WELD OVERLAY DEPOSIT and SUBSEQUENT NDE

[roca]

What are your thoughts on the required NDE for alloy weld overlay deposit in a pressure vessel.
Is it necessary to apply UT to check for dis-bonding (as is applied to clad plate) given that with weld overlaid plate fusion strength between the alloy material and the base carbon steel has to be proven in the PQR.
For fully automatic processes like electroslag welding we would not expect fusion problems as long as the correct procedure is followed?
The overlaid surface should of course be dye penetrant checked to ensure no flaws or cracks in the surface.
Thanks

 

[Metalguy]

We are cladding as you have written, and always perform UT checks for bonding after an intermediate HT. Haven't found many defects, but this is nuke work.

We also clad with 2 layers minimum.

 

[sayee1]

Normally, in my experience with pressure vessels, DPE/LPI is suffucient for overlay on most components except for components like ttubesheets in a HEx for e.g. UT to check dis-bonding is normally for clad plates as posted and not for weld overlays especially when the regions being overlaid to restore cladding would be the welds where strip back of clad techniques have been employed.

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
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End of all knowledge is the attainment of immortality!

 

[priyasachin]

Priyasachin.

Dear friend,

In a pressurevessel, the carbon backing material is to withstand the pressure, and the overlay material to counter the corrosive environment or to maintain meaterial purity etc., In either case the tests need to be conducted while qualifying is the chemical composition at the required depth to be equivalent to better than intended, and the shear test as enunciated in ASTM A 263, 264 for the overlay. The thickness of iverlay is not considered for the thickness calculation for holding the designed pressure.

When this basic requirement is understood, the tests particularly NDE desired are to see that ther are no through opening to enable the service fluid to reach the base metal. Any test to evaluate the porosity level and and its depth should be sufficient. Please remember that if the overlay is Austenitic SS the options reduces further as the weld overlay wil not respond well to ultrasonic testing.

Regards,
MRCN

 

[mirzabaig]

I fully agree with Priyasachin, besides even we do the same think. UT is not mandatory unless and until specifically asked by your client, for which u may charge.

 

[stanweld]

If you are concerned with disbonding of the overlay during operation (as in a hydrocracker reactor), UT is recommended for submerged arc or electroslag applied strip overlays. These processes often provide very low dilution with the base metal and ASME IX qualification does not assure freedom from disbondment. Note; qualifcation on a 1/2" thick base plate qualifies 1/2" to unlimited thickness. When applying the overlay with GMAW, FCAW or SMAW process, UT is not highly useful to determine full fusion of the overlay to the base metal and is not recommended.

Liquid penetrant inspection is recommended to confirm freedom from cracking and excessive porosity.