Phased Array Ultrasonic (UT) vs Radiograghic (RT) Weld Inspection

[mktaylor]

Has anyone had experience comparing the results of phased array UT to those of RT? As part of a High Energy Piping management program we are periodically inspecting selected welds to check for age related degradation. What we are seeing is that the phased array UT is more sensitive than the original RT and is picking up weld defects that were present since day one but undetected in the initial RT results.

Does ASME B31.1 account for efficiency of the inspection technique so that these weld errors are allowable under code?

 

[stanweld]

We have compared phased aray and P-Scan UT with ASME V radiography with fine grain slow speed film on two projects involving Hot Reheat installation and repair of main steam. Both UT methods were superior to radiography in locating and sizing flaws.

 

[metengr]

We are in the midst of having our main steam line girth welds examined using a combination of linear phased array and annular phased array UT examinations that can detect in-situ creep damage. These UT examination techniques are highly specialized and are performed by only a few organizations in the US.

Radiography (RT) is fine for new construction weld quality but I would not use it for any in-service high energy pipe condition assessment program. You need to use more sophisticated NDT methods to locate creep damage along the base metal HAZ and within the weld metal itself (automatic SAW). There have been some serious issues raised with subsurface creep damage in submerged arc welds (SAW) versus field welds made using the SMAW process.

 

[stanweld]

mktaylor,
AMSE B31.1 does not take into account for effeciency of NDE method. B31.1 design safety & acceptance criteria is based on Radiographic Testing of high energy pipe systems. RT techniques have also much improved in locating the predominantly workmanship flaws defined in B31.1 decades ago. B31.1's RT acceptance criteria has demonstarted safe operation in service but is not applicable for detection of creep damage in operating pipe systems.

As metengr stated, examination for subsurface creep damage should be done using sophisticated UT methods. A number of Owners have initially used TOF UT to examine for more gross damage then follow up with phased array UT to detect the finer flaws.

 

[EdStainless]

RT is done to specific sensitivites. We have had material rejected becuse the RT guys were showing off. When it was re-RTed at the correct sensitivity the material was fine.
For service damage I believe that UT is clearly superior.

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