Film and intensifying screen
1 . Film
The film system is divided into four categories according to GB/T19384.1, namely T1, T2, T3, T4. T1 is the highest category and T4 is the lowest category. Class A and Class AB are used for T3 or higher class film, Class B is for Class T2 or higher film, Class B is for Class T2 or higher. The background fog of the film should be greater than 0.3.
2. Intensifying screen: using metal intensifying screen or no intensifying screen.
3. Film and intensifying screens should always be in close contact during transillumination.
4. Image quality meter
4.1 The image quality of the film is measured by a line image quality meter. The type and specification of the linear image quality meter shall comply with the provisions of JB/T7902. The wire diameter, line number and content not included in JB/T7902 shall comply with the relevant provisions of HB7684.
4.2 According to the transillumination thickness (W), the transillumination method and the image quality meter are placed on the source or film to select the image quality meter number. Single-wall transillumination and double-wall transillumination use a common line-type image quality meter. The double-wall transillumination of the small-diameter tube (D0≤100mm) should use the special-purpose image quality meter of JB/t4730.2 Appendix F.
4.3 Image quality placement and quantity
The image quality meter should be placed on the working surface butt joint at one end of the wire should be across the weld and the filament placed on the outside. When multiple butt joints are simultaneously exposed on a piece of film, the image quality meter should be placed on the weld at the edge of the transillumination zone. The length of the wire on the thinner side of the base material should be at least 20 mm to determine the image quality sensitivity.
(1) Double-wall single-eye transillumination requires that the image quality meter be placed on the film side, and the double-walled double-shadow transillumination specification image quality meter can be placed on the source side or on the film side.
(2) Single-wall transillumination requires that the image quality meter be placed on the source side. If the image quality meter cannot be placed on the source side, it is allowed to be placed on the film side, but a comparative test should be performed.
(3) When the image quality meter is placed on the film side, the typeface "F" should be placed on the image quality meter as the mark, and the "F" mark image should appear on the film at the same time as the mark of the image quality meter. Indicated in the test report.
Image quality count
In principle, each film should have an image of the quality meter. When multiple exposures are taken in one exposure, the amount of image quality used can be reduced. However, the following requirements should be met:
(1) For the annular butt joint, when the source is placed in the center circumferential exposure, at least three image quality meters are placed at equal intervals on the circumference.
(2) When multiple films are continuously arranged in one exposure, at least one image meter is placed at each of the first sheet, the middle sheet and the last sheet.
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