GB/T 7735-2016Automated eddy current testing of seamless and welded (except submerged arc-welded) steel tubes for detection of imperfections (English PDF)

3.1 Standard contrast defect

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

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

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

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.

4.1

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.

5.1 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;

deltaV 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;

deltaV 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

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.

7.2

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.

8.1

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.