ASME BPVC V 2023

NONMANDATORY APPENDIX L
TOFD SIZING DEMONSTRATION/DUAL PROBE COMPUTER
IMAGING TECHNIQUE
L-410 SCOPE
This Appendix provides a methodology that can be
used to demonstrate a UT systems ability to accurately
determine the depth and length of surface machined
notches originating on the examination surface from the
resulting diffracted signals when a nonamplitude, timeof-
flight diffraction TOFD, dual probe, computer imaging
technique CIT is utilized and includes a flaw classification/
sizing system.
L-420 GENERAL
Article 4 requirements apply except as modified herein.
L-430 EQUIPMENT
L-431 SYSTEM
System equipment [e.g., UT unit, computer, software,
scanners, search units, cables, couplant, encoder
s, etc.] shall be described in the written procedure.
L-432 DEMONSTRATION BLOCK
a The block material and shape flat or curved shall
be the same as that desired to demonstrate the systems
accuracy.
b The block shall contain a minimum of three notches
machined to depths of T/4, T/2, and 3T/4 and with
lengths L and, if applicable, orientation as that desired
to demonstrate the systems sizing accuracy. See Figure
L-432 for an example.
Additional notches may be necessary depending on:
1 the thickness of the block;
2 the number of examination zones the block thickness
is divided into;
3 whether or not the zones are of equal thickness
for example: three zones could be broken into a top 1/3,
middle 1/3, and bottom 1/3 vs. top 1/4, middle 1/2, and bottom
1/4; and
4 the depths desired to be demonstrated.
c Prior to machining the notches, the block material
through which the sound paths must travel shall be examined
with the system equipment to ensure that it contains
no reflectors that will interfere with the demonstration.
L-460 CALIBRATION
L-461 SYSTEM
The system shall be calibrated per the procedure to be
demonstrated.
L-462 SYSTEM CHECKS
The following checks shall be performed prior to the
demonstration:
a Positional Encoder Check. The positional encoder
shall be moved through a measured distance of 20 in.