Abstract: For the application of GB/T 3323—2005, JB/T 4730.2—2005, DL/T 821—2002 in the ray detection of metal parts of power stations, the applicable scope, detection technology grading and detection process of three standards A detailed comparison of the contents provides a reference for the correct understanding and use of radiographic standards for power plant metal parts.
1 Overview
The radiographic inspection of metal parts in power plant infrastructure and maintenance mainly involves GB/T 3323-2005 "Metal fusion welding joints radiography", JB/T 4730.2-2005 {non-destructive testing of pressure equipment", DL/T821-2002{steel Three standards for technical regulations for ray inspection of butt welded joints for pressure pipes. At present, three standards are applied in the radiographic inspection of metal parts of power plants. GB/T 3323—2005 is mainly applied to the welded joints of power supply parts and the load-bearing parts and structural parts of power stations that cannot be covered by JB/T 4730.2-2005. Docking of joints and ray inspection of angle joints; JB/T 4730.2-2005 is mainly used for ray inspection of butt welds of boilers, pressure vessels and pressure pipes; DL/T 821-2002 is mainly used for pressure pipes during power station installation Detecting the weld seam of the butt joint of the small diameter pipe of the heated surface during maintenance.
2 Comparison of radiographic standards
2.1 Reference to international standards
a. GB/T 3323—2005 is equivalent to the European standard EN1435—1997 {non-destructive testing of welding—radiation detection of welded joints”. In order to ensure the coordination with JB/T 4730.2-2005, the quality classification of welded joints has been added. It is deleted that “the same transillumination and technical methods can ensure the image quality of the ray film is the same, and it is not necessary to place the image quality meter for each film”. The provision of "radiation detection for materials with a tendency to delay cracks, at least 24 h after welding" has been added.
b. JB/T 4730.2—2005 is based on European standards and refers to American standards. The main reason is that European standards have advantages over US standards in terms of technological advancement, structural integrity, narration and ease of use.
C. DL/T 821—2002 is mainly based on the international standard ISO5579-1998 {Non-destructive testing of basic rules for X-ray 7-ray photography of metallic materials”, while retaining the long-term practice and effective testing process clauses in the previous version.
2.2 Scope of application
GB/T 3323—2005 is the basic method of x-ray and γ-ray photography. It is suitable for the radiation inspection and quality classification of molten-welded joints of sheet metal and pipe. It is suitable for butt joints, angle joints and T of various metal materials. Detection of type joints, etc. JB/T4730.2—2005 is applicable to the radiation inspection technology and quality classification requirements of fusion welding butt joints for sheet metal and pipe of pressure equipment. It is applicable to the detection of fusion welded butt joints of steel, copper, aluminum, nickel and their alloy materials. DL/T 821—2002 is applicable to the ray inspection and quality classification of butt fusion welded joints of steel pressure-bearing steel pipes. The applicable materials are carbon steel, low alloy steel and stainless steel commonly used in power plants. JB/T 4730.2—2005 specifies the applicable thickness range in the rating clause. The thickness of the steel weld is 2～40O mm. The applicable thickness range is not specified in GB/T 3323—2005. Less than 1.2mm, the upper limit of thickness can be greater than 375 mm; DL/T 821-2002 is applicable to a thickness range of 2 to 175 mm.
It can be seen from the above comparison that GB/T 3323—2005 has the widest application range in terms of materials, joint forms, components, etc., JB/T4730.2—2005 is the second, and DL/T 821—2002 has the narrowest application range. But the most targeted.
2.3 Detection Technology Classification
GB/T 3323—2005 divides the radiation detection technology into two grades: A grade (normal grade) and grade B (optimal grade); JB/T 4730.2—2005 classifies the radiation detection technology into grade A (low sensitivity technology), Class AB (medium sensitivity technology) and class B (high sensitivity technology) three levels; DL/T 821-2002 did not perform detection technology level division. GB/T 3323—2005 completely divides the inspection technology level according to international standards; JB/T 4730.2—2005 increases the AB level detection level according to the actual situation in China, which is more convenient for practical application; and DL/T821—2002 removes ISO 5579— In 1998, the classification of detection levels was analyzed from the requirements of geometric unsharpness and K-value control, which is equivalent to JB/T 4730.2-2005 Class AB detection technology level.
2.4 Transillumination thickness and image quality sensitivity
GB/T 3323—2005 and JB/T 4730.2—2005 both stipulate that when single-wall transillumination, the thickness of the transillumination takes the nominal wall thickness T of the material, and when the double-wall transillumination, the nominal wall of each layer of the material through which the radiation passes is taken. Thickness sum, transillumination thickness does not consider the weld height h; and DL/T 821-2002 specifies single wall transillumination, the transillumination thickness is the actual wall thickness of the steel pipe plus the weld height (T+ h), double wall When single-shadow transillumination, the transillumination thickness is 2 times the thickness of the steel pipe plus the weld height (2T+h). When the double-wall double-shadow is transilluminated, the transillumination thickness is TA-O. 8 J (Oo-butyl) T+T, wherein Dn is the outer diameter.
Under the same transillumination thickness, GB/T 3323—2005 A, B and JB/T 4730.2—2005 AB and B sensitivity levels basically correspond. When the image quality meter is placed on the source side, the image quality sensitivity (class AB) specified in JB/T 4730.2-2005 is generally higher than DL/T 821-2002, but due to the difference in the position of the image quality meter, The sensitivity of the two is basically the same; when the image quality meter is placed on the film side, DL/T 821—2002 requires that the image quality meter number be increased by one level or the pair is compared with the source side.
Compared with the test, and JB/T 4730.2—2005 directly stipulates that the image quality meter is placed on the film side, it is selected according to Table 7 of the standard. Although most of the image quality gauges are increased by one level than the source side, they exist simultaneously. More than one level, JB/T 4730.2-2005 is relatively strict in terms of transillumination sensitivity than DL/T 821-2002.
2.5 Image type and placement
GB/T 3323—2005 stipulates the use of linear image quality meter and stepped hole image quality meter; JB/T 4730.2—2005 stipulates that only linear image quality meter is used, including ordinary and special (equal diameter) image quality meter. 2 kinds. DL/T 821-2002 stipulates that D. For pipes of >89 mm, the butt joints shall be transilluminated according to R in JB/T 7902-1999 "Linear Image Quality". Series image quality meter; 76 mm
When the large-diameter pipe is transilluminated, the DL/T 821-2002 image quality meter is basically the same as JB/T 4730.2-2005; when the small-diameter pipe is transilluminated, the number of small-diameter pipes in the power industry inspection object is considered. In the case, it is specified in detail that different sizes of small diameter pipes should use different types of dedicated image quality meters. For D. The tube of ≤76 mm adopts the type II special image quality meter, which not only reflects the transillumination sensitivity, but also reflects the translucent area of the weld seam when the double-wall double-shadow transillumination is reflected to some extent.
2.6 film blackness requirements
The requirements for GB/T 3323—2005, JB/T 4730.2—2005, and DL/T821—2002 for the blackness D of the film are shown in Table 1.
GB/T 3323-2005 stipulates that the minimum blackness level A can be reduced to 1.5, and the B level can be reduced to 2.0. The brightness of the viewing light can meet the requirements, and a larger blackness can be used. JB/T 4730.2-2005 stipulates that when X-rays are used to illuminate small diameter pipes or other workpieces with large variations in section thickness, the minimum blackness of class AB is allowed to drop to 1.5, and the level of B can be reduced to 2.0. When the degree is >4.0, if the measurement verification report proves that the brightness of the viewing lamp used can meet the requirements, the evaluation is allowed.
The three standards have roughly the same black limit and the black limit is different. GB/T 3323—2005 does not limit the upper limit of blackness, while JB/T 4730.2—2005 does not exceed the limit of 4.0, but the upper limit of blackness can be improved when certain conditions are met, DL/T 821—2002 The specified black limit is the lowest and no exception is allowed. In the actual evaluation, if the brightness of the viewing lamp can be guaranteed, it is advantageous to improve the detection sensitivity of the blackness to the defect. Therefore, GB/T 3323—2005 does not limit the upper limit of blackness, JB/T 4730.2—2005 It is stipulated that the brightness of the viewing lamp meets the requirements, the blackness exceeds the upper limit, and the evaluation can still be performed, and the provisions of DL/T 821-2002 are not reasonable enough.
2.7 Transillumination method and number of transillumination of small diameter tubes
GB/T 3323—2005 and JB/T 4730.2—2005 have the same requirements for the transillumination of small-diameter tubes. According to the difference of wall thickness, weld width and tube outer diameter, the small-diameter tube oblique transillumination ellipse is specified in detail. Selection criteria for imaging and vertical transillumination overlay imaging, 100% number of transilluminations detected. JB/T4730. 2-2005 The number of times of transillumination is used to limit the transillumination thickness ratio, improve the lateral crack detection rate, and ensure the weld quality. JB/T4730.2-2005 also specifies the conditions for allowing one transillumination. DL/T 821—2002 only stipulates the number of double-wall double-shadow transillumination of small-diameter pipe butt joints according to the difference of outer diameter of the pipe. The regulation of the number of transillumination is relatively loose, which is beneficial to the on-site implementation. DL/T821—2002 and JB/T 4730.2—2005 have different regulations on the small-diameter tube transillumination, mainly in the following aspects:
a. JB/T 4730.2-2005 stipulates that the small diameter tube adopts double wall double shadow transillumination arrangement. When the wall thickness T ≤ 8 mm, the weld width g ≤ D. /4 and T/D. ≤O. At 12 o'clock, elliptical imaging should be performed using oblique transillumination, separated by 90. Transmitted 2 times. When T ≤ 8 mm, g ≤ D. /4 and T/D. >0.12, elliptical imaging should be performed by oblique transillumination, which is transilluminated 3 times at 120° or 60°. When elliptical imaging, the width of the image opening should be controlled to be about 1 times the width of the weld. If the above conditions are not met, or elliptical imaging is difficult, the vertical transillumination method may be used for overlapping imaging, separated by 120. Or 60. Transmitted 3 times. If it is impossible to perform multiple transillumination due to structural reasons, elliptical imaging or overlapping imaging may be used for transillumination once, and effective measures shall be taken to expand the detectable range of defects and ensure that the blackness and sensitivity meet the requirements.
b. DL/T 821-2002 stipulates that D. The butt weld of ≤89 mm pipe can be transilluminated by double wall double shadow. For 76
3 Conclusion
a. As a national standard, GB/T 3323—2005 has the widest scope of application and can be used in the radiographic inspection of various metal parts of power stations that cannot be covered by JB/T 4730.2—2005.
b. The JB/T 4730.2-2005 standard has strict requirements on transillumination methods and transillumination parameters, and has certain advantages in sensitivity and defect detection rate. It should be preferred in the radiographic inspection of pressure equipment parts of power stations. However, due to strict requirements on process parameters, it is sometimes difficult to meet the requirements of the site conditions, which will have a certain impact on its application.
c. DL/T 821—2002 as the power industry standard for on-site adaptability and D of large-scale radiation inspection of power station boiler installation site. <76 mm small diameter tube ray transillumination has an advantage and can be used as a useful supplement to the above two standards.