GB1174932A - Improvements in or relating to Radiographic apparatus for Examining Welds - Google Patents

Abstract

1,174,932. Radiographic apparatus. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 13 March, 1967 [16 March, 1966], No. 11600/66. Heading H5R. An apparatus for the examination of annular end edge welds comprises means for supporting the object having the weld in a stationary position, a radiation source unit producing a narrow near-parallel beam of penetrating radiation, a container unit for radiation sensitive film, equipped with means for moving the film past an exposure aperture therein, means for mounting said units so that they can be moved together in a planetary manner bodily around the said object whilst disposed at opposite sides of said object in a radial plane which intersects the surface said object, the beam of radiation produced by the source being continually directed at the exposure aperture of the film container during movement, said means for moving the film being related to the means inducing the planetary motion so that moving the radiation source around the weld produces a linear record of it on the film. In Fig. 1, the object is cylindrical nuclear fuel can having two welded ends, and in this preferred embodiment the two welds are examined simultaneously by two radiological apparatuses according to the invention. The tube 1 is supported on a stationary stand 2, and the rotatable assemblies of radiation source 4 and camera 6 mounted on discs 3 to rotate about axes 3<SP>1</SP> are moved forward on frames 7 along slides 8 into the appropriate position. The axes 3 are rotated at constant speed by driving means 10, 11, the driving means being reversible so that after one revolution in one direction the wheel 3 is turned one revolution in the other direction which action unwinds the cables 13 from drum 14 round which they passed during the first revolution. Arrangements are made so that during the reverse phase the radiation source is cut off, and the film in container 6 is not moving. Preferably, during the forward motion the wheel completes slightly more than one revolution and the film moves correspondingly but the radiation source is cut off at the complete revolution so that a small amount of unexposed film separates the filmed record of each weld examined. Figs. 2 and 3 (not shown), illustrate how the movement of the disc 3 and the film are co-ordinated by means of a stationary sun gear and a planetary gear having equal numbers of teeth, the film being driven by the planetary gear and the film drive means having a diameter corresponding to that of the tubular object being examined so that one complete revolution of the disc exposes a length of film equal to that of the weld under examination. A mild steel backing piece 44 is attached to disc 3 to absorb any stray radiation emerging from the camera. The rim of disc 3 is supported by rotatable bearings attached to frame 7.