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    The Gamma-Ray Radiography of Welded High Pressure Power Plant Piping


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    This paper discusses the apparatus necessary, and the procedure used in the gamma-ray radiography of both circumferential and longitudinal seams in welded piping. Also discussed is the effect of size of radiant source, distance from source to film, metal thickness, and type of film on the resultant radiographic sensitivity.

    An accurately drilled test block, having three series of holes of 116, 18, and 316-in. diameters, and depths of 0.010 to 0.100 in. in steps of 0.010 in., was radiographed using many combinations of source to film distance and metal thickness, using both a 25- and 100-mg. radium source. The smaller source definitely proved superior to the larger for short source-to-film distances but offered little if any advantage as the source-to-film distance increased beyond 6 in.

    Two circumferential test pipe welds were made in which many defects, common to welded piping, were purposely made. These welds were first radiographed and then sectioned in many places, polished and etched and used to check the actual defect with the radiograph.

    Two types of penetrameters were placed on both the source side and film side of the pipe welds. It is the author's opinion that there is little if any practical difference in the results obtained with the penetrameters in the two positions (at least for wall thickness up to 1.5 in.). It is agreed, however, that penetrameter detail is slightly better when the pentrameters are placed on the film side, which of course does not give an absolutely true picture of the detail of a defect comparable to the size of the penetrameter holes which is close to the root of the weld.

    Also discussed and illustrated are a few of the various types of piping radiography encountered in the piping industry.

    Author Information:

    Emerson, R. W.
    Metallurgist, Pittsburgh Piping and Equipment Co., Pittsburgh, Pa

    Committee/Subcommittee: E07.01

    DOI: 10.1520/STP43914S