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ULTRASONIC INSPECTION OF PIPE,
.J. K. White'
No development work on the ultrasonic method
for the inspection of pipe had been planned, be-
cause' the currently employed contact method was
reported to be adequate. Preliminary attempts
to employ this method, however, revealed several
problems that detracted ' from the reliability of
contact inspection. It was found to be very diffi-
cult to fabricate Lucite shoes that would fit the
contour of the pipe and would, at the same time,
limit the sound beam to the proper spectrum of
incident angles. A sizable part of the sound was
propagated as a surface wave and produced inordi-
nately large signals from surface scratches. For
this reason, defects and scratches could not be
separated. Also, the contact method requires that
a thin film of oil be maintained between the trans-
ducer and the pipe surface, and, thus, any surface
roughness, vibration, ovality, or an inadequate
supply of oil resulted in a loss of signal and
frequent failure to detect defects on the inner
surface. Immersed ultrasound permitted a solution
to these difficulties, and the use of the "B" scan
for data ,presdntati:m permitted a high inspection
speed with rapid interpretation of .the signals
produced in the tube wall.
A scanning tank of maximum simplicity was
designed and fabricated for the ultrasonic inspec-
tion of pipe. The tank is 26 ft long, 14 in. wide,
and 20 in. deep and is equipped with a variable-
speed headstock and chuck and an assembly of
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%n assignment to Homogeneous Reactor Project.
two 3-in.-dia casters, in lieu of a tail stock. This
assembly contains and rotates the pipe around
its own axis. The transducer mounting is aligned
with reference to the pipe axis. by a pair of Micarta
guides, and it is manually translated along the
pipe. Very straight pipe can be rotated at speeds
of 200 rpm, but much of the pipe is too crooked
for this speed. Even.in the worst case, however,
rotational speeds of 60 to 100 rpm are attainable.
This equipment is being used for the inspection
of large quantities of pipe in sizes from to
6 in. IPS for the ETU and the ART.
Satisfactory inspection of tubular shapes is de-
pendent upon obtaining reference notches of the
proper depth (3 to 5% of the wall thickness) on
both the inner and outer surfaces. A known, re-
producible notch is easily produced on the outer
surface of both pipe and tubing; however, it is
difficult to produce such notches on the inner
surface of even large pipe. No really satisfactory
notch has yet been produced on the inner surface
of small-diameter tubing, and the inside reference
notch is necessary to prove that the alignment
will reveal defects on the inner surfa
this method'is not being used for
of small-diqmeter tubing.
Four of the eight nozzle welds on the cell being
fabricated to house the ART in Building 7503
were inspected by the ultrasound method. The
observed indications of cracking in the weld and
in the heat affected zone resulted in the removal
of all the welds. The cracks revealed were con-
firmed by arc gouging and by Magnaflux tests with
sufficient frequency to justify the rejection of the
welds on the basis of the ultrasound indications.
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