African Fusion March 2015

No Orient Flaw Type

Flaw Size(inch) Length Depth % Depth

mens and six flaws in total were inserted into the specimens. Types of inserted flaws include a fatigue crack developed from the triple point, horizontal lack of fusion (HLOF), which occurs at the boundary of the piping and the weld metal, and vertical lack of fusion (VLOF), which occurs at the boundary of the coupling and the weld metal. Detailed specifications of the flaws inserted are provided in Table 2. Experiment apparatus The ultrasonic probe was manufactured based on design parameters verified through the modelling. Figure 5 displays the shear wave phased array ultrasonic probe manufactured in this study. For the phase array ultrasonic instrument, ZETEC’s Omnis- can, which has 16 channel operation capability and is portable for site inspection, was used. The signal obtained from the Omniscanwas connected via TCP/IP communication protocol for storage on a laptop computer, andUltravison version 1.1Q6 was usedas the signal evaluation software. For the experiment, the apparatus was set up as shown in Figure 6. For the experiment, a scanner was clamped to the flawed specimens and then a base point was determined. Subse- quently, the scanner revolved 360 ° in the circumferential direction around the specimens and captured the signal. The setting values of the phased array ultrasonic test instrument used for the experiment are seen in Table 3. After entering the setting values for operation of the probe, the ultrasonic beam was generated at angles ranging from 35 ° to 80 ° . Results and review The experiment was carried out using the flawed socket weld specimens with a fatigue crack and lack of fusion (LOF) flaws. Based on the results, the signal was evaluated. For the fatigue crack specimen, as the coupler welded onto the piping was elbow-shaped and manufactured from a casting, inspection of the coupler was not possible. The scanner was therefore clamped to part of the piping before obtaining the signal. Figure 7 illustrates the results of the inspection using a flawed specimen with a nominal diameter of 1.0″ and a leg length of 1:1. As seen in the figure, three flaws including the LOF and a fatigue crack were detected at the front and a rear angle of 46.5 ° – within the range of refraction angles from 35 ° to 80 ° – and the length of the flaws was measured at the signal of the B-scan. As a result of measuring the length of the specimen with a leg length of 1:1, the length of the fatigue crack and LOF flaws were measured to be slightly longer than the actual length. As the crack tip signal was not confirmed at the obtained signal, it was not possible tomeasure the depth. TheNo. 3 crack flawapplied to the specimenswas a fatigue crackoriginatingfromthetriplepointandevolvedintotheinter- nal diameter of the piping. As the crack grew in the same direc- tionas theultrasonicwaveheaded toward it and tiltedat a large angle, a relatively small amplitude was identified for the flaw. Figure 8 shows the results of an experiment for a flawed speci- men with a leg length of 1:2 . As seen in the figure, one LOF flaw and two fatigue cracks were detected and the length of the flaws was measured from the B-scan signal. In the case of a flawed specimenwitha leg lengthof 1:2, the No. 5 crack and No. 4 HLOF flaw were found to have a higher level of amplitudewhile aNo. 6 crack flawwith 20%depthwas found to have a low level of amplitude. A size evaluation of the six flaws included in the flawspecimens is presented inTable 4.

1 2 3 4 5 6

Circ. Circ. Circ. Circ. Circ. Circ.

Crack VLOF Crack HLOF Crack Crack

0.30 0.40 0.42 0.36 0.71 0.48

0.085 0.085 0.035 0.102 0.050 0.032

55 55 22 66 32 20

Table 2: Detailed information of the flaws contained in flawed specimens.

Figure 5: The shear wave phased array ultrasonic probe for small bore piping socket weld.

Figure 6: Experimental setup of phased array ultrasonic system.

Parameter

Setting

Gain

37 dB

Digitising frequency Inspection mode

50 MHz

Pulse-echo

Steering angle Angle resolution

35°to 80°

1.0° 80 V

Voltage

Table 3: Experimental parameters.

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March 2015

AFRICAN FUSION