How to Calculate Equivalent Penetrameter Sensitivity

A penetrameter is a radiographic device used to measure the penetrating power of radiation. It is made of aluminum and built-up in steps of varying thickness. The radiographic penetrameter uses X-rays to create a range of images on a radiograph with different exposure intensities. These intensities help analyze the penetration of the radiations. The quality of this radiograph is expressed in its ability to identify flaws or thickness changes in a specimen and is referred to as its sensitivity. It is expressed as the Image Quality Indicator or penetrameter sensitivity. The American Society for Testing and Materials gives the standard method for calculating equivalent penetrameter sensitivity in the United States.

Things You'll Need

• Penetrameter
• Specimen
• X-ray source
• ASTM standard guide

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Instructions

• 1

  Place the specimen parallel to the weld plate near the area of poorest sensitivity for a plaque-type penetrameter. For a wire-type penetrameter, place the specimen across the weld. Place the penetrameter on the source side of the specimen.

• 2

  Adjust the exposure time for each specimen-film system, and perform three shots on each system. Observe the number of holes or wires on the film. The computations are made based on this number.

• 3

  Calculate the radiographic sensitivity for a wire-type penetrameter using the formula:

  Sensitivity (%) = Thickness of the thinnest hole * 100/Specimen thickness

• 4

  Calculate the equivalent penetrameter sensitivity for a plaque-type penetrameter using the formula:

  Sensitivity= (100/x) {√(th/2)}

  Where "x" is the thickness of the specimen, "t" is the thickness of the penetrameter and "h" is the diameter of the smallest hole.

• 5

  Estimate the quality of the radiograph using the equivalent sensitivity of the penetrameter with the help of the standard table stated in the ASTM guide.