Home - Education Resources - NDT Course Material - Radiography - Real-Time

 

PROCEDURE DEVELOPMENT/ASME CODE

When work is being done to the American Society for Mechanical Engineers (ASME) code, there are procedure requirements in Article 2 (a mandatory appendix). These are for use in examination of ferrous and nonferrous weldments. Section II-221 lists specific areas that must be addressed in a written procedure; they are as follows:

  1. Material and thickness range
  2. Equipment qualification
  3. Test-object scan plan
  4. Radioscopic parameters
  5. Image processing parameters
  6. Image display parameters
  7. Image archiving

Sections of ASTM E1255 are referenced with the procedure requirements. Some requirements are addressed as follows: examination data shall be recorded and stored on videotape, magnetic disc, or optical disc.

A calibration block must be made of the same material type and product form as the test object. The block may be an actual test object or fabricated to simulate the test object with known discontinuities.

An LP test pattern shall be used to evaluate system resolution. A step wedge must be used to evaluate system contrast sensitivity. This wedge must be made of the same material as the test object and have steps representing 100%, 99%, 98%, and 97% of the thickest and the thinnest sections to be inspected. The system must be calibrated in the status mode (no motion between object and image detector) to satisfying LP test pattern resolution, step wedge contrast sensitivity, and calibration test block detection requirements.

System performance parameters must be determined initially and monitored on a regular basis with the system in operation to ensure consistent results. (Image intensifiers do degrade.) Here, once again, the LP test pattern, step wedge, and calibration block must be used; and the golden image can be compared with images produced over time.

The calibration block must be placed in the same position and manipulated through the same range and speed of motion as the actual test object. This will be a check on the system performance in the dynamic mode.

The system must have, at a minimum, the following features:

  1. Radiation source
  2. Manipulation system
  3. Detection system
  4. Information processing system
  5. Image display system
  6. Archiving system for records

Minimum information regarding radioscopic techniques must accompany test data. These must include at least operator identification and system performance test data. The manufacturer must interpret test data for acceptability before giving them to the inspector (an individual who checks for code compliance, independently of the manufacturer.

Appendix IV contains a set of questions that should be answered about RTR specifications.