The comparison test block shall be selected from the non-defective steel pipe of the heat treatment process and the surface condition of the safety door guide pipe material. The 2.3.2 circumferential test comparison test block shall be selected from the section length 30.1 mountain 1 and the inner and outer walls shall be added 1 length 4 , 60-point slot with a depth of 1.5, the sharp-angle groove along the axial direction of the sample tube. Test block size 1.
1 Equipment situation Our factory slogan furnace is made in the Soviet Union to type boiler, 50s products, equipment overtime service, running time up to 29 force 1 than far from design life, gold, tube aging is serious. The safety door guide pipe uses a temperature of 540, a pressure of 10 cubits, 3; a specification of 019481 material is 12, side, steel pipe.
2 preparation work 21 instrument using = pharyngeal pulse reflection type ultrasonic flaw detector. In the case of contact method, the ultrasonic energy can meet the relevant standards. 22 Coupling agent coupling agent should be selected to have a correspondingly higher viscosity from the cleaning material.
2.3.3 Axial test comparison test block Select the length of 300 claw-like tube, the inner and outer walls are processed to a depth of 1.5, 60 sharp angle ring groove, the test block size 2.
3.1 Circumferential Scanning Detection Process 3.1.1 The choice of the head is to check the sensitivity of the small defect in the film height. Select 5 to add the head of the piezoelectric wafer size 144, and the detecting surface of the probe is ground to match the surface of the steel pipe to be inspected. Surface.
32 When the probe is selected to use the transverse wave outer circumferential direction to detect the pipe workpiece, for the determined pipe diameter and wall thickness, the following formula should be satisfied to ensure that the ultrasonic energy can be scanned to the inner wall. 5 small.
The diameter of the ultrasonic wave is 12;P ultrasonic incident angle, which is the selected probe value. Only when the type 1 is satisfied, the ultrasonic beam can be scanned to the inner wall of the tube. According to the boiler safety door guide steam, the probe can be selected when the probe is actually used for the actual flaw detection. 3.3.1 The scanning speed is adjusted. The scanning speed is adjusted on the comparison test block according to the sound path. The sharp corner of the inner wall of the steel tube should be observed on the fluorescent screen. Slot defect wave and outer wall sharp groove defect wave.
3.1.4 Injury Sensitively Set the head of the head to be placed on the comparative test block to make a week of sweeping apricots, adjust the echo height of the artificial sharp corner groove on the inner wall to 80 of the full scale of the fluorescent city, and then move the probe to find the artificial tip of the outer wall. The maximum echo of the angular slot is the distance amplitude curve of the probe connected to the screen by 2 points. As the reference sensitivity, the sensitivity is increased by 6 on the basis of the reference sensitivity.
3.1.5 å–³ mode probe is spirally running in the circumferential direction of the steel pipe. The pitch of the spiral wire should not be too large when scanning; the scanning speed of the probe on the steel pipe should not exceed 15, 18; the ultrasonic beam should be 100 for the steel pipe. Scanning, and coverage of not less than 15; each steel pipe should be tested once from the opposite ends of the pipe in the circumferential direction.
3.1.6 Defect determination During the scanning process, when the defect is found, the instrument should be adjusted to the baseline sensitivity. If the defect echo amplitude is equal to or greater than the artificial sharp groove defect echo of the comparison test block, it is determined to be unqualified. .
3.2 Axial scanning detection process 3.2.1 Probe selection According to the wall thickness of the steel pipe, choose the special value, choose the large fire value as the thin plate, so as to avoid the influence of the near-field area; choose the small value in the thick plate to shorten the sound path and reduce the sorrow. The sensitivity of the detection is still reduced. In the actual flaw detection, considering the refraction angle of the probe in the range of 3555, the detection sensitivity of the crack is high, and the probe of the first is used. Similarly, the probe surface of the probe is ground to a curved surface that matches the surface of the pipe to be inspected.
2 The adjustment of the drawing speed adjusts the scanning speed according to the depth, and the sharp groove wave inside and outside the steel pipe should be observed on the fluorescent screen.
3 Detection sensitivity On the contrast test block of 2, the highest echo of the internal artificial defect is adjusted to 80 of the full scale of the fluorescent screen, and then the highest echo of the artificial defect is found, and the peak connection is the depth amplitude curve, which is used as the detection sensitivity. , flaw detection, sensitivity and then mention 6 3.2.4 scanning method When the defect is found, you can use the corner scan to determine the defect orientation; use the surrounding scan to determine the shape of the defect.
3.2.5 Defect determination In the scanning process, when the defect is found, the instrument should be adjusted to the baseline sensitivity. If the core defect wave amplitude is greater than or equal to the comparison of the 1st block artificial sharp groove defect echo, it is determined to be unqualified.
4 On-site actual flaw detection When testing the safety door guide steam pipe base material of 12 boilers, it was found that two serious defects were about 10, 1 strip-shaped inclusions, the length of the section was 30, and the inner wall of the steel pipe was about 24, and the tortoise was large. The timely detection of the defects at the crack 2 avoids the occurrence of major accidents in the plant equipment. When the inclusions in the base material of the steel pipe are in the vicinity of the base material, there is a defect wave near the outer side of the base material, and there is a considerable length of about 01 claws along the axial direction of the tube, and the probe moves parallel in the axial direction. In 10,1, the wave height is basically equal, and the defect 艮 linear training ratio test block owing phase groove wave 184 from the steel tube outer clothing blood observation without cracks and scratches changed to the foot 8 probe re-examination, the defect wave still exists. After comprehensive analysis, it was determined that the strip-shaped defects were inside the tube. After the defect tube was cut, the position of the defect wave was polished from the outer thin corner to the machine, and 1 grinding was deep and found. 1 strip of length 105 inclusions. , 4.2 steel tube base material crack with fire 1 probe along the axial direction of the pipe, when the position of 6 is checked, firstly in the axial direction, there are many abnormalities in the inner wall of the lower half of the steel pipe in the range of length 301. Wave = analysis of the safety door guide steam pipe operating state This part is in normal operation, squatting tube. Easy to accumulate water. The temperature difference changes fire, generates temperature difference stress, and is prone to thermal fatigue cracks.
Observing the waveform and dynamic range, it is found that the peak of the defect is sharper and higher, and the wave height is much larger than the artificial peak angle of the contrast test block. When the probe is translated, the amplitude of the wave is high and low, and the peak of the wave is shifted up and down when the probe rotates. .
Superheater outlet header safety door steam guide with a ruler 1 probe along the circumferential direction also found a number of crack characteristic cracks on the site will be safe door steam pipe cutting tube, the inner wall can observe the network turtle crack. 7 no.
5 Conclusions In recent years, the above method was used to ultrasonically inspect the outer tube of the No. 16 high-pressure furnace of our factory, and many defects such as heavy cracks in the steel pipe were found.
The method of ultrasonic flaw detection on the outer base material of the boiler furnace is simple, reliable and easy to grasp. It is an effective method and has a certain promotion value.
Wang Huaisi, male, engineer, metal room of Fuxin Power Plant is engaged in non-destructive testing.
Received date 200009
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