GOST 28277-89
GOST 28277−89 nondestructive testing. Welded connections. Electroradiography method. General requirements
GOST 28277−89
Group B09
STATE STANDARD OF THE USSR
NONDESTRUCTIVE TESTING.
WELDED CONNECTIONS
Electroradiography method.
General requirements
Nondestructive testing.
Welded joints. Electroradiography method.
General requirements
AXTU 0011
Date of introduction 1991−01−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of erection and special construction works of the USSR
DEVELOPERS
Yu. V. Popov, Cand. tech. Sciences (chair); E. Yu. Kryukov, V. A. Filippenkov, PhD. tech. Sciences
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from
3. The check date — 1994
4. INTRODUCED FOR THE FIRST TIME
5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
The designation of the reference document referenced |
Item number |
GOST |
5.2 |
| GOST 7512−82 |
2.7, 3.1, 3.3, 3.6, 3.15, 4.3, 4.5 |
| GOST 9095−89 |
2.4 |
| GOST 15843−79 |
2.8 |
| ГОСТ 18510–87 |
2.4 |
| GOST 20426−82 |
2.5 |
| GOST 21444−75 |
2.4 |
6. REPRINTING. December 1993
This standard specifies a method electroradiographic control of welded joints of metals and their alloys, made by fusion welding with application of braking and gamma radiation and electroradiographic media image (electroradiographic plates).
1. GENERAL PROVISIONS
1.1. Electroradiographic control is used to identify welded joints of cracks, lack of penetration, pores, slag, tungsten, oxide and other impurities, and to detect burn-through, undercut and offset welded edges, inaccessible for external inspection.
1.2. When electroradiographic control can be not revealed any discontinuities and inclusions with a size in the direction of scanning at least twice the sensitivity of control, lack of fusion and cracks, the plane of the disclosure which do not coincide with the direction of transmission and (or) the value of disclosure is less than 0.1 mm for the radiation thickness up to 5 mm and less than 2% of the radiation of the radiation thickness for thickness over 5 mm, as well as any discontinuities, and inclusions, if their images in the picture match the image of extraneous details, sharp corners or zone of the edge effect of sharp changes in the thickness of the illuminated elements.
1.3. Electroradiographic control is subjected to a welded joint having symmetrical access, providing the possibility of inserting the cassette with electroradiographic plate and the radiation source in accordance with the requirements of this standard.
1.4. For control of welded joints electroradiographic method allowed the radiographers have passed theoretical training and practical training in an approved program, passed the exam and have the appropriate certificate for inspection. The radiographers undergo annual recertification.
2. HARDWARE REQUIREMENTS AND ACCESSORIES TO CONTROL
2.1. When electroradiographic control should be used electroradiographic equipment and plates intended for industrial application. Use electroradiographic medical equipment and plates if they provide the desired sensitivity of control.
2.2. Electroradiographic plate should be placed in a light-tight cassette with a detachable tonneau. Plates shall comply with the technical requirements.
2.3. For the manifestation of the image, use the black electrophotographic toner. Allowed to use electrophotographic toners of other colors, provided that requirements for quality established by this standard.
2.4. The transfer of toner image should be on paper # 0 according to GOST 18510, No. 1 grade according to GOST 9095, GOST 21444.
2.5. When electroradiographic control should use the radiation sources under GOST 20426. The type of radioactive source, the voltage at the x-ray tube and the energy of the accelerated electrons should be set depending on the radiation thickness of the material in the technical documentation for control or acceptance of welded joints.
2.6. To protect electroradiographic plate from the back scattered radiation of the metal shields according to GOST 7512.
2.7. To determine the sensitivity control should be applied to the wire and grooving standards of sensitivity as per GOST 7512.
2.8. When electroradiographic control use marks according to GOST 15843 made of a material that provides a receipt of their clear pictures to pictures.
2.9. Electroradiographic equipment when working outdoors should be installed in a place protected from the action of precipitation, wind and direct sunlight.
3. REQUIREMENTS FOR THE PREPARATION AND CONDUCT OF MONITORING
3.1. Preparation of welded joints to control (cleansing, elimination of external defects, marking and marking of sites) must be performed according to GOST 7512.
3.2. On the controlled section of the welded connection should be set to two sensitivity standard: standard wire directly on the seam direction of the wires across the joint and grooving Etalon at a distance of not less than 5 mm from the weld with the direction of the grooves across the joint. When you weld without weld reinforcement use two wire sensitivity standard.
The standards establish the sensitivity of the controlled area from the side facing the radiation source, one in the middle part of the controlled area, and the other from its edge.
3.3. If you can’t install standards of sensitivity and (or) markings on the controlled section of the welded joint in accordance with the requirements of this standard the procedure of conducting monitoring without installation standards of sensitivity and (or) markings shall be provided in the technical documentation for control or acceptance of welded joints (GOST 7512).
3.4. Under the control of circumferential welds of pipelines with diameter less than 100 mm grooving is allowed to set standards of sensitivity with the direction of the grooves along the seam.
3.5. In case of impossibility of installation of standards of sensitivity from the radiation source to weld cylindrical, spherical and other hollow objects through two walls with decryption only adjacent to the cassette area of the welded joint is allowed to set the standards of sensitivity on the part of the cassette with electroradiographic plate.
3.6. The installation of marking signs — according to GOST 7512.
3.7. All operations electroradiographic process (electrification, manifestation, image transfer and fixation of the image) should be performed in electroradiographic apparatus in accordance with the operation manual.
3.8. The time between the charging plate and its exposure and time between exposure and manifestation of plates should be minimized and specified in the documentation to control.
3.9. The manifestation should be to the negative electroradiographic pictures. Allowed to electroradiographic positive images in order to determine the size of defects.
3.10. Control of butt, lap, corner and t-welds must be performed in accordance with the schemes given on features. 1, 2.
Scheme of the testing of butt, lap, corner and t-welds
1 — radiation source; 2 — controlled land; 3 cassette with electroradiographic plate
Damn. 1
Schematic of the control ring (butt, lap, corner and t -) of welded joints
1 — radiation source; 2 — controlled land; 3 cassette with electroradiographic plate
Damn. 2
3.11. If you weld for shit. 2 (a, d) the direction of radiation must coincide with the plane of the monitored weld.
3.12. If you weld for shit. 2 (b) the direction of radiation should be chosen so, in which images of tangential sections do not overlap each other. The angle between the radiation direction and the plane of the monitored weld should not exceed 30°.
If these conditions are not feasible, control should be carried out for God. 2B in accordance with clause 3.11 decoding only adjacent to electroradiographic plate site welded joints.
3.13. When you weld with large difference in thicknesses, as well as in cases when the monitored weld does not protect electroradiographic layer from direct irradiation, the weld inspection to be performed using compensators. Use the compensators of any material providing the required attenuation of radiation.
3.14. For all types of welded connections and circuits transmission control may be performed with a different radiation direction than PP. 3.10 — 3.12. The direction of radiation must be specified in this case in the technical documentation for control or acceptance of welded joints, the angle between the radiation direction and the normal to electroradiographic plate and the distance between the positive welded connection and electroradiographic plate should not exceed 45°, and 150 mm.
3.15. Parameters electroradiographic control (the allowable value of the geometric blur and the relative increase in size of the image defects, the distance from the radiation source to the controlled weld, the dimensions of the zones of welded joints that are controlled in a single exposure, the maximum length or the minimum number of plots required length and width of the images) should be determined by GOST 7512, the size electroradiographic the tape must be not less than the required size.
4. PROCESSING OF INSPECTION RESULTS
4.1. Viewing and decoding images should be carried out after transferring the toner image from electroradiographic layer on the paper and fixing. Images should be viewed in ambient light.
4.2. Pictures, admitted to the transcript must meet the following requirements:
the photographs should not be spots, stripes, impurities and traces of images of previously completed picture, complicating its decoding;
the photographs must be visible image and the restrictive markings and standards of sensitivity;
the density of blackening of the image of the weld in the picture must exceed the optical density of the material to which the transferred toner image, is not less than 0.2 units of optical density;
the difference between the densities of blackening of the image, defined in transmitted light at different portions of the image with the same radiation thickness should not exceed 0.3 units of optical density;
negative image should not contain elements of a positive image and Vice versa. There may be elements of a positive (negative) image on the negative (positive) images in the image labels or portions of the image that are not subject to interpretation.
4.3. The control sensitivity determined by GOST 7512, must meet the requirements of the technical documentation for the control. For different values of the sensitivity control, defined by the wire and grooving standards, should adopt a larger value of the sensitivity in millimeters.
4.4. The visible image on the length of the groove of the standard, which is the definition of sensitivity must be equal to the width of the Etalon. Allowed reducing the width of the image of the grooves at the edges of the grooving of the standard, as well as increase visible in the picture the wire diameter of the wire reference in the section of the wires situated on the weld reinforcement.
4.5. The sizing of discontinuities and inclusions, record inspection results and notations of defects should be carried out by GOST 7512.
5. SAFETY REQUIREMENTS
5.1. When conducting electroradiographic control must be provided for safety in accordance with the requirements of «the Main sanitary rules of works with radioactive substances and other ionizing radiation sources» of OSP-72/87 No. 4422−87, «radiation safety Norms» NRB-76/87 No. 4392−87, «Sanitary rules when conducting x-ray radiography» No. 2191−80 approved by the USSR Ministry of health.
5.2. Electrical installations for electroradiographic control shall conform to the requirements of GOST
5.3. When operating connected to industrial mains installations for electroradiographic control must be provided for safety in accordance with the requirements of «Rules of technical operation of electrical installations» and «safety Rules at operation of electrical installations», approved by Slavenergoprom in 1984
5.4. Enterprises and organizations performing work electroradiographic control, needs to develop documentation that defines the rules and methods of safe organization of works subject to the conditions of production.
