JPS5925008Y2 - Eddy current flaw detector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an eddy current flaw detector improved so that the probe is always guided to the center line of the tube even at a U-shaped tube bend.

Conventionally, eddy current flaw detectors used for flaw detection of thin tubes, etc.
As shown in FIG.
It is connected to probe 1 via.

When traveling inside the U-shaped tube 5, the flaw detection coil 2 does not pass over the center line of the tube, but with a certain amount of eccentricity due to the elastic rod 4, as shown in the opening of the figure.

That is, the deviation between the center line of the flaw detection coil 2 and the center line of the five bent portions of the U-shaped tube generally changes as the position of the flaw detector changes.

Since this variation is detected as noise in the flaw detection signal, conventional methods have had the problem of unavoidable reduction in S/H.

Therefore, this invention provides an eddy current flaw detector in which the probe is always guided on the center line of the tube in order to obtain a stable signal even at the U-shaped tube bend.

The eddy current flaw detector of this invention is characterized in that a number of guide plates each having elastic pieces provided radially through connecting members are attached to the front and rear of a probe equipped with a flaw detection coil.

Hereinafter, this invention will be explained in detail based on an illustrated embodiment.

In FIG. 2, 6 is a guide located at the tip of the tube 11, 7 is a guide plate formed by thin elastic pieces attached to the outer periphery of the tube 11 in a radial shape, for example, in the shape of a gear, and 8 is a guide plate engraved on the outer periphery. The probe has a flaw detection coil 9 installed in a groove, and a lead wire 10 of the flaw detection coil 9 passes through a tube 11 and is connected to a flaw detection device (not shown).

A large number of guide plates 7 are attached to the front and rear of the probe 8, and are made of materials that are highly abrasion resistant and have excessive elasticity, such as Teflon, nylon, vinyl chloride resin, etc.
Mylar, celluloid, etc. are used, and when attached to the tube 11, they are individually defined at small pitches by inserting inclusions or using adhesive.

Its maximum diameter is the same as the inner diameter of the U-shaped tube.

Further, as the material of the tube 11, a material having appropriate elasticity such as Teflon, nylon, or vinyl chloride resin is used.

Next, the operation of the above flaw detector will be explained.

FIG. 3 shows a state in which the flaw detector is inserted into the vertical U-shaped tube 12, and the flaw detector is inserted from A to the opening along the direction of the arrow.

Move to eight.

The attitude of the probe 8 during movement and the state of the guide plate 7 are as shown in the figure.

A force for moving the flaw detector is acting on the tube 11, and at the same time, the tube 11 tends to approach a straight line due to its own elasticity.

Therefore, the center of the tube 11 tends to move away from the center of the U-shaped tube 12.

However, when the center of the tube 11 and the center of the U-shaped tube 12 deviate from each other, the gear-shaped elastic piece forming the guide plate 7 on the outside of the tube 11 curves.

Since the guide plate 7 has appropriate elasticity, the guide plate 7
A force that attempts to remove the curvature of the tube, that is, a force that attempts to align the center of the tube 11 with the center of the U-shaped tube 12, is transmitted to the tube 11.

This force exerted by each guide plate 7 has the function of correcting the deviation between the center of the tube 11 and the center of the U-shaped tube 12, and around the probe 8 with a large number of guide plates 7 arranged on both sides. The center of the tube 11 and the center of the U-shaped tube 12 are
It passes through the U-shaped tube 12 while being consistent at all positions.

Therefore, the probe 8 is always connected to the U-shaped tube 12 as shown in the figure.
The vehicle will be traveling on the center line of

In addition, for the straight pipe portion of the U-shaped tube 12 other than the curved portion, the guide plate 7 always works to align the center of the tube 11 and the center of the U-shaped tube 12, so that the probe 8 is stabilized along the center line of the U-shaped tube 12. can be run on.

Therefore, flaw detection can be performed over the entire length of the U-shaped tube 12.

It should be noted that the guide plate 7 may be one in which elastic pieces are provided radially, and it is not limited to a gear-shaped one as in the above embodiment, but may be, for example, a brush-shaped one.

Conditions such as its thickness, installation pitch, and number of installations may be adjusted as appropriate depending on the radius of curvature of the test tube, the degree of improvement in signal reliability, the force required to move the flaw detector, the elasticity of the guide plate, etc.
It is determined.

As is clear from the above, according to the eddy current flaw detector of this invention, a stable flaw detection signal can be obtained because the probe is always guided on the center line of the tube even at a U-shaped tube bend.

Furthermore, the entire length of the pipe to be inspected, including the straight pipe section, can be inspected with high accuracy.

[Brief explanation of the drawing]

FIG. 1A7 is an explanatory diagram showing the posture of a conventional eddy current flaw detector inside a U-shaped tube. Figure 2 shows an eddy current flaw detector according to an embodiment of this invention, where A is a left side view, and Figure 2 is a front view showing a partial cross-sectional structure.
C is a right side view. FIGS. 3A and 3B are explanatory diagrams showing the posture of the flaw detector of the above embodiment in the U-shaped tube. 1...Probe, 2...Flaw detection coil,
3... Ball-shaped guide, 5... U-shaped tube, 6... Guide element, 7... Elastic guide plate, 8... Probe, 9...Flaw detection coil, 10...Lead wire, 11...Tube, 12...U-shaped tube.

Claims (1)

[Scope of utility model registration request] An eddy current flaw detector characterized in that a number of guide plates each having elastic pieces arranged radially through connecting members are attached to the front and back of a probe equipped with a flaw detection coil.