JP3358413B2 - Non-contact insulation defect inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type insulator defect inspection method for measuring the gap between a metal body and an insulator and specifying the presence or absence of the gap and the substance in the gap.

[0002]

2. Description of the Related Art When a coating or a coating material is applied to a surface of a metal body, the coating or the coating material moves between the coating and the metal body,
Gaps such as blisters and air voids occur.

[0003] Poor construction such as blows, blisters, air voids, etc., reduces the adhesive strength per unit area or the impact resistance. In addition, blister which water penetrates,
Paint coating, may be used as an indicator of coating deterioration, not only to determine the presence or absence of the gap, the substance in the gap to determine whether the substance is water or air, to investigate the cause, paint or coating It is necessary to improve the materials and coating method.

As a non-contact measuring method for measuring the gap, a distance (L ₁ ) between the sensor and a metal body is measured by an eddy current sensor, and the distance is measured by a laser type distance sensor which is a light wave type distance sensor. The distance (L ₂ ) between the sensor and the surface of the insulator such as the coating device is measured, and the difference (L ₁ −L) is measured.
A method of measuring the thickness of an insulator by calculating ₂ ) is known.

Further, the distance (L ₁ ) between the sensor and the metal body is measured by an eddy current sensor, and the capacitance between the sensor and the insulator is measured by a capacitance type distance sensor. A method of measuring the thickness of the insulator by performing the measurement is also known.

[0006]

However, the anticorrosion coating of polyethylene or the like used for the on-site welded joints of the pipeline sometimes has a gap between the metal body and water. When it enters, the anticorrosion performance is greatly reduced. Therefore, the gap is regarded as a defect.

[0007] If the gap is large, it can be detected by a finger touch test. However, if the gap is small, it is difficult to determine whether or not there is a strict gap even by a finger touch test. In most cases, they were inspected.

For this reason, it is necessary to repair the portion from which the polyethylene has been peeled off, and the repair work requires time and increases costs.

In the above-mentioned prior art, it is possible to measure the film thickness of an insulator such as an anticorrosive coating.
It is impossible to determine whether or not there is a gap between the metal body and the insulator, and whether or not water has entered the gap.

According to the present invention, the adhesion between a metal body and an insulator is continuously determined without contact, and if there is a gap, whether the gap contains water or air. The purpose of the present invention is to enable the determination of

[0011]

An object of the present invention is to provide a metal body.
(1) For a material whose surface is coated with an insulator (2) ,
An eddy current placed at a predetermined position from the material surface or
An electromagnetic first distance meter (3) from the distance meter to the surface of the metal body
To the specified position from the material surface.
With a laser or ultrasonic second rangefinder (4)
Measure the distance from the distance meter to the surface of the insulator, the material
The capacitance meter (5) placed at a predetermined position from the surface
The capacitance formed between the capacitance meter and the metal body
And the distance measured by the first distance meter (3), and
And the distance measured by the second distance meter (4)
Based on the capacitance measured by the capacitance meter (5)
A noncontact insulator defect inspection method is characterized in that the presence or absence of a gap between the metal body and the insulator and the substance in the gap are determined.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a measuring device used for a non-contact type insulator defect inspection method according to the present invention.

1 is a metal body such as a steel plate, and 2 is a coating of the metal body 1 which is an insulator. 3 is the distance to the metal body 1 (L
₁ ) is an eddy current or electromagnetic distance meter for measuring the distance; 4 is a laser or ultrasonic distance meter for measuring the distance (L ₂ ) to the surface of the coating device 2; Is a capacitance meter for measuring the capacitance (C) including the air layer between the substrate and the coating device 2, and 6 is a calculator and a monitor.

In the present invention, first, the distance (L ₁ ) to the metal body 1 is measured with an eddy current or electromagnetic distance meter 3, and then the surface of the coating 2 is measured with a laser or ultrasonic distance meter 4. Is measured (L ₂ ). Next, the capacitance (C) between the air layer and the metal body 1 including the coating 2 is measured by the capacitance meter 5.

The following relationship is established between the measured values. L ₁ −L ₂ = t ₁ + t _{2 −−} (1) C _a = ε ₀ × ε _a × S / L ₂ −−− (2) C ₁ = ε ₀ × ε ₁ × S / t ₁ −− − (3) C ₂ = ε ₀ × ε ₂ × S / t _2- (4) 1 / C = 1 / C _a + 1 / C ₁ + 1 / C _2- (5) where t ₁ Is the thickness of the coating, t ₂ is the value of the gap between the coating and the metal body, C _a is the capacitance of the air layer, C ₁ is the capacitance of the coating, and C ₂ is the thickness of the coating and the metal body. The capacitance ε ₀ of the gap is the dielectric constant of vacuum (= 8.855 × 10 ⁻¹² F /
m) epsilon _a is the dielectric constant of the air (= 1.0) ε ₁ is the dielectric constant epsilon ₂ of Nurikutsugae Paneling is the dielectric constant of the material that meets the gap of the coating-covering and the metal body S is the effective electrode area of the capacitance meter.

Therefore, when the above equations (1) to (5) are arranged, L ₁ −L ₂ = t ₁ + t _{2 −} (1) 1 / C = ( L ₂ / ε _a + t ₁ / ε ₁ + t ₂ / ε ₂ ) / (ε ₀ × S) − (− 6)

In the above equation, L ₁ , L ₂ , and C are measured values, and ε ₀ , ε _a , and S are known values. Also,
Dielectric constant epsilon ₁ of Nurikutsugae Paneling is determined in advance by test piece, and the like. Further, the thickness t ₁ of the coating is determined by measuring a sound portion where it is known that there is no gap between the coating and the metal body in the vicinity of the measurement portion and setting t ₂ = 0 in the equation (1). You can ask. If there is no abrasion of the coating, the initial thickness of the coating may be used.

Therefore, the value t of the gap between the coating and the metal body
₂ and the relative permittivity ε ₂ of the substance that fills the gap between the coating and the metal body are unknown, so the values are (1),
It can be obtained from equation (6).

As a result, if t ₂ = 0, there is no gap between the insulator and the metal body. If t ₂ ≠ 0, there is a gap between the insulator and the metal body. If the obtained relative dielectric constant ε ₂ is compared with the relative dielectric constant of various substances measured in advance, the substance that fills the gap can be known.

When the substance filling the gap between the insulator and the metal body is a conductive liquid such as water, (6)
Expression becomes _{1 / C = (L 2 /} ε a + t 1 / ε 1) / (ε 0 × S) --- as (7).

Therefore, if it is known that the substance that may fill the gap between the coating and the metal body is a conductive liquid, the thickness t ₁ of the coating must be determined in advance. At least, the thickness t _{1 of the} coating and the value t ₂ of the gap can be obtained from the equations (1) and (7).

[0022]

EXAMPLES The following comparative tests were performed on the present invention and the conventional example. In Tables 1 and 2 below, a mark “〇” indicates a good judgment, and a mark “X” indicates that the judgment is impossible.

Embodiment 1 FIG. Specimen 300 × 300 × 8t
(Mm) is subjected to a grinder treatment, an adhesive layer 1.5 mm is formed thereon, and the outer layer is a polyethylene layer 1.5 mm.
It was constructed with painted coating. At the time of construction, a test body intentionally provided with a void 7 was prepared as shown in FIG. 2 (cross-sectional view). The size of the void was three kinds of 20 mm, 10 mm, and 5 mm in width, and was a strip-shaped void having a length of 200 mm and a height of 0.6 mm. The void contains air. In addition, the adhesive layer 2
The combination of a and the polyethylene layer 2b is an insulator.

As a comparative example with the present invention, the results of comparison with visual observation and finger touch are shown in Table 1.

[0025]

[Table 1]

Embodiment 2 FIG. The test body and the void were the same as in Example 1, and the void contained water.

As a comparative example with the present invention, the results of comparison with visual observation and finger touch are shown in Table 2.

[0028]

[Table 2]

[0029]

As described above, according to the present invention, the inspection of the presence or absence of air bubbles, blisters, and voids between an insulator such as a coating or a coating material on a metal body and the metal body is accurately measured without contact. it can.

Further, it is possible to determine whether water or air is present in the gap between the insulator and the metal body, and there is an effect that cost can be reduced for on-site response.

[Brief description of the drawings]

FIG. 1 is a block diagram of a measuring device used in a non-contact type insulator defect inspection method of the present invention.

FIG. 2 is a sectional view of a test body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal body 2 Painted covering (insulator) 3 Eddy current or electromagnetic range finder 4 Laser or ultrasonic range finder 5 Capacitance meter 6 Calculator and monitor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/00-27/24 G01B ⁷ /00-7/34

Claims (1)

(57) [Claims] An eddy current or a eddy current placed at a predetermined position from a surface of a metal body (1) coated with an insulator (2).
An electromagnetic first distance meter (3) from the distance meter to the surface of the metal body
Measuring the distance to the laser or a laser placed at a predetermined position from the material surface
Using an ultrasonic type second distance meter (4), an insulator table is obtained from the distance meter.
A capacitance meter that measures a distance to a surface and is arranged at a predetermined position from the material surface
(5) The cap formed between the capacitance meter and the metal body
The distance measured by the first distance meter (3);
The distance measured by the distance meter (4) and the capacitance meter
A noncontact insulator defect inspection method, comprising: determining whether or not a gap exists between a metal body and an insulator and determining a substance in the gap based on the capacitance measured in (5) .