What is the weld joint ratio? How is NDT defined?

Selection of welding joint coefficient Φ welded joint coefficient refers to the butt welded joint strength and ratio of material strength, to reflect due to factors such as weld defects and welding residual stress in welding joint strength is weakened, is a comprehensive reflection of welded joint mechanical properties. The weld joint coefficient shall be determined according to the weld process characteristics of the welded joint of the container pressure element (single or double welded, with or without backing) and the length ratio of the nondestructive testing. Double-sided welding (equivalent to full-penetration joint of double-sided welding) : 1.0 for 100% NDT; Local nondestructive testing was 0.85. Single side welding (along the full length of the root of the weld with a pad close to the base metal) : 100% NDT = 0.9; Local nondestructive testing is 0.8. Radiographic testing (AB: sensitivity technology) : 100% qualified nondestructive testing take Ⅱ level; Local level take Ⅲ nondestructive testing qualified. Ultrasonic testing (pulse reflection method (B)) : 100% qualified nondestructive testing take Ⅰ level; Local level take Ⅱ nondestructive testing qualified. Ultrasonic testing (diffraction time difference method (B)) : 100% qualified nondestructive testing take Ⅱ level; Local level take Ⅱ nondestructive testing qualified. Determining principle of welding joint coefficient (1) Welding joint coefficient of cylinder body When the structure and nondestructive testing ratio of longitudinal joint and circumferential joint are not consistent, such as double-sided welding, 100%RT or UT for longitudinal joint, and single-sided welding for circumferential joint and RT or UT testing is not possible, the welding joint coefficient of longitudinal joint is generally taken in the design calculation of the vessel. The detailed reasons are as follows: the calculation formula of inner pressure cylinder thickness is derived from the intensity of circumferential overall (primary) film stress in the cylinder, so the welding joint coefficient corresponding to it should be the longitudinal welding joint coefficient of the cylinder. In the tiny section of cylinder ring to joint also exists in the ring to the circumferential membrane stress, in addition, although the ring to the joint in the axial stress of the cylinder only half of the ring to stress, but as a complete pressure vessel, in order to ensure the strength and security of the whole cylinder, general joint and longitudinal joint ring should be asked to have the same quality level, which requires the same coefficient of welding joint. If there are manufacturing difficulties, it can be according to GB/T 150.4 10.3.4 (for the last circum-sealing weld between the cylinder and the head with the diameter of the container no more than 800mm, when the single-side welding butt joint without backing plate is adopted and no radiographic or ultrasonic testing is possible, no testing is allowed, but gas shielded welding is required to be used for backing.) The execution. In this case, although the mass of the circumferential joint (welding joint coefficient) may not be exactly the same as that of the longitudinal joint (welding joint coefficient), the welding joint coefficient of the longitudinal joint is still taken when calculating the thickness of the cylinder. (2) Joint coefficient of head splicing joint Head splicing joints shall be tested by 100%UT or RT, but there is no stipulation on how to select the joint coefficient of head splicing joints. The requirements of nondestructive testing for splinted joint of head are mainly put forward in view of the large deformation of head forming and the easy expansion of defects, which has nothing to do with the calculation of head thickness. Therefore, although a 100%UT or RT test is required for head splits, this test is still only part of the test for the entire container, and its eligibility criteria are determined according to the requirements for the container as a whole. Therefore, the welding joint coefficient of head splicing joint is generally taken as the welding joint coefficient of longitudinal joint of pressure vessel. For the whole steel plate suppression, small diameter of the head, because there is no welding joint and the thickness calculation of Φ = 1.0.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods