What is non-destructive testing of steel pipes? What kinds of flaw detection methods are included?

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What is non-destructive testing of steel pipes? What kinds of flaw detection methods are included?

Non-destructive testing, referred to as NDT, is a modern inspection technology that detects the shape, position, size and development trend of internal or external defects without damaging the object to be tested. In recent years, it has been widely used in steel pipe production. The non-destructive testing methods used in the production of seamless steel pipes mainly include ultrasonic testing, eddy current testing, and radiographic testing.
All inspection operators (except visual inspection) involved in this standard shall be qualified non-destructive inspection personnel according to ISO11484 or ASNT SNT-TC-1A: 1984.
In addition to wall thickness testing, ultrasonic and electromagnetic inspection systems should use the notched or drilled reference standards given in the table to verify the response of the equipment to manual reference standards.
If the artificial reference standards described in the table can be dynamically detected by ultrasonic or electromagnetic inspection methods under normal operating conditions, the manufacturer may use any documented procedure to define its rejection limits and shall dynamically demonstrate such detection capability. Selected by the manufacturer, can be detected online or offline.
If drill holes are used for electromagnetic inspection equipment calibration, the inspection system shall be capable of producing signals from internal and external notches that are equal to or greater than the rejection limits established using drill holes.
Records of NDT System Capability
The manufacturer shall maintain records of the non-destructive testing system demonstrating the ability of the system to test the reference standards used to determine the test sensitivity of the equipment. Verification includes at least the following basis:
a) Coverage calculation (ie: scanning mode), including wall thickness detection;
b) Detection capability of predetermined wall thickness;
c) repeatability;
d) the orientation of the probe to detect typical defects in the manufacturing process;
e) Documents demonstrating that the non-destructive testing method in Table C.62 or E.62 was used to detect typical defects in the manufacturing process;
f) parameters for determining the limits;
In addition, the manufacturer should keep the following related documents:
g) the operation method of the non-destructive testing system;
h) Instructions for use of non-destructive testing equipment;
i) NDT personnel qualification information;
j) Dynamic test data demonstrating the ability of the NDE system/operation under production test conditions.
Tube or Coupling Blank Inspection —–General
Unless agreed, all NDE inspection operations (other than visual inspection, but including final pipe end dead zone inspection) shall be performed after final heat treatment and rotational straightening, with the following exceptions:
a) Except for specific types of short sections;
b) If more than one non-destructive testing method is used, one of the methods (other than ultrasonic testing) may be used before heat treatment for rotational straightening.
Overall NDE Inspection of Casing and Tubing —–N80Q, M65, L80 and C95 Grades
All pipes shall be inspected for longitudinal defects on the inner and outer surfaces, and the acceptance level shall be L4. The inspection shall be carried out by one or more of the following methods:
a) Ultrasonic inspection is performed according to ISO 9303 or ASTM E213;
b) Magnetic flux leakage inspection is performed according to ISO 9402 or ASTM E570;
c) Eddy current inspection is performed according to ISO 9304 or ASTM E309;
d) Magnetic particle inspection (for the outer surface of the pipe) is performed in accordance with ISO 13665 or ASTM E709.
Overall NDE inspection of casing and tubing —–P110 steel grade implements A.10 (SR16) requirements
All pipes shall be inspected for longitudinal and transverse defects on the inner and outer surfaces, and the acceptance level shall be L4. The inspection shall be carried out by one or more of the following methods:
a) Ultrasonic inspection according to ISO 9303 or ASTM E213 (longitudinal) and ISO 9305 or ASTM E213 (transverse);
b) Magnetic flux leakage inspection according to ISO 9402 or ASTM E570 (longitudinal) and ISO 9598 or ASTM E570 (transverse);
c) Eddy current inspection is performed in accordance with ISO 9304 or ASTM E309.
See Appendix H for additional requirements for PSL-3 products.
10.15.8 Overall inspection of casing and tubing—–P110 steel grade and P110 steel grade implement the requirements of A.10 (SR16) and A.3 (SR2)
All pipes shall be inspected for longitudinal and transverse defects on the inner and outer surfaces, with an acceptance level of L2, by one or more of the following methods:
a) Ultrasonic inspection according to ISO 9303 or ASTM E213 (longitudinal) and ISO 9305 or ASTM E213 (transverse);
b) Magnetic flux leakage inspection according to ISO 9402 or ASTM E570 (longitudinal) and ISO 9598 or ASTM E570 (transverse);
c) Eddy current inspection is performed in accordance with ISO 9304 or ASTM E309.
Overall inspection of casing and tubing—–C90, T95 and Q125 grades
All pipes shall be ultrasonically inspected for longitudinal and transverse defects on the inner and outer surfaces to an acceptance level of L2 in accordance with ISO 9303 or ASTM E213 (longitudinal) and ISO 9305 or ASTM E213 (transverse).
In addition, all pipes shall be inspected for external surfaces by one of the following methods:
a) Magnetic flux leakage inspection, acceptance level L2, according to ISO 9402 or ASTM E570 (longitudinal) and ISO 9598 or ASTM E570 (transverse);
b) Eddy current inspection, acceptance level is L2, according to ISO 9304 or ASTM E309;
c) Magnetic particle inspection, according to ISO 13665 or ASTM E709.
NDE inspection of welded pipe welds
Arrangements for weld inspection are at the discretion of the manufacturer, and unless agreed by the user, all weld inspection of quenched and tempered heat treated steel tubes shall be performed after final heat treatment and subsequent rotational straightening.
The non-destructive testing equipment for welded pipe welds should be able to test the entire wall thickness area within 1.5mm on both sides of the fusion line.
The longitudinal defect inspection of all grades of Group 1 and Group 2 welds shall be carried out by one or more of the following methods:
a) Ultrasonic inspection, acceptance level is L3, according to ISO 9764 or ASTM E273 or ISO 9303 or ASTM E213;
b) Magnetic flux leakage inspection, the acceptance level is L3, according to ISO 9402 or ASTM E570;
c) Eddy current inspection, acceptance level L3, according to ISO 9304 or ASTM E309.
For grades P110 and Q125, the requirements of A.6.5 (SR11.5) apply.
Coupling stock, pup joints and accessories
When NDE is required for the coupling stock, Table C62 or E62 shall be followed. All pipes shall be inspected for longitudinal and transverse defects on the outer surface. The acceptance level shall be L2. The inspection shall be carried out by one or more of the following methods:
—–Ultrasonic inspection is performed according to ISO 9303 or ASTM E213;
—– Magnetic flux leakage inspection is performed according to ISO 9402 or ASTM E570;
—– Eddy current inspection is performed according to ISO 9304 or ASTM E309;
—–Magnetic particle inspection is performed according to ISO 13665 or ASTM E709.
Pup joints and accessories shall be inspected as required for casing and tubing.
a) For pup joints and accessories made from a single piece of casing or tubing without subsequent thickening or heat treatment, the required inspection of internal and external surface defects shall be carried out before or after cutting to final length;
b) For pup joints or accessories machined from pipe or bar stock, the required inspection shall be carried out before or after machining to final product dimensions, except that visual inspection of the outer surface shall be carried out after machining into final product;
c) Except for round threaded pup joints and accessories in d), all other required inspections of pup joints and accessories shall be carried out according to a);
d) For ISO/API round thread pup joints and accessories of the specifications listed in Table C.3 or E.3 of Group 1, Group 2, grades L80 and C95 and Group 3, unless otherwise specified by the purchaser and manufacturer Outside the agreement, the required inspections shall be carried out in accordance with e) and f) below;
e) Outer surface and end area of ​​the steel tube. The required inspection of the outer surface and end area shall be carried out immediately after any upsetting process and final heat treatment. For Group 3 pup joints and accessories, the magnetic particle inspection for longitudinal and transverse defects may be In lieu of the required external surface inspection;
f) For internal surfaces, the required inspection may be performed either before or after cutting into single tubes, any thickening process or final heat treatment.
g) The manufacturer uses the reference defect to calibrate the compression and shear wave ultrasonic equipment. The outer surface near the reference defect shall be painted with the letters “RI”. Reference defects shall be regarded as defects and marked with b) spelling.
Uninspected pipe ends
Inspection of the end regions shall be carried out after all heat treatments.
It should be emphasized that many of the automatic NDE inspection methods specified in this standard may have a small section of pipe end that cannot be inspected. In this case, the pipe end that cannot be inspected shall:
a) excision or;
b) Use the magnetic particle method to inspect the entire circumference of the uninspected pipe end and the range exceeding the length of the blind zone to inspect the inner and outer surface defects or;
c) Adopt manual/semi-automatic inspection method, as a minimum requirement, have the same inspection quality as automatic NDE inspection.
Tube end thickening
Except for grades H40, J55 and K55, for the upsetting and thickening parts (including the thickening transition zone) of all other steel grades, after all heat treatment, the NDE inspection method shall be used for the inspection of transverse defects on the inner and outer surfaces. The basis for acceptance is Follow Section 8.13. For all quenched + tempered grades, the inspection of the tube end area includes longitudinal defects.
Requirements for further qualified steel pipes, coupling stock and accessories
Evaluation of display signals (validation)
For the signal greater than or equal to the rejection limit, the manufacturer may evaluate it according to this clause, and the evaluation of the displayed signal shall be carried out by a qualified inspector with level I under the supervision of an inspector with a level II or level III qualification, or by a qualified inspector with level I. Class II or III qualified inspection personnel, the evaluation of the displayed signal shall be carried out in accordance with the documented procedures.
When no defect can be found in the area where the original signal was generated and the signal cannot be explained, the pipe should be rejected or the manufacturer decides to use the same method as the original, or to re-test the full length by ultrasonic method, the manufacturer decides , the inspection equipment should be adjusted to the same sensitivity as the original inspection, or it can be adjusted to a lower sensitivity that meets the specified requirements.
For the evaluation of revealed defects, their depth shall be measured by one of the following methods:
a) Measure with a mechanical measuring device (depth gauge, caliper, etc.). Grinding or other means to remove material for ease of measurement shall not allow the remaining wall thickness to be less than 87.5% of the specified wall thickness for steel tubes. Coupling stock shall not allow residual wall thickness to be less than the minimum specified in the contract. Sudden changes in wall thickness caused by grinding during validation should be removed.
b) Ultrasonic methods (time and/or amplitude based), or other possible methods. Verification by the ultrasonic method shall be documented and shall have the ability to identify defects larger or smaller than those specified in 8.13.
If the purchaser and the manufacturer dispute the results of the evaluation test, either party may request a destructive inspection of the material.
Treatment of Containing Defective Tubes
Defects that meet the material requirements and defects smaller than the specified size are allowed to exist on the pipe, and repair welding is not allowed. Defective pipes shall be disposed of in one of the following ways:
a) Grinding or machining
Quenching cracks are not allowed to be ground or machined. If the remaining wall thickness is within the specified limits, the defects should be completely removed by grinding or machining, and the fillet radius should be large enough to prevent sudden changes in wall thickness. After the defect has been removed, the affected area shall be re-inspected to determine that the defect has been completely removed. The re-inspection shall be:
1) use the same inspection equipment and the same sensitivity as the original inspection, or;
2) Adopt other NDE methods or combined methods, and prove that they have equal or higher sensitivity than the original NDE method;
When using method 2) above, this NDE (or combined method) should be documented to have equal or higher sensitivity than the original NDE method, and method 2) should take into account the possibility of other overlapping defects in the affected area .
b) excision
The defective pipe section shall be cut off, and the length of the cut pipe shall be within the required length.
c) Rejection
Tubes should be rejected.
Handling of Coupling Stocks Containing Defects
Defects that meet the material requirements and defects smaller than the specified size are allowed to exist on the coupling blank, and repair welding is not allowed. Coupling blanks with defects shall be

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