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Crack Detection by Eddy CurrentCrack Detection by Eddy Current

Instructions for eddy current inspection of ShockGuards.


This inspection process is accurate only on parts that have been stress relieved. The temperature of the standard needs to be the same as the work piece + or- 10 F.


  1. Balance ED520 in Dome area using the Standard.
    1. Plug in ED520 if external power is available.
    2. Turn "ON\OFF" knob to "TEST" position and insure that the needle reads at least "390" {at the red mark}
    3. Plug in probe to ED520
    4. Turn "ON\OFF" knob to "LO" position.
    5. Turn "SENSITIVITY" knob to about the center.
    6. Place probe in Dome Balance Area, angled at 90 degrees to the work surface.
    7. With probe held steady on work surface in Balance Area, adjust the "BALANCE" knob so the needle is centered at 250 + or -20
    8. Hold probe in air, at least 6 inches away from anything, and adjust "LIFT-OFF\FREQUENCY" knob so the needle is centered at 250 + or - 20.
    9. Repeat steps G. and H.,in order, until the needle remains at 250 + or - 20 whether the probe is in the BALANCE or LIFT-OFF position or not.
    10. Turn on "THRESHOLD" knob to the "DN" position.
    11. Place probe on the Dome surface by the "H2" hole until needle reads 150 + or - 10 degrees. {Always hold probe at 90 degrees to the work surface}
    12. With probe held in step "K" position, turn "GATE" knob counterclockwise until red buzzing light starts to flicker.
    13. Move the probe across the "H1" hole and the buzzing red light should flicker or go on.

Note: When moving probe across the Standard or work piece, apply probe with minimal pressure {about 1/2 oz. pressure}

Note: Whenever probe is moving across the surface, watch the probe {not the needle} to insure that the probe is always held 90 degrees to the work surface.

We are now ready to test the work piece.

  1. Inspect work pieces in Dome area.
    1. Area of interest is complete Dome area.
    2. Look down at the work piece, convex side, and picture a clock divided into 12 segments.
    3. Starting at the 12 O:Clock position, move the probe to the 6 O:Clock position at the rate of about 1 inch per second.
    4. Next, move the probe starting at the 1 O:Clock position to the 7 O:Clock position.
    5. Then, 2 to 8, 3 to 9, 4 to 10, and 5 to 11 O:Clock position. {always watching to ensure that the probe is as close to 90 degrees to the work surface as possible}

Note: At least once for every inspection piece, take note of the position of the needle when the probe is in the LIFT-OFF position, to ensure needle is at 250 + or - 20. {Rebalance if necessary}

Note: If, at any time, during the inspection process, the red buzzing light goes off while the probe is 90 degrees to the work surface, and the machine is balanced and set up according to 1.D. through 1.M. the piece is considered a non-conformity.

  1. Balance ED520 in internal reverse crown radius area on Standard.
    1. Follow steps 1.A THROUGH 1.M.
    2. Follow NOTES in step 1.
  2. Inspect work pieces in internal reverse crown radius area.
    1. Area of interest is approx. 7mm wide strip indicated by the "PROBE PATH DURING INSPECTION" line, on the Standard.
    2. Looking down at the work piece concave side, move the probe, at the rate of about 1/2 inch per second, in a "zigzag" pattern around complete circumference in the area of interest as you watch the probe for proper 90 degree angle to work piece.
    3. All previous notes in 1. and 2. apply.

Liquid Dynamics International

Issue No.: 3
Amendment No.:
July 29, 1996