DEF STAN 02-729 Part 5 (2009-02).pdf

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Requirements for Non-Destructive Examination Methods Part 5 Ultrasonic Reprinted February 2009 Incorporating Amendment 2 Ministry of Defence Defence Standard 02-729 Issue 2 Publication Date 18 August 2006 Category 2 DEF STAN 02-729 Part 5 Issue 2 (Amd 2) ii Contents Foreword .v Introduction.viii 1 Scope.1 2 Warning.1 3 Related Documents.2 4 Definitions.3 5 Acceptance Standards.3 6 Inspection.3 7 General Inspection Requirements.3 8 Plate Material .8 9 Plate Thickness Measurement.10 10 Butt Welding .11 11 Tee-Butt Welding.16 12 Time-of-Flight Diffraction .19 13 Phased Array .27 14 Overlay Cladding.31 15 Brazed Pipe Joints .32 16 Pipes and Tubes.35 17 Pipe or Tube Wall Thickness Measurement.35 18 Forgings - including Forged, Extruded and Wrought Bars.36 19 Castings .39 20 GRP.40 Annex A Procurement Check-List .42 Annex B Weld Surface Finish and Limitations.43 B.1 Introduction.43 B.2 Surface finish, SF1: Undressed.43 B.3 Surface Finish, SF2: Partially dressed to a smooth profile.44 B.4 Surface Finish, SF3: Partially dressed to a near-flat profile .44 B.5 Surface Finish, SF4: Fully dressed to a flat profile.44 Annex C Ultrasonic ToFD Technique.46 C.1 General.46 C.2 Scan Types and Surface Finish.47 C.3 Limitations.49 C.4 Pre and Post Processing .50 Annex D ToFD Probe Separation Distance, Look-up Tables.53 D.1 PSD for 45 probes in thicknesses 13 to 25 5 10 2 - 6 45 - 60 0.75T or 1T 25 to 50 5 6 - 12 55 - 60 0.667T 50 to 100 2 5 6 - 12 55 - 60 0.75T and 0.375T 100 2 5 12 - 25 55 - 60 0.8T and 0.5T and 0.25T NOTE In thicknesses greater than 100mm at a focus of 0.25T the use of 45 wedges is recommended. 12.6.2 On coupling the probes, the electronic settings that control the transmitter pulse HT voltage (typically 100V to 200V), the pulse width (typically adjustable over the range of 35s to 500s) and the bandpass filters (upper and lower filters) are to be adjusted to optimise the Lateral Wave pulse shape and amplitude, i.e. maximum signal-to-noise ratio with a clear distinct shape and the shortest pulse length. 12.6.3 The sensitivity gain is then set by adjusting the gain to show discernible acoustic grain scatter in the digitiser scale over the region of interest beyond the Lateral Wave. This is to be at least 6dB higher than the amplitude of the electronic noise prior to the arrival of the Lateral Wave. The gain should then be adjusted to give a Lateral Wave that is between 5% and 20% of the amplitude scale without saturating the reflected BWE. If the BWE is saturated the gain should be backed off until the BWE is at 100% amplitude and then re- set to give the desired level of Lateral Wave. The amount of BWE saturation should be recorded. NOTE The use of 45 wedges with wide PSDs will result in weak, even non-existent, Lateral Wave signals. In this case the gain should be adjusted so that the Lateral Wave is just discernible (3% to 6%) and the BWE is not saturated by more than 12dB. 12.7 Calibration 12.7.1 A calibration scan, B-scan or D-scan, with the examination probe and sensitivity gain settings shall be undertaken on the item under examination. The scan shall be performed on the main parent plate (thicker plate) forming the joint or the continuous member across a T-butt weld. The probes are to be positioned on the surface within 200mm of the joint to be examined. The scan shall be at least 150mm in length and shall capture the ToFD A-scan data from 1s to 2s before the Lateral Wave to at least 1s after the first mode- converted backwall echo signal. The plate thickness and/or compression wave sound velocity shall be determined prior to scanning in accordance with Clause 9. 12.7.2 The method of controlling the probe movement and method of measuring the distance moved shall be calibrated in accordance with the prescribed instructions for the equipment in use. It is recommended that the system be capable of recording one A-scan per millimetre of probe displacement. The scanning rate, e.g. X A-scans per Y millimetres, is to be recorded, 12.9.1. 12.7.3 It is acceptable to perform a calibration scan on a calibration block as used in 12.6, in which case the block should contain a perpendicular spark eroded semi-elliptical notch with a vee-tip profile on the remote surface. The notch should be not less than 60mm long, 1mm to 2mm wide with a 60 include angle vee-tip and be 0.2T deep (T = plate/butt thickness) at its deepest point. The block is to be large enough to allow scanning across the notch (B-scan) and scanning along the notch (D-scan). Each scan is to contain at least 50mm of uninterrupted BWE signal. An example of the calibration block is given in informative Annex E. DEF STAN 02-729 Part 5 Issue 2 (Amd 2) 24 12.7.4 The time-of-flight to the Lateral Wave and the BWE shall be measured from the scan. These values and the difference between them shall be recorded and used as datum values in the analysis of ToFD scans taken along undressed butt welds (weld caps proud of the surface), along the weld toe edges and ce
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