A method for correcting the defect depth of TOFD detection of longitudinal welds of cylinder

Abstract

The present invention relates to the field of special equipment detection. The purpose is to provide a method for correcting the depth of defects in TOFD detection of a longitudinal weld of a cylinder. The method can significantly improve the depth positioning accuracy of defects by correcting the display depth, bringing convenience to subsequent defect repair. The technical scheme is: a method for correcting the depth of defects in TOFD detection of a longitudinal weld of a cylinder, which is carried out according to the following steps: 1) Calculate the process parameters according to the flat plate butt weld, and use two probes arranged at an interval distance to perform TOFD detection on the longitudinal weld of the cylinder according to the process parameters to obtain the propagation time t0 of the straight wave, the propagation time t1 of the diffraction wave of the upper end point of the defect, and the propagation time t2 of the diffraction wave of the lower end point of the defect; 2) Select the process parameters required for defect depth calculation: the center distance between the two probes 2S, the outer radius R of the cylinder, and the inner radius r of the cylinder; 3) Calculate the display depth of the defect; 4) Calculate the correction amount Δh of the defect depth; 5) Defect depth correction.

Description

Technical Field

[0001] The invention relates to the field of special equipment detection, and in particular to a method for correcting defect depth during TOFD detection of a longitudinal weld of a cylinder, which is used for correcting defect depth during TOFD detection. Background Art

[0002] TOFD (Time-of-Flight Diffraction Ultrasonic Testing Technology) has been widely used in the inspection of welding joints of special equipment such as boiler drums and spherical tanks. During TOFD inspection, it is necessary to measure the parameters such as the defect position, defect length, defect depth, and defect height found during the inspection to evaluate the degree of damage of the defect.

[0003] The welding joints tested by TOFD include flat butt welds, cylinder butt girth welds, and cylinder butt longitudinal welds. The setting of the detection parameters and the calibration of the existing TOFD testing instruments are designed based on flat butt welds. The process parameter setting methods of flat butt welds and cylinder butt girth welds are the same, but the cylinder butt longitudinal weld will produce relatively large deviations when setting process parameters and calculating defect depth. If the defect depth is not corrected, it will affect the accuracy of the defect parameter evaluation and will also cause trouble when repairing defects that exceed the standard. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned background technology and provide a method for correcting the depth of defects in TOFD detection of a longitudinal weld of a cylinder.

[0005] The technical solution of the present invention is:

[0006] A method for correcting the defect depth of a shell longitudinal weld by TOFD detection is carried out in the following steps:

[0007] 1) Calculate the process parameters according to the flat plate butt weld, and use two probes arranged at an interval to perform TOFD detection on the longitudinal weld of the cylinder according to the process parameters to obtain the propagation time t0 of the straight wave, the propagation time t1 of the diffraction wave at the upper end of the defect, and the propagation time t2 of the diffraction wave at the lower end of the defect;

[0008] 2) Select parameters: Select the process parameters required for defect depth calculation: the center distance between the two probes 2S, the outer radius R of the cylinder, and the inner radius r of the cylinder;

[0009] 3) Calculating the display depth of the defect; based on the data of step 1) and step 2), calculating the display depth h1′ of the upper endpoint of the defect and the display depth h2′ of the lower endpoint of the defect;

[0010] 4) Calculate the correction amount Δh of the defect depth;

[0011] 5) Defect depth correction; according to the correction amount of the defect depth in step 4), the display depth of the upper endpoint of the defect and the display depth of the lower endpoint of the defect are corrected to obtain the upper endpoint depth h1 of the defect and the lower endpoint depth h2 of the defect.

[0012] The calculation formula for measuring the display depth of the defect in step 3) includes: the display depth of the upper end point of the defect Display depth of the lower endpoint of the defect c is the ultrasonic wave propagation velocity in the workpiece.

[0013] The correction amount Δh for calculating the defect depth in step 4) includes:

[0014] ① If the instrument is calibrated on a flat test block and the TOFD test uses a scan of the outer surface of the cylinder, then:

[0015]

[0016] ② If the instrument is calibrated on a flat test block and TOFD testing uses scanning of the inner surface of the cylinder, then: Δh = r(1-cosθ);

[0017] ③ If the instrument is calibrated on the cylinder and TOFD detection uses scanning of the outer surface of the cylinder, then: Δh = R (1-cosθ);

[0018] ④ If the instrument is calibrated on the cylinder and TOFD detection uses scanning of the inner surface of the cylinder, then: Δh = r(1-cosθ);

[0019] θ is half of the angle between the normals of the two probe center points.

[0020] The defect depth correction of step 5) includes:

[0021] ① When TOFD inspection uses the outer surface of the cylinder to scan, the depth of the upper end point of the defect h1 = h1′ + Δh, and the depth of the lower end point of the defect h2 = h′2 + Δh;

[0022] ②When TOFD detection is performed by scanning the inner surface of the cylinder, the depth of the upper end point of the defect h1≈h1′-Δh, and the depth of the lower end point of the defect h2≈h′2-Δh.

[0023] The process parameters of step 1) include: probe center distance 2S, cylinder outer radius R, and cylinder inner radius r.

[0024] The two probes are respectively arranged on both sides of the longitudinal weld of the cylinder to perform TOFD detection.

[0025] The beneficial effects of the present invention are:

[0026] In order to solve the problem of large quantitative error in the depth of defects in the longitudinal weld of a cylinder, the present invention proposes a method for correcting the depth of defects in TOFD detection of the longitudinal weld of a cylinder. This method can significantly improve the depth positioning accuracy of defects by correcting the displayed depth, thus bringing convenience to subsequent defect repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of TOFD inspection of flat plate butt weld.

[0028] Figure 2 It is a schematic diagram of TOFD inspection of the longitudinal weld of the cylinder (external surface scanning).

[0029] Figure 3 It is a schematic diagram of TOFD inspection of the longitudinal weld of the cylinder (inner surface scanning).

[0030] Figure 4 It is a flow chart of defect depth correction of the present invention. DETAILED DESCRIPTION

[0031] See also Figure 4 A method for correcting the defect depth of a shell longitudinal weld by TOFD detection is carried out in the following steps:

[0032] 1) Calculate the process parameters according to the flat plate butt weld, perform TOFD inspection on the longitudinal weld of the cylinder according to the process parameters, and obtain the propagation time t0 of the straight wave, the propagation time t1 of the diffraction wave at the upper end point of the defect, and the propagation time t2 of the diffraction wave at the lower end point of the defect;

[0033] The process parameters include: probe center distance 2S, cylinder outer radius R, cylinder inner radius r.

[0034] 2) Select parameters; Select the process parameters required for defect depth calculation: probe center spacing (PCS) 2S, cylinder outer radius R, cylinder inner radius r;

[0035] 3) Calculating the display depth of the defect; based on the data of step 1) and step 2), calculating the display depth h1′ of the upper endpoint of the defect and the display depth h2′ of the lower endpoint of the defect;

[0036] Display depth of the upper endpoint of the defect Display depth of the lower endpoint of the defect c is the ultrasonic wave propagation velocity in the workpiece;

[0037] h1′ and h2′ are calculated based on the butt weld of the flat plate; h1′ and h2′ can also be calculated on the TOFD instrument. The depth obtained by the TOFD instrument is also calculated based on the butt weld of the flat plate;

[0038] 4) Calculate the correction value Δh of the defect depth (as shown in Table 1)

[0039] ① If the instrument is calibrated on a flat test block and the TOFD test uses a scan of the outer surface of the cylinder, then:

[0040] ② If the instrument is calibrated on a flat test block and TOFD testing uses scanning of the inner surface of the cylinder, then: Δh = r(1-cosθ);

[0041] ③ If the instrument is calibrated on the cylinder and TOFD detection uses scanning of the outer surface of the cylinder, then: Δh = R (1-cosθ);

[0042] ④ If the instrument is calibrated on the cylinder and TOFD detection uses scanning of the inner surface of the cylinder, then: Δh = r(1-cosθ); Table 1

[0043]

[0044] θ is half of the normal angle between the two probe center points;

[0045] 5) Defect depth correction: The correction amount of defect depth is related to whether the TOFD test is performed inside the cylinder or outside the cylinder, and whether the TOFD test process parameters are adjusted on the flat test block or on the cylinder (as shown in Table 2);

[0046] According to the correction amount of the defect depth in step 4), the display depth of the upper endpoint of the defect and the display depth of the lower endpoint of the defect are corrected to obtain the upper endpoint depth h1 of the defect and the lower endpoint depth h2 of the defect:

[0047] ① When TOFD inspection uses the outer surface of the cylinder to scan, the depth of the upper end point of the defect h1 = h1′ + Δh, and the depth of the lower end point of the defect h2 = h′2 + Δh;

[0048] ②When TOFD inspection uses the inner surface of the cylinder to scan, the depth of the upper end point of the defect h1≈h1′-Δh, and the depth of the lower end point of the defect h2≈h′2-Δh;

[0049] Table 1

[0050]

[0051] The corrected defect depth is the actual depth of the defect, which can accurately evaluate the defect parameters and bring convenience to defect repair.

[0052] Example

[0053] TOFD test was carried out on the longitudinal weld of a boiler drum. The material of the boiler drum was 13MnNiMoR with the specification of φn1600×90. TOFD test was carried out in accordance with NB / T 47013.10-2015 Nondestructive Testing of Pressure Equipment.

[0054] Step 1: Perform thickness zoning during testing. Channel 1 uses a 5MH probe at φ6mm with a wedge angle of 70° to test the 0-36mm area. Channel 2 uses a 3.5MH probe at φ10mm with a wedge angle of 60° to test 36-90mm. The sound beam of each channel is focused at 2 / 3 of the test area. According to the process parameters calculated for the flat butt weld, the probe center spacing (PCS) of Channel 1 is 132mm, and the probe center spacing (PCS) of Channel 2 is 249mm.

[0055] According to the calculated process parameters, TOFD inspection is performed on the longitudinal weld of the cylinder;

[0056] Step 2: Select parameters; channel 1 probe center spacing (PCS) 2S = 132mm, channel 2 probe center spacing (PCS) 2S = 249mm, cylinder outer radius R = 890mm, cylinder inner radius r = 800mm;

[0057] Step 3: Measure the display depth of the defect. Use the defect depth measurement function on the TOFD instrument to measure the display depth of the upper and lower endpoints of the defect. The measurement results are as follows:

[0058] 1) Scan the outer surface of the cylinder, and the detection results of channel 1 are: the displayed depth h1′ of the upper end point of the defect is 28mm, and the displayed depth h2′ of the lower end point of the defect is 31mm;

[0059] 2) Scan the inner surface of the cylinder, and the detection results of channel 2 are: the display depth h1′ of the upper end point of the defect is 66.5mm, and the display depth h2′ of the lower end point of the defect is 69.5mm;

[0060] Step 4: Calculate the correction amount for defect depth

[0061] 1) Scan the cylinder surface

[0062] ① If the process parameters are adjusted on the flat test block, the depth correction Substitute the value R = 890mm, So Δh=2.45mm;

[0063] ② If the process parameters are adjusted on the barrel, the depth correction Δh=R(1-cosθ), where (Unit: °), substitute the values ​​R = 890mm, S = 66mm, and calculate: (Unit: °), Δh = 890 × (1-cos4.25) = 2.44 mm;

[0064] 2) Scan the inner surface of the cylinder

[0065] ①If you adjust the process parameters on the plate, (Unit: °), Δh = r (1-cosθ), substitute the value r = 800mm, get: (Unit: °), Δh = r (1-cosθ) = 800 × (1-cos8.953) = 9.75 mm;

[0066] ② If the process parameters are adjusted on the cylinder, (Unit: °), Δh = r (1-cosθ), substitute the numerical value to get:

[0067] (Unit: °),

[0068] Δh=r(1-cosθ)=800×(1-cos8.916)=9.67mm;

[0069] Step 5: Defect depth correction: Based on the displayed depth of the defect and the depth correction amount, the actual depth of the defect can be obtained according to the calculation formula.

[0070] 1) Scan the cylinder surface

[0071] ① If the process parameters are adjusted on the flat test block, the actual depth of the upper end point of the defect is h1 = 28 + 2.45 = 30.45 mm, and the actual depth of the lower end point of the defect is h2 = 31 + 2.45 = 33.45 mm;

[0072] ② If the process parameters are adjusted on the cylinder, the actual depth of the upper end point of the defect is h1 = 28 + 2.44 = 30.44 mm, and the actual depth of the lower end point of the defect is h2 = 31 + 2.44 = 33.44 mm;

[0073] 2) Scan the inner surface of the cylinder

[0074] ① If the process parameters are adjusted on the flat plate, the actual depth of the upper end point of the defect h1≈66.5-9.75=56.75mm, and the actual depth of the lower end point of the defect h2≈69.5-9.75=59.75mm;

[0075] ② If the process parameters are adjusted on the cylinder, the actual depth of the upper end point of the defect h1≈66.5-9.67=56.83mm, and the actual depth of the lower end point of the defect h2≈69.5-9.67=59.83mm.

[0076] Derivation process of TOFD defect depth correction

[0077] 1. TOFD detection of flat plate butt welds (such as Figure 1 (shown)

[0078] There are two probe groups on the workpiece, one for transmitting and one for receiving, which are used to excite and receive ultrasonic signals respectively. There is a defect in the workpiece, the upper end point of the defect is marked as 1, and the lower end point of the defect is marked as 2. Assume that probe A is used as an ultrasonic transmitting probe, and probe B is used as an ultrasonic receiving probe. The incident point of the sound beam of probe A is A, and the incident point of the sound beam of probe B is B. The signals received by probe B include the straight wave signal (along the A→B path), the diffraction signal of the upper end point of the defect (along the A→1→B path), the diffraction signal of the lower end point of the defect (along the A→2→B path), the bottom surface reflection wave signal (along the A→K→B path), and the deformation wave signal (not used for defect location calculation, not considered here).

[0079] The distance between the probe incident points A and B (PCS) is defined as 2S, the distance between the defect and the upper surface of the workpiece is the defect depth, the depth of the upper end point of the defect is recorded as h1, the depth of the lower end point of the defect is recorded as h2, and the ultrasonic propagation speed in the workpiece is recorded as c.

[0080] Direct wave propagation time:

[0081] Diffraction wave propagation time of the upper defect endpoint 1

[0082] Diffraction wave propagation time of the defect lower end 2

[0083] Defect endpoint 1 depth

[0084] Defect endpoint 2 depth

[0085] 2. Cylinder longitudinal weld inspection (external surface scanning)

[0086] TOFD inspection of longitudinal weld of cylinder (external surface scanning) Figure 2 When the TOFD test is performed on the longitudinal butt weld of the cylinder, due to the curvature of the surface, the straight wave does not propagate along the arc surface, and the calculation method of the defect depth is still based on the calculation of the flat plate butt weld, without considering the influence of the curvature of the cylinder surface.

[0087] There are two probe groups on the workpiece, one for transmitting and one for receiving, which are used to excite and receive ultrasonic signals respectively. There is a defect in the workpiece, the upper end point of the defect is marked as 1, and the lower end point of the defect is marked as 2. Assume that probe A is used as an ultrasonic transmitting probe, and probe B is used as an ultrasonic receiving probe. The incident point of the sound beam of probe A is A, and the incident point of the sound beam of probe B is B. The signals received by probe B include the straight wave signal (along the A→n→B path), the diffraction signal of the upper end point of the defect (along the A→1→B path), the diffraction signal of the lower end point of the defect (along the A→2→B path), the bottom surface reflection wave signal (along the A→K→B path), and the deformation wave signal (not used for defect location calculation, not considered here).

[0088] The distance between the two probe incident points A and B (PCS) is defined as 2S, the distance between the defect and the upper surface of the workpiece is the defect depth, the depth of the upper end point of the defect is recorded as h1, the depth of the lower end point of the defect is recorded as h2, and the ultrasonic propagation speed in the workpiece is recorded as c. The distance between points m and n is Δh.

[0089] There are generally two ways to perform TOFD testing on the longitudinal weld joints of the cylinder:

[0090] 1. Adjust the instrument on a flat test block. This adjustment method is characterized by the chord length It is equal to the calculated distance between the two probe incident points (PCS), 2S.

[0091] Direct wave propagation time:

[0092] Diffraction wave propagation time of the upper defect endpoint 1:

[0093] The propagation time of the diffraction wave at the upper end point 2 of the defect:

[0094] The depth deviation is:

[0095] The depth calculated by the instrument according to the flat workpiece (displayed depth):

[0096]

[0097] Correct the defect depth: h1=h1′+Δh, h2=h′2+Δh.

[0098] 2. Adjust the instrument on the cylinder. This adjustment method is characterized by the arc length It is equal to the calculated distance between the two probe incident points (PCS), 2S.

[0099] (Unit: °);

[0100] S'=Rsinθ

[0101] Δh=R(1-cosθ)

[0102] Direct wave propagation time:

[0103] Diffraction wave propagation time of the upper defect endpoint 1:

[0104] The propagation time of the diffraction wave at the lower end 2 of the defect:

[0105] The instrument calculates the depth (displayed depth) based on the flat workpiece:

[0106] Defect upper endpoint: Defect upper endpoint:

[0107] Correct the defect depth: h1=h1′+Δh, h2=h′2+Δh.

[0108] 3. TOFD inspection of longitudinal weld of cylinder (inner surface scanning)

[0109] TOFD inspection of longitudinal weld of cylinder (inner surface scanning) Figure 3 As shown. There are two probe groups on the workpiece, one for transmitting and one for receiving, which respectively excite and receive ultrasonic signals. There is a defect in the workpiece, the upper end point of the defect is marked as 1, and the lower end point of the defect is marked as 2. Assume that probe A is used as an ultrasonic transmitting probe, and probe B is used as an ultrasonic receiving probe. The incident point of the sound beam of probe A is A, and the incident point of the sound beam of probe B is B. The signals received by probe B include the straight wave signal (along the path A→m→B), the diffraction signal of the upper end point of the defect (along the path A→1→B), the diffraction signal of the lower end point of the defect (along the path A→2→B), the bottom surface reflection wave signal (along the path A→K→B), and the deformation wave signal (not used for defect location calculation, not considered here).

[0110] The distance between the two probe incident points A and B (PCS) is defined as 2S, the distance between the defect and the upper surface of the workpiece is the defect depth, the depth of the upper end point of the defect is recorded as h1, the depth of the lower end point of the defect is recorded as h2, and the ultrasonic propagation speed in the workpiece is recorded as c. The distance between points m and n is Δh.

[0111] There are generally two inspection methods for TOFD inspection of longitudinal welded joints of the cylinder:

[0112] 1. Adjust the instrument on a flat test block. This adjustment method is characterized by the chord length It is equal to the calculated distance between the two probe incident points (PCS), 2S.

[0113] (Unit: °)

[0114]

[0115] Direct wave propagation time:

[0116] Diffraction wave propagation time of the upper defect endpoint 1:

[0117] The propagation time of the diffraction wave at the upper end point 2 of the defect:

[0118] Where the depth deviation Δh=r(1-cosθ)

[0119] The depth calculated by the instrument according to the flat workpiece (displayed depth):

[0120] Defect upper endpoint

[0121] Defect lower endpoint

[0122] When TOFD is performed on the longitudinal seam of a cylinder, the outer diameter (or inner diameter) of the cylinder is generally large, s≈s′, then

[0123] The upper endpoint of the defect h′1≈h1+Δh,

[0124] The lower end point of the defect h′2≈h2+Δh

[0125] Correct the defect depth: h1≈h1′-Δh, h2≈h′2-Δh.

[0126] 2. Adjust the instrument on the cylinder. This adjustment method is characterized by the arc length It is equal to the calculated distance between the two probe incident points (PCS), 2S.

[0127] (Unit: °);

[0128] Δh=r(1-cosθ)

[0129] S′=r·sinθ

[0130] Direct wave propagation time:

[0131] Diffraction wave propagation time of the upper defect endpoint 1:

[0132] The propagation time of the diffraction wave at the upper end point 2 of the defect:

[0133] The depth calculated by the instrument according to the flat workpiece (displayed depth):

[0134] Depth of upper endpoint of defect:

[0135] Depth of lower end point of defect:

[0136] When the longitudinal seam of the cylinder is tested by TOFD, the outer diameter (or inner diameter) of the cylinder is generally large, s≈s′, then the upper end point of the defect h′1≈h1+Δh,

[0137] The lower end point of the defect h′2≈h2+Δh

[0138] Correct the defect depth: h1≈h1′-Δh, h2≈h′2-Δh.

Claims

1. A method for correcting the defect depth of a shell longitudinal weld by TOFD detection, which is carried out in the following steps: 1) Calculate the process parameters according to the flat plate butt weld, and use two probes arranged at a distance to perform TOFD detection on the longitudinal weld of the cylinder according to the process parameters to obtain the propagation time of the straight wave t 0 , the propagation time of the diffraction wave at the upper end of the defect t 1 , the propagation time of the diffraction wave at the lower end of the defect t 2 ; 2) Select parameters; Select the process parameters required for defect depth calculation: the center distance between the two probes is 2S, the outer radius of the cylinder R , Inner radius of cylinder r ; 3) Calculate the display depth of the defect; Based on the data from step 1) and step 2), calculate the display depth of the upper endpoint of the defect h 1´ and the displayed depth of the lower end point of the defect h 2´; 4) Calculate the correction value Δ of the defect depth h ; 5) Defect depth correction: According to the correction amount of the defect depth in step 4), the display depth of the upper endpoint of the defect and the display depth of the lower endpoint of the defect are corrected to obtain the depth of the upper endpoint of the defect. h 1 and the depth of the lower end point of the defect h 2 ; The correction amount of the defect depth calculated in step 4) is include: ① The instrument is calibrated on a flat test block, and TOFD testing uses a scanning method on the outer surface of the cylinder: ; ② The instrument is calibrated on a flat test block, and TOFD testing uses a scan of the inner surface of the cylinder, then: ; The instrument is calibrated on the cylinder, and TOFD inspection uses the outer surface of the cylinder to scan, then: ; The instrument is calibrated on the cylinder, and TOFD inspection uses the inner surface of the cylinder to scan, then: ; θ is half of the angle between the normals of the two probe center points.

2. A method for correcting the defect depth of a longitudinal weld of a cylinder by TOFD detection according to claim 1, characterized in that: The calculation formula for measuring the display depth of the defect in step 3) includes: the display depth of the upper end point of the defect , the display depth of the lower endpoint of the defect , c is the ultrasonic wave propagation velocity in the workpiece.

3. A method for correcting defect depth of a shell longitudinal weld by TOFD detection according to claim 2, characterized in that: The defect depth correction in step 5) includes: ① When TOFD inspection uses the outer surface of the cylinder to scan, the depth of the upper end point of the defect , the depth of the lower end point of the defect ; ② When TOFD inspection uses the inner surface of the cylinder to scan, the depth of the upper end point of the defect , the depth of the lower end point of the defect .

4. A method for correcting defect depth of a shell longitudinal weld by TOFD detection according to claim 3, characterized in that: The process parameters of step 1) include: probe center distance 2S, cylinder outer radius R, and cylinder inner radius r.

5. A method for correcting the defect depth of a longitudinal weld of a cylinder by TOFD detection according to claim 4, characterized in that: The two probes are respectively arranged on both sides of the longitudinal weld of the cylinder to perform TOFD detection.

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