JP2956512B2 - Method of measuring wall thickness of tubular material - Google Patents

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 the thickness of a tubular material at a plurality of positions in a circumferential direction using radiation.

[0002]

2. Description of the Related Art In the process of manufacturing various metal pipes, it is desired to measure the thickness of a tubular material flowing in a non-contact manner in order to use the process control in each process. As a method for enabling such a measurement, there is a thickness measuring method using radiation.

[0003] This method is intended for a material having a uniform density, such as a metal, and utilizes the characteristic that the intensity of radiation passing through such a material is attenuated according to the transmission distance. By arranging a radiation source and a detector opposite each other with the tubular material interposed therebetween, when the radiation emitted from the source enters the tubular material from the outside to the inside and emits the outside again, the procedure of capturing by the detector is adopted. Done. The radiation is
Between the radiation source and the detector, the light passes through the thick portion of the tubular material to be measured twice and attenuates according to the transmission distance. Therefore, by comparing the intensity of the radiation emitted by the source and the intensity detected by the detector, the transmission distance,
That is, the thickness of the tubular member can be obtained.

However, the transmission distance obtained by the above comparison is the sum of the thicknesses at the circumferential positions opposed to each other.
When the tubular material to be measured has an uneven wall thickness distribution in the circumferential direction, there is a problem that the wall thickness at both positions cannot be obtained with high accuracy, and in order to solve this problem, Japanese Patent Publication No. 60-44602
Japanese Patent Application Laid-Open Publication No. H11-64131 discloses a wall thickness measuring method for measuring the wall thickness of a tubular member including a circumferential distribution.

In this method, as shown in FIG. 8, an odd number (in the figure, an outer periphery of a tubular member P to be measured) is set on an appropriate circumference set at the same center as the tubular member P. Three)
Are arranged at equal intervals in the circumferential direction, and the beams of radiation 3, 3,... Emitted from these sources intersect each other inside the arrangement circumference. Are positioned so as to form the vertices of a regular polygon within the thickness range of P. Further, each of the separate detectors 2 is opposed to each of the radiation sources 1, 1. 2 ... is arranged.

The above-mentioned radiation sources 1, 1... And detectors 2, 2
..., the radiation emitted by each radiation source 1, 3, 3 ...
Is incident on the outer side of the tubular material P to be measured at a predetermined angle inclining, passes through the thick portion in this direction, enters the inside, retransmits through the thick portion, and emits outward at the predetermined angle. And is captured by the corresponding detector 2.

Accordingly, the intensity of the radiation 3 at the time of emission from the source 1 is represented by E _i (i is the number of the sources 1, 1,..., I = 1).
3), the detected intensity of the radiation 3 transmitted through the tubular member P twice and captured by the corresponding detector 2 is represented by e _i (i = 1 to 3).
Then, the relationship between these two is expressed as follows as a basic formula of the radiation thickness gauge.

E _i = E _i · exp ｛−μ (ξ _i1 + ξ _i2 )｝ (1)

In the equation (1), ξ _i1 and ξ _i2 are transmission distances of the radiation 3, and the former is the first transmission distance of the radiation 3 emitted from the i-th source 1, that is, the transmission distance of the tubular material P. The latter indicates the transmission distance from the outside to the inside, and the latter indicates the second transmission distance of the radiation 3 emitted from the i-th source 1, that is, the transmission distance from the inside to the outside. Further, μ in the expression (1) is an attenuation coefficient representing the degree of attenuation of the radiation 3 during transmission, and is given as a constant specific to the material of the tubular material P to be measured. Tests can be performed and calibrated.

Therefore, in the equation (1), the attenuation coefficient μ and the emission intensity E _i (i = 1 to 1) from each of the radiation sources 1, 1...
3) is known, and when the detection intensities e _i (i = 1 to 3) obtained by the detectors 2, 2... Corresponding to the respective radiation sources 1, 1,. Thus, the sum (ξ _i1 + ξ _i2 ) of the transmission distance of each radiation 3 is obtained.

The transmission of each radiation 3 from the outside to the inside and from the inside to the outside of the tubular material P is as described above.
It passes through the intersection position with another radiation 3 set within the thickness range of the tubular material P, and corresponds to a half of the angle at which the two radiations intersect at each intersection position with respect to the radius line at this position. Since the wall thickness of the tubular material P to be obtained is a thickness measured along the radius line, (1)
The thickness x _i1 at the first transmission position of the i-th radiation 3 (i = (i = i cos θ)) is calculated by the following expression that multiplies the sum of transmission distances (ξ _i1 + ξ _i2 ) obtained from the expression by a predetermined conversion constant k (= cos θ). 1 to
3) and the thickness x _i2 (i = 1 to 3) at the second transmission position
(X _i1 + x _i2 ).

T _i = x _i1 + x _i2 = k (ξ _i1 + ξ _i2 ) (2)

The inclination angle θ is, as described above,
1, the crossing angle of the radiations 3, 3,..., That is, one side of a regular polygon having the vertex at the crossing point at which any two of the radiations 3, 3. And is given as the half value of the vertex angle of the isosceles triangle formed by For example, as shown in FIG. 8, when the number of the radiation sources 1, 1,... Is three, the conversion constant k is cos (π / 6).

The actual conversion constant k includes an error relating to the shape of the tubular member P to be measured and the beam size of the radiation 3, 3,... And has a diameter similar to that of the tubular member P. By calculating the error component by a test using a test tube having a known thickness and correcting the conversion constant k based on the result, the calculation accuracy by the equation (2) can be improved.

Of the thicknesses x _i1 and x _i2 included in equation (2),
There are two each passing through a common intersection,
It is substantially the same under the condition that the circumferential thickness of the tubular material P to be measured changes slowly. For example, as shown in FIG. 8, the number of radiation sources 1, 1,.
If it is, the x ₁₁ in x _32, x ₂₁ and x _12, and x
₃₁ is substantially equal s husband and x _22. Therefore, the i-th source 1
Assuming that the thickness at the position where the radiation 3 emitted from the first crossover with the other radiation 3 first is x _i (i = 1 to 3), the following three equations are established from the above equation (2). By solving this simultaneous equation, the wall thickness x _i (i = 1 to 3) can be obtained individually.

X ₁ + x ₂ = T ₁ x ₂ + x ₃ = T ₂ (3) x ₃ + x ₁ = T ₃

[0017]

However, in the conventional measuring method performed as described above, as described above, the radiations 3, 3,... Emitted from the radiation sources 1, 1,. When the intersection is not satisfied, that is, when the intersection position is deviated to the inside or outside of the tubular member P, (3)
There is a drawback that the calculation accuracy of the wall thickness x _i obtained by the equation is reduced.

On the other hand, in various pipe-making processes in which application of the above-described measuring method is strongly desired, tubular materials P having variously different pipe diameters and wall thicknesses are often measured. In order to implement the conventional measuring method, the radiation sources 1, 1... And the detectors 2, 2. There is a problem that a movable mechanism for changing the position is required, and much trouble is required for operation and maintenance of the movable mechanism.

When the thickness of the tubular material P to be measured has a complicated variation component in the circumferential direction, the radiation source 1
1 and the number of detectors 2, 2,... Need to be increased, but the structure of the movable mechanism is complicated and increased in size with the increase in the number of detectors. ,
It became difficult to secure a space for installing the movable mechanism around the tubular material during pipe production, and there was even a possibility that the measurement method described above could not be performed.

The present invention has been made in view of the above-mentioned circumstances, and is applicable to a tubular member having various diameters and wall thicknesses without changing the positions of the radiation source and the detector. It is an object of the present invention to provide a method for measuring a wall thickness, which can accurately measure wall thicknesses at a plurality of locations in a direction and is convenient for application to various pipe-making processes.

[0021]

According to the present invention, there is provided a method for measuring the thickness of a tubular material, the method comprising: measuring the radiation emitted from an odd number of radiation sources arranged at equal intervals in a circumferential direction outside a tubular material to be measured; Any two of them intersect at the vertices of a regular polygon inside these arrangement perimeters, and detect the intensity of each radiation transmitted again outside through the inside of the tubular material,
These detected intensities are applied to a predetermined arithmetic expression including a conversion constant related to the crossing angle of the radiation, and the wall thickness of the tubular member for obtaining the wall thickness of the tubular member at a circumferential position corresponding to the crossing position. In the measurement method, when the crossing position of the radiation is out of the thickness range of the tubular member, the conversion constant is determined based on a radius of a circle connecting these crossing positions, a radius of the tubular member, and the crossing angle. And correcting the calculation result by the calculation formula using the corrected conversion constant based on a circumferential positional deviation angle between the radiation incident position on the tubular member and the intersection position. Features.

[0022]

According to the present invention, the same procedure as in the prior art is used for a tubular material in which the crossing position of the radiation emitted by an odd number of sources arranged at equal intervals outside the tubular material to be measured is within the thickness range. On the other hand, for the tubular material whose crossing position is deviated inside or outside the thickness range, the thickness is measured from the radiation detection intensity of each detector by applying a predetermined arithmetic expression. When calculating, the conversion constant included in this arithmetic expression and used to convert the transmission distance of radiation into a wall thickness, the radius of the circle connecting the intersection positions of the radiation, the radius of the tubular material, and the intersection angle of the radiation And correcting the result obtained by the arithmetic expression including the corrected conversion constant based on the circumferential positional deviation angle between the radiation incident position on the tubular member and the intersection position. And said pipe at a circumferential position corresponding to each crossover position Determine the thickness of the wood.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a schematic view showing an example of an embodiment of a method for measuring the thickness of a tubular material according to the present invention (hereinafter, referred to as the present invention method).

As shown in the figure, the method of the present invention is similar to the conventional method, except that an odd number is formed on the outside of a tubular member P to be measured and on an appropriate circumference set to have the same center as the tubular member P. N (in the figure, N = 3) radiation sources 1, 1,... Are arranged at equal intervals in the circumferential direction, and beams of radiation 3, 3,. Positioning such that the intersection occurs at the vertices of a regular N-gon,
Are arranged so as to face each other with the tubular member P interposed therebetween.

When the crossing position of the radiations 3, 3,... Is within the thickness range of the tubular material P to be measured, the radiation emitted from each radiation source 1 in the method of the present invention similarly to the conventional method described above. Intensity E _i (i = 1)
To N) and twice through the thick portion of the tubular material P
Detection intensity e _i (i = 1 to
N) and (1), and the sum of each transmission distance (ξ _i1
+ Xi] _i2) asking, this result (2), by applying the equation (3), the thickness x _i at each crossing position is determined. Here, the E _i, subscript i of e _i, the source 1, 1 ...
Indicates the number, subscript i of x _i is, i-th source 1
The crossing position where the radiation 3 emitted from the first crosses with the other radiations 3, 3,...

The method of the present invention is intended for the case where the crossing position of the radiations 3, 3 ... is outside or inside the thickness range of the tubular material P to be measured.
To determine the wall thickness x _i without changing the ... and detector 2, 2 ... arrangement position of, performing the first, second correction described below.

FIG. 1 shows an embodiment in which the crossover position is outside the thickness range of the tubular member P. Subscript i of the measured thickness x _i is as described above, the radiation 3 emitted from the i-th source 1 indicates the intersecting position intersecting the other radiation 3,3 ... and the first, FIG. 1 also in the state shown in, the wall thickness x _i in the radial line passing through the respective intersecting position is measured.

[0028] At this time, the transmission position of the radiation 3 on the circumference of the tubular member P is different from the measurement position of the wall thickness x _i,
The sum of the transmission distances of each radiation 3 (ξ _i1 + の_i2 ) is the intensity E _i of the radiation 3 at the time of emission from each source 1 (i =
1 to N) and the detection intensities e _i (i = 1 to N) of the radiation 3 captured by the corresponding detector 2 can be obtained by substituting into the equation (1).

The sum of the transmission distances thus obtained (ξ _i1
+ Ξ _i2 ) is the distance along the transmission path of each radiation 3,
The above equation (2) corresponds to an equation for converting this length into a length along the radius line of the tubular material P. However, the conversion constant k in this equation is intended for the case where the crossing position of the radiation 3 is within the thickness range of the tubular material P, and in the state shown in FIG. The inclination angle is
Since it is different from that in FIG.
Cannot be used.

The first correction in the method of the present invention is to correct the conversion constant k so as to eliminate the error caused by the difference in the inclination angle. Figure 2 is an explanatory view of the correction contents, the crossing position of the radiation 3, as shown in the diagram in the tubular member P ₁ within the thickness range, of the radiation 3 to the radius line R ₁ passing through the intersecting position Is the half of the crossing angle between the radiations 3 and 3, and the sum of the transmission distances of the radiation 3 (ξ _i1 + ξ _i2 ) is calculated by multiplying by the conversion constant k given as the cosine of the inclination angle. It can be converted to a length along the line.

Similarly, in the tubular member P ₀ where the crossing position of the radiation 3 is outside, the sum of the transmission distances of the i-th radiation 3 (ξ _i1 + _{ｉ i2} ) obtained by the equation (1) is calculated. And an angle θ ′ formed between this and a radius line R ₀ including the transmitting portion thereof.
Conversion coefficient k '(= cos θ') given as the cosine of
Is multiplied by the thickness x at the first and second transmission positions.
The sum (x _i1 ′ + x _i2 ′) of _{i 1} ′ and x _i2 ′ can be obtained.

T _i ′ = x _i1 ′ + x _i2 ′ = k ′ (ξ _i1 + ξ _i2 ) (4)

As is apparent from FIG. 2, the radiation 3 and the radius R
_The angle θ ′ formed between the center line ′ between the radius line R ₁ passing through the intersection with the other radiation 3 and the radius line R ₀ and the half value (= θ) of the intersection angle at the intersection position ) And the conversion constant k ′ is obtained by the following equation.

K ′ = cos θ ′ = cos (θ + ψ) (5)

In this equation, the inclination angle θ as a half value of the crossing angle is a constant determined according to the number of the radiation sources 1, 1,..., As shown in FIG. Are three, θ = π / 6, and more generally, the number of the radiation sources 1, 1,... Is N, and the radiations 3, 3,.
In the case of intersecting in a regular polygon, the inclination angle θ is represented by the following equation.

Θ = π / 2N (6)

On the other hand, the central angle [psi, from the geometric relationships shown in FIG. 2, the radius r ₁ of the circle passing through radiation 3,3 ... intersecting position of the reference radius r ₀ of the tubular member P _0, and the inclined It can be obtained by the following equation including the angle θ.

[0038]

(Equation 1)

The reference radius r ₀ in the equation (7) is equal to the tubular material P ₀
An appropriate radius within the range of the thickness can be adopted. In FIG. 2, although the mean radius of the inner and outer diameters are a reference radius r _0, it is also possible to reference the radius r ₀ of the inner diameter or outer diameter of the tubular member P. The tilt angle θ is uniquely determined by the equation (6) using the number N of the arranged sources 1, 1,..., And the radius r ₁ of the circle passing through the intersection position is determined by the arrangement of the sources 1, 1,. It is uniquely determined according to the configuration. Therefore, the central angle ψ can be determined by the above equation (7).
By substituting into the equation, the conversion constant k 'when the crossing position of the radiations 3, 3 ... is outside the thickness range of the tubular material P is determined. The conversion constant k 'is conventionally determined based on the radius r _{1 of} a circle passing through the intersection of the radiations 3, 3,..., The reference radius r ₀ of the tubular member P ₀ to be measured, and the intersection angle between the radiations 3, 3. Is converted to the conversion constant k.

Using the conversion constant k 'determined in this way, the sum T _i ' of the thickness at each of the first and second transmission positions of each radiation 3 can be obtained by the operation according to the equation (4).
Further, by solving a simultaneous equation in which T _i in Expression (3) is replaced with T _i ′, x _i ′ can be obtained as the wall thickness. However, when the crossing position of the radiations 3 and 3 is outside the thickness range of the tubular material P, the T _i ′ is a value obtained by adding the desired measurement position, that is, the thickness on the radial line passing through each crossing position. Not
Since it is merely the sum of the thicknesses of the positions on the both sides in the circumferential direction of the radius line which are separated by a considerable distance of the central angle ψ, a large error occurs in x _i ′ obtained by solving the equation (3). I do.

The second correction in the method of the present invention is (4)
This is performed in order to convert the calculation result by the expression and the expression (3) into the wall thickness at the intersection position. This correction is based on the premise that the thickness variation of the tubular material P consists only of the addition of components having periodicity in the circumferential direction, or that the variation component having no periodicity is extremely small. FIG. 3 shows a typical thickness pattern of various tubular materials P exhibiting a thickness variation having a single period.

The tubular member P shown in FIG. 3 (a) has one thin portion and one thick portion at positions circumferentially separated from each other by π, and the thickness between them is sinusoidal. It has a thickness pattern that changes in a wavy manner, and in the following description, this type of tubular material P is described as having a first-order thickness variation.
Further, the tubular material P shown in FIG. 3B has two thin portions and two thick portions at positions spaced apart from each other by π / 2 in the circumferential direction, and the thickness between them is sinusoidal. It has a wavy varying thickness pattern, and this type of tubular material P is described as having a secondary thickness variation.

The tubular member P shown in FIG. 3C generally has M thin portions and thick portions at positions circumferentially spaced apart from each other by π / M. Has a wall thickness pattern in which the wall thickness varies sinusoidally, and in the following description, this kind of tubular material P is described as having an Mth-order wall thickness variation. The actual tubular material P is in a state where the thickness fluctuations of the 1st to Mth order are mixed, and in the method of the present invention, the tubular material P including the thickness variation of the Mth order is measured, and the accurate measurement result is obtained. In order to obtain the number of radiations 3,3 ... N
Must satisfy the following equation.

N ≧ 2M + 1 (8)

Here, as shown in FIG.
The second correction will be described for the case where the number N of... This correction is effective because the tubular material P to be measured includes only the primary thickness variation, or the secondary or greater thickness variation is sufficiently smaller than the primary thickness variation. Is the case.

Using T _i 'obtained from equation (4),
The solution obtained by solving the simultaneous equations of the equation (3) is generally given by the following equation.

X ₁ ′ = x _a + xδ ₁ ′ x ₂ ′ = x _a + x δ ₂ ′ (9) x ₃ ′ = x _a + xδ ₃ ′

The first term (average thickness x _a ) of the expression (9) is the thickness of the radiation 3, 3,... At the transmission position of each of the radiations 3, 3,. Sum, T _i '
Is obtained as the average value of

X _a = (T ₁ ′ + T ₂ ′ + T ₃ ′) / 6 (10)

The second term of the equation (9) is generated due to the circumferential thickness variation of the tubular material P to be measured, and the above-mentioned (4) is applied to each of the three radiations 3, 3,. It is expressed by the following equation using the operation result T _i 'of the equation.

Xδ ₁ ′ = {(T ₃ ′ −T ₂ ′) − (T ₂ ′ −T ₁ ′)} / 3 xδ ₂ ′ = {(T ₁ ′ −T ₃ ′) − (T ₃ ′ − T ₂ ′)｝ / 3 (11) xδ ₃ ′ = {(T ₂ ′ −T ₁ ′) − (T ₁ ′ −T ₃ ′)} / 3

Here, when the tubular material P mainly including the primary thickness variation is measured, the thickness x of the tubular material P is
It is expressed by the following equation including the circumferential angle φ.

X = x ₀ + δ ₁ sin (φ + α ₁ ) (12)

At this time, as shown in FIG. 4, at a measurement point n (crossing position of the radiation 3) having a circumferential angle of φ _n from an appropriate reference line passing through the center O of the tubular material P, the equation (11) is obtained. (T _{n + 1} ′ −T _n ′) included in the left side of is represented by the following equation.

T _{n + 1} ′ −T _n ′ = 2δ ₁ cos (φ _n + α ₁ ) {sin} + sin (π / 3 + ψ)｝ (13)

When the intersection position of the radiations 3, 3,... Is within the thickness range of the tubular body P, δx _i ′ obtained by the equation (11)
Is high, and x _i ′ obtained by the equation (9) corresponds to the wall thickness value x _i at each measurement position with high accuracy.
In this case, the central angle ψ is zero. Therefore, the crossing position of the radiations 3, 3,... Is outside the thickness range of the tubular body P, and
If ≠ 0, the second term xδ _i ′ of equation (9) (i = 1 to
3) based on the thickness value x _i at each measurement position, and has a _1-fold error ratio C expressed by the following equation.

[0057]

(Equation 2)

In the above description, the case where the crossing position of the radiations 3, 3,... Is outside the tubular material P has been described.
When the crossing position is inside the tubular member P, by setting the central angle 負 to be negative, the above-described equations are satisfied, and the same correction can be performed.

Next, a more general case in which the thickness x of the tubular body P to be measured is represented by the following equation using the phase angle φ will be described.

[0060]

(Equation 3)

J in the expression indicates the order of the thickness variation component in the tubular material P. When the measurement channel (the number of radiations 3, 3,... Used for measurement) is N, M = (N−1).
/ 2th order thickness variation component can be measured. In this case, the error ratio C _j (j = 1 to M) with respect to the jth order variation component
Is calculated based on the concept described in the case of three channels (N = 3), and is expressed by the following equation.

[0062]

(Equation 4)

[0063] That is, errors due to the circumferential direction of the misalignment between the radiation 3,3 ... transmission position and radiation 3,3 ... intersecting position of the, 1 to M following fluctuation component is C ₁ -C _M times In the method of the present invention, the second correction is performed by paying attention to this.

Specifically, first, using T _i ′ obtained by using the equation (4), an N-order simultaneous equation similar to the above equation (3) is solved, and the thickness x _i ′ (i = 1 to N), and the fluctuation component is obtained by Fourier series expansion as shown in the following equation.
It is separated into the M-th order fluctuation component. X _a in the equation is an average value of the wall thickness of the tubular material P.

X _i ′ = x _a + A ₁ sin (φ _i + α ₁ ) + A ₂ sin (2φ _i + α ₂ )... + A _M sin (Mφ _i + α _M ) (18)

Here, φ _i indicates the circumferential angle of the radius line R ₀ passing through the intersection where the i-th ray 3 first intersects the other rays 3.

Next, (16), (17) using a seek error ratio C _j appearing in 1~M pieces of each fluctuation component, the error ratio C corresponding fluctuation component of each of the in (18) By dividing by _j , the error associated with the displacement described above is eliminated,
The sum x _{i of the} thicknesses on the radius line R _O passing through the intersections of the radiations 3, 3,... Is obtained.

X _i = x _a + A ₁ sin (φ _i + α ₁ ) / C ₁ + A ₂ sin (2φ _i + α ₂ ) / C ₂ ... + A _M sin (Mφ _i + α _M ) / C _M (19)

The error ratio C _{j serving as} a correction coefficient can be corrected based on the result of a measurement experiment using a tubular member P having a known thickness variation component, thereby improving accuracy. It is possible.

Note that, strictly speaking, the above correction by the method of the present invention is performed when the number of measurement channels is N, that is, when the number of radiations 3 used for measurement is N, the M of the tubular material P to be measured is M (= (N-1) / 2) It is effective only for the thickness fluctuation component of the order or less, but also for the tubular material P including the fluctuation component of the order M or more, these are the fluctuation components of the order M or less. Is effective when it is smaller than

FIG. 5 is a flowchart showing the procedure for implementing the method of the present invention. Each step enclosed by a solid line in the drawing is a process unique to the method of the present invention, and each step enclosed by a broken line is performed in the same manner as in the related art.

FIG. 6 shows an embodiment of the method of the present invention using a 9-channel device, and FIG. 7 shows the measurement results obtained with this device. The device shown in FIG. 6 has nine sources 1, 1,... And detectors 2, 2,.
Are arranged at an interval of 40 °, and the radiations 3, 3,... From the respective radiation sources 1, 1,... Cross each other on a circumference having a diameter of 180 mm.

In FIG. 7, the marks Δ and × indicate the measurement by the conventional method for the tubular material P whose tube diameters are 120 mm and 340 mm, and where the intersections of the radiations 3, 3... Each result is shown, and in this case, a result deviating from the actual thickness distribution shown by the solid line in the figure is obtained.
On the other hand, the circles in the figure indicate the measurement results after correction by the method of the present invention, and these are correctly matched on the curve showing the actual wall thickness distribution. It is clear from the figure. The correction conversion factor k 'and local correction coefficient C ₁ -C ₄ was used in obtaining the above results are shown in Table 1.

[0074]

[Table 1]

[0075]

As described above in detail, according to the method of the present invention, when the crossing position of the radiation is out of the thickness range of the tubular material to be measured, it is reduced according to the transmission distance of the thick portion. A first correction for correcting a conversion constant for converting the detected intensity of radiation to a distance along a radial line based on a radius of a circle connecting intersections of the radiation, a radius of the tubular material, and an intersection angle; The second correction is performed to correct the calculation result of the thickness using the conversion constant obtained by the correction based on the positional deviation angle in the circumferential direction between the incident position and the intersection position of the radiation. It is possible to accurately measure the thickness of the tubular material having various diameters without changing the position of the radiation source for emission and the detector for detecting the radiation transmitted through the tubular material, and a movable mechanism for changing the position. Is no longer required, allowing for various pipe production processes Such application is facilitated, the present invention provides excellent effects.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an embodiment of the method of the present invention.

FIG. 2 is an explanatory diagram of correction contents of a conversion constant.

FIG. 3 is an explanatory diagram of a thickness variation component held by a tubular material to be measured.

FIG. 4 is an explanatory diagram of an error correction content accompanying a positional shift in a circumferential direction.

FIG. 5 is a flowchart showing a procedure for implementing the method of the present invention.

FIG. 6 is a schematic diagram showing an embodiment of the method of the present invention using a nine-channel device.

FIG. 7 is a diagram comparing thickness measurement values obtained by the method of the present invention and a conventional thickness measurement method.

FIG. 8 is a schematic diagram showing an implementation state of a conventional thickness measuring method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Source 2 Detector 3 Radiation P Tubular material

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01B 15/00-15/08

Claims (1)

(57) [Claims] 1. Any two of radiations emitted from an odd number of radiation sources arranged at equal intervals in the circumferential direction on the outside of a tubular material to be measured, any two of the radiations are positive inside these arrangement circumferences. Intersect at the vertices of the polygon, to detect the intensity of each radiation transmitted again through the inside of the tubular material and outside,
These detected intensities are applied to a predetermined arithmetic expression including a conversion constant related to the crossing angle of the radiation, and the wall thickness of the tubular member for obtaining the wall thickness of the tubular member at a circumferential position corresponding to the crossing position. In the measurement method, when the crossing position of the radiation is out of the thickness range of the tubular member, the conversion constant is determined based on a radius of a circle connecting these crossing positions, a radius of the tubular member, and the crossing angle. And correcting the calculation result by the calculation formula using the corrected conversion constant based on a circumferential positional deviation angle between the radiation incident position on the tubular member and the intersection position. Characteristic method for measuring wall thickness of tubular material.