AS ISO 17643:2020 – Non-destructive testing of welds —Eddycurrent testing of welds by complex-plane analysis.
6.4 Equipment
6.4.1 Instrumentation (excluding probe) General
The instrument used for eddy current testing in accordance with this International Standard shall be capable of analysis and display in the complex plane. The amplitude and phase of eddy current signals shall be measurable. Frequency
The eddy current instrumentation shall be able to operate at a selected frequency within the range
1 kllzto 1 MHz. Signal display
The display shall include the facility to freeze eddy current signals on screen until reset by the operator. The trace shall be clearly visible under all lighting conditions expected during testing. Phase control
The phase control shall be able to give complete rotation of displayed signals (3600) in steps of no mare than 10° each.
6.4.2 Surface probes Probes for measuring coating thickness and material evaluation relative to calibration block
The probe shall operate in the absolute mode at a selected frequency in the range from I kHz to 1 MHz. All the probes shall be clearly marked with their operating frequency range. Probes for testing of welds
For testing of ferritic welds, probes specially designed for this purpose shall be used.
The coils assembly shall be orthogonal, tangential or equivalent.
The electrical connection shall enable differential measurements which are characterized by having a minimal dependency on continuous or small variations In conductivity, permeability and llft•off In the welded and heat-affected zones.
The diameter of the probe shall be selected relative to the geometry of the component under test. Such probes shall be able to operate when covered by a thin layer of non-metallic wear-resistant material over the active lace. lithe probe is used with a cover, then the cover shall always be in place during calibration. The probe shall operate at a selected frequency in the range from 100 kHz to 1 MHz
6.4.3 AccessorIes CalibratIon block
A calibration block, of the same type of material as the component to be examined, shall be used. It shall have EDM (electric discharge machined) notches of 0,5 mm, 1.0 mm, and 2,0 mm depth, unless otherwise specified, for example in an application standard. The tolerance on the notch depth shall be ±0.1 mm. The recommended width of the notches Is sO,2 mm. An example of a calibration block is shown in Figure 1.
64.3.4 Remote display and control
For operation with long extension cables, the equipment shall include a device For remote signal display at the operator’s location.
6.4.4 Systematic equipment maintenance Calibration certificate
The equipment (instrument and probes) shall have a currently valid calibration certificate. This may be issued by the manufacturer, (in accordance with ISO 15548-1 and ISO 15548-2) a recognized calibration laboratory or an authorized agency. FunctIonal check
Maintenance shall follow ISO 15548-3 or a written procedure. The results of maintenance checks shall be recorded.
6.5 Test procedure
6.5.1 F.valuation mode
The evaluation mode shall use both phase analysis and amplitude analysis of a vector traced to the complex plane display. Evaluation may be by comparison of this display with the reference data previously stored.
6.S.2 Procedure for measuring coating thickness and material comparison relative to calibration block
Connect the probe for absolute measurements to the instrument, Select the appropriate frequency
Set the gain of the instrument in order to obtain a full screen deflection lift-off signal when the probe is moved From an uncoated spot on the calibration block to a spot covered with the maximum coating thickness expected on the structure to he tested.
Set the phase of the lift-of! signals to display them as shown on Figure 2.
The coating thickness on the raw surface of a weld Is never constant. As It will Influence the sensitivity of crack detection, it is necessary to get an estimate of the maximum coating thickness in the heat- affected zone prior to the eddy current testing of the weld.
The lift-oil signal obtained from the component to be tested shall be similar to the signal obtained from the calibration block, i.e. it shall be within 5 ° either side of the reference signal see Figure 2). In the event that the signal Is out of this range, a calibration block more representative of the material to be examined shall be produced/manufactured.