UT methods applicability 1

[Murec]

We suspect corrosion in the HAZ on a circular seam of a vessel.
We had two kinds of UT inspection - Phased Array and Time of Flight - with quite different results. The inspections were done while the vessel was in operation.
We will know the truth soon, when we have a turnaround and enter the vessel.
I was told that Phased Array UT is not recommended for in-service inspections - can anyone comment on that?

 

[r6155]

Try with Acoustic Emission Examination (AE)

Regards
r6155

 

[EdStainless]

The Phased array should work, but you really need a reference that looks just like your vessel, corrosion and all, for calibration.

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P.E. Metallurgy, Plymouth Tube

 

[TGS4]

r6155 - again, AE is completely unacceptable for this type of inspection. How many times must you be told? Furthermore, the OP very specifically asked a query for UT, so not only are you wrong, but you are completely off-topic.

 

[r6155]

@ TGS4

The principal objective is help to resolve the problem posted,

A lot of information is in internet about AE to detect corrosion.

1)

http://www.nationalboard.org/Index.aspx?pageID=164&ID=210

Acoustic Emission Examination of Metal Pressure Vessels

Dennis A. White
President of Measurement Services International, Inc.
Member ASNT, ASTM, ASM, TAPPI, AWEG, and ASME Subcommittee V
Chairman for the Special Working Group on Acoustic Emission

Metals deform in localized areas. Examples of small deformation could be a plastic zone, or metal embrittlement. Large visual examples of deformation can be erosion pitting and cracks. These deformations may be generated during vessel manufacture or operation. Many "events" can be generated from each area of metal deformation. Each one of these events creates a stress wave that travels through the metal. If there is no metal deformation, there will be no event activity. Special sensors are needed to detect acoustic emission events caused by metal deformation.
2) Also see
NATIONAL BOARD INSPECTION CODE NB-23 Part 2 - Inspection
2015 EDITION
8) Chemical Attack
Some chemicals are known to cause damage to composite materials. Environmental exposure or
direct contact with solvents, acids, bases, alcohols, and general corrosives can cause damage to
vessels. Long-term contact with water can also contribute to corrosive damage. Chemicals can
dissolve, corrode, remove, or destroy vessel materials. Chemical attack can result in a significant
loss of strength in the composite material. Chemical attack can appear as discoloration and in more
extreme cases the composite overwrap can feel soft when touched. If there is any suspicion of damage, the vessel shall be re-qualified using acoustic emission examination

3) ASME V you can see too.

Can you help to Murec (OP)?

Regards
r6155

 

[TGS4]

When you can show me how AE can provide the level of detail required for an API-579 LTA evaluation (Levels 1, 2, and 3), then I will start to listen to you regarding AE. Until then, for this topic, you are off-topic. Not only did you not answer the OP's question (EdStainless did), but your answer doesn't come remotely closer to solving his/her problem.

Maybe next time, you can reply with an AE answer if someone asks for it. Otherwise, you just look like a shill for it, which is really riding the acceptability limits of this forum.

 

[r6155]

@ TGS4
You continue with aggressive / offensive to me. Try stop

Can you help Murec (OP)?

Regards
r6155

 

[Murec]

Thank you for your comments!
AE will not work here for several reasons. The vessel is in operation and there is a lot of background noise. We did AE on a storage tank and it required changing the level/pressure, not feasible while the vessel is in operation. Most important we do not expect cracks, that are easy to detect with AE.
We are trying to determine the depth and extent of the material loss in order to plan the repair. PAUT and TOFD gave us very different numbers, I am looking for opinions on which one to believe. We will enter the vessel anyway in a few months and find out.