UT for overlays - cladding and ring grooves

[HotStab]

API 6A (Spec for Wellhead and Christmas Tree) requires for PSL3 equipment UT inspection for CRA overlay. For overlay applied in ring grooves there is no volumetric inspection prescribed, not even for bond integrity evaluation. Its seams strange because, in my opinion, in the majority of cases the overlay in ring grooves for metal sealing rings would be under much higher tension than a simple cladding overlay.
I would be glad to have any reasonable explanation for this.
Could someone help me?

 

[roadapple]

UT will work for bonding integrity. RT of ring grooves will not work in most situations due to the geometry of the ring groove. Bonding integrity in this sense is that there is "tie-in" to the base material with the filler metal. The integrity that you are implying is the strength of the overlay on the base metal. API 6A - if I remember - makes the statement that the filler metal can not be considered part of the design. The weld procedure for the overlay will basically nail down the varibles to ensure the overlay sticks to the base metal.

We did this for years and for the most part API 6A doesn't like welding - or at least makes it difficult for the non-standard (high strength-non ASME recognized materials).

Hope this helps.

roadapple