Welded joints using a UT tester checking for lack of penetration?

Question

Ok. Any ultrasound gurus out there. This Q is out of my realm. I am looking at a pipe weld with a solid cap that has a penetration of 1 mm in dept in the parent metal. I'm using a UT tester that is checking the lack of pen. The block that has a transducer in it that I'm using is perp. to the weld. How is the UT transducer looking at the joint ? Is it sounding at a Vert. or Hort.or cone, type picture, all I have is what we call a gate, If I see a spike thru the gate I have a flaw. I understand the theory of sound and echos. I have seen some surface features that has caused some false spikes or voids

Answer 1

How large is the spike and how deep your spike will tell you that by how wide the spike is and the depth will be the length of the spike depending if you set the thickness of the parent material into the UT.
The only UT's I'm familiar with just check for voids in the weld the only way you can check for penetration is x-ray or cross sectional acid etch.

Answer 2

That's whymost people don't use UT to check the quality of a weld. Only thing that will certify is x-ray.