Sensitivity better than 2%

Which you should note in the project specifications?

  • Percentage of RT requirement,
  • RT method and source,
  • Acceptance criteria,

Sensitivity formula:

= wire (diameter) / thickness of base metal.

(*) IQI selection accordance to Table T-276 of ASME Section V 2017, IQI diameters are acc. to T-233.2 in ASME Section V.

There are two examples regarding to selection of radiograph source.

  • Example 1: RT (X-ray) shot for Pipe NPS 2" Sch 80 (5.54 mm), DWDI method, IQI selection Set A, placed Film Side, should achieve wire no. 4 (0.1 mm).

  • Example 2: RT (Gama Ir192) shot for Pipe NPS 6" Sch 40 (7.11 mm), DWSI method, IQI selection Set A, placed Film Side, should achieve wire no. 5 (0.2 mm).

(**) Low energy beam components will improve sensitivity.


Sensitivity [Example 1] = 0.1 / 5.54 = 0.018 (1.8%)
Yes, the sensitivity achieved 2% requirement if you used X-ray source or Gama isotope Se75 source (in my point during reviewing RT film).


Sensitivity [Example 2] = 0.2 / 7.11 = 0.028 (2.8%)

So, If you want to achieve 2%, the wire no. 4 (0.1 mm) should visible on RT film. Assume, all essentials are unchanged, I sure, an Ir192 is unable to achieve 2% sensitivity for material less then 9.5 mm.

:stop_sign: If you want to use Ir192 source, please check with sub-contractor before bidding by demonstrate on material thickness application.

How to correct a RT report if the job done?

You may change the required sensitivity to wire no. designation in report to make sure a minimum IQI selection meet Table T-276.

Which factors influence in the sensitivity a radiograp? here.