MSS SP55 - hot can I spot a hot tear?

[Gorman3]

I have a valve that failed an inspection due to a visual hot tear. The same valve passed RT. How is this possible?

Isn't a hot tear a crack but without separation? It's a dangerous failure and no doubt that it is a discontinuity and at any size needs repair, but how can it be seen if the metal hasn't separated. A magnifying glass?

Even if I could see it shouldn't it come up on the RT?

I think this may be a mistake on their part but need the facts first.

 

[Metalmeister]

Let me offer you some general information. By definition a hot tear originates from within the steel and occurs during solidification and cooling, and does not extend to the surface. Cracks originate from the surface and go into the steel. Liquid penetrant inspection or magnetic particle testing is excellent at detecting surface defects. If the crack plane or hot tear is oriented perpendicular to the RT direction, it would be very difficult, if not impossible, to see the defect by RT. UT would readily detect such a defect orientation.