【国外标准】 Standard Practice for Mechanized Ultrasonic Testing of Girth Welds Using Zonal Discrimination with Focused Search Units

4.1 This practice is intended primarily for the mechanized ultrasonic examination of pipe girth welds used in the construction of gas and oil pipelines. This practice, with appropriate modifications due to changes in weld profile, may also be used to examine repaired welds. Manual techniques such as described in Practice E164 may also be used to examine production or repaired welds. This practice, with appropriate modifications, may also be used to examine other forms of butt welds including long seams.4.2 Techniques used are to be based on zonal discrimination whereby the weld is divided into approximately equal vertical examination sections (zones) each being assessed by a pair of ultrasonic search units. See Fig. 1 for typical zones.FIG. 1 Schematic Representation of Weld Zones and Discontinuities4.3 Thicknesses of material examined are normally 7 to 25 mm (0.28 to 1.00 in.) and pipe diameters 15 cm (6.0 in.) and greater but this standard may apply to other thicknesses and diameters if the techniques can be proven to provide the required zonal discrimination.4.4 Examination zones are typically 2 to 3 mm (0.08 to 0.12 in.) in height. For most applications this will require the use of contact focused search units to avoid interfering signals originating from off-axis geometric reflectors and to avoid excessive overlap with adjacent zones.1.1 This practice covers the requirements for mechanized ultrasonic examination of girth welds. Evaluation is based upon the results of mechanized ultrasonic examination. Acceptance criteria are based upon flaw limits defined by an Engineering Critical Assessment (ECA) or other accept/reject criteria defined by the Contracting Agency.1.2 This practice shall be applicable to the development of an examination procedure agreed upon between the users of this practice.1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.