for measuring thickness of refractories using elastic wave - Google Patents

Abstract

PURPOSE: To accurately measure the thickness of a fire brick lined to the inside of an iron skin from the surface thereof using elastic wave by measuring a vibration response frequency spectrum obtained by removing a specific frequency from the response to a vibration applied to the iron skin. CONSTITUTION: A vibration is applied, by means of a hammer 4, to the surface of an iron skin 1 above a fire brick 3 of which the thickness is measured. A hard plastic impact chip 5 is fixed to the tip of the hammer 4 in order to generate an elastic wave in the frequency band required for measurement. An impact strength meter 6 is fixed to the rear of the chip 5. Response of the iron skin 1, a stamp material 2 and the fire brick 3 to the impact of hammer is sampled by means of a vibration sensor 7. The vibration response signal thus sampled is amplified 8a and fed through a filter 9a to a frequency analyzer 10 where the vibration response frequency spectrum is calculated. Furthermore, thickness of the refractories is calculated by means of a signal processor 11 based on the peak frequency of the vibration response frequency spectrum.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thickness measuring method for highly accurately measuring the thickness of a refractory brick or the like lined on the inside of an iron furnace of an industrial furnace, particularly a blast furnace for iron making, from the surface of the iron shell using elastic waves. Regarding

[0002]

2. Description of the Related Art For example, a blast furnace for iron making has an outer shell made of a steel shell, and a refractory brick is lined inside. Since the refractory bricks at the bottom of the blast furnace are constantly exposed to hot metal, they gradually wear away as the blast furnace operates, and the thickness of the refractory that was 2,000 mm or more at the time of firing was reduced to about 300 mm at the end of blowing after 10 years. It may be decreasing. Accurately estimating the life expectancy of a blast furnace by accurately measuring the transition of the remaining thickness of refractory during blast furnace operation is
It is very important to prevent serious accidents such as damage to the steel skin due to hot metal or outflow of hot metal, and to effectively use blast furnace assets.

Conventionally, many methods have been proposed for measuring the remaining thickness of refractory bricks in a blast furnace. The main method is illustrated below.

(1) As the simplest method, the surface of the iron shell of the blast furnace is hit with a hammer or the like, the elastic wave generated by this hit propagates in the refractory, is reflected on the surface of the core side, and again. Measure the round trip time to return to the surface of the iron skin,
There is a method of measuring the thickness of the refractory brick from the propagation velocity of the elastic wave in the refractory and the round-trip time which are obtained in advance.

(2) In JP-A-49-50961, a sinusoidal excitation force of audio frequency is applied to a brick to be measured by changing the frequency, the mechanical impedance is measured, and the peak value of the mechanical impedance is measured. Has proposed a method for non-destructively measuring the brick thickness for industrial furnaces from outside the furnace, which measures the brick thickness.

(3) In Japanese Patent Laid-Open No. 58-27002, an opening is formed in a part of an iron shell, a metal rod is directly connected to a refractory material, and one end of the metal rod is hit to efficiently fire-proof. A method has been proposed in which an elastic wave is generated in an object, the time required for the elastic wave to make a round trip in a refractory is measured, and the thickness of the refractory is measured from the round-trip time and the propagation speed of the elastic wave in the refractory. .

(4) By applying a potential pulse to a mutually insulated metal coaxial line or metal parallel line buried in the thickness direction of the furnace wall, and measuring the reflection time from the tip of the metal conductor of the potential pulse. TD for obtaining metal conductor length and furnace wall thickness
A method called R (Time Domain Response) method has also been proposed.

[0008]

The method of using the reflected wave described in (1) above has the advantage that the processing contents for calculating the refractory brick thickness from the device configuration and the measurement data are extremely simple, and measurement can be performed at any location. However, due to the following problems, it has not yet been put to practical use.

Most of the vibration energy due to the impact is consumed as the vibration energy of the iron shell itself, and the efficiency of conversion into elastic waves propagating in the refractory brick is extremely low. For this reason, the vibration of the iron shell itself is larger than the vibration of the elastic wave propagating in the refractory brick and reflected. Therefore, it is very difficult to detect a weak elastic wave that is mixed with these in the refractory brick, propagates in the refractory bricks, and returns and is detected on the surface of the iron skin and identify it as a reflected wave.

The measurement accuracy in the round-trip time measurement method for propagation in bricks is about one quarter of the wavelength. The wavelength of the elastic wave propagating in the refractory is considerably long, and the accuracy of the refractory thickness measurement by this method becomes considerably poor (frequency 10
About 600 mm at 00 Hz). With this,
The detectability of cracks existing in refractory bricks is also extremely low.

In the measuring method described in JP-A-49-50961 described above (2), in order to obtain the peak value of the mechanical impedance of the brick to be measured by applying the sine wave exciting force of audio frequency to the brick to be measured. , It is necessary to apply a sufficiently large sine wave excitation force, and at the same time, it is necessary to sweep the frequency of the excitation force within a predetermined range. Therefore, the apparatus for implementing this method is extremely complex and bulky.

In the method for measuring the thickness of the refractory material described in JP-A-58-27002 (3), it is necessary to open the steel skin at the measurement point and directly connect the refractory material to the metal rod. However, the measurement work is extremely complicated, and the time and cost required for the measurement become enormous. Further, it is difficult to always keep the state of connection between the refractory and the metal rod and the state of impact of the metal rod by the hammer (impact strength, impact position, etc.) constant,
Poor reproducibility of measurement results.

Further, in the above TDR method (4),
In order to measure the thickness of the furnace wall, it is necessary to bury the metal conductor at the measurement location in advance, so the measurement location is limited to the location where the metal conductor was embedded before the blast furnace firing. In addition, for example, if a metal conductor wire breaks or insulation failure occurs during a blast furnace operation period of ten or more years, measurement at that location becomes impossible thereafter.

The present invention has been made in view of the problems of the prior art, and is a thickness for highly accurately measuring the thickness of a refractory brick or the like lined inside the steel skin from the surface of the steel skin using elastic waves. The purpose is to provide a measuring method.

[0015]

The present invention is a method for measuring the thickness of a refractory material stretched on the inner surface of a steel shell from a resonance frequency component obtained when an elastic wave is propagated. ) To (3) are the gist.

(1) First Method A method for measuring the thickness of a refractory material, which is characterized in that the steps from the following steps are performed.

Vibration is applied to the iron skin.

A vibration response frequency spectrum in which a predetermined frequency is removed from the vibration response to the vibration is measured.

The thickness of the refractory is calculated from the peak frequency of the vibration response frequency spectrum.

(2) Second method A method for measuring the thickness of a refractory material, which is characterized in that the steps from the following steps are performed.

A plurality of vibrations having different vibration intensities are applied to the iron shell.

The vibration response frequency spectrum corresponding to the above-mentioned plurality of vibration intensities is measured.

Difference processing is performed on the values of the vibration response frequency spectrum for each of the vibration intensities.

The thickness of the refractory is calculated from the peak frequency of the vibration response frequency spectrum subjected to the difference processing.

(3) Third Method A method for measuring the thickness of a refractory material, which is performed by the following steps.

Vibration is applied to the iron skin.

The vibration frequency spectrum and the vibration response frequency spectrum in which predetermined frequencies are removed from the vibration applied to the iron shell and the vibration response thereto are measured.

The vibration response frequency spectrum is normalized by taking the ratio between the vibration response frequency spectrum and the vibration frequency spectrum.

The thickness of the refractory is calculated from the peak frequency of the normalized vibration response frequency spectrum.

As the normalized vibration response frequency spectrum used in the above, it is desirable to use one that has been subjected to the difference processing by a plurality of excited vibrations performed in the second method.

[0031]

FIG. 1 is a diagram schematically showing the structure of an apparatus for carrying out the method of the present invention (first to third methods). The part surrounded by the broken line in the figure is used when the third method is carried out.

Reference numeral 1 is an iron skin of a furnace (for example, a blast furnace), 3 is a refractory brick, and 2 is a stamp material in the middle. In the method of the present invention, the thickness of the refractory brick 3 is measured.

First, based on FIG. 1, a procedure and an apparatus configuration common to the execution of the first method to the third method of the present invention will be described.

Vibration is applied to the surface of the iron shell 1 on the refractory brick 3 whose thickness is to be measured. As a method of this vibration, in order to propagate the elastic wave in the refractory brick with good reproducibility, it is performed by hitting with a hammer 4 composed of an air hammer or an electric hammer. An appropriate hard plastic impact tip 5 is attached to the tip of the hammer 4 in order to generate an elastic wave in a frequency band (for example, 500 to 3000 Hz) required for measurement.

A striking strength meter 6 is attached to the rear of the striking tip 5 to monitor the striking strength of the hammer 4 on the iron skin. The vibration response of the iron skin 1, the stamp material 2 and the refractory brick 3 at the time of hammering is collected by the vibration sensor 7 attached to the surface of the iron skin. An accelerometer is used as the vibration sensor 7,
In addition, a sensor such as a displacement gauge that measures vibration can be used. The vibration response signal collected by the vibration sensor 7 is amplified by the amplifier 8a by a predetermined magnification and then input to the frequency analysis device 10 via the filter 9a to calculate the vibration response frequency spectrum y (f).

The calculated vibration response frequency spectrum is stored in a predetermined position of the memory 12 and then stored in the signal processor 1.
1 is used for the arithmetic processing described later.

In the embodiment shown in FIG. 1, the frequency analysis apparatus 10 is provided with an A / D converter and a Fourier transform unit for Fourier transforming the vibration response signal that has been A / D converted to calculate a frequency spectrum. Was used. In addition, it is also possible to use a commercially available FFT analyzer (which can change the frequency band to be analyzed by changing a built-in program) as the frequency analysis device 10. Further, it may be an A / D converter and a device that takes in the A / D converted signal into a computer and calculates the frequency spectrum by software. Further, an analog frequency analysis device may be used which analyzes the frequency of the band-limited vibration signal as an analog signal using a heterodyne detector or the like.

The principle and specific embodiments of the first to third methods of the present invention will be described below with reference to FIG.

[First Method] The vibration response signal of the iron skin or the iron skin and the stamp material (hereinafter referred to as the skin material) is 500.
It remarkably appears in a frequency band of about 700 Hz. In this method, a vibration response signal in the frequency band is investigated in advance, and a band pass filter is used as the filter 9a to remove the signal in this frequency band and transmit the vibration response signal of only refractory bricks. It is an embodiment. This method is effective when the resonance peak of the vibration response frequency spectrum of the refractory brick is clear and appears at a position sufficiently separated from the resonance peak of the vibration response frequency spectrum of the skin material.

First, a vibrating force having a strength and a frequency band necessary for measuring the thickness of the refractory brick is applied to the surface of the iron shell 1 by hitting the hammer 4. The vibration response at the time of impact is sampled by the vibration sensor 7 and amplified by the amplifier 8a, and then the bandpass filter 9a uses the vibration response signal to detect the vibration response signal of the above-mentioned iron-clad material and mechanical noise generated during blast furnace operation. Remove electrical noise. The vibration response signal subjected to the band limitation is input to the frequency analysis device 10 to calculate the vibration response frequency spectrum y (f).

Next, in the signal processor 11, the frequency fp giving the peak of the vibration response frequency spectrum y (f).
The brick thickness d is calculated by using the following equation (1).

D = (n · v) / (2 · fp) −dm −ds (1) where dm is the thickness of the iron shell, ds is the thickness of the stamp material,
n: integer, v: iron wave, stamp material and elastic wave propagation velocity function in brick As described above, the first method exhibits the following effects.

(1) By hitting the surface of the iron skin with an air hammer or the like, an elastic wave having a required strength and frequency range (for example, 500 to 3000 Hz) can be propagated in the refractory brick with good reproducibility.

(2) When a low-frequency elastic wave (frequency: 500 to 3000 Hz) is propagated in a refractory brick by measuring the thickness of the brick using the frequency that gives the peak of the vibration signal on the frequency axis. It suppresses the decrease of measurement accuracy.

(3) Since the vibration response signal of the iron crust and the mechanical noise and the electrical noise generated during the operation of the blast furnace are removed from the vibration response signal, the vibration response signal of only refractory bricks is detected. Measurement accuracy is improved.

[Second Method] In the method, when extracting the vibration response of only the refractory bricks in the first method, the vibrations of a plurality of intensities and the differences between the respective vibration response frequency spectra obtained from them are extracted. This is done by processing. This method, in the vibration response frequency spectrum, when the resonance peak of the skin material and refractory bricks appear at positions relatively close to each other, when the measurement area of the refractory brick is relatively wide, and the resonance peak of the skin material changes depending on the measurement position. It is effective in some cases.

Similar to the first method, the following description will be given based on an example in which the apparatus structure shown in FIG. 1 is used to strike the surface of the steel skin with two kinds of strengths, strong and weak, as vibrations of multiple strengths. The striking strength / strong is a strength enough to vibrate the refractory brick through the skin material (for example, about 2000 Kgf), and the striking strength / weak is a strength to vibrate only the skin material ( (About 200 Kgf).

As the filter 9a, a filter (for example, a low-pass filter) that roughly limits the frequency band for removing mechanical noise and electrical noise generated during blast furnace operation is used. If you apply this band limitation,
It also has the merit that the calculation time when the frequency spectrum is calculated by the frequency analysis device 10 can be shortened and the alias noise at the time of A / D conversion can be suppressed.

First, similarly to the first method, strong / weak 2
Vibration response frequency spectra ys (f), yw obtained when the surface of the steel skin is hit with various kinds of hit strength
(F) is calculated and stored in the memory 12. Next, in the signal processor 11, differential processing is performed by the following equation (2), and the differential vibration response frequency spectrum y2 (f) y2 (f) = ys (f) -c.yw (f). ) Here, c: constant The difference vibration response frequency spectrum y2 of the difference processing result.
The brick thickness d is calculated by the above equation (1) using the frequency fp giving the peak of (f). As described above, when this method is applied, the following effects are further added to the first method.

Among the vibration responses obtained by two types of impact strength, strong and weak, ys (f) includes the vibration response of the skin material and refractory brick, while yw (f) includes the skin response. The vibration response of only the material is included. Therefore, by performing the difference processing between ys (f) and yw (f), the vibration response of the skin material can be removed and the vibration response of the refractory brick can be detected with high accuracy, which improves the measurement accuracy. .

[Third Method] In this method, in order to suppress the influence of variations in the reproducibility of the vibration state (striking strength, frequency distribution of elastic waves generated at the time of striking, etc.), the above-mentioned first method and The ratio of the vibration response frequency spectrum collected by the vibration sensor attached to the surface of the iron skin of the method 2 to the vibration signal frequency spectrum obtained by the impact strength meter attached to the hammer is calculated. It is normalized by that.

First, the vibration response frequency spectrum y (f)
Is calculated in the same manner as in the first method and the second method. At the same time, similarly to the vibration response signal sampled by the vibration sensor 7, the vibration signal sampled by the percussion intensity meter 6 attached to the hammer 4 is converted into an amplifier 8b and a filter 9b (see FIG. 1).
Input to the frequency analysis device 10 via the broken line encircled part). Here, as the filter 9b, a bandpass filter having the same frequency band as the bandpass filter 9a used in the first method and the second method is used. The excitation frequency spectrum x (f) is calculated in the frequency analysis device 10 from the excitation signal whose band is limited. After the vibration response frequency spectrum y (f) and the vibration frequency spectrum x (f) are stored in the predetermined memory 12, respectively,
The vibration response frequency spectrum is normalized by calculating the ratio by the signal processor 11. Examples of the method for calculating the normalized vibration response frequency spectrum h (f) include the following equations (3) and (4), but it is preferable to use the equation (4).

H (f) = y (f) / x (f) ... (3) h (f) = {x (f) '. Y (f)} / {| x (f) | ² + / C} ... (4) where f: frequency (KHz) x (f): excitation frequency spectrum, y (f): vibration response frequency spectrum, c: constant, x (f) ': x ( f) Conjugate complex number When the method is applied to the second method, the second
In the same manner as in the above method, the normalized vibration response frequency spectra hs (f) and hw (f) corresponding to the above-described plural vibrations are calculated, and h2 (f) is calculated by the following equation (5).

H2 (f) = hs (f) −c · hw (f) ··· (5) where c: constant Then, signal processing is performed in the same manner as in the first method and the second method. In the instrument 11, the normalized vibration response spectrum h
The brick thickness d is calculated by the equation (1) using the frequency fp that gives the peak of (f) or h2 (f).

As described above, when this method is applied, the following effects are further added to the first method and the second method.

By normalizing the vibration response frequency spectrum with the vibration signal frequency spectrum, the vibration state (striking intensity,
Variations in measurement due to fluctuations in the frequency distribution of elastic waves generated at the time of impact are suppressed, and measurement reproducibility is improved.

In any of the above first to third methods, when the stamp material is peeled off from the iron skin or the refractory brick or is slipped off in the vicinity of the measurement location, the iron skin and the fireproof material are used. Since an air gap is created between the brick and the brick, it becomes extremely difficult to transmit the elastic wave into the refractory brick even if the surface of the iron skin is hit. In this case, it becomes impossible to specify the resonance peak frequency fp of the refractory brick on the vibration response frequency spectrum y (f) or h (f). At this time, the brick thickness can be measured by the above method by press-fitting the mortar material in the vicinity of the measurement location and performing pretreatment for eliminating the gap between the iron shell and the refractory brick.

Further, when the refractory can be directly vibrated due to the opening of the iron shell, vibration of the refractory obtained when the surface of the refractory is hit with a hammer is refractory. Measure with a vibration sensor attached to the surface of the object,
It goes without saying that the thickness of the refractory can be measured by the method of the present invention.

[0059]

FIG. 2 shows the measurement process of an example in which the second and third methods of the present invention were carried out with the apparatus configuration shown in FIG. FIG. 2 is a normalized vibration response frequency spectrum hs (f) obtained when the surface of the iron skin is hit with impact strength / strong (about 2000 Kgf) and impact strength / weak (about 200 Kgf) [FIG. 2]
(A)], hw (f) [FIG. 2 (b)] and the difference processing result h2 (f) [FIG. 2 (c)]. In FIG. 2, the resonance peaks of the surface material and the like are dominant in FIGS. 2A and 2B, but the resonance peaks are removed in FIG. 2C as a result of the difference processing. The process by which the resonance peak of refractory bricks becomes apparent is well understood.
The frequency f of the resonance peak of this difference processing result h2 (f)
The brick thickness obtained from p using equation (1) is about 65.
It was 0 mm.

On the other hand, FIG. 4 schematically shows the measurement result of the core sample at the measurement place. In FIG. 4, the solidified material is a portion where refractory brick waste and the contents of the furnace are mixed and solidified, and the embrittlement portion is a portion where the refractory brick is deteriorated into pieces due to thermal stress (about 130 m).
m), the sound part indicates the part of the refractory brick which still has the refractory function for the purpose of measurement. In FIG. 4, the brick thickness of the sound part at the measurement location was about 630 mm, and it was confirmed that the thickness of the refractory brick could be accurately measured by the method of the present invention.

Further, FIG. 3 shows a measuring process of another embodiment similarly performed by the first and third methods.

FIG. 3 shows the impact strength and strength (about 2000 Kgf).
And vibration response frequency spectrum ys obtained when the surface of the iron skin was hit with a weak impact strength / weakness (about 200 Kgf)
An example of (f) [FIG. 3 (a)], yw (f) [FIG. 3 (b)] and difference processing result y2 (f) [FIG. 3 (c)] is shown. From this FIG. 3, in FIG. 3 (a) and FIG. 3 (b),
Although the resonance peaks of the surface material and the like are dominant, the process in which the resonance peaks are removed and the resonance peaks of refractory bricks become apparent are well understood in FIG. 3C as a result of the difference processing. The brick thickness obtained by using the equation (1) from the frequency fp of the resonance peak of the difference processing result y2 (f) was about 880 mm. On the other hand, the measurement result of the refractory brick thickness by the core sample at this measurement location is about 90.
It is 0 mm, and both are in good agreement.

[0063]

As described above, according to the method of the present invention, the following effects are exhibited in the thickness measurement using the elastic wave, and it becomes possible to realize the excellent thickness measurement accuracy of the refractory material.

(1) By measuring the thickness of the brick using the resonance frequency, the low frequency elastic wave (frequency band: 50
(0 to 3000 Hz) is suppressed in the measurement accuracy when it is propagated in the refractory brick.

(2) The measurement accuracy is improved by removing the vibration response of the skin material and the like which hinders the measurement and detecting the vibration response of only the refractory bricks.

(3) By normalizing the vibration response frequency spectrum with the vibration frequency spectrum, the influence of the vibration state is suppressed, and the reproducibility and accuracy of the measured values are improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of an apparatus that implements a method of the present invention.

[Fig. 2] Normalized vibration response frequency spectrum hs obtained when striking the surface of a steel skin with two types of striking strength, strong and weak
(F), hw (f) and the difference processing result h2 (f)
It is a spectrum distribution diagram which shows an example.

FIG. 3 is an example of vibration response frequency spectra ys (f) and yw (f) obtained when the surface of the steel skin is hit with two types of impact strength, strong and weak, and the difference processing result h2 (f). It is a spectrum distribution diagram shown.

FIG. 4 is a schematic diagram of a measurement result using a core sample.

[Explanation of symbols]

1 Iron Skin 2 Stamp Material 3 Brick 4 Hammer 5 Hitting Tip 6 Hitting Strength Meter 7 Vibration Sensor 9 Filter (Bandpass Filter or Lowpass Filter) 10 Frequency Analysis Device 11 Signal Processor

Claims (3)

[Claims] 1. A method for measuring the thickness of a refractory material stretched on the inner surface of an iron shell from a resonance frequency component obtained when an elastic wave is propagated, wherein vibration is applied to the iron shell and then the vibration is applied. A method for measuring the thickness of a refractory by elastic waves, characterized by measuring a vibration response frequency spectrum in which a predetermined frequency is removed from the vibration response to, and calculating the thickness of the refractory from the peak frequency of the vibration response frequency spectrum. 2. A vibration response frequency spectrum corresponding to each of the plurality of vibration intensities is measured after a plurality of vibrations having different vibration intensities are applied to the iron skin, and a value of the vibration response frequency spectrum for each of the vibration intensity is measured. The refractory thickness measurement method using elastic waves according to claim 1, wherein the refractory thickness is calculated from the peak frequency of the difference frequency spectrum obtained by the difference process. 3. The method for measuring the thickness of a refractory by elastic waves according to claim 1 or 2, wherein the vibration response frequency spectrum is normalized by an excitation frequency spectrum added to the iron skin.