JPH05288735A - Ultrasonic probe for flaw-detecting boiler tube - Google Patents

Abstract

PURPOSE:To perform inspection on a crack and a thinned-out volume of a tube in a tube axial direction and a circumferential direction occurring on an attached metal joint of a boiler tube at almost the same time by single insertion for one loop of the boiler tube. CONSTITUTION:A single vertical probe 8 for confirming a welding beam shape and position and measuring a thinned volume of a tube is mounted on a probe body 7 inserted into a boiler tube so that it is movable in an axial direction and rotatable around a tube axis. Further two bevel probes 9a, 9b for the tube axis and two bevel probes 10a, 10b for a circumference are mounted with their backs facing each other respectively. Thus inspection on a crack in a tube axis direction and a circumferential direction and the thinned volume can be performed approximately at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe for boiler tube flaw detection, which is suitable for flaw detection in a welded portion of a metal attachment of a boiler tube or the amount of thinning of the tube.

[0002]

2. Description of the Related Art In a superheater or reheater of a thermal power boiler, a fatigue crack caused by thermal stress due to start and stop occurs in a welded metal part of a boiler tube, and the tube also corrodes at high temperatures and ash cuts. Due to such factors, the thickness is reduced, causing stress corrosion cracking. However, the superheater, reheater, etc., have a narrow tube interval of 50 to 100 mm and are inaccessible to the inspector. Therefore, conventionally, the fatigue crack and the amount of wall thinning are confirmed by collecting the sample tube. There is. However, this method is a sampling inspection, and there are concerns that it may be overlooked because the inspection points are limited. As one of the solutions to this problem, the ultrasonic immersion flaw detection method has been used in recent years to detect the cracks in thin metal deposits on boiler tubes and the thinning amount of the tubes from the inside of the tubes. Non-destructive inspection methods using offspring have been studied and are being applied on a trial basis.

However, cracks in the axial direction and the circumferential direction of the welded metal welded portion of the boiler tube and the amount of wall thinning of the tube can be measured from the inside of the tube by using the water immersion ultrasonic flaw detection method. When inspecting using an ultrasonic probe, currently, there is a dedicated ultrasonic probe required for each flaw detection, that is, a probe for crack detection in the axial direction of the pipe and a probe for crack detection in the circumferential direction. , 3 types of probe for thinning amount flaw detection are inserted into the pipe by reassembling, and each flaw detection is performed individually. However, with this method, the time required for reassembling for insertion, the time required for each flaw detection, etc. becomes long, the work efficiency is poor, and the target boiler tube of the target is in the process permitted for the inspection. 100% inspection may be difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above circumstances, and reduces cracks and pipes in the axial direction and the circumferential direction that occur in the welded metal welded portion of the boiler tube. An object of the present invention is to provide an ultrasonic probe for flaw detection in a boiler tube, which enables inspection of the meat amount to be performed at approximately the same time by inserting once for one loop of the boiler tube.

[0005]

To this end, the present invention is a probe for inspecting cracks in the axial direction of a boiler tube and the circumferential direction of the boiler tube and the amount of thinning of the tube from the inside of the tube by means of water immersion ultrasonic flaw detection. A probe body inserted into the pipe so as to be movable in the pipe axis direction and rotatable around the pipe axis, and the shape and position of the weld bead mounted on the probe body, the position is confirmed, and the wall thickness reduction of the pipe is measured. And a beveled probe for detecting cracks in the pipe axis direction and the circumferential direction, which are mounted on the probe body two by two. It is characterized by

[0006]

According to the ultrasonic probe for boiler tube flaw detection of the present invention, the amount of cracks and thinning amount of the tube generated in the welded metal deposit of the boiler tube and the like can be determined from the inside of the pipe by the water immersion type ultrasonic flaw detection. Since non-destructive inspection is possible, 100% inspection is possible even with boiler tubes such as superheaters and reheaters that are inaccessible to inspectors, and polishing of the outer surface of the pipe and scale removal for inspection are unnecessary. Also, in the past, when inspecting cracks in the axial direction and circumferential direction of welded metal welds, etc., and the amount of thinning of the pipe, each one required a dedicated flaw-detection probe. By assembling the five probes having the above as a composite probe, it is possible to perform a composite inspection at approximately the same time with one insertion of one loop of the boiler tube, and the workability is greatly improved.

In order to collect a plurality of flaw detection probes as a composite probe, the probes are arranged by the probe mounting method as seen in each dedicated flaw detection probe. Therefore, as a composite probe, the length in the tube axis direction becomes long, and there is a possibility that the passability through the curved tube portion will deteriorate. Therefore, the two sides of each of the two probes for crack detection in the tube axis direction and the circumferential direction are placed back to back on the side that does not radiate ultrasonic waves, and the ultrasonic waves are radiated in the same 180 ° different directions. The length is shortened by mounting it in the state.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ultrasonic probe for boiler tube flaw detection of the present invention will be described with reference to the drawings. FIG. 1 shows the present probe, FIG. 1 (a) is a side view, and FIG. FIG. 2 is a front view, FIG. 2 is a vertical cross-sectional view of the above rotating mechanism, FIG. 3 is an explanatory view of an inspection procedure using a vertical probe, FIG. 4 is an explanatory view of an inspection procedure using a bevel probe for a tube axis, and FIG. FIG. 6 is an explanatory view of an inspection procedure using a bevel probe for a circumference, FIG. 6 is a side view showing a mode in which the present probe passes through a curved pipe portion, and FIG. 7 is a diagram for detecting an adhered metal weld portion by the present probe. FIG. 8 is a perspective view showing a mode, and FIG. 8 is an explanatory view of the aligning jig in the above.

In FIG. 1, a vertical probe 8 for inspecting the amount of thinning of the pipe and confirming the shape of the weld bead is mounted in the center of a probe body 7 that can move in the pipe axis direction and rotate about the pipe axis. In the front of the probe main body 7, pipe-angle oblique probes 9a and 9b for pipe axial crack inspection are mounted back-to-back, and at the rear of the probe main body 7 in the circumferential direction. Circumferential bevel probes 10a and 10b for crack inspection are mounted back to back. Further, one cantilever 11 is attached to the probe main body 7 with a pin 12, and the cantilever 11 is mounted with the oblique angle probes 9a and 9b for pipe axes. The cantilever 11 has a spring 13 and a pin 1 attached to a fulcrum.
2 always tries to be eccentric in the outer diameter direction of the pipe, but the eccentricity adjustment ring 14 and the ring fixing cap nut 15 provided in the probe main body 7 restrain the eccentricity, and the cantilever 11 moves to the ring 14. Since the eccentricity can be achieved only up to the contact position, the optimum eccentricity amount can be varied according to the pipe specifications.

Further, in order to hold the probe main body 7 on the tube axis center line, the spring shaft 1 is provided at both ends of the probe main body 7.
6 is attached, and a centering jig is attached. As shown in FIG. 2, this spring shaft 16 is directly connected to bearings 18 attached to both ends of the probe main body 7, and the vertical probe 8 and the four beveled probes 9a, 9b, 1
The probe main body 7 on which 0a and 10b are mounted is a rotary shaft 17 having a double structure with the spring shaft 16.
Is driven to rotate in the circumferential direction. That is, since the bearing 18 is built in between the probe main body 7 and the spring shaft 16 and the probe main body 7 and the rotary shaft 17 are directly connected by the fixing screw 19, the probe 18 is rotated as the rotary shaft 17 rotates. The child body 7 also rotates.

In such an ultrasonic probe, a procedure for confirming the weld bead shape and position and measuring the amount of wall thinning by the vertical probe 8, the oblique angle probes 9a and 9b for pipe axes and the oblique angle for circumference. FIG. 3 shows how to detect cracks by the angle probes 10a and 10b.
5 will be described. In FIGS. 3 to 5, 1 is a boiler tube, 2a is a pipe axis adhered metal, 2b is a circumferential adhered metal, 3a is a pipe axis welded part, 3b is a circumferential welded part, 4a is a pipe axial crack, 4b is Circumferential cracks, 5 is water, and 6 is a thinned portion. First, FIG. 3 shows the inspection of the thinned portion 6 of the boiler tube 1 with the vertical probe 8 and the welding portions 3a and 3b.
The vertical probe 8 is held on the diametrical tube center line, and while actually rotating in the circumferential direction and moving in the tube axial direction, The amount of thinning of the thinned portion 6 and the bead shape and position of the welded portions 3a and 3b are checked. When the vertical probe 8 is at the position of the pipe axial direction c, ultrasonic multiple echo by the thinned portion 6 of the pipe is obtained. Similarly, when it is at the position of the pipe axial direction b, the wall thickness of the base metal of the pipe is obtained. Multiple echoes are obtained. On the other hand, when the vertical probe 8 is in the position of the pipe axis direction a or the position of the pipe axis direction d, the ultrasonic wave incident on the pipe material propagates into the welded portions 3a and 3b, and the outside of the welded portions 3a and 3b. Ultrasound reflection echo cannot be obtained due to diffuse reflection on the surface. As shown in these figures, the case where an ultrasonic multiple echo is obtained is used for the inspection of the thinning amount of the pipe, and the case where the ultrasonic multiple echo is not obtained is used for the confirmation of the welding bead.

FIG. 4 shows a crack 4a in the axial direction of the tube, which is generated in the tube axis welded portion 3a of the tube axis attached metal 2a of the boiler tube 1.
Shows the case of inspecting with two tube-angle bevel probes 9a and 9b in consideration of the directionality of defect detection. The bevel probes 9a and 9b are the ones that do not emit ultrasonic waves. They are back-to-back with each other, and are held at a position that is eccentric to the pipe axis by an arbitrary amount δ that maximizes the detection of cracks in the pipe diametrical direction and rotates in the circumferential direction and in the pipe axial direction. It shows how to move. Further, FIG. 5 shows two circumferential bevel probes for the circumferential crack 4b generated in the circumferential welded portion 3b of the circumferentially adhered metal object 2b of the boiler tube 1 in consideration of the directionality of defect detection. In the case of inspecting with 10a, 10b, the beveled probes 10a, 10b have their sides that do not emit ultrasonic waves back to back, and the angle θ at which the detection of a defect is maximum with respect to the diametrical tube center line of the tube is shown. Only _i is held by being tilted in the tube axis direction, and it is shown that it rotates in the circumferential direction and moves in the tube axis direction.

FIG. 6 shows a state where the probe main body 7 passes through the curved pipe portion. Since both ends of the probe main body 7 are supported by the spring shafts 16, the curved pipe of the boiler tube 1 is shown. It is easy to pass through the department.

Further, referring to FIG. 7, a description will be given of a mode in which the ultrasonic probe is used to detect flaws in the vicinity of the weld metal welded portion (circumferential direction welded portion) of the boiler tube. The centering jig 20 thus prepared holds the boiler tube 1 on the center line of the tube axis. As a result, each probe 8, 9a, 9b, 10a, 10b is constantly fed in the tube axial direction by running water or the like while rotating in the boiler tube 1 under a constant condition, inspecting the amount of thinning of the tube, and welding bead Check the shape and position, and also inspect the cracks in the welded portion of the adhered metal in the axial and circumferential directions. 21 in the figure
Is a centering jig holding spring, 22 is a holding spring adjusting nut,
Reference numeral 23 is a guide.

Now, the aligning mechanism of the aligning jig 20 and the structure of the guide 23 will be described. The aligning jig 20 uses nylon 24 as a material, and the number of strands per share is The length of the material is controlled, and as shown in FIG. 8, when the diameter of the aligning jig 20 is larger than the inner diameter of the tube, the nylon 24 is uniformly crushed and the probe main body 7 can be aligned. Becomes In this case, if the probe main body 7 is not properly aligned, each of the probes 8, 9a, 9b, 10a, 10b during rotation and tube feed.
The holding conditions for the tube axis, etc. are not constant and the inspection performance deteriorates or the inspection becomes impossible. Further, the guide 23 has a Teflon ball attached to the tip of the spring shaft 16 and prevents the tip of the spring shaft 16 from sticking to a protrusion such as the inner surface of the welded portion.

Thus, according to such an ultrasonic probe, the amount of thinning of the thinned portion 6 of the boiler tube 1 and the adhered metal welded portions 3a, 3b etc. are generated from the inside of the boiler tube 1 by the water immersion method. Since the cracks 4a and 4b can be inspected, it is not necessary to polish the outer surface of the pipe or remove scale for inspection. Further, the vertical probe 8 for inspecting the amount of thinning of the pipe is used for confirming the shape and position of the welding bead, so that it is generated in the welded portion by the beveled probes 9a, 9b, 10a, 10b. When inspecting the cracks 4a and 4b, it is easy to identify the weld bead and the defect and to determine the positional relationship.
Also, a bevel probe 9 for pipe axial and circumferential crack inspection.
a, 9b, 10a, and 10b are mounted so that two of them are back-to-back, regardless of the welding root and welding toe, either channel is always formed at the corner formed by the pipe surface and cracks. Since ultrasonic waves can be injected, it is possible to inspect regardless of the direction of pipe axis feed, and one looped boiler tube is inserted into the pipe once, and the thinning amount of the pipe and the welded metal deposits are generated at approximately the same time. It is possible to inspect cracks in the pipe axial direction and in the circumferential direction, and it is possible to perform precise inspection with extremely good workability.

[0017]

In summary, according to the present invention, a probe for inspecting a crack in the axial direction of the boiler tube and a circumferential method and a thinning amount of the tube from the inside of the tube by a water immersion type ultrasonic flaw detection. , A probe body inserted into the pipe so as to be movable in the pipe axis direction and rotatable about the pipe axis, and a shape for welding bead mounted on the probe body, confirmation of the position, and measurement of the amount of wall thinning of the pipe. Two vertical probes and two back to back of the above probe body.
4 for detecting cracks in the axial and circumferential directions mounted individually
Since it is equipped with a single angle probe, it is possible to check the cracks in the axial and circumferential directions of the welded metal parts of the boiler tube and the amount of thinning of the tube per one loop boiler tube. INDUSTRIAL APPLICABILITY The present invention is extremely useful industrially because it provides an ultrasonic probe for boiler tube flaw detection that can be performed at approximately the same time with one insertion.

[Brief description of drawings]

FIG. 1 shows an embodiment of an ultrasonic probe for boiler tube flaw detection according to the present invention. FIG. 1 (a) is a side view and FIG. 1 (b) is a front view.

FIG. 2 is a vertical cross-sectional view of the above rotating mechanism.

FIG. 3 is an explanatory diagram of an inspection procedure using a vertical probe.

FIG. 4 is an explanatory diagram of an inspection procedure using a bevel probe for a tube axis.

FIG. 5 is an explanatory diagram of an inspection procedure using a circumferential bevel probe.

FIG. 6 is a side view showing a mode in which the present probe passes through a curved tube portion.

FIG. 7 is a perspective view showing a mode in which the present probe detects flaws on an adhered metal welded portion.

FIG. 8 is an explanatory view of an aligning jig in the above.

[Explanation of sign]

 1 Boiler tube 2a Pipe shaft attached metal 2b Circumferentially attached metal 3a Pipe shaft weld 3b Circumferential weld 4a Pipe axial crack 4b Circumferential crack 5 Water 6 Thin wall portion 7 Probe body 8 Vertical probe 9a, 9b Angle probe for shaft axis 10a, 10b Angle probe for circumference 11 Cantilever 12 Pin 13 Spring 14 Eccentricity adjustment ring 15 Ring fixing cap nut 16 Spring shaft 17 Rotary shaft 18 Bearing 19 Fixed Screw 20 Aligning jig 21 Aligning jig Holding spring 22 Holding spring adjusting nut 23 Guide 24 Nylon

Claims (1)

[Claims] 1. A probe for inspecting a crack in a tube axial direction of a boiler tube and a circumferential method and a thinning amount of the tube by a water immersion ultrasonic flaw detection from the inside of the tube, wherein the tube axial direction is in the tube. A probe main body inserted so as to be movable and rotatable around the pipe axis, and one vertical probe mounted on the probe main body for confirming the weld bead shape and position and measuring the amount of thinning of the pipe. , A super-boiler tube for ultrasonic flaw detection, comprising four beveled probes for detecting cracks in the pipe axial direction and in the circumferential direction, each of which is mounted two back to back on the probe body. Sonic probe.