IQI - IMAGE QUALITY INDICATOR

 

What is Image Quality indicator(IQI) or Penetrameter?

The time of  radiographic testing, the use of Image Quality Indicator (IQI) or Penetrameter, provides the first indication of the quality of the radiograph. The IQI is used in RT to establish the RT film image quality. It is placed on the test object that has to be radiographed to evaluate the radiograph sensitivity. The Image Quality Indicator (IQI) consists of wires of different thickness (where wire material is the same as the test piece material), which are welded into a plastic film. The thinner the depicted wire on the radiograph, the higher the image quality level.

Penetrameters

It is  used to determine the sensitivity of the radiograph by placing it on the test piece. Generally these are made of the same material that is being radiographed. Thus, if the penetrameter can be seen clearly on the radiograph any change in thickness of the test object (2% or more) will be seen clearly also.

Radiographic Sensitivity

 Radiographic sensitivity 

Radiographic sensitivity is a measure of the quality of an image in terms of the smallest detail or discontinuity that may be detected. Radiographic sensitivity is dependent on the combined effects of two independent sets of variables.

Radiography sensitivity formula

Assuming a radiograph has 3% sensitivity for 12 mm (1/2-inches) thick material, so the smallest flaw or discontinuity that can be located will be:

0.03 x  12 = 0.36 mm

Sensitivity is one of the important parameters that has to be considered for radiographic testing.

Types of IQI in Radiographic Testing

Two types of Image Quality Indicators or IQI used in industries are:

1.       Hole Type IQI

2.       Wire type IQI

Hole Type IQI

Hole-type image quality indicators are relatively thin pieces of material with radiation absorption characteristics similar to the workpiece to be radiographed. Hole-type IQI contains holes with diameters that are 1, 2, and 4 times its thickness. The following is the illustration of a hole-type IQI:

 

 

 

A two-part expression (A−BT) designate the quality level required for a radiograph:

·       “A” is the maximum thickness permitted for the IQI; the thickness is determined as a percentage of the thickness of the workpiece.

·       “B” is the diameter of the hole as a multiple of the thickness.

·       “T” is the thickness.

 

A quality level of 2-2T is adequate for most radiographic testing industrial applications. A 2-2T IQI means that it has a thickness of 2% of the material thickness and that a hole that is twice the IQI thickness must be detectable on the radiograph. This presentation verifies that the radiographic technique can show a material loss of 2% in the area of interest.

 

 

Wire Type IQI

For wire type IQI there are four sets i.e -  A, B, C & D. They have 6-wires of different wire diameters & their selection is based on the material thickness that has to be radiographed.

 

How to make the selection of Image Quality Indicators ( IQI)

The wires are mounted side by side in a flexible plastic sheath which also carries appropriate identification, generally lead letters that will be clearly seen on the radiograph. The IQI is selected with respect to the metal type and the component thickness; the thicker the component the thicker the IQI's wires

 

There many videos available on YouTube as example

click on these links

https://www.youtube.com/watch?v=OcKqY8BdxAQ

https://www.youtube.com/watch?v=EUUjAEgy644