JP3154948B2 - Flaw detection sensor unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current inspection / ultrasonic inspection probe used for inspection of heat transfer tubes of various heat exchangers of a nuclear power plant, and an eddy current used for inspection of various small diameter pipes of a petroleum / chemical plant. The present invention relates to a flaw detection / ultrasonic flaw detection probe, a laser inner diameter measurement probe, and a flaw detection sensor unit that can be used for a small CCD camera or a fiberscope casing used for visual inspection of a thin tube.

[0002]

2. Description of the Related Art Conventionally, when inspecting a long (about 100 m) thin tube (heat transfer tube) having a curved tube portion (minimum bending R160) using eddy current or ultrasonic waves, it is necessary to send a flaw detection probe into the tube. At the same time, a spherical float (pressure receiving body) is provided at equal intervals on the cable, and gas pressure or water pressure is applied to the float at the same time as the mechanical pressure is applied to the float, and the transport cable is driven (propelled) by the pressure difference generated at this time, The flaw detection probe is inserted. A method of inserting such a flaw detection probe will be described with reference to FIG. This example is a steam generator 1
This is a case where the inspection of the heat transfer tube 11 is performed. The tube 22 is extended from the probe insertion device 20 to the tube sheet positioning device 12 to which one end of the heat transfer tube is connected, and the transfer cable 2 gripped in the cable storage tank 20a of the probe insertion device 20 is connected to the tube by the rotation of the motor. At the same time, nitrogen gas is pressurized and sent from the gas supply / distribution unit 21 to the storage tank 20a. The pumped gas flows through the helical coil portion 11a, the vent portion 11b, and the downcomer portion 11c of the heat transfer tube 11 through the tube 22, and is exhausted from the tube sheet positioning device 13. In the drawing, the gas is exhausted for convenience. However, the gas is collected in the gas supply and distribution unit 21 without actually exhausting the gas. A flaw detection probe 1 is attached to the front of the transport cable 2, and floats 3 are attached to the transport cable 2 at equal intervals. FIG.
As shown in the figure, the gas flows and a pressure difference occurs before and after the float, and when the pressure difference exceeds a certain value, the float starts to move, and as a result, the entire transport cable moves and the flaw detection probe is inserted. .

When pulling out the flaw detection probe 1, the delivery port of the gas supply / distribution unit 21 is connected to the tube sheet positioning device 13.
Next, the suction ports are connected to the storage tanks 20a, respectively, and gas is pressure-fed in the opposite direction to the heat transfer tubes 11, and the transport cable is rewound by the motor of the probe insertion device 20.

The float and the probe are attached to the carrier cable by opening a through hole in the center of the float and the probe, passing the cable through the hole, and fixing the cable with an adhesive and a wedge.

[0005]

However, in a case where the subject has a long and curved tube portion and has a complicated helical shape, the fluid to be pumped as the insertion distance into the tubule increases. There is a problem that the flaw detection sensor unit rattles due to the fluid force or the contact with the inner wall of the subject, or the vibration in the tube radial direction or the tube axis direction is generated, giving wobbling noise to the flaw detection signal. Therefore, the pumping fluid (gas,
There is a strong need for a flaw detection sensor unit that absorbs vibration and rattling of the flaw detection sensor unit caused by the flow force of water, the contact with the inner wall of the subject, and the like, and reduces wobbling noise as much as possible.

SUMMARY OF THE INVENTION An object of the present invention is to reduce wobbling noise caused by vibration of a flaw detection sensor unit caused by the flow force of a pumping fluid (gas, water) or contact with an inner wall of a subject when a flaw detection probe is inserted into a thin tube. And to improve the detectability of the eddy current inspection data. Further, an object of the present invention is to change the structure, shape, material, etc. of the alignment mechanism (contact portion with the inner wall of the subject) incorporated in the flaw detection sensor unit, so that the flaw detection sensor unit absorbs vibration and backlash. It is to provide a possible flaw detection sensor unit. Also,
SUMMARY OF THE INVENTION An object of the present invention is to provide stable flaw detection data with reduced wobbling noise in eddy current flaw detection of a long length, which has been relatively difficult so far, and a helical thin tube having a curved pipe portion. Is to get it.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an apparatus for attaching a flaw detection probe to a cable provided with a plurality of floats and inserting the cable into a long thin tube by fluid pressure to detect a flaw in the thin tube. O-ring rubber fins for absorbing vibration and backlash are embedded in grooves provided on the outer periphery of the casing of the current flaw detection sensor unit to reduce wobbling noise. Further, the present invention is characterized in that the O-ring shaped rubber fins are provided before and after the sensor unit.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In the following, an eddy current inspection probe will be described as an example, but the present invention can be similarly applied to an ultrasonic inspection probe. FIG. 1 is an overall view of a transport cable of the present invention, FIG. 2 is a view for explaining the principle of eddy current flaw detection, and FIG.
FIG. 3 is an explanatory diagram of an eddy current flaw detection sensor unit of the present invention.
In addition, 1 is an eddy current flaw detection probe, 2 is an eddy current flaw detection sensor unit, 3 is a float, 4 is a transport cable, 5 is a casing, 6 is a rubber rubber fin, 7 is a detection coil, 8
Indicates a coil wire connection groove. In FIG. 1, a transfer cable float 3 serves as a pressure receiving body when the eddy current flaw detection probe 1 is inserted into a thin tube by a fluid pressure such as gas pressure or water pressure, and is connected to the flaw detection probe 1. It is attached to the cable 4 at equal intervals (about 100 mm pitch). A plurality of eddy current flaw detection sensor units 2 are arranged in the flaw detection probe 1, connected to the transport cable 4, and inserted into the thin tube by fluid pressure such as gas pressure or water pressure. The driving force (thrust) for inserting the flaw detection probe 1 into the pipe is obtained by the pressure difference between the individual floats 3 attached to the transport cable 4.

The principle of measurement of the eddy current flaw detection method will be described with reference to FIG. 2. For example, when an eddy current flaw detection sensor having a transmission coil and a reception coil is inserted into the heat transfer tube 11 and an alternating current is applied to the transmission coil, the current As a result, a magnetic field (direct magnetic field) is generated, and an eddy current flows in the heat transfer tube 11 so as to cancel the magnetic field directly. A magnetic field (indirect magnetic field) is generated by the eddy current. If a defect exists in the heat transfer tube, these magnetic fields are disturbed. Therefore, a defect can be detected by detecting the magnetic field with the receiving coil. Specifically, the impedance change of the coil is detected, and in the case of the inductive self-comparison method, two coils having different winding directions are connected to a bridge circuit to serve as a transmission coil and a reception coil, and the impedance change is measured. Thus, defect detection is performed. In this case, if the sensor vibrates radially or axially in the heat transfer tube or rattles, the relative position between the tube and the coil changes even in a portion where there is no defect, a signal is generated, and a noise signal is generated. Will be.

The present invention is characterized in that the generation of such a noise signal is reduced. The eddy current testing probe of the present invention is shown in FIG.
(B) As shown in (cross-sectional view), the sensor unit is housed in a circular casing. FIG.
The upper half of (a) shows a cross section, and the detection coil 7 serves both to generate a magnetic field and to detect eddy current. The coil is wound in a groove formed in the circumferential direction of the cylindrical sensor unit, and the two coils are Each is wound in the opposite direction and connected to a bridge circuit (not shown) in the sensor unit. After the coil is wound around the groove, as shown by hatching in the lower half of FIG. 3A, a resin-based adhesive is poured to fix the coil. Of course, a type in which the transmission coil and the reception coil are separated (remote field method) may be used.

Rubber rubber fins 6 are provided before and after the casing 5 of the sensor unit. The rubber rubber fin 6 is an O-ring made of a silicone rubber material, and is fixed by being fitted into a groove on the outer periphery of the casing 5. The outer diameter of the rubber rubber fin 6 is φ21 mm smaller than the outer diameter φ20 mm of the eddy current flaw detection sensor unit.
mm. Therefore, when the eddy current flaw detection sensor unit 2 is inserted into the subject, the outermost periphery of the rubber rubber fin 6 contacts (collides) with the inner wall of the subject. At this time, the rubber rubber fins 6 reduce the contact impact between the eddy current flaw detection sensor unit 2 and the inner wall of the subject. The axial length of the eddy current flaw detection sensor unit 2 is shown in FIG.
As shown in (a), the rubber rubber fins 6 are arranged at two front and rear positions of the casing 5 of the sensor unit 2 in order to widen the contact position with the subject because of the cylindrical shape having about 50 mm.

With such a configuration, it is possible to absorb vibrations and rattling of the flaw detection sensor unit caused by the fluid force of the pumping fluid, the contact with the inner wall of the subject, and the like, thereby suppressing the occurrence of wobbling noise. Became.

[0013]

As described above, according to the present invention, when the flaw detection probe is inserted into the subject (small tube), the flaw of the flaw detection sensor unit caused by the flow force of the pumping fluid or the contact with the inner wall of the subject is reduced. The wobbling noise caused by vibration can be reduced. Also, until now, for example,
By using the eddy current flaw detection sensor unit of the present invention, the wobbling noise which was about 4 V in the eddy current flaw detection signal value is reduced to about 0.5 V or less, which is a level at which the flaw detection signal is not affected. It became possible to do. Further, it can be inserted into the entire length of a helical object (capillary tube) having a long length (about 100 m) and a curved tube portion (minimum bending R160), and reduce wobbling noise in the entire length of the object. Is now possible.

[Brief description of the drawings]

FIG. 1 is an overall view of a transport cable of the present invention.

FIG. 2 is a diagram illustrating the principle of the eddy current flaw detection method.

FIG. 3 is an explanatory diagram of an eddy current flaw detection sensor unit of the present invention.

FIG. 4 is a diagram illustrating a method of inserting a flaw detection probe.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Eddy current eddy flaw detection probe, 2 ... Eddy current flaw detection sensor unit, 3 ... Float, 4 ... Transport cable, 5 ... Casing, 6 ... O-ring rubber rubber fin, 7 ... Detection coil, 8 ... Coil wire connection groove.

Claims (2)

(57) [Claims] 1. An apparatus for attaching a flaw detection probe to a cable provided with a plurality of floats and inserting the cable into a long thin tube by fluid pressure to test the inside of the thin tube. Vibration in the groove provided
A flaw detection sensor unit in which wobbling noise is reduced by embedding O-ring rubber fins for absorbing rattling . 2. The flaw detection sensor unit according to claim 1, wherein the O-ring rubber fins are provided before and after the sensor unit.