replacement of UT by RT

[asad azmi]

Dear ALL,

 

Can we replace UT by RT for any weld joint.

 

can somebody expalin me advantage/disadvantage of UT over RT.

 

Thanks and Regards

 

Asad Azmi

[Vikas Bhandari]

For projects, replacement of one NDT technique to another is subject to company approval or as per customer welding and fabrication specification. For example Usually for carbon steel material, MPT may be replaced by LPT.

However, practically speaking UT cannot be replaced by RT (as a blanket cover for all the requirements). It can/may be replaced on case to case bases.

UT can find planer defects better than RT. RT is a hazardous technique.RT is a slow process. Below are few examples where UT cannot be replaced by RT.

1.  Grooves with high depth to width ratio.. as there are more chances that defect would be parallel to RT beam.

2.  During laying of pipes (relay, Jlay etc)     

Best regards

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[JASPAL SINGH]

Dear Asad,

The examination either RT or UT, I have the following view point.
- As per ASME Section VIII-1 & 2, RT is only the mandatory requirement
& UT in accordance with UW-53 may be substituted for radiography for
the final closure seam of a pressure vessel if the construction of the
vessel does not permit interpretable radiographs in accordance with
Code requirements. The absence of suitable radiographic equipment
shall not be justification for such substitution
- Why UT is not mandatory, the fracture mechanics gives some details
as per this many conditions rejected by RT do not affect in-service
integrity. With RT the worst-case depth must be assumed, through wall.
But not all cracks need repair
- Similarly for RT examination geometry is important factor, sometimes
it is impossible to interpret the radiograph like in set-in or set on
type nozzle to shell joints.
- RT sometimes cannot interpret side wall lack of fusion, cold laps &
laminations in base metal, which can be better seen in UT.

Regards

Jaspal Singh
Quality Assurance
ISGEC-Yamunanagar
09996624244