Goodrich NDT

GOODRICH CORPORATIONNONDESTRUCTIVE TESTING (NDT) MANUAL

PART 6EDDY CURRENT TEST - Procedure 3 (Pencil Probe)

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6. PROCEDURE 3 - Eddy Current Test with a Pencil Probe

A. Effectivity

Use a pencil probe to find defects in aluminum piston housings.

Use a wheel inspection machine or a contour probe to inspect for cracks in aluminum alloy or magnesium alloy wheel halves and wheel bases. Then, if necessary, use a pencil probe to find the exact location of a defect in these parts. Also use a pencil probe to inspect areas on these parts that cannot be inspected with a wheel inspection machine or a contour probe.

B. Equipment

NOTE: The probe must be able to find the electrical-discharge-machined (EDM) inspection notch in the Calibration Blocks (refer to paragraph 6.B.(2) that follows).

(1) Portable Eddy Current Test Instrument and Pencil Probe Sources:

Agfa NDT (Krautkramer Branson) Centurion NDT, Inc.50 Industrial Park Road 1400 Yorkshire DriveLewistown, Pennsylvania 17044 Streamwood, Illinois 60107U.S.A. U.S.A.Telephone: (717) 242-0327 Telephone: (630)736-5500Fax: (717) 242-2606 Fax: (630) 736-5700www.krautkramer.com www.centurionndt.com

or or

Staveley Instruments, Inc. Zetec, Inc.421 North Quay Street 1370 NW Mall StreetKennewick, Washington 99336 Issaquah, Washington 98027-0140U.S.A. U.S.A.Telephone: (509) 735-7550 Telephone: (425) 392-5316www.staveleyndt.com Toll-free: 1-800-643-1771

Fax: (425) 392-2086www.zetec.com

or

Versatile ProductsPO Box 567Higgins Lake, Michigan 48627U.S.A.Telephone: (989) 821-7424Fax: (989) 821-7424



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(2) Calibration Block (available from Goodrich) Refer to the NOTE that follows:

A typical calibration block has three EDM test notches, one that is 0.008 inch (0,2 mm) deep, one that is 0.020 inch (0,5 mm) deep, and one that is 0.040 inch (1,00 mm) deep (for calibration and lift-off of a hand-held probe).

NOTE: Calibration blocks are available (at no cost) only from:

Goodrich CorporationAttn: Metallurgical LabPO Box 340101 Waco StreetTroy, Ohio 45373U.S.A.

Telephone: (937) 339-3811

C. Preparation of the Part for the Test

(1) Clean the inspection area on the part to remove contamination such as dirt, tire rubber, small non-ferrous metal particles, etc. (refer to CLEANING in PART 1, GENERAL DATA). Also clean the part with a solvent and permit the part to dry.

(2) Repair damaged areas in the inspection area that could cause the probe to lift off of the part (refer to the applicable Component Maintenance Manual (CMM) for repair limits and procedures).

Inspection can be done on a corroded area that is not repaired, but the corrosion can cause indications of a crack.

D. Preparation of the Eddy Current Test Instrument for the Test

Prepare and calibrate the test instrument at the start of each day that parts will be inspected with the instrument. Prepare and calibrate the test instrument as follows:

NOTE: Because there are many brands and models of test instruments, refer to the applicable manual for instructions on correct use of your instrument.

NOTE: It is not necessary to have the test instrument calibrated by the manufacturer or some other company if the instrument can be calibrated as follows:

(1) Examine the Teflon® tape on the probe. If the end the probe is exposed, remove the worn tape and install new tape on the probe.

(2) Adjust the test instrument to the recommended settings.



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(3) Attach the inspection probe to the cable on the instrument. Attach a test load ("dummy load") or another similar probe to the other cable on the instrument. If the "overload" light turns on, adjust the "probe drive" just enough to turn off the light.

(4) Press the balance or null button on the instrument to center the indicator dot on the display. Watch the indicator dot and carefully move the cable connection. If the dot moves, tighten or repair the connector or replace the cable.

(5) Clean the calibration block with a solvent and permit the calibration block to dry.

(6) Hold the pencil probe perpendicular (in a vertical 90° position) to the calibration block, but not over an EDM test notch in the calibration block. Press the balance or null button to center the indicator dot on the display. If necessary, turn the position knob to center the dot.

(7) Adjust the phase ("lift-off") control until the dot moves in a horizontal direction each time that the probe is lifted from the surface of the calibration block.

(8) Slide the pencil probe over the EDM test notch that is 0.040 inch (1,00 mm) deep in the calibration block. Adjust the sensitivity to cause the signal to move one square or more in the up direction and in the down direction as the probe moves over the notch.

E. Inspect Wheel Halves, Wheel Bases, Side Rims, or Piston Housings with a Pencil Probe

(1) Put the probe on the part and press the balance or null button or the position knob on the instrument to center the indicator dot on the display.

(2) Put a wheel half, wheel base, or side rim on a turntable. Move the probe in a"zig-zag" or "circular" pattern over the area to be inspected (refer to Figures 6and 7). Make sure that each probe movement path overlaps the previous path.

If the probe is held by a probe holder, a round part centered on a turntable can be slowly turned past the probe. Each full turn of the part, with the position of the probe changed for each full turn, permits a complete inspection of the area (refer to Figure 7). Make sure that the probe is always perpendicular (in a vertical 90° position) to the area being inspected.

Refer to paragraph (F) that follows to identify defects.

After a part is repaired, do another inspection. If the test result is satisfactory, the part is satisfactory for service.



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Figure 6. Typical "Zig-Zag" Scan Pattern

Figure 7. Typical "Circular" Scan Pattern



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F. Identification of Typical Indications of Defects

If the signal gives an indication of a crack, but the signal is smaller than the signal from the notch in the calibration block, visually inspect the area for contamination, corrosion, or shallow damage. A small crack is possible.

NOTE: Shallow pits or corrosion can possibly cause indications that are not shown by repeated inspection scans.

If the signal is larger than the signal from the notch in the calibration block, the part usually has a crack. Also, a crack usually causes a quick change in the signal as the probe passes over the crack.

If visual inspection of the area(s) shows a defect, discard the part or repair the defect(s) (refer to the applicable CMM for repair procedures and limits).

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