We did some test on DSS material with Phased Array technique because
of problems with ordinary UT examinations. The NDE company told us
that they will get a better view when using Phased Array but at the
end they couldn't get a clear view. Probably the cause for this are
the different wall thickness in such pump casing which will cause
different cooling rates when perform forged cooling after solution
heat treatment. Due to this differences you also will get different
grain sizes afterwards and those transition areas to different grain
size also causes reflections during ordinary and Phased Array UT
examination. This also can be the problem with heavy wall thicknesses,
the core of the material will cool down much slower as the material
near the surfaces. When having material with similar properties
through the thickness (mostly not the case for catings) Phased Array
will give you a better view as ordinary UT but when we looking at
small pinholes you will also have the problem that it isn't a flat
indication and therefore UT waves will spread without a clear view of
the indication of interest.
You may give it a try but I don't think you will get a clear view of
the exact location of the pinhole with Phased Array, we performed some
tests on pump casing in materials 1.4470 / 1.4469, depending on the
type A891 could be the EN 10213 equivalent for your material. During
this we sometimes did found some indication but this was never a
pinhole, detected indications were mostly related to shrinkage and/or
slag inclusions and general have more volumetric dimensions.
When you decide to repair the casing always perform GTAW process for
the first layer and execute visual examination after the first layer
in order to ensure that there is no crack present. Incase of doubts
always perform PT examination before welding a second layer. Once you
have sound material you may go for an other welding process such as
GMAW in order to reduce the heat imput.
I hope this helps you out to decide how to go on.
Best Regards,
Herman Pieper
On 8 mrt, 06:08, Hari Srinivasa Murthy <harimur...@gmail.com> wrote:
> Dear Mr.Herman Pieper ,
>
> Thanks for your detailed reply. Initially we also thought of repairing it
> upto 15 mm thk. But our previous experience in the company on DSS shows
> internal creater cracks inside castings though they appear to be pinholes
> from outside. Cobalt RT source is not available in our place for RT of the
> defect location.One of my colleague suggested me to carryout Phased Array
> Technique.
>
> Can you please write me your experience with phased array technique on such
> castings.
>
> Regards
>
> Srinivasa Murthy Hari
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