Use of multilayer film holders for radiographic control of welded joints

Study on the dependence of sensitivity of radiographic control and optical density achieved in different layers of a multilayer cassette on thickness of intermediate screens is conducted. It is stated that for assuring the equality of control sensitivity attained on the front and back films of a two-layer cassette at radiographing steel welded joints at constant or slightly varying thickness, the thickness of lead intermediate screens (δint.) should not exceed 0.02; 0.04 and 0.06 mm for X-radiation with U<200 kV, U=200-300 kV and U=300-420 kV respectively; 0.5 and 0.2 mm for gamma-radiation of Co and 192Ir respectively; 0.1 mm for bremsstrahlung of electron accelerators. A multilayer cassette with standard thickness δstv of a lead screen of the front film and increased up to (5-10)δstv total thickness of intermediate screens may be used for expansion of the range of thickness of a welded joint of variable cross section controlled per one exposure