UT inspection applicability

[Murec]

We suspect corrosion in the HAZ on a circular seam of a vessel.
We had two kinds of UT inspection - Phased Array and Time of Flight - with quite different results. The inspections were done while the vessel was in operation.
We will know the truth soon, when we have a turnaround and enter the vessel.
I was told that Phased Array UT is not recommended for in-service inspections - can anyone comment on that?

 

[brimmer]

Makes absolutely no difference, sound will either give a reflection or it won't. The only thing I can think of that would change the results from in service or not is temperature, if there are elevated temperatures, or fluctuations, this can affect readings. I'm unsure why you would use phased array or time of flight for corrosion...

 

[vanmorrison]

Agree with Brimmer.
Why not use 0 deg?- Calibration block and vessel should be at same temp when setting up.