ISO 10893-7 pdf download – Non-destructive testing of steeltubes — Part 7: Digital radiographic testing of the weld seam of welded steel tubes for the detection of imperfections.
c) digital radioscopy with image integration (e.g. EN 13068-I, EN 13068-2 and EN 13068-3).
6 Test method
6.1 The weld seam shall be tested by a digital radiographic technique corresponding to ClauseS a) to c).
6.2 Two Image quality classes. A and B. conforming to ISO 17636.2. shall be specified:
— class A: radiographic examination technique with standard sensitivity;
— class B: radiographic technique with enhanced sensitivity.
NOTE Image quality class A is used for most applications. Image quality class B is intended for applications where increased sensitivity is required to reveal all the imperfections being detected.
The required image quality class should be stated in the relevant product standard.
6.3 The digital Image displayed shall meet the required image quality class A or B.
6.4 The beam of radiation shall be directed at the centre of the section of the weld scam under examination and shall be normal to the rube surface at that point.
6.5 The diagnostic length shall be such that the increase in penetrated thickness at the ends of the useful length of the sensitive detector input screen shall not exceed the penetrated thickness at the centre of the detector by more than 10 % for image quality class B or by more than 20 % for image quality class A, provided the specific requirements of 6.9 and Chiusel are satisfied.
6.6 The single wall penetration technique shall be used. When the single wall technique Is impracticable for dimensional reasons, the use of the double wall penetration technique may be used, by agreement, if the required sensitivities can be showi to be achievable.
6.7 If the geometric magnification technique (see 6.) is not used, the detector shall be placed as close to the object as possible.
The minimum value of the source-to-weld distance, f. shall be selected such that the ratio of this distance to the effective focal spot size. d. Le.f/d, conforms to the values given by Formulae (1) and (2):
for image quality class A:
Detector-side positions typically show I or 2 more wires, or hales, than if the same IQI was on the source side. Customers may ask for a trial exposure to be carried out on a sample piece of pipe, with IQIs placed on both source and detector sides as a comparison. see ISO 17636.2:2013, 6,7. for details
When the tubes under inspection have the same dimensions and grade, it is sufficient to use the IQI only every 4 h, or twice a shift, to check image sensitivity. When carrying out the sensitivity checks, though. the IQI shall he placed on the source side.
The parameters used with the trial exposures (settings of X-ray source, detector and geometry) shall not be changed for the subsequent images acquired with detector-side 1Q15. Far stable systems and processes, such as automated testing systems using DDAs, it Is sufficient to prove the image quahty once per shift as long as the tube dimension, tube material and testing parameters remain unchanged. In this case, the image quality proof should be performed only with source side IQIs.
By usage of the duplex wire IQI. conforming to ISO 19232-S. the image unsharpnrss. 11g. shall he measu red.
The read-out unsharpness, U5, value for the duplex wire IQI is the smallest wire pair element number (largest wire diameter) with a dip separation below 20 %, measured with a profile plot across the duplex wire in the digital image,
The duplex wire lQl should be positioned on the surface of parent metal at an approximately 50 angle towards the pixel orientation In order to avoid abasing effects.
7.2 The basic spatial resolution of the digital detector, R1,detectr, which is fixed by the construction and hardware parameters, shall be determined by placing the duplex wire IQI directly in front of the detector.
ISO 10893-7 pdf download – Non-destructive testing of steeltubes — Part 7: Digital radiographic testing of the weld seam of welded steel tubes for the detection of imperfections
