JPS6254113A - Thickness measuring method for scale in pipe - Google Patents

Abstract

PURPOSE:To measure the thickness of scale in a pipe with good accuracy by arranging the ultrasonic wave transmitters and receivers in opposition with a prescribed interval from the outside wall of the pipe at both sides of the pipe with the pipe between and filling a sound joining liquid in the clearance. CONSTITUTION:When electric energies pa and pb with short pulses with two frequencies are impressed on the transmitters 4a and jb by transmission circuits 8a and 8b, the ultrasonic waves are transmitted and propagated through the sound joining liquid 6, a wall thickness, a scale layer 2 and a fluid 3 of the pipe 1 through propagation paths j1 and j2 and received with receivers 5a and 5b. These received signals qa and qb are amplified with the transmission circuits 9a and 9b and an attenuation rate is divided with an attenuation rate dividing circuit 10. This value is inputted to an arithmetic circuit 12 and the arithmetic operation is performed with an attenuation factor correction value 11 obtained on the known scale thickness is advance and the actual scale thickness D-d stuck to a pipe to be measured is calculated and its value is displayed. In this case, since the clearance between the transmitters and receivers and the pipe 1 is filled with the sound joining liquid, a sound joining condition is kept constant and there is no possibility being influenced by a disturbance by the contact pressure and the high measuring accuracy is obtained.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method of measuring the thickness of scale generated inside a pipe through which fluid flows using ultrasonic waves.

[Prior art and its problems]

The thickness of the scale formed inside the pipe can be measured using radiographic photography using a radiation source, radiation measurement method that uses the property that radiation is absorbed and attenuated by the scale, and measures the attenuation rate. Conventionally known methods include an electromagnetic measurement method that utilizes the property that magnetic permeability changes, and a measurement method that uses the property that thermal conductivity within a pipe changes depending on the scale and determines the scale thickness from the temperature gradient. However, all of these conventional measuring methods lack the simplicity of measurement and have problems such as limited applicability. Another measurement method is the ultrasonic reflection measurement method, which uses the properties of ultrasonic waves reflected by the scale to measure the thickness of the scale in the pipe from the reflection time of the ultrasonic waves. In the method, since the interface between the scale and the fluid has almost the same acoustic impedance as the fluid, it is difficult to obtain a reflected wave from the aforementioned interface corresponding to the thickness of the scale in the pipe, and the obtained reflected wave is It is difficult to obtain highly accurate measurement results due to difficulties in the measurement principle, such as the possibility that the waves are reflected from halfway through the thickness of the scale attached to the pipe, and the influence of multiple reflections within the pipe. .

[Purpose of the invention]

This invention has been made in consideration of the above points, and it solves the difficulties of the various conventional measurement methods mentioned above, improves it in nine aspects such as ease of measurement and restriction of applicable objects, and improves the attenuation of ultrasonic waves. It is an object of the present invention to provide a measurement method that enables accurate measurement of scale thickness inside a pipe from the outside of the pipe.

[Key points of the invention]

The above object is achieved by the present invention, in which an ultrasonic transmitter and a receiver are arranged facing each other with a predetermined gap from the outer wall of the tube on both sides of the tube, and the gap is filled with the same type of acoustic wave as the fluid flowing through the tube. It is filled with a bonding liquid, and in this state, the ultrasonic wave is propagated through the fluid from the transmitter to the receiver, and the attenuation rate of the ultrasonic wave is detected from the emitted sound pressure and the received sound pressure, and the detected value and the previously known The thickness of the scale attached to the inside of the pipe is determined by calculation from the calibration value of the ultrasonic attenuation factor determined for the scale thickness. That is, the ultrasonic waves are emitted from the ultrasonic transmitter to the receiver into the fluid in the tube through the acoustic bonding liquid that filled the gap and the tube wall to maintain constant acoustic coupling with the tube. It passes through the scale and fluid and is received by the receiver. In this case, the attenuation rate of ultrasonic waves in the fluid is proportional to the propagation distance and the frequency raised to the power of a number. Therefore, the attenuation rate of the ultrasonic wave is determined from the frequency of the ultrasonic wave emitted into the fluid and the distance of the ultrasonic propagation path, and the ultrasonic attenuation rate is calculated separately from this detected value for a known scale thickness under the same measurement conditions. By performing calculations using the calibrated value of the ratio, it is possible to measure the thickness of the scale attached to the inside of the pipe to be measured.

[Embodiments of the invention]

Next, embodiments of the present invention will be described based on the drawings. 1st
The figure shows the principle of this invention, FIG. 2 shows the configuration of a specific embodiment for carrying out the invention, and FIG. 3 shows a cross-sectional view of the arrangement of FIG. 2. In each figure, 1 is a A pipe through which fluid flows; 2 is scale generated inside the pipe and deposited on the pipe wall;
3 is a fluid flowing through the pipe; 4a, 4b are two sets of ultrasonic transmitters; 5a, 5b are the transmitters 4a, 4b.
It is an ultrasonic receiver that is paired opposite to the transmitter 4a+.
4b and the receivers 5a, 5b are arranged facing each other on both sides of the tube with a predetermined gap set between them and the outer wall of the tube 1, and between the transmitters 4a, 4b and the tube 1 and the receiver 5.
In order to maintain constant acoustic bonding conditions between the tubes a and 5b and the tube, the gap is filled with an acoustic bonding liquid that is the same type of fluid as the fluid flowing through the tube 1. In addition, the symbol JI+ Jz is the propagation path of the ultrasonic wave, Sa and Sb are the thicknesses of scale 2 deposited inside the tube, D is the inner diameter of the tube, d is the effective diameter of the flow path when scale is attached inside the tube, and f+ , fz represent the ultrasonic transmission frequencies of the transmitters 4a+4b, respectively. First, the principle of the measuring method according to the present invention will be explained with reference to FIG. Two ultrasound propagation paths 1 and 1 in the figure.
The transmitter 4a, 4b shown in the figure is wrapped around the receiver 4a+.
When an ultrasonic wave is emitted toward 4b, the following equation is established between the transmitted sound pressure and the received sound pressure. In(r+/Io) = lnK −A (Ss 1 Sb) L” ---filIn(It/I.) −In
K −A (Sa +sb)fg” −−−−−−
--f21 However, Io is the transmitting sound pressure, L, It is the receiving sound pressure corresponding to the transmitting frequency fl+f, K is the sound pressure transmittance, A
is a coefficient of an ultrasonic attenuation constant, and X is a coefficient representing the influence of frequency on attenuation. In the above equations (11, (21), the sound pressure transmittance has a scale of 2
If the acoustic impedance of fluid 3 is known in advance,
It is a known number because it is calculated from the acoustic impedance of . Therefore, the following equation holds true from 21. However, αz = ft/f*.The reason why two frequencies are used for the ultrasound in the above is that the higher the frequency, the more attenuated the ultrasound is. Since it increases, it is clear that 2i1
This is to set the ultrasonic wave at one frequency to cover the target measurement range and to increase the accuracy of the calibration value of the scale attenuation rate. In the above equation (4), Af♂ represents the attenuation rate per unit length, and Sa + Sb represents the scale thickness, where the oscillation sound pressure r,
A calibration value for the attenuation rate of the scale is calculated and prepared from equation (4) using the received sound pressure I, and the calculated sound pressure i3 pass rate K. Next, to measure the scale thickness inside the pipe to be measured, the same measurement operation as described above is performed on the pipe to be measured, and the thickness of the scale can be determined by the following equation. [Ar1”) (Art”) Here, D-d is the scale thickness (Sa+Sb), and CA
r+fuki), (Ar1”] represents the calibration value of the scale attenuation rate obtained for the above-mentioned known scale.Equation (5) expresses the scale attenuation rate at frequency f11 and expression (6) expresses the scale attenuation rate at frequency f2. This is the case when the calibration is performed. Therefore, the equation (5
) or (6), when actually measuring the pipe to be measured, In
(to/r+) and In(Klo/Ig), and calculate the thickness of the scale attached inside the pipe to be measured by calculating this value and the attenuation rate calibration value calculated in advance for a known scale. It is possible to obtain s[)-d. Next, a specific apparatus for carrying out the method for measuring scale thickness based on the above principle will be described with reference to FIG. 2. That is, in the embodiment shown in FIG. 2, two sets of ultrasonic transmitter elements, each pair consisting of an ultrasonic transmitter 4a and a receiver 5a, and an transmitter 4b and a receiver 5b, are placed on the outer wall of the tube 1 with the tube between them. are arranged facing each other, and each oscillation and receiver is connected to tube 1.
It is fixedly supported on a mounting base 7 installed on the pipe with a predetermined gap from the pipe, and is housed in a water tank 6a filled with an acoustic bonding liquid 6 as shown in FIG. Note that the propagation angle of the ultrasonic waves is set perpendicular to the tube l. Further, the ultrasonic transmitters 4a and 4b each include a transmitting circuit 8a of an electronic circuit.
, 8b are connected to one of the receivers 5a and 5b, and receiving circuits 9a and 9b, an attenuation ratio indexing circuit 10, an arithmetic circuit 11, and an output display section 12 are connected to one of the receivers 5a and 5b. Note that 13 is a selection switch. With the above circuit configuration, the transmitting circuits 8a and 8b generate short pulses of electrical energy p, p, with a frequency fl+ft.
b is applied to the transmitters 4a+4b, the ultrasonic waves pass through the propagation paths j1 and jt to the acoustic bonding liquid 6. The receiver 5 is transmitted through the tube wall of the tube 1, the scale N2, and the fluid 3.
a. 5b. Further, the ultrasonic reception signal Q*-Qb received by the receivers 5at and 5b is transmitted to the receiving circuit 9at.
The equation (5) described above is amplified by the attenuation ratio determining circuit 10. The term of the attenuation ratio In(Kl./II) or In(Kl./■,) in (6) is determined. This value is input to the arithmetic circuit 12, where it is used for the previously known scale thickness. Using the calculated attenuation rate calibration value, formula (51, (6
1 to calculate the actual scale thickness D−d attached to the tube to be measured, and output the value to the display section 13 for display. Furthermore, in this case, the gap between the ultrasonic transmitter and receiver and the tube is filled with the same type of acoustic 8I bonding liquid as the 1ii12it liquid in the tube, so the acoustic bonding conditions between the transmitter, the receiver and the tube are constant. High measurement accuracy can be obtained because there is no risk of being affected by disturbances due to contact pressure, which would occur if the transmitter and receiver were brought into direct contact with the outer wall of the tube. [Effects of the Invention] As described above, the present invention provides an ultrasonic transmitter and a receiver that are disposed opposite to each other with a predetermined gap from the outer wall of the tube on both sides of the tube, and that the gap is used to pass through the tube. It is filled with an acoustic bonding liquid of the same type as the flowing fluid, and in this state, ultrasonic waves are propagated into the fluid from the transmitter to the receiver, and the attenuation rate of the ultrasonic waves is detected from the transmitted and received sound pressures. The thickness of the scale adhering to the inside of the pipe is calculated by calculating the detected value and the calibrated value of the ultrasonic attenuation factor determined in advance for the known scale thickness.This eliminates the drawbacks of conventional measurement techniques. The thickness of the scale that has been removed and adhered to the inside of the tube can be accurately measured from outside the tube.

[Brief explanation of drawings]

FIG. 1 is a diagram of the principle of the present invention, FIG. 2 is a specific configuration diagram of an apparatus for carrying out the measuring method of the present invention, and FIG. 3 is a sectional view of the arrangement and configuration of FIG. I: tube, 2 scales, 3: fluid, 4a, 4b: ultrasonic transmitter, 5a, 5b: receiver, 6: acoustic bonding liquid, 8a,
8b: Transmission circuit, 9a, 9b: Receiving circuit, 1o: ill
Side split circuit, 11: Arithmetic circuit, D: Inner diameter of pipe, Sa. Sb: Thickness of the scale inside the pipe, Jl+ jz: Ultrasonic propagation path, f+, tz: Ultrasonic transmission frequency. Figure 1

Claims (1)

[Claims] 1) A method of measuring the thickness of scale formed inside a pipe through which fluid flows using ultrasonic waves, in which an ultrasonic transmitter and a receiver are placed on both sides of the pipe with a predetermined gap from the outer wall of the pipe. are arranged facing each other, and the gap is filled with an acoustic bonding liquid of the same type as the fluid flowing in the pipe, and in this state, the ultrasonic wave is propagated into the fluid from the transmitter to the receiver, and the ultrasonic attenuation rate is reduced. The scale thickness inside the pipe is characterized in that the thickness of the scale adhering to the inside of the pipe is calculated by calculating from the detected value and a calibration value of the ultrasonic attenuation factor calculated in advance for a known scale thickness. How to measure