Appendix A- Ultrasound Flaw Detector Requirements.pdf

ABC

DOWTY PROPELLERS STANDARD PRACTICES MANUAL

60-00-00

NDT 5DAP

Jun 30/15

GE AVIATION SYSTEMS LTD PROPRIETARY INFORMATION

Use or disclosure of data contained on this sheet is subject to the restrictions on the cover or first page.

5. Equipment Calibration Requirements

A. Electronic Flaw Detector Unit.

(1) Calibration Requirements:-

(a) Electronic Flaw Detector units which are to be used for immersion techniques are to be calibrated annually in accordance with the procedure stated in paragraphs 5.A.(2) (a) to (e).

This is to be carried out by a level II or III approved NDT Technician and tagged with a calibration label. All calibration graphs are to be kept on file in the calibration control area.

(b) Electronic Flaw Detector units which are to be used in the contact mode alone are to be calibrated in accordance with the procedure stated in paragraphs 5.A (2) (a), (b) and (e).

This calibration is to be carried out be a level II or II approved NDT Technician on a 6 monthly basis and tagged with a calibration label. All calibration graphs are to be kept on file in the calibration control area.

(2) Calibration Procedure This procedure is based on the requirements and methods described in ASTM-E-317. If this procedure is used for evaluating contact sets consistent and uniform coupling must be ensured.

When used for immersion equipment ensure the probe exit surface and test blocks are free form air bubbles, always allow time for equipment to stabilise.

(a) Horizontal limit and linearity Select an appropriate test block that when coupled to the search unit (either by contact or immersion) will produce eleven back reflections on the flaw detector which is being checked. Use the instrument gain, delay and calibration settings to set the leading edge of the third and ninth back reflection at 20% and 80% scale division respectively (when reading reflection positions always set at the amplitude of that reflection to 50% full screen height). Once the third and ninth reflections are positioned at 20% and 80%, read and record the scale position of each other multiple.

Interpretation of results:- The horizontal limit is given by the maximum available trace length falling within the screen graticule. This must, in all cases be 100%. Failure to obtain full scale deflection may indicate an equipment malfunction. Horizontal linearity results are best plotted in graphical form as shown in figure 3. The deviation is given by the displacement (in % of full scale) from the straight line through the set up points, which represents ideal linearity. The maximum displacement allowed is 5% of full scale.

(b) Vertical limit and linearity This check requires the use of a test block which, when coupled to a suitable search unit will produce signals having an amplitude ratio of 2 to 1 on the flaw detector being examined. (Signals do not have to be successive or in any particular order). Designate these signals HA and HB (HA being larger) and ensure that there is sufficient range in the gain control to vary HA from 10% fsh to 100% fsh. Set signal HA to 60% fsh, this should give a resultant HB signal of 30% fsh (some deviation allowed see Table 1).

Once this is set adjust the gain control to increase HA upto 100 fsh in increments of 10% or less. At each step read and record the amplitude of HA and corresponding amplitude HB.

Return gain setting to original position and check that HA and HB are also at original levels.

Now, reduce gain to bring HA to 10% fsh in increments of 10% or less, read and record HA/HB values at each increment.

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ABC

DOWTY PROPELLERS STANDARD PRACTICES MANUAL

60-00-00

NDT 5DAP

Jun 30/15

GE AVIATION SYSTEMS LTD PROPRIETARY INFORMATION

Use or disclosure of data contained on this sheet is subject to the restrictions on the cover or first page.

(e) Linearity of equipment gain This check relies upon the vertical linearity of the flaw detector previously being established as acceptable [see paragraph 5.A.(2) (b)].

Using test block ASTM-E-127 5-0300 establish by probe manipulation and flaw detector adjustments, an 80% fsh indication from the flat bottomed hole. Note the gain setting and designate this XdB. Next, ensuring constant probe coupling and no other flaw detector alterations adjust the gain settings by the dB amounts shown in Table 2, and record the resultant % fsh indications from the flat bottomed hole.

Interpretation of results.

All the indications must lie between the maximum and minimum limits as designated in Table 2.

B. Calibration and Control of Transducers. (Probes).

This section covers calibration of contact probes (both compressional and shear wave) and immersion probes (focused and unfocused). All immersion probes must be calibrated annually, the calibration certificate kept on file and the probe tagged with a calibration due date. For all probe calibrations use a flaw detector calibrated to paragraph 5.A.

(1) Contact Transducers Providing a contact transducer meets the set-up and calibration requirements of a specific technique it can be used for that technique, therefore there would be no requirement to asses the transducer for parameters such as dead zone, beam profile, resolution, sensitivity etc.

(2) Calibration of Unfocused immersion transducers

(a) This procedure is to be carried out on all unfocused water immersion probes.

(b) Equipment

1 An immersion tank of suitable size with an adjustable probe manipulator is to be used.

2 A 12,5 mm diameter ball is to be used as the target.

3 An instrument, capable of measurement of 0,025 mm or better is to be used to measure beam width.

(c) Procedure

NOTE: For the Beam Axis alignment procedure which follows, use the bracketed alternative position when NF is less than 150 mm.

1 Carry out the following calculations.

a Calculate the theoretical Near Field (NF) distance for the probe:

NF=(D x F) where D = Probe diameter 8c F = Frequency of probe c = Speed of sound in immersion fluid water = 1483 m/s at 20°C b Calculate the 2/3 rds NF distance

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