Understanding Image Quality Indicators (IQI)

An Image Quality Indicator (IQI), commonly known as a penetrameter, is a vital device used in industrial radiography. Its primary purpose is to determine and verify the quality, clarity, and overall sensitivity of a radiograph. By placing an IQI on the part being inspected (typically on the source side), radiographers can visually prove that the imaging setup is capable of detecting microscopic flaws and discontinuities within the material.

Wire-type IQIs consist of a series of parallel wires of varying, standardized diameters encapsulated in a protective sheath. The radiographic sensitivity is determined by the smallest wire diameter that is clearly discernible on the final radiographic image. Different geographic regions and industrial sectors rely on specific governing standards, such as ASTM E747 (widely used in the Americas) and EN 462-1 / ISO 19232-1 (widely used internationally and in Europe), to define these wire dimensions and grouping sets.

ASTM SE 747 Reference Table

Standard reference sizes for source and film side wire requirements based on weld thickness.

NF EN 462-1 Reference Table

Standard reference requirements for identifying the smallest visible wire per weld thickness bracket.