GB/T 7735-2016 PDF in English
GB/T 7735-2016 (GB/T7735-2016, GBT 7735-2016, GBT7735-2016)
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Automated eddy current testing of seamless and welded (except submerged arc-welded) steel tubes for detection of imperfections
| Valid |
| GB/T 7735-2004 | English | 359 |
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Steel tubes -- The inspection method on eddy current test
| Obsolete |
| GB/T 7735-1995 | English | 519 |
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Steel tubes--The inspection method on eddy current test
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| GB 7735-1987 | English | RFQ |
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Eddy current testing for the compactness of steel pipes and tubes
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Standards related to (historical): GB/T 7735-2016
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GB/T 7735-2016: PDF in English (GBT 7735-2016) GB/T 7735-2016
Automated eddy current testing of seamless and welded (except submerged arc-welded) steel tubes for detection of imperfections
ICS 77.040.20
H26
National Standards of People's Republic of China
Replacing GB/T 7735-2004
Seamless and welded (except submerged arc) steel imperfections
Automatic eddy current testing
Automatededdycurrenttestingofseamlessandwelded (exceptsubmerged
arc-welded) steeltubesfordetectionofimperfections
[ISO 10893-2.2011, Non-destructivetestingofsteeltubes-
Part 2. Automatededdycurrenttestingofseamlessandwelded
(Exceptsubmergedarc-welded) steeltubesfordetectionofimperfections, IDT]
Published 2017-09-01 2016-12-30 implementation
Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China
Standardization Administration of China issued
Table of Contents
Introduction Ⅲ
1 Scope 1
2 Normative References 1
Terms and definitions 1 3
4 General requirements 2
5 Detection Method 2
5.1 Detection 2
5.2 Detection Equipment 3
Comparative 4 sample tube 6
6.1 General requirements 4
6.2 technology through coil 5
6.3 Technical sector coil 5
6.4 stationary and rotating probe/flat coil technology 5
Comparative Sample 5 6.5 Size
Calibration and 7 check 7
Acceptance 7 8
9 8 Test Report
Annex A (normative) eddy current testing method described limitations guidance 9
Foreword
This standard was drafted in accordance with rules GB/T 1.1-2009 given.
Instead of the standard GB/T 7735-2004 "steel pipe eddy current testing method." As compared with the present standard GB/T 7735-2004, mainly
Technical changes as follows.
--- modified the standard name;
--- modified the standard scope (see Chapter 1, 2004 Edition 1);
--- increase the content of normative references, terms and definitions, the general requirements (see Chapter 2, Chapter 3, Chapter 4);
--- modify the contents of the detection method (see 51, 2004 version 5.1.);
--- modify the contents of the detection device (see 52, 2004 edition of Chapter 7);
--- modify the material requirements of comparative sample tubes (see 612, 2004 Edition 6.1.1.);
--- modify requirements groove width and length (see 6522, 2004, version 6.4...);
--- modify the acceptance level and identification (see 6.5.1 and 6532, the 2004 version 6.4.1 and 6.4.2...);
--- After acceptance rating by injection, indicating the level of acceptance of alternative hydrostatic test (see 6.5.1 and 6.5. 2. 2, 2004 edition of 6.4.1 and
6.4.2);
--- check and modify the equipment inspection requirements (see Chapter 7, Chapter 8, 2004 edition);
--- modify the judgment suspicious steel pipe (see 8.2, 9.2, 2004 edition)
--- modify the contents of Appendix A (see Appendix A, 2004 edition of Appendix A).
This translation method using identical with standard ISO 10893-2.2011 "non-destructive testing of steel tubes - Part 2. seamless and welded (SAW
Excluding) steel imperfections automatic eddy current testing "(in English).
Consistency correspondence relationship with the international standard in normative documents referenced in our files are as follows.
--- GB/T 9445-2015 NDT personnel qualification and certification (ISO 9712.2012, IDT)
This standard also made the following editorial changes.
--- According to China habits modified the standard name;
--- For ease of use, increase in 6.5.1 "NOTE. E4H acceptance level as an alternative to pressure test the acceptance level of the eddy current testing";
Increasing 6.5.2.2 "NOTE. E4 acceptance level as an alternative to pressure test the acceptance level of eddy current testing."
The standard proposed by China Iron and Steel Association.
This standard by the National Steel Standardization Technical Committee (SAC/TC183).
This standard was drafted. Hunan Hengyang Steel Tube (Group) Co., Ltd., Shanxi Taigang Stainless Steel Co., Ltd., metallurgical industry-standard information
Associate Research Institute.
The main drafters. Deng Shirong, Yu Hongxin, Zhang Lin, Dong Li, Zhao Bin, Yao Peng Sheng.
This standard supersedes the previous editions are.
--- GB/T 7735-1995, GB/T 7735-2004.
Seamless and welded (except submerged arc) steel imperfections
Automatic eddy current testing
1 Scope
This standard specifies the requirements for automatic eddy current testing of seamless and welded (SAW excluded) of the defect, the defect level of acceptance, see
Tables 1 and 2.
This standard applies to the outer diameter of not less than 4mm pipe eddy current testing. This standard is also applicable to the detection of the hollow member.
2 Normative references
The following documents for the application of this document is essential. For dated references, only applies to the version dated paper
Pieces. For undated references, the latest edition (including any amendments) applies to this document.
ISO 9712 NDT personnel qualification and certification (Non-destructivetesting-Qualificationandcertifica-
tionofNDTpersonnel)
ISO 11484 NDT personnel qualification employer steel products system (Steelproducts-Employer'squalifi-
cationsystemfornon-destructivetesting (NDT) personnel)
3 Terms and Definitions
Defined in ISO 11484 and the following terms and definitions apply to this document.
3.1
Standard contrast defect referencestandard
Artificial defect nondestructive testing apparatus (such as drilling, grooves and dents) for verification.
3.2
Comparative sample tube referencetube
Comparative Sample containing steel or pipe section.
3.3
Comparative sample referencesample
Comparative sample containing standard sample (e.g., pipe, sheet or strip).
NOTE. This standard uses only the term "control sample tubes", also includes the term comparative sample.
3.4
Steel tube
Any cross-sectional shape are open at both ends of the hollow elongated products.
3.5
Seamless seamlesstube
The solid product obtained a perforated hollow tube, and then by hot working or cold working to obtain the final dimensions.
3.6
Pipe weldedtube
By welding adjacent edges of the flat product made of the steel pipe together, after welding can be subjected to further hot or cold working,
To obtain the final dimensions.
3.7
Manufacturers manufacturer
Products manufactured in accordance with relevant standards and statements delivered products meet the relevant standards applicable to all organizations clauses.
3.8
Protocol agreement
At the time of inquiry and order, the contract between the manufacturer and the purchaser.
4 General requirements
4.1 Unless the product specification or supply and demand sides agreed, steel pipe eddy current testing should operate in all major production processes (rolling, heat in
Li, cold and hot processing, sizing and straightening basic like) after completion of all.
4.2 detected steel pipe should have enough flatness to ensure the effectiveness of detection. The surface should not affect detection reliability of foreign bodies.
4.3 Detection shall be in accordance with ISO 9712, ISO 11484 or equivalent standard trained and qualified operator appointed by the manufacturer have owned
Carried out under the supervision of personnel grid. In the case of testing by a third party, this should be consultation between the supplier.
The employer shall file a certificate issued by the authority to operate. NDT personnel shall be approved by the Employer of a NDT Level 3
Members authorized.
NOTE. 1,2,3 definitions can be found in the corresponding international standards such as ISO 9712 and ISO 11484.
5 Detection
5.1 Detection Technology
5.1.1 Steel imperfections should follow mode "absolute" and/or automatic or semi-automatic method for eddy current "differential" is detected.
a) passing through the coil art --- entire periphery (see FIG. 1);
b) fixed or pivot point probe/flat coil technology --- entire periphery (see FIG. 2);
c) only for the sector coil technology --- welds (see FIG. 3) or a full tube (see FIG. 4).
All of the above detection, the relative volatility of the selected detection speed should not exceed ± 10%.
Pipe ends have a short length can not be detected. Any undetected tube end should be carried out according to the respective requirements of the product standards
Line processing.
NOTE. See Appendix A limitation of eddy current testing method for guidance instructions.
5.1.2 When passing through the coil technique employed, the maximum outer diameter of the subject steel should be limited to 180mm (acceptance level is employed E4H
250mm). Using a suitable probe may also be taken when the square and rectangular structural steel tubes for which the maximum value of not more than 180mm diagonal
Detected by encircling coil technique.
5.1.3 when the fixed or rotating probe/flat coil technology, steel probe/movement should be relatively flat coil, the flat probe alone or
Li between single probe to simulate electronically commutated relative movement, so that the entire surface of the steel pipe is detected. Using this technology, steel
The maximum outside diameter of no limit.
Note. only emphasizes the defect detection cracking outer surface when using this technology.
5.1.4 When the sector detection coil weld pipe, there is no limit on the maximum outer diameter. Detecting coils should maintain concentricity of the weld, so that
Weld can be found throughout the sweep.
5.1.5 When using a fan coil to detect the whole tube, the maximum outside diameter steel pipe to be inspected is limited as follows.
--- coil for 2 × 180 °, the maximum outer diameter of 219.1mm;
--- coil for 4 × 100 °, the maximum outer diameter of 508.0mm.
NOTE. emphasis on the detection sensitivity at the maximum detection coil near the surface of the steel pipe, pipe wall thickness increases and decreases (see Appendix A).
5.2 Testing Equipment
Pipe testing equipment should be qualified or suspected steel tube automatically triggers/markers and the alarm threshold and/or sorting systems to distinguish.
Description.
1 --- secondary coil 1;
2 --- primary coil;
3 --- 2 coil;
4 --- steel;
~ --- alternating excitation current;
ΔV signal output ---.
Note. This figure is a schematic layout more than one row of coils, which may comprise a plurality of sets of coils, such as sub primary coil, double differential coil and the calibration coil.
1 a schematic view through a coil technology
a) rotating probe/steel flat coil straight forward technology --- b) fixed probes/steel flat spiral coil technology advances ---
Description.
1 --- probe/position of the flat coil;
2 --- steel;
3 --- stationary flat coil;
4 --- idler;
A --- the rotational direction of the probe;
B --- the rotational direction of the steel pipe.
Note. the flat coil a) and b) may have different forms, such as a single coil, multiple coils of different configurations, depending on the equipment used and other factors.
FIG 2 Probe/flat coil art schematic
Description.
1 --- weld;
2 --- coil 1;
3 --- primary coil;
4 --- coil 2;
5 --- steel;
6 --- coil;
~ --- alternating excitation current;
ΔV signal output ---.
3 a schematic sector coil weld detection method of FIG.
a) 2 × 180 ° sector coils b) 4 × 100 ° coils
Description.
1 --- sector coil;
2 --- steel.
4 a schematic view of the eddy current coil technology sector
Comparative sample tube 6
6.1 General requirements
6.1.1 Comparative sample tube defined in this standard is used to calibrate the non-destructive testing apparatus. The size of these comparison criteria such defects should not be seen
The device can detect the smallest defect size.
6.1.2 Comparison sample tube and the subject steel should have the same nominal diameter and wall thickness, the surface state and the same delivery conditions (e.g., as-rolled condition, n
Fire, quenching and tempering) and similar grades. He said the thickness exceeds 5mm, if the groove depth of the subject is based on the nominal wall thickness of steel pipe
Calculated, comparison may be greater than the wall thickness of the tube-like male subject said steel pipe wall thickness. Upon request, the manufacturer should have proved their method
Effectiveness.
6.1.3 Comparison of different predetermined standard detection techniques as follows.
a) passing through the coil technique, employing one or more through-holes in predetermined 6.2 and 6.5.1;
b) sector coil technology, one or more through holes in predetermined 6.3 and 6.5.1;
c) fixed or rotating probe/flat probe technology, one or more notches defined in 6.5.2 and 6.4.
Note 1. In special cases, such as heat pipes or detect the detection device installed in a continuous production line plant, can be negotiated or parity check mode change
Check the program.
NOTE 2. When using encircling coil technique available after consultation longitudinal groove or circumferential groove as a comparative standard.
6.1.4 comparison to a standard defect (see 6.2 to 6.4) and comparison to a standard inter-defect spacing should be sufficient and the tube end on the pipe longitudinal direction, to obtain
You have clearly distinguished display signal.
6.2 through coil technology
6.2.1 encircling coil technology employed, comparison with a sample to be three or four circular radial through-hole tube. In each well of a round two modes
In the circumferential direction to be 120 ° or 90 ° respectively distributed.
6.2.2 can also be processed on the sample tube only one radial through-hole, in this case when the checksum verification, the through hole should sample tube was 0 °, 90 °,
180 °, 270 ° position by the device.
6.3 sector coil technology
6.3.1 When the sector coil technology, with a control sample should separate circular radial through-hole on the tube, the through holes should be in the position near the weld or
The weld.
6.3.2 using a fan coil technology full tube testing, the sample tube should contrast with three circular radial through-hole. Each sector coil
Application control sample tubes were checked, three radial openings arranged following requirements shall.
--- 180 ° sector coils. coil center to prevail by 0 °, 90 °, -90 ° distribution;
--- 100 ° sector coils. coil center to prevail by 0 °, 45 °, -45 ° distribution.
6.3.3 can also be processed only one radial through holes in the sample tube, when the sample tube calibration and inspection, for the 180 ° sector coils should in this case
The pores are wound from 0 °, 90 °, -90 ° position by the apparatus; to 100 ° sector coils are wound hole should be from 0 °, 45 °, -45 ° position through
Through the apparatus. Each sector coil is for this operation.
6.4 stationary and rotating probe/flat coil technology
When the fixed and rotating probe/flat coil technology, should Comparative sample tube with a longitudinal groove than the outer face.
Comparative Sample size 6.5
6.5.1 through holes
Hole diameter corresponding to the outer diameter of the steel pipe should not exceed specified in Table 1. By machining the through-holes should be, etched or otherwise EDM
Processing.
NOTE. E4H acceptance level as an alternative to pressure test the acceptance level of eddy current testing.
Table 1 nominal pipe acceptance level of each said through-hole corresponding to the diameter
Nominal diameter steel pipe
mm
Acceptance level and through-hole diameter
mm
E1H E2H E3H
Nominal diameter steel pipe
mm
Acceptance levels and
Through-hole diameter
mm
E4H
4≤D≤10 0.60 0.70 0.80 4≤D≤15.8 1.20
10 \u003cD≤20 0.70 0.80 1.00 15.8\u003cD≤26.9 1.40
20 \u003cD≤44.5 0.80 1.00 1.30 26.9\u003cD≤48.3 1.70
44.5 \u003cD≤76.1 1.00 1.20 1.60 48.3\u003cD≤63.5 2.20
76.1 \u003cD≤180 1.20 1.40 2.00 63.5\u003cD≤114.3 2.70
180 \u003cD 1.40 1.80 2.20 114.3\u003cD≤139.7 3.20
139.7 \u003cD 3.70
6.5.2 groove
6.5.2.1 General requirements.
a) Comparative should notch "N" type (see FIG. 5) and parallel to the main axis of the pipe. Two edge notch should be nominally parallel and notch
Nominally be perpendicular to the bottom edge.
b) Comparison should notch, etching or spark otherwise processed by machining.
Note. the bottom or bottom corners may be rounded.
Description.
--- width W;
d --- depth.
FIG. 5 "N" groove type
6.5.2.2 Artificial notch dimensions.
a) a width, w (see FIG. 5). Comparative notch width should not exceed the depth of groove or 1mm, whichever is greater of the two.
b) depth, D (see FIG. 5). Comparative groove depth should prevail in Table 2, the groove depth tolerance notch depth should be ± 15%, and follow
The following restrictions.
--- minimum groove depth. 0.3mm;
--- maximum groove depth. 1.5mm.
NOTE. E4 acceptance level as an alternative hydraulic test acceptance level of eddy current testing.
c) Length. Unless otherwise specified standard product manufacturer or purchaser agreed, each notch should be greater than the length of single probe/flat wire
Or twice the ring width of the sensor. In any case, the length of the groove should not exceed 50mm.
Table 2 Acceptance levels and corresponding outer groove depth (for fixed and rotating probe/flat coil technology)
The percentage acceptance level with the groove depth of the nominal wall thickness
E2 5
E3 10
E4 12.5
E5 15
Note. In all NDT standards relating to different acceptance levels of steel in the same notch depth value for a respective predetermined category in this table. although
However, the same comparison standard sample, various detection methods may be different according to the detection result, therefore, the use of acceptance level prefix E (vortex) with
To avoid any direct estimation and other equivalent detection methods.
6.5.3 Comparison of standard verification
6.5.3.1 using the diameter of the through hole when the through-hole comparison (see Table 1) should be verified, and should not exceed the values specified in Table 1.
6.5.3.2 groove size and shape should be verified by appropriate technologies.
7 Calibration and inspection
Legible Comparative Sample 7.1 at the beginning of each signal detection cycle, the device should be calibrated to produce a consistent (e.g., a test for
3 consecutive signal samples by the device), these signals are used to trigger their respective alarm levels, as follows.
a) When using a plurality of through-holes comparative sample tube (or through the coil technique to detect the entire surface of the coil segment) should be used to give more
Minimum signal through-hole as a trigger device/alarm level. When using a single via the comparative sample, shall 6.2.2
Continuous operation a predetermined sampling tube, and wherein the minimum signal taken as a trigger device/alarm level.
b) When using a single through-hole of the control samples (sector coils to detect pipe welds), taking as the minimum signal apparatus wherein
Trigger/alarm level.
C) When a contrasting groove (or a fixed point of rotation of the probe/probe technology flat), the signal takes the minimum groove signal as a contact device
Hair/alarm level.
7.2 Check calibration process, the same speed relative moving speed between the control sample and the probe tube and the means to be detected Product
(See 5.1.2,5.1.3 and 5.1.4). And set the device should be the same, such as frequency, sensitivity, phase discrimination, filters may be employed, and
Magnetic saturation.
7.3 said diameter, wall thickness, and grade of steel production testing process using the comparative sample tube should be calibrated by detecting the device in the same apparatus known
Conduct regular inspections. Inspection frequency calibration should be performed at least once every 4h, and whenever replacement of equipment and production operations team opening
Start and end calibration check should be carried out.
7.4 If any of the parameters changed using the initial calibration should be re-calibrated.
7.5 In the production process of detecting, if the calibration pass the inspection, the all steel since the last calibration after passing recalibrate the device
Again after passing the test.
8 Acceptance
8.1 Any signal generated by the steel pipe below the trigger/alarm level shall be considered the qualified.
8.2 Any generated signal is equal to or greater than steel Trigger/alarm level should be considered suspect products, determined by the manufacturer, or whether re
New testing. If, after re-tested twice in a row, all the signals are below the trigger/alarm level, the pipe shall be deemed passed inspection
Measurement; otherwise the pipe should be considered suspicious items.
8.3 pairs suspicious steel, according to the requirements of the standard product should be one or more of the following processes.
a) should be suspect areas or grinding processes using appropriate methods, and confirm the remaining wall thickness within the allowed tolerance range, this
Pipe shall be re-tested according to the method previously specified. If no signal is equal to or greater than the trigger/alarm level,
This pipe shall be deemed passed this test.
Suspicious areas can also be used to detect other NDT methods and re-tested by the supply and demand sides agreed acceptable
Acceptance levels.
b) suspicious areas should be removed, the manufacturer shall ensure that all suspected areas are cleared.
c) The pipe shall be deemed unqualified.
9 test report
Such provisions, the manufacturer shall provide the purchaser test report containing at least the following information.
a) standard number;
b) Description of compliance;
Any deviation, a predetermined protocol c), or other program file;
d) Grades and specifications;
Type e) detecting technique and details;
f) The method of calibrating equipment used;
g) Comparative Sample acceptance level description;
h) the date of detection;
i) The operator qualifications.
Appendix A
(Informative)
Eddy current testing method described limitations guidance
A.1 penetration depth of the eddy current testing
When performing eddy current testing steel, on the steel surface adjacent and near the surface of the detection coil, the detection sensitivity is the highest. Due to the skin
Effects of, and between the detection coil with increasing distance, the detection sensitivity decreases. Thus, for the same size defect,
Signal amplitude at the wall of the tube defect will be less than the defect reflected on the outer wall. Missing detection apparatus in the outer and inner surfaces of the probe
Underdetermined regard is determined by many factors, but the main pipe wall thickness depending on the subject and eddy current excitation frequency and magnetic saturation
strength.
Under certain conditions of magnetization, the excitation frequency is applied to the detection coil, the eddy current field determines the strength of steel can penetrate established
The depth of the wall thickness. The higher the excitation frequency, the lower the penetration; conversely, the lower the excitation frequency, the higher the penetration. In the choice of instrument parameters,
Effects of physical parameters of the subject steel conductivity, permeability and the like, should also be considered.
A.2 through the coil/coil technology sector
This technique is suitable for the detection of surface or near the detection coil short longitudinal and lateral imperfections near surface imperfections.
The minimum length of this technique is theoretically longitudinal imperfections that can be detected by the detection coil arrangement and the cutout section along the longitudinal direction becomes
Rate decision.
With this detection technique ferromagnetic steel material inspection process should be subject to magnetic saturation material may be placed in a strong external
Magnetic field to achieve. Purpose is to stabilize the magnetic saturation and reduce the permeability of the material, increasing the penetration of eddy currents, the magnetic material itself to reduce
noise.
A.3 fixed or pivot point probe/flat coil technology
This technique utilizes one or more probes/steel coils helical scanning surface. Therefore this technique can detect longitudinal imperfections
The minimum length depends on the width and the scanning pitch search coils. This technique is often unable to detect transverse imperfections.
Since the frequency of this excitation technique is significantly higher than the frequency of passing through the coil/sector coil technology, he can detect approaching of the detection wire
Ring surface imperfections.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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