b. The search unit shall then be moved slowly in a direction parallel
to the weld centerline and zigzagged across an area equivalent to the
welded thickness to make sure that waves penetrate the entire welded
cross section.
c. The rate of movement shall be dependent on the operator's ability
to clearly see and identify all reflections.
3.3
GENERAL ACCEPTANCE/REJECTION REQUIREMENTS
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NOTE: The designer will designate whether
ultrasonic inspection will take precedence over
radiography or will be used to supplement
radiography when both methods of inspection are to
be used. The designer will delete portions in
brackets when they do not apply or remove brackets
when they do.
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Discontinuities shall be evaluated only when the ultrasonic equipment is
calibrated properly. If discontinuities are detected, the sound beam shall
be directed to maximize the signal amplitude. To determine the length of a
discontinuity, the search unit shall be moved parallel to the discontinuity
axis in both directions from the position of maximum signal amplitude.
One-half the amplitude or a 6-dB increase in sensitivity from a point at
which the discontinuity signal drops rapidly to the baseline shall be
defined as the extremity of the discontinuity. At this point, the scanning
surface shall be marked at the position indicated by the center of the
transducer. This shall be repeated to determine the other extremity. The
length of the discontinuity shall be defined as the distance between these
two marks. For discontinuities with signal amplitudes exceeding full
screen height, 50 percent of full screen shall be considered half-peak
amplitude. At this point, the scanning surface shall be marked at the
position indicated by the center of the transducer. This shall be repeated
to determine the other extremity. The length of the discontinuity shall be
defined as the distance between these two marks. The maximum signal
amplitude, length, depth, and position within the inspection zone shall be
determined and reported for discontinuities yielding a signal amplitude
equal to or exceeding the reject/repair line. The minimum recordable
length of a discontinuity shall be 3 mm 1/8 inch. When evaluating welds
joining two members with different thicknesses at the weld, the thickness T
shall be the lesser of the two thicknesses. The criteria for acceptance or
rejection based on ultrasonic inspection will supplement a visual
inspection. The sizes and surface conditions of the welds shall conform to
the requirements indicated on the applicable plans and drawings and other
sections of the specification. When ultrasonic inspection is used along
with radiography, the limits specified under paragraph REFERENCE STANDARDS
FOR EQUIPMENT, QUALIFICATIONS, AND CALIBRATION shall [be the primary
standard] [supplement the radiographic standards].
3.3.1
Investigation of Questionable Indications
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NOTE: This paragraph will be deleted if Class I and
Class II in paragraph ACCEPTANCE/REJECTION LIMITS
are deleted.
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SECTION 05091A
Page 22
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