(11) Examine all noise signals to make sure the signal-to-noise ratio is larger than 3:1. If the
signal-to-noise ratio is less than 3:1, try a different transducer or a higher frequency transducer.
NOTE: Make sure the initial pulse is not more than 20% of full screen width. If necessary, adjust
the instrument controls or use a different transducer.
(12) Put couplant on the fuse pin to be examined. Then put the transducer guide with the transducer
on the end of the fuse pin.
(13) Set the back wall signal to 100% of full screen height.
(14) Add 8 dB. During the inspection, if there are cracks, the crack signals will be above 40% of full
screen height.
5. Inspection Procedure
NOTE: Each fuse pin must be examined from the inboard and outboard ends of the fuse pin. Each scan will
examine the far side of the fuse pin for cracks. This is done so that internal reflection signals will not
appear in the inspection area and will not be incorrectly identified as cracks. See Paragraph 4.
A. Prepare for the inspection as specified in Paragraph 3.
B. Do the instrument calibration as specified in Paragraph 4.
C. Put couplant on the area at one end of the fuse pin that the transducer will touch. See Figure 9.
D. Put the transducer guide on the fuse pin. Make sure the signal from the back surface is at the correct
screen location identified in Table 1 for the specific fuse pin that is examined. If you do not get a back
surface signal, move the transducer and guide to a different position on the fuse pin and try again.
E. Make a scan of the fuse pin. As you make a scan, monitor the ultrasonic signals which occur between
42% of full screen width and the back surface signal. Also monitor the first signal from the back surface
to make sure the transducer fully touches the fuse pin.
NOTE: A loss of back surface signal can be caused by a cracked fuse pin.
F. Do Paragraph 5.C. thru Paragraph 5.E. again on the opposite end of the fuse pin.
G. Refer to Paragraph 6. to make an analysis of the ultrasonic signals that occurred during this inspection.
6. Inspection Results
NOTE: (1) Some bottlebore design fuse pins can have ultrasonic signals that are out of the area of interest
(between 20% and 35% of full screen width) but stay on the screen during the full inspection of the
fuse pin. These signals can occur because of internal reflections of the ultrasonic sound waves (see
Figure 7, Detail I). Cracks which are located on the near end of the pin will show on the screen in
the internal reflection area (outside the area of interest) or close to the initial pulse. These cracks will
be found when the inspection is done from the opposite end of the fuse pin.
(2) A crack will usually cause the ultrasonic signal from the back surface to decrease below 100%
full screen height.
A. A fuse pin that does not have a crack indication is acceptable.
B. Do more analysis on a fuse pin with an ultrasonic signal in the inspection range that is 40% or more of
full screen height. See Note 1 at the start of Paragraph 6. and then do more analysis as follows:
(1) Make sure that the signal is not caused by too much couplant. Clean the inspection area of all
couplant and then put only a small quantity of couplant on the inspection area. Do the inspection
one more time. If the ultrasonic signal was caused by too much couplant, it will be gone. If the
ultrasonic signal does not go away, continue to Paragraph 6.B.(2).
747
NONDESTRUCTIVE TEST MANUAL
PART 4 54-30-10
Page 4
Nov 15/2015D6-7170
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
EFFECTIVITY
ALL
To Next Page
Loading...
