JPH0513242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention comprises a metal structure made of a plate-shaped metal material and in which a fluid is disposed, and the outer surface of the metal structure is connected to the outer structure. For equipment that is hidden by objects, a corrosion inspection method that inspects the corrosion state of the hidden part of the outer surface of the metal structure that is hidden by the external structure, for example, This invention relates to a corrosion inspection method for invisible parts of the surface such as those in contact with the frame.

[Prior art]

Conventionally, methods include (a) measuring the thickness of the concealed part from the inner surface of the metal structure using an ultrasonic thickness gauge, or (b) lifting the metal structure with a crane, etc.
A method of exposing the hidden part was used (I cannot provide references).

[Problem that the invention seeks to solve]

However, with method (a) above, if fuel gas, oil, etc. are present on the inner surface of the metal structure, it takes a lot of time and money to purge and charge the internal fluid, and workers have to enter the interior. The associated work, such as assembling, dismantling, and cleaning the scaffolding, requires a lot of time and money, and there are also drawbacks such as the inability to operate equipment formed of metal structures.

In addition, with the method (b) above, it takes a lot of time and money to disconnect and reconnect other equipment parts and stands, and to expose hidden parts such as hanging, and the metal structure There was a drawback that the equipment formed by the system could no longer be operated.

An object of the present invention is to enable corrosion inspection of concealed parts to be carried out in a short time and at low cost, and furthermore, while the equipment is in operation.

[Means for solving problems]

The characteristic means of the present invention is to arrange transmitting probes and receiving probes at set intervals on both sides of the outer surface of the metal structure of the part hidden by the structure, and to the ultrasonic wave incident on the metal structure from the transmitting probe is received by the receiving probe to examine the intensity attenuation state of the ultrasonic wave as it propagates in the metal structure; A transmitting probe and a receiving probe are set at the set interval on a healthy part of the outer surface of the metal structure, and the intensity attenuation state of the ultrasonic wave as it propagates in the metal structure is investigated, By comparing the state of strength attenuation between the healthy part and the concealed part, the amount of thinning of the concealed part is measured and the corrosion state of the concealed part is inspected.The functions and effects are as follows.

[Effect]

In other words, the attenuation state of ultrasonic waves as they propagate through a metal structure mainly depends on the propagation path, the uniformity and surface roughness of the material and structure of the metal structure, and the type of couplant with the metal structure. Kimimaru.

Therefore, when adopting the characteristic configuration of the present application, the material, structure, and couplant of the metal structure can be the same in the concealed part and the healthy part, so that only changes in the propagation path and scattering due to surface roughness affect the attenuation. I will do it. Here, if the corrosion state of the outer surface of the hidden part is mild (assuming that there is no thinning due to corrosion), the wave received by the receiving probe will change in path. However, it is attenuated by scattering at corroded surface areas. As corrosion progresses further, thinning occurs and the thickness of the plate becomes thinner, the path changes, the central beam of the ultrasonic wave no longer enters the receiving probe, and it is significantly attenuated due to an increase in the number of reflections.

On the other hand, in a healthy part without corrosion, the path is determined and the central beam of the ultrasonic wave enters the receiving probe, and scattering is less likely to occur, so attenuation is very small.

Here, by comparing and examining the attenuation state of ultrasonic waves in the concealed part and the healthy part as described above, the degree of corrosion (the state of surface roughness and thinning due to corrosion) can be reliably grasped.

That is, as shown below, the inventors have confirmed for the first time through various experiments that there is a quantitative correlation between the amount of corrosion and the value of strength attenuation. An example of the experimental results is shown in FIG. The amount of corrosion on the vertical axis is calculated by (minimum wall thickness of corroded sample) ÷ (thickness of healthy sample), and the intensity attenuation value on the horizontal axis is (received intensity in corroded sample) - ( (reception strength in a healthy sample).

Therefore, by determining the difference between the strength attenuation value in the healthy part and the strength attenuation value in the concealed part, it is possible to quantitatively understand the extent to which corrosion has progressed.

〔Effect of the invention〕

As a result, corrosion inspection of hidden parts on the outer surface of metal structures can be performed from the outside of the metal structure without exposing the hidden parts, and with high accuracy, greatly reducing the time and expense required for inspection. In addition, equipment made of metal structures can be operated during inspections, making inspections extremely advantageous in terms of workability and economy as a whole.

〔Example〕

Next, an example will be shown with reference to FIGS. 1 and 2.

When inspecting the corrosion state of the part 1a of the outer surface of the metal cylindrical horizontal tank 1 that stores liquid or gas, which is hidden by the pedestal 2 that supports the tank 1,
First, on both sides of the concealed portion 1a in the width direction,
Outer surface portion 1 that moves the probes 3a and 3b
After cleaning (painting, removing rust, etc.), uniformly apply glycerin as a couplant.

Next, a pair of rails 4a, 4b made of spring plates
are adsorbed in a floating state relative to the tank 1 by the magnets 5 attached to them, and are fixed to the tank 1 by the turnbuckles 7 and the ropes 6 such as belts and wires wrapped around the tank 1, and then probed. Children 3a, 3b
is placed outside each of the outer surface portions 1b on which it acts. Incidentally, one of the frames 8a and 8b that connects the rails 4a and 4b can be freely disconnected, and when the frame 8b is in the disconnected state,
Both frames 4a and 4b are inserted into both sides of the pedestal 2.

Catasoles 9a and 9b are movably attached to the rails 4a and 4b, respectively, and a transmitting probe 3a is attached to one cassole 9a and a receiving probe 3b is attached to the other cassole 9b. Interlocked drive rollers 10a and pulleys 10b that can freely rotate
By connecting both cathodes 9a and 9b, both probes 3
A and 3b are configured to integrally move at a constant speed at a set interval l.

Then, while moving both probes 3a and 3b uniformly in the longitudinal direction of the concealed portion 1a in the direction and speed set by the controller 12, the ultrasonic waves projected from the transmitting probe 3a to the tank 1 are transmitted to the receiving probe. Received by child 3b,
The intensity of the received ultrasonic waves is observed with an oscilloscope 13a of a flaw detector 13 connected to both probes 3a and 3b, and is recorded with a recorder 14 connected to the flaw detector 13.

Further, both the probes 3a and 3b are moved across the healthy parts 1c of the outer surface located on both longitudinal sides of the hidden part 1a, and the hidden part 1a and both healthy parts 1 are moved.
Observe and record the intensity of the received ultrasound at both points.

Next, based on the records, the presence or absence of corrosion and the location of corrosion in the hidden portion 1a are determined based on the difference between the received ultrasonic intensity at the hidden portion 1a and the received ultrasonic intensity at the healthy portion 1c, and then The state of corrosion is determined quantitatively using a glass or table prepared in advance as shown in FIG.

[Another example]

Next, another embodiment will be described.

The objects to be inspected may be various tanks, piping, or anything else, which will be collectively referred to as the metal structure 1. Also, any object that hides a part of the outer surface of the metal structure 1 may be used. These are collectively referred to as external structures 2.

Hiding part 1a for transmitting and receiving probes 3a and 3b
Any jig or means may be used to distribute the probes on both sides of the metal structure 1 and set them on the outer surface of the metal structure 1. Also, any jig or means may be used to move the probes 3a and 3b. The means can also be changed as appropriate.

In order to examine and compare the intensity attenuation state of the ultrasonic waves in the concealed portion 1a and the sound portion 1c, various methods such as those described below can be used, for example.

(b) Before or after the measurement at the hidden part 1a, measure the healthy part 1c at an appropriate position using the same or different transmitting and receiving probes 3a, 3b.

(b) When measuring in the concealed part 1a, as shown in Fig. 4, the difference (ΔS) with respect to the received ultrasonic intensity in the healthy part 1c measured or set in advance is:
Display and record the received ultrasonic intensity at the hidden part 1a, or as shown in FIG.
The difference (ΔS) may be displayed and recorded as the thickness of the hidden portion 1a. Furthermore, Figures 4 and 5
The horizontal axis of the figure indicates both probes 3a,
3b shows the distance traveled, and in FIG. 5, the solid line shows the minimum wall thickness and the dotted line shows the average wall thickness.

(c) If the received ultrasonic intensity at the healthy portion 1c is known by measurement in advance, measurement at the time of inspection may be omitted.

The specific structure of the transmitting and receiving probes 3a, 3b can be changed as appropriate, for example, it is possible to fill the space between the vibrator and the metal structure 1 with water or the like as a couplant.

The intensity attenuation state of the ultrasonic waves may be measured intermittently, continuously, or at one or several points, and the measurement points may be determined as appropriate depending on the situation.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is a conceptual diagram of the main part of the inspection, and FIG. 2 is a schematic diagram of the inspection state. FIG. 3 is a graph showing experimental results, and FIGS. 4 and 5 are graphs showing recording examples. 1... Metal structure, 1a... Concealing part, 1a...
...Healthy part, 2...Structure, 3a...Emitting probe, 3b...Receiving probe, l...Setting interval.

Claims (1)

[Scope of Claims] 1. A metal structure 1 made of a plate-like metal material and having a fluid disposed therein, the outer surface of the metal structure 1 being hidden by an external structure 2. A corrosion inspection method for inspecting equipment for the corrosion state of a concealed portion 1a hidden by the external structure 2 of the outer surface of the metal structure 1, the method comprising: a transmitting probe 3a and a receiving probe. The probes 3b are arranged at set intervals l on both sides of the concealed portion 1a and set on the outer surface of the metal structure 1, and the ultrasonic waves incident on the metal structure 1 from the transmitting probe 3a are transmitted. The receiving probe 3b examines the intensity attenuation state of the ultrasonic wave as it propagates through the metal structure 1, and transmits the ultrasonic wave to a healthy portion 1c of the outer surface of the metal structure 1. Probe 3a and receiving probe 3
b is set at the set interval 1, the intensity attenuation state of the ultrasonic wave accompanying propagation in the metal structure 1 is investigated, and the intensity attenuation state in the healthy portion 1c and the concealed portion 1a is compared to determine the intensity attenuation state. A corrosion inspection method for inspecting the corrosion state of the concealed portion 1a by measuring the amount of thinning of the concealed portion 1a. 2 The transmitting and receiving probes 3a and 3b are connected to the concealed portion 1a while maintaining the set interval 1.
1. The ultrasonic wave is moved between a measurement position for the metal structure 1c and a measurement position for the healthy portion 1c, and the intensity attenuation state of the ultrasonic wave as it propagates in the metal structure 1 is intermittently examined. Corrosion testing method.