BSI 20/30392796 DC 2020

This document specifies the application of the FMC/TFM technique for the ultrasonic testing of fusion- welded joints in metallic materials of minimum thickness 3,2 mm. This document is applicable only to components with welds fabricated using metals which have isotropic (constant properties in all directions) and homogeneous conditions. This includes welds in low carbon alloy steels and common aerospace grade aluminium and titanium alloys, provided they are homogeneous and isotropic.

This document applies to full penetration welded joints of simple geometry in plates, pipes and vessels. Coarse-grained metals and austenitic welds may be tested when testing level “D” is applied and the provisions in clause 17 of this document have been taken into account.

Where material-dependent ultrasonic parameters are specified in this document, they are based on steels having an ultrasonic sound velocity of (5920 ± 50) m/s for longitudinal waves, and (3255 ± 30) m/s for transverse waves. It is necessary to take this into account when testing materials with different velocities.

This document gives guidance on the specific capabilities and limitations of the FMC/TFM technique for the detection, locating, sizing and characterization of discontinuities in fusion-welded joints. The FMC/TFM technique can be used as a stand-alone approach or in combination with other non-destructive testing (NDT) methods for manufacturing, in-service and post-repair tests.

This document specifies four testing levels, each corresponding to a different probability of detection of imperfections.

This document permits assessment of indications for acceptance purposes based on either amplitude (equivalent reflector size) and length or height and length.

This document does not include acceptance levels for discontinuities.

Two typical scanning techniques for welded joints will be referred to in this document. These are:

1. Side scanning, where the probe(s) is positioned on the surface adjacent to the weld cap on wedges. Side scanning can be performed from one side or both sides of the weld.

2. Top scanning where the probe is positioned on top of the weld cap with a flexible wedge or using immersion, or in contact after removing the weld cap. Top scanning where the probe is positioned on top of weld cap with a flexible or conformable wedge or using immersion, or in contact after removing the weld cap.

“Semi-automated testing” encompasses a controlled movement of one or more probes on the surface of the test object along a fixture (guidance strip, ruler, etc.), whereby the probe position is unambiguously measured with a position sensor. The scan is performed manually. “Fully automated testing“, includes mechanized propulsion in addition.