JPH0563722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wall thickness measuring device that measures the wall thickness of a clad pipe or the like by using both ultrasonic waves and eddy current.

[Conventional technology]

A clad pipe has a laminated structure in which a clad material is metallurgically bonded to the outer or inner periphery of a base material.
By selecting a cladding material according to the application, it is possible to maintain material strength, has excellent acid resistance under special atmospheres, and is widely used as a material that can reduce the cost of pipe materials. The thickness of the cladding material is an extremely important control item in order to guarantee the performance and lifespan of the cladding pipe. Conventionally, the thickness of the cladding material is an extremely important control item in order to guarantee the performance and lifespan of the cladding pipe. A device using a combination of eddy current and eddy current has been proposed (Japanese Patent Application Laid-open No. 54902/1983).

However, with a device that uses only ultrasonic waves, it is necessary to detect the reflected waves from the interface between the base material and the cladding material, but when the acoustic impedances of the base material and the cladding material are similar, The drawback was that the measurement itself was extremely difficult.

On the other hand, devices that use a combination of ultrasonic waves and eddy currents include an ultrasonic wall thickness measurement system that measures the total wall thickness between the base material of the clad pipe and the clad material, and an eddy current wall thickness measurement system that measures the wall thickness of the clad material. The measuring system is configured to measure the total wall thickness and the wall thickness of the cladding material by bringing the measurement head into contact with each measurement point defined on the surface of the cladding tube.

[Problem to be solved by the invention]

By the way, such conventional devices are of a contact type in which measurements are made sequentially by bringing the measurement head into contact with the measurement points, so for example, when determining the wall thickness distribution of the cladding material at each longitudinal section of a cladding pipe, etc. When the number of measurements is increased, the measurement work becomes extremely troublesome and continuous measurement is difficult. In addition, when continuously measuring the wall thickness of a cladding pipe without contact, the measurement head of the ultrasonic wall thickness measurement system and the measurement head of the eddy current wall thickness measurement system are usually placed side by side with a required spacing, Since measurements are taken while moving the cladding tube in a spiral manner, a means for synchronizing the positions of the measured values from both measurement heads is required, making the apparatus complicated. Furthermore, if a slip occurs during movement of the clad tube, the positional synchronization of both measured values becomes inaccurate, resulting in a problem in that sufficient measurement accuracy cannot be obtained.

The present invention was made in view of the above circumstances, and its purpose is to utilize the difference in ultrasonic properties and electromagnetic properties even when the acoustic impedances of the base material and cladding material are similar. To provide a wall thickness measuring device capable of effectively and accurately measuring wall thickness continuously.

[Means to solve the problem]

The wall thickness measuring device according to the present invention includes an ultrasonic wall thickness measuring system that measures the total wall thickness including the wall thickness of the clad material and the wall thickness of the base material, and a vortex system that measures the wall thickness of the clad material. A wall thickness measuring device equipped with a current wall thickness measuring system, comprising: a housing having a water chamber inside and having a nozzle at a tip for spraying water supplied to the water chamber toward a surface of a point to be measured; An ultrasonic device that is provided on the base end side of the housing and transmits and receives ultrasonic waves whose propagation direction is perpendicular to the surface of the point to be measured between the point to be measured and the point to be measured through the water in the water chamber and the water flow jetted from the nozzle. A probe of the sonic wall thickness measurement system is arranged on the outer periphery of the housing concentrically with a nozzle provided at the tip thereof within the housing, and is applied to the surface of the same point to be measured as the point to be measured by the probe. The present invention is characterized in that a measuring head portion comprising a coil of an eddy current wall thickness measuring system that forms a magnetic field in orthogonal directions is disposed opposite to the surface of the cladding material at a distance.

[Effect]

With the apparatus of the present invention, the measured values of the ultrasonic wall thickness measuring system and the eddy current wall thickness measuring system can be obtained at the same time at the same measurement point of the cladding material.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof.

FIG. 1 is a schematic diagram of the apparatus of the present invention, in which P indicates a clad pipe and 1 indicates a measuring head.

The clad pipe P is made by metallurgically joining a clad material P ₂ made of stainless steel such as austenitic steel to the outer periphery of a base material P ₁ made of carbon steel. The measuring head section 1 includes a housing 2 equipped with a water chamber 2a, an ultrasonic transmitter/receiver 3 which is a probe for measuring the total wall thickness of the pipe, and a first probe for electromagnetic induction for measuring the wall thickness of the cladding material. It is equipped with a coil 4 and a second coil 5 for electromagnetic induction to correct the temperature of water, which is the propagation medium of ultrasonic waves, and is arranged at a predetermined distance from the surface of the clad tube P, which is the object to be measured. The cladding tube P is disposed opposite to the cladding tube P, and measurements are continuously performed while moving the cladding tube P in a spiral manner.

The housing 2 is provided with a water chamber 2a that is long upwardly and downwardly in the center thereof, and has two water chambers on the sides of the water chamber 2a.
A water supply pipe 2b is connected thereto, and a nozzle 2c opening facing the cladding pipe P is formed at the lower end of the water chamber 2a. The transmitter/receiver 3 is disposed on the upper wall of the water chamber 2a so that the propagation direction of the ultrasonic wave passes through the center of the nozzle 2c and is perpendicular to the surface of the clad pipe P.
Further, the first coil 4 is arranged concentrically around the outer periphery of the nozzle 2c, and the second coil 5 is arranged concentrically with the outer periphery of the lower water supply pipe 2b near the first coil 4. An ultrasonic wall thickness measuring system A is connected to the probe 3, and an eddy current wall thickness measuring system B is connected to the first and second coils 4 and 5, respectively.

(Ultrasonic wall thickness measurement system A) When the clock pulse emitted from the clock circuit 11 is input to the gate circuit 12, the gate circuit 1
2 is a flip-flop circuit 3 constituting a switching means;
The on/off control is performed based on the signal input from eddy current thickness measuring system B, and the clock pulses are outputted to the oscillation circuit 13 at predetermined timings so as to alternate with the output of the eddy current wall thickness measuring system B. The oscillation circuit 13 outputs an oscillation signal to the transmitter/receiver 3 based on the command signal, causing the transmitter/receiver 3 to emit ultrasonic waves. The ultrasonic waves propagate in the water column in the water chamber 2a and are incident at right angles into an area approximately 1 mm in diameter on the surface of the cladding material _P2 of the cladding pipe P, which is the object to be inspected.

A portion of the ultrasonic waves incident on the cladding material P ₂ is reflected by the surface of the cladding material P ₂ and the inner surface of the base material P ₁ in the cladding pipe P, and the respective reflected waves S, as shown in FIG. B ₁ propagates through the water in the water chamber 2a again and is captured by the transmitter/receiver 3.

The reflected wave captured by the transmitter/receiver 3 is converted into an electrical signal and amplified by the amplifier 14, and then sent to the comparator 15.
and is compared with a predetermined reference value,
Only the reflected waves S and B ₁ from the outer surface of the cladding material P ₂ and the inner surface of the base material P ₁ are extracted and input into the timing generation circuit 16 .

The timing generation circuit 16 outputs a gate signal having a length corresponding to the time t between the rises of the reflected waves S and _B1 to the T/A (timing analog) converter 17 as shown in FIG. After being converted into an analog signal here, it is converted into a digital signal by an A/D (analog-digital) converter 18 and output to a central control unit (CPU) 30.

(Eddy current thickness measurement system B) 21 is an oscillator, and its oscillation signal is input to the gate circuit 22. The gate circuit 22 is controlled to be on/off based on the signal input from the flip-flop circuit 31, and the signal from the oscillator 21 is sent to the first gate via the amplifier 23 and the bridge circuit 24 with timing shifted from the ultrasonic wall thickness measurement signal. It outputs to the second coils 4 and 5.

When a current is passed through the coil 4, a magnetic field is formed in a direction perpendicular to the surface of the cladding material _P2 , which is the object to be tested.This induces an eddy current on the surface of the cladding material _P2 , and the coil 5 When a current is passed through the water supply pipe 2b, a magnetic field is formed in the same direction as the flow direction of the water in the water supply pipe 2b.

When the lift-off amount and the wall thickness of the cladding material P ₂ change, the impedance of the first coil 4 changes, and when the water temperature changes, the temperatures of the first and second coils 4 and 5 change, and the impedance changes. . The first and second coils 4 and 5 are connected in series to two adjacent sides of the bridge circuit 24, and are detected by a detector such as a photo sensor (not shown) provided immediately before the measurement head 1. When the tip of the clad pipe P is detected and the first coil 4 is in an empty core state, that is, when the clad pipe P is not facing the first coil 4, water is flowed into the water supply pipe 2b, and water is poured from the nozzle 2c. The bridge circuit 24 is adjusted to be in an equilibrium state while injecting the fuel.

Therefore, from the bridge circuit 24, the first and second
Only a signal in which impedance changes caused by the water temperature of the coils 4 and 5 are canceled out, that is, a signal that is unaffected by temperature changes in water, which is an ultrasonic propagation medium, is output. In other words, the clad pipe P is connected to the first coil 4.
The bridge circuit enters an unbalanced state only when the impedance of the first coil 4 is changed and the unbalanced state occurs depending on the distance between the first coil 4 and the cladding pipe P and the thickness of the cladding material _P2 . The balanced signal is outputted to the synchronous detection circuit 26 via the amplifier 25.

The synchronous detection circuit 26 analyzes the phase of the input signal and
The signal is divided into two signals in the axial direction and the Y-axis direction and output to the phase rotator 27, and from the phase rotator 27, the phase rotator 27 and the amplifier 25 are adjusted in advance using a reference piece as shown in FIG. By adjusting the frequency of the oscillator 21 in advance, the amplitude of _the lift-off amount is used as a Y-axis signal _V
It is set to be expressed as V _X.

Each signal in the X and Y axis directions of the phase rotator 27 is A/
It is converted into a digital signal by the D converter 28 and output to the central control device 30. Central control device 30
calculates the total wall thickness D of the cladding pipe P based on the input from the ultrasonic wall thickness measurement system A, and calculates the total wall thickness D of the cladding material P ₂ in the cladding pipe P based on the input from the eddy current wall thickness measurement system B. The thickness D _P2 is calculated, and the wall thickness D _P2 of the clad material P ₂ is subtracted from the total wall thickness D to calculate the wall thickness D _P1 of the base material P ₁ , and these are sent as an analog signal through the D/A converter 32. Data will be output to a chart (not shown).

An outline of the calculation process performed by the central controller 30 is as follows.

The total wall thickness D of the cladding tube P is determined as the product of the time t between the reflected waves S and _B1 and the speed of sound in the propagation medium, as shown in FIG. 2B. Also, the wall thickness D _P2 of the cladding material P ₂ in the cladding pipe P is determined by the value d corresponding to the signal _V
It is expressed as the sum of the equation (1) below.

D _P2 = d + Δd ... (1) Now, if we express the conversion formula between thickness d and signal V _X as shown in equation (2) below, d = AV _X ² + _BV C...Coefficient The correction amount Δd varies depending on the range of the thickness d,
It is defined as follows.

FIG. 4 is a graph showing the relationship between the lift-off amount and the correction value for different cladding thicknesses, with the horizontal axis representing the lift-off amount and the vertical axis representing the correction value.

As is clear from this graph, the correction value increases when the thickness of the object to be measured is smaller than the reference thickness, and conversely, the correction value decreases as the thickness of the object to be measured increases. I understand. Therefore, the wall thickness of the object to be measured is d ₁ - d ₂ , d ₂ - _{d 3} ,
...Divide it into d _o-1 ~ d _o and find the correction values Δd ₁ , Δd ₂ ... Δd _n as shown in the formula below in each region,
All that is required is to perform lift-off correction.

That is, when d ₁ ≦ d < d ₂ , Δd ₁ = A ₁ V _Y ² + B ₁ V _Y + C ₁ d ₂ ≦ d < d ₃ , Δ d ₂ = A ₂ V _Y ² + B ₂ V _Y + C ₂ 〓 〓 〓 d _{o -1} ≦d<d _o , Δd _n =A _n V _Y ² +B _n V _Y +C _nIn addition, in this embodiment, the second coil 5 is provided around the outer periphery of the water supply pipe 2b, and the first coil for wall thickness measurement is The impedance change caused by the temperature change of the coil 4 is corrected, but instead of this, the water temperature is controlled within a certain range, and the second coil 5 is omitted.
An element having the same impedance as the first coil 4 may be connected to a portion of the two adjacent sides of the bridge circuit 24 corresponding to the second coil 5. Moreover, if the water temperature change can be ignored, water temperature control can also be omitted. Furthermore, in this embodiment, the flip-flop circuit 31 and the gate circuits 12 and 22 are used to alternately switch between the ultrasonic wall thickness measurement system and the eddy current wall thickness measurement system. If the eddy current wall thickness measurement system has a large difference or the signal obtained by the eddy current wall thickness measurement system is large and mutual interference between the two measurement systems does not occur, these circuits may be omitted and measurements may be always performed using both measurement systems.

〔effect〕

In the device of the present invention as described above, the housing has a water chamber inside and a nozzle at the tip of which injects the water supplied to the water chamber toward the surface of the point to be measured. The coil of the eddy current wall thickness measurement system is arranged around the outer periphery of the eddy current wall thickness measurement system and forms a magnetic field in a direction perpendicular to the surface of the same point to be measured as the point to be measured by the probe of the ultrasonic wall thickness measurement system. Because of this, it is possible to simultaneously measure the wall thickness of the cladding material and the base material, as well as the total wall thickness, at the same measurement point, and the mutual influence of both measurement systems can be eliminated, greatly improving measurement accuracy. Furthermore, the present invention has excellent effects such as being able to make the measuring head itself smaller and more compact.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the measurement system shown together with the measurement head of the device of the present invention, Fig. 2 is an explanatory diagram of total wall thickness measurement using an ultrasonic measurement system, and Fig. 3 shows changes in lift-off amount and cladding material thickness. FIG. 4 is an explanatory diagram showing a mode in which the phase of the output signal is analyzed, and FIG. 4 is an explanatory diagram showing the relationship between the lift-off amount and the correction value. 1...Measuring head, 2...Housing, 2a...
...Water chamber, 3...Ultrasonic transmitter/receiver, 4...First coil, 5...Second coil, 15...Comparator, 2
6... Synchronous detection circuit, 27... Phase rotator, 30
... Central control unit, P ... Clad tube, P ₁ ...
Base material, P ₂ ... clad material, A ... ultrasonic wall thickness measurement system, B ... eddy current wall thickness measurement system.

Claims (1)

[Claims] 1 A wall thickness system equipped with an ultrasonic wall thickness measurement system that measures the total wall thickness including the wall thickness of the clad material and the wall thickness of the base material, and an eddy current wall thickness measurement system that measures the wall thickness of the clad material. The measuring device includes a housing that has a water chamber inside and has a nozzle at its tip that injects the water supplied to the water chamber toward the surface of the point to be measured; A probe of an ultrasonic wall thickness measurement system that transmits and receives ultrasonic waves whose propagation direction is orthogonal to the surface of the point to be measured between the probe and the point to be measured through water in a room and a water stream jetted from a nozzle, and the housing. An eddy current layer is arranged on the outer periphery of the nozzle concentrically with the nozzle provided at the tip of the nozzle, and forms a magnetic field in a direction perpendicular to the surface of the same point to be measured as the point to be measured by the probe. 1. A wall thickness measuring device characterized in that a measuring head portion including a thickness measuring coil is disposed facing the surface of a cladding material with a gap therebetween.