Understanding NRT- Reading 1- 2 of 2- Radiogaphic Testing A

Hole-Type IQIs
ASTM Standard E1025 gives detailed requirements for the design and
material group classification of hole-type image quality indicators. E1025
designates eight groups of shims based on their radiation absorption
characteristics. A notching system is incorporated into the requirements
allowing the radiographer to easily determine if the penetrameter is the
correct material type for the product. The thickness in thousands of an inch is
noted on each pentameter by a lead number 0.250 to 0.375 inch wide
depending on the thickness of the shim. Military or Government standards
require a similar penetrameter but use lead letters to indicate the material
type rather than notching system as shown on the left in the image above.
Image quality levels are typically designated using a two part expression such
as 2-2T. The first term refers to the IQI thickness expressed as a percentage
of the region of interest of the part being inspected. The second term in the
expression refers to the diameter of the hole that must be revealed and it is
expressed as a multiple of the IQI thickness. Therefore, a 2-2T call-out would
mean that the shim thickness should be two percent of material thickness and
that a hole that is twice the IQI thickness must be detectable on the
radiograph. This presentation of a 2-2T IQI in the radiograph verifies
Charlie Chong/ Fion Zhang