GOST 25225-82

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  ГОСТ 25225-82

GOST 25225−82 nondestructive testing. The seams of welded connections of pipelines. Tape method

GOST 25225−82

Group В08

STATE STANDARD OF THE USSR

NONDESTRUCTIVE TESTING

THE SEAMS OF WELDED CONNECTIONS OF PIPELINES

TAPE METHOD

Non-destructive testing. Welded joints of tubing. Magnetographic method

Date of introduction 1983−07−01

1. DEVELOPED AND INTRODUCED by the Ministry of erection and special construction works of the USSR

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards of 23 April 1982, No. 1644

3. REPRINT (December 1993)


This standard specifies the tape method of non-destructive testing of annular butt welds of steel pipelines of different diameters with wall thickness from 2 to 25 mm, made by fusion welding.

Tape method can be used to weld other structures of cylindrical shape.

The standard does not apply to a control corner, lap and t-joints and welds made by means of contact welding.

The need for tape control, the volume control and the limits of defects are set in the technical documentation for control of butt joints of pipelines.

Terms used in the standard and their definitions are given in Appendix 1.

1. THE MAIN PROVISIONS OF THE

1.1. Tape control method serves to identify in butt welded joints of pipelines of low and medium-alloyed and carbon ferromagnetic steel exterior and interior cracks, lack of fusion, chains of inclusions and pores, oriented predominantly along the seam, as well as other contaminants, dramatically different in its magnetic properties from weld metal.

The minimum size of detectable defect should be no more than 10% of the thickness of the base metal of the monitored weld.

When testing of butt welds made unilateral welding, this method does not guarantee identification of the root lack of penetration less than 5% of the wall thickness of the pipes and a single slag inclusions and gas pores are rounded, having a relative value of less than 15% and located at a considerable depth from the surface of the weld, i.e. closer to the root.

1.2. Tape testing should be conducted after welding of pipes, butt weld cools to a temperature below + 60 °C, before the start of insulation work.

1.3. Tape control can be butt joints of pipes of the same diameter, same wall thickness, and weld joint raznostnykh pipes if wall thickness of the abutting pipes differ from each other by not more than 20%.

1.4. Tape control can be butt welds of pipes made automatic, semi-automatic and manual arc or gas welding is adopted for visual inspection and having:

a smooth transition from the deposited weld metal to the base;

the bead height of the weld reinforcement is not more than 25% of the thickness of base metal, for pipes with wall thickness up to 16 mm and not more than 4 mm for pipes with greater wall thickness;

the shape factor weld reinforcement not less than 7;

the shape factor of the weld is not less than 2.5 for thicknesses of the base metal up to 8 mm, not less than the values from 2.5 to 2 for thicknesses from 8 mm to 16 mm inclusive, and not less than 1.8 m for thicknesses over 16 mm;

the height of the irregularities (cheshuichatoe) on the surface seam of not more than 25% of the height of the reinforcement bead, but not exceeding 1 mm.

1.5. Tape control can be butt welds with the shot roller bonuses.

2. CONTROLS

2.1. For conducting tape of the testing of butt welded joints of pipelines used:

magnetic tape;

the magnetizing device;

reproducing device;

the source of electric current to power the electromagnet of the magnetizing device;

auxiliary device for pressing the magnetic tape to the surface of the controlled weld and fixing it (could be part of the magnetizable device);

demagnetization device;

a prototype for production control of a magnetogram;

test magnetogram for setting the sensitivity of the instrument.

2.2. Tape for inspection of the butt welds in pipelines from steels of magnetic magnetic with a coercivity up to 10 A/cm to apply a magnetic tape with a coercive force of 80 to 100 A/cm.

When testing weld seams of the pipelines of high-alloy and carbon steels with the coercivity from 10 A/cm type or settings used magnetic tape in each case should be specified in the technical documentation for tape testing.

2.3. Calibration of the flaw detector and magnetizer is performed in the manner and within the time specified in technical documentation for these devices.

2.4. The detector should be synchronized playback on the screen of a cathode-ray tube or on the recording medium of the Registrar of image prints magnetic fields of defects such as the brightness of the display and the amplitude and shape of signals in the pulse display, or chart the maximum values of the signals from the defects along the weld.

2.4.1. The screen of a cathode-ray tube for pulse indication and the diagram, the maximum values of the signals from the defects on the media, the Registrar shall biggy is provided with a scale, the graduation of which is determined in relative units when setting up the detector at the reference magnetogram.

2.4.2. Flaw detector with a scan of the diagram maximum values of the signals characterizing the change of depth of defects along the joint should be capable of dimensional adjustment of the width of the zone of the transverse play of a magnetogram of the weld on the recording medium of the recorder.

2.5. Magnetization controlled pipeline welded joints shall be performed using magnetizers:

mobile that allows you to magnetize a butt joint in the process of continuous or stepping around the perimeter of the tubing along the weld seam;

stationary, allowing you to simultaneously magnetizing the entire perimeter of the weld or its significant part with one setup.

2.5.1. The magnetizer must have a pole with a given radius of curvature, providing a uniform gap between the poles of the movable devices with continuous movement and pipe surface or snug fit of the poles of the movable device with a stepping movement and the poles of the fixed device to the surface of the pipe to magnetize a welded joint with no gap.

2.6. The source of electric current should provide most of the required modes of magnetization indicated in the technical documentation for tape testing of butt welded joints of pipelines of various sizes.

2.6.1. To set the mode of magnetization of the electric current source must be capable of continuous or stepwise control of the output voltage with built-in or external adjusting device, equipped with ammeter for a given limit of measurement. The throttle interval between steps should not exceed 5 V.

2.7. For tape control should be applied to the magnetic tape, the width of which is not less than 10 mm greater than the width of the reinforcement bead of the controlled butt seam.

2.8. For tape control should be applied to devices (e.g., elastic waistband), ensuring tight adherence of a tape to the surface of the controlled weld and fixed fixing tape butt seam during the magnetization of the latter around the perimeter.

2.9. Requirements for test specimens set out in Annex 2.

2.10. Requirements for the control of the magnetograms presented in Annex 3.

3. PREPARATION FOR CONTROL

3.1. Before conducting tape control each weld must be checked by visual inspection for the absence of invalid external defects.

3.2. Before inspection, the surface of butt joint, especially made by manual arc welding, and heat affected zones (with a minimum width of 20 mm on each side of the reinforcement bead) must be removed the gross irregularities (excessive scaliness, solidified molten metal splash and nodules) that exceed the height specified in section 1.4. In addition, the surface of welds and heat affected zone should be removed the remains of slag, dirt, snow, ice and other extraneous layers that prevent the tight fit of the magnetic tape.

3.3. When tape control of welded joints of pipe lying on the ground, under each butt seam you need to dig a pit or lay support (maturation) to ensure free access to the lower part of the circumferential welds during his external examination and preparation for the control in accordance with the PP. 3.1. and 3.2., as well as to overlay the magnetic tape on the surface of the butt joint and its magnetization.

3.4. For magnetization of welded joints and write the fields of the defects on magnetic tape shall be such size magnetizer, the scope of which is in accordance with the technical documentation applies to the inspection of the butt welds of the specified pipeline with the given diameter and wall thickness.

4. CONTROL

4.1. When conducting control tape to the surface of the weld should be prepared to impose a magnetic tape to a magnetic layer fits close to the seam around the width of the platen gain and were located symmetrically to the middle of the butt joint along the whole perimeter.

Notes.

1. Allowed local offset magnetic tape in either direction from the middle of the seam no more than 2 — 3 mm.

2. Reuse of used segments of the magnetic tapes after degaussing (erasing the old record), if they have no tears, punctures, delamination, neraspavsheysya wrinkles and other mechanical damages.

4.2. The cut length of magnetic tape used for recording fields of defects must be less than 120 mm larger than the perimeter of the controlled butt seam tubing.

On one of the free ends of the tape length 60 — 70 mm from the side of its magnetic layer must be applied with a soft pencil with a hardness of 2M — 4M the following information:

name of construction facility (allowed in abbreviated form);

pipeline diameter and thickness of its walls;

room butt seam or drawing number and the mark of the welder;

the type of magnetizer (in abbreviated form) and the mode of magnetization of a welded joint;

date of control and the name of the inspector.

This end of the magnetic tape should be combined with the conditional beginning of the butt joint.

4.2.1. After the overlay weld magnetic tape must be firmly pressed and fixed to it an elastic waistband or other soft clamping device.

4.3. The controlled magnetization of welded joints produced with the help of magnetizing devices. The power of magnetizing device comprising an electromagnet, carry out regular (rectified) or aperiodic pulse of current.

Duration (not less than 100 MS), and form an aperiodic current pulse should exclude the possibility of eddy currents and to ensure a uniform magnetization throughout the thickness of the test weld.

4.3.1. The force constant or aperiodic pulse current in the magnetizing device must provide identification of different size and depth of defect.

4 3.2. Recommended modes of magnetization for the control of butt joints of pipelines of different steel grades, types and sizes of pipes and magnetizers should be indicated in the technical documentation for tape testing.

4.3.3. In the process of the tape control of welded joints of pipelines mode of magnetization should be set and monitored by the ammeter, located in the regulating device, a source of electric current (section 2.6.1).

4.3.4. Under the control of butt joints of pipes raznostnykh (paragraph 1.3) the mode of magnetization must be chosen at the large wall thickness of the two abutting pipes.

4.3.5. Under tape control the speed of the movable magnetizing device along the perimeter of butt joint to prevent the occurrence of welded joints eddy current should not exceed 400 mm/s.

4.4. After magnetization of the controlled weld joint tape must be removed and delivered to the playback the resulting recording precautions against the possibility of impact on the magnetogram weld extraneous magnetic field strength exceeding the coercive force of the used magnetic tape.

4.5. Before playback of magnetic recording controlled weld flaw detector must be configured on the control magnetogram recorded on the weld of the test piece, or built-in calibrator.

The acceptance level on a scale pulse display or chart of the Registrar must correspond to the minimum value of the invalid defect set of normative-technical documentation for the control of welded joints of the pipeline.

4.6. When playing a magnetogram of the butt joint on the flaw detector with frame scan for the luminance and the pulse indications on the screen of a cathode-ray tube sequentially viewing images of magnetic stray fields of the adjacent sections of the weld.

4.6.1. If the screen luminance of the display is blank magnetic prints field defects, then browsing the magnetogram controlled weld frame by frame without any interruption.

4.6.2. In the case of any image frame of the magnetic imprint of the field defect cut off feeding of the magnetic tape and the vertical scan, the luminance of the display determine the nature of the defect, its location across the width of the weld and the length of the length of the seam; the pulse indication to determine the relative magnitude of the defect.

if the amplitude of the signal from the identified defect is below the acceptance level set on the screen pulse display when setting the sensitivity of the detector control magnetogram, the magnitude of the defect is valid;

if the pulse amplitude from the defect exceeds the acceptance level, its value is invalid.

4.7. When using flaw detector with continuous recording of an image of a magnetogram of the weld and chart the magnitude of the signal from defects on any recording medium, the decoding results of the controls carried out after playback of the whole magnetogram of the seam.

4.7.1. When registrarme image of the magnetic imprint of the field defect, reduce the width of the zone of playback across the magnetogram of the weld to the disappearance of signals from the edges of the reinforcement bead, and then include registration of the diagram of amplitude signal values from the identified defect. For invalid defect the height of the figure the amplitude values of the signal from it exceeds the rejection level set on the recorder when setting up the detector at the reference magnetogram.

4.7.2. The nature of the defects is determined by the shape, orientation and degree of darkening grayscale images prints magnetic fields of these defects are reproduced on the recording medium corresponding channel of the data logger.

4.8. The size of defects in butt welded seam pipe raznostnykh (paragraph 1.3) should be expressed in percentage in relation to smaller wall thickness.

4.9. With the use of tape flaw detectors without analyzer the frequency of the reproduced signals this method is one-sided access to the weld control provides the ability to accurately determine the size of defects to be detected regardless of the depth.

If necessary to clarify the nature and magnitude of the defect identified by the tape method, apply other types of non-destructive testing.

4.10. Tape method duplicate method for radiographic inspection:

when controlling for the qualification of the welds performed by a welder before beginning his work on the construction of the pipeline;

under the control of repaired areas of welds;

in the process of acquiring the necessary operator experience in the initial period of his work.

5. PROCESSING OF THE RESULTS

5.1. Evaluation of quality of butt welded joints is performed according to the results of the analysis of information obtained in the verification process.

5.2. The main characteristics of the identified defect are:

the amplitude and duration of the signal from the defect on the screen pulse display, or chart on the media of the Registrar;

conditional length of the defect along the weld seam at a predetermined sensitivity of the detector;

conditional distance between the adjacent defects;

the location of defects across the width of the seam.

5.3. Butt welded joints of pipelines according to the results tape control can be assessed fit or unfit for use.

5.4. The tape control results should be recorded in the laboratory journal and on the form of the conclusion in the prescribed form, which must include:

the name of the construction object (can be abbreviated);

the diameter of the pipeline, the thickness of its walls and steel grade;

type of welding;

the indexes of welded joints;

type flaw detector and magnetizer;

mode of magnetization;

the list of defects, indicating their nature and value;

an overall assessment of the weld quality of «Fit», «unfit»;

date of control and the name of the inspector.

The need for recording the opinions of additional information or clarifications listed must be installed in the technical documentation for control of butt joints of pipelines.

5.5. In compiling the findings, the inspector is guided by the following:

upon detection of the off-seam cracks is only their length;

upon detection of lack of penetration, slag inclusions and then fixed with their relative value (e.g., «10%" or «less than 10%").

for fusion — their total length, indicating the individual fusion;

for single pores and slag inclusions — their number is on the length of a particular segment of the weld, the set of technical documentation for inspection;

for a chain, pores and slag inclusions — their total length.

5.6. When placing the results of monitoring should be used to the symbology of the defects used in radiographic testing.

6. SAFETY REQUIREMENTS

6.1. When using a tape flaw detector and magnetizer have to comply with the electrical safety in accordance with GOST 12.1.013−78, GOST 12.1.019−79, rules of technical operation of electrical installations and safety rules at operation of electrical installations, approved by Gosenergonadzor.

6.2. If you want to check the voltage of the electric current at the terminals of the magnetizing and reproducing devices should be used only with special devices (a voltage tester or a test lamp).

6.3. Requirements of fire safety — GOST 12.1.004−91.

6.4. During preparation and inspection, the NDT inspectors should not be under the raised pipe.

6.5. To move through pipes with diameter of 1020 mm and more is necessary to use an inventory ladder.

6.6. For lifting and moving the magnetizing device weighing more than 50 kg should be used means of mechanization.

6.7. Additional security requirements set in the technical documentation for control of butt joints of concrete pipes.

ANNEX 1 (reference). THE TERMS AND THEIR DEFINITIONS

ANNEX 1

Reference

ANNEX 2 (mandatory). REQUIREMENTS FOR TEST SPECIMENS

ANNEX 2

Mandatory

1. Test specimens of butt welded joints should be manufactured for each wall thickness and steel grade of the pipes and welded in the same manner and on the same technology (welding electrodes, wire, flux, weld) butt welds of the pipeline, the quality of which is subject to monitoring tape method.

Note. If at this facility, pipeline construction used pipe supplies from various steels with the same or similar magnetic properties, can be manufactured in one common test piece for pipes of these steels with the same wall thickness.

2. As the test sample can serve as a shell or part of a length less than the circumference of the two welded rings of pipe of the same diameter as the controlled pipeline.

3. Welding of butt weld of the test piece should be made so that the surface of the weld satisfied the requirements of section 1.4 of this standard and in some parts of the seam had internal defects (lack of fusion or chain of inclusions mainly in the root of the weld) a length of at least 40 mm and the value corresponding to the minimum acceptance level.

Allowed the use of welded test specimens according to claim 2 of the present application with artificial defects in the form of grooves with a width of 2 — 2.5 mm and a length of at least 40 — 50 mm, progressirovanii in the middle of the butt joint from the side of its root. In the presence of the root weld the inner roller of strengthening in the areas milling must be previously removed.

The depth of the artificial defects shall meet the minimum acceptance level for a predetermined thickness of the tube wall is established by normative-technical documentation.

4. After welding the joints of the test specimens should be educated x-ray or gamma-rays using sources of soft radiation to determine the exact species, size and location control of defects in high quality x-ray or radiographic images.

5. On the weld the test piece shall be marked with paint marks the location and boundaries of the defective areas, indicating the type and magnitude of defects.

In addition, it should be noted the boundaries of x-ray films, indicating their indices.

6. Each test sample needs to be tested and adopted by the Commission, made up of steering and technical staff of construction and installation organizations and units control.

7. Test specimens, radiographic images and the reference number they should be stored in the area of control, together with the acceptance of the test sample by the Commission.

APPENDIX 3 (obligatory). REQUIREMENTS FOR THE CONTROL OF THE MAGNETOGRAMS

APPENDIX 3

Mandatory

1. Control of a magnetogram recorded at the butt joints of the test specimens with magnetization last the same devices and the same modes that are used to control welded joints of the pipeline on the facility construction.

2. For the manufacture of the control magnetograms use magnetic tape of the same type as in the testing of butt welds of the pipeline.

3. At each change of batch of magnetic tape used for inspection of the butt welds shall be made new magnetogram of a new batch of tape.

The batch number of the magnetic tape specified by the manufacturer on the label pasted on the packaging tin box, in which the tape is delivered to the consumer.

4. In the manufacture of the control of the magnetograms, the requirements of PP 4.1−4.7 of this standard for the imposition of the magnetic tape on the weld seam, pressing the tape to the surface and regimes of magnetization.

5. The control magnetogram must be marked with a pencil the boundaries of the defective areas, indicating the type and magnitude of defects, the thickness of the base metal of the test sample, the mode of magnetization and the date of its manufacture.

6. The control number shall be kept by the operator in a closed tin box to protect them from the effects of random magnetic fields.

7. Control magnetogram cannot be used until its complete wear and should be periodically replaced with a new one as the appearance of mechanical damage (peeling or abrasion of the magnetic layer, punctures, tears, etc.).

8. When sharing with one flaw multiple magnetizers, each of them needs to be written to the control magnetogram, each of which should be setting the sensitivity of the flaw detector in accordance with the methodology set out in the standards or technical specifications for the detector.

9. When setting the sensitivity of the detector control magnetogram on the screen pulse display or chart of the Registrar should establish a certain level of signal from the control defect in the test sample.

Brightness indication of the instrument it should be adjusted so that during playback the control grayscale image magnetogram of the magnetic field of the control imprint of the defect on the screen of a cathode-ray tube or on registrarme had the most clear-cut.

10. Setting the sensitivity of the detector control magnetogram must be carried out before every start of operation according to the method described in the standards or technical conditions on the flaw of a particular type.