Ultrasonic testing of high thickness plate welds with CRA weld overlay

[vrkleo]

Hi,

We need to carry out ultrasonic testing of welds on 106 mm thick SA 516 Gr. 70 Plate with 6mm thick SS 316 weld overlay. What would be the effect of attenuation and how it can be taken care during Ultrasonic tesing? Carrying out UT before overlay is not an option as UT need to be done after post weld heat treatment.

Please suggest recommended UT techniques for this case. Thanks in advance.

 

[ndeguy]

vrkleo

The expense of welding and heat treating 106mm material warrants NDT prior to overlay and PWHT to remove any rejectable defects. If you dont do this the risk is of a repair and subsequent re-PWHT when you do your inspection after PWHT.

For the initial pre-overlay inspection, most efficiently would be ToFD and Phased Array. Use a simialr but refined technique for after overlay and PWHT.

 

[vrkleo]

ndeguy,

Thanks for the response, UT is being carried out before PWHT as well, but before weld over lay on the joint. Re examination after PWHT is customer requirement.

 

[ndeguy]

vrkleo

If you have internal access, the overlay can be checked from the inside both before and after PWHT using longitudinal wave zero degree probes for bonding between the 316 and 516 materials.

 

[vrkleo]

ndeguy,

Thanks! Apart from weld overy, CS weld also need to be examined. Is it possible with any conventional UT technique?

 

[ndeguy]

vrkleo

For completeness I should state the obvious of which I am certain you are aware - penetrant test of the overlay for surfface defects allowing a long dwell and development time.

 

[ndeguy]

Very difficult for a narrow gap weld (my assumption) - you would need to use zonal discrimination with tandem techniques for sidewall LOF detection - why would you (apart from top fills due to the TOFD lateral wave dead zone) when ToFD covers the whole thickness?

You will need to run several TOFD pairs focusing on near mid and far wall zones with different parameters. See ASTM E-2373 for example.

 

[Duwe6]

I would UT-shearwave the c/s buttweld(s) prior to overlay, and UT-straightbeam the overlay from the c/s side [assuming accessibility].

 

[JR97]

vrkleo,

The easiest approach would be to conduct all testing from the non-clad side. Limit the angle beam testing to 1/2 node. You may get signals from the cladding interface, but those should be relatively easy to identify and disposition. Reference the ASME Code Section V, Article 4, paragraph B463.2 for a cal procedure.

If the non-clad side is not accessible, it gets a bit more troublesome. With only 1/4" of cladding, attenuation is not a concern. The bonding condition and possible beam mis-direction at the cladding base material interface are more of an issue. A straight beam inspection using a dual element transducer can verify good bonding. Angle longitudinal waves will be substantially less susceptible to misdirection, but testing will be limited to 1/2 node.

What you need are some proto-typical mock-up blocks with cladding that you can test to determine what problems you are facing. I have tested welded steel pieces with both Stainless and Inconel cladding with good success.

JR97

 

[ndeguy]

vrkleo

You havent described your bevel profile nor how the 6mm of overlay is applied (e.g. multiple manual beads, strip weld, number of runs).

These items significantly affect your best choice of NDT method

 

[vrkleo]

ndeguy,

45° and 60° V groove and cladding is done by single layer ESW srtip cladding.

JR97,

Thanks for the inputs.