THE DEVELOPMENT OF EFFICIENT AND RATIONAL SAMPLING SCHEMES FOR THE NDT OF WELDED FABRICATIONS

Statistical sampling techniques in manufacturing industries are by and large statistically unsound, and this field in general is lacking in quantitative information on the distribution of individual defects. Work on circular aluminium vessels and four storage tanks illustrated how various sampling techniques can be used in practice and indicated their use with acceptance standards. However, because of the lack of data, these statistical methods cannot be used to set acceptable levels in terms of the number of defects. Usually 10% of the welds are examined by non-destructive testing methods and the defect level in the sample is assumed to reflect the defect level in the whole fabrication. These simple sampling schemes regularly used for weld acceptance inspection do not rationally relate the amount of inspection to the expected level of defects, the acceptable quality level, the size of the inspection batch, and the cost of inspection; consequently the most efficient and reliable sampling scheme possible is rarely used. This paper describes the analyses of the weld-defect distribution in some welded fabrications and how sampling schemes can be used to provide more rational and efficient sampling schemes for quality control purposes.

  • Corporate Authors:

    Welding Institute

    Abingdon Hall
    Cambridge CB1 6AL,   England 
  • Authors:
    • Rogerson, J H
  • Publication Date: 1977

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Filing Info

  • Accession Number: 00179632
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Sep 14 1978 12:00AM