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Radiographic Testing

Radiographic testing is a non-destructive testing of components and assemblies that is based on differential absorption of penetrating radiation- either electromagnetic radiation of very short wave-lengths or particulate radiation by the part or test piece being tested. Because of differences in density and variations in thickness of the part, or differences in absorption characteristics caused by variation in composition, different portions of a test piece absorb different amounts of penetrating radiation. Unabsorbed radiation passing through the part can be recorded on film or photosensitive paper, viewed on a florescent screen or monitored by various types of electronic radiation detectors.

The term radiography testing usually implies a radiographic process that produces a permanent image on film or paper. Although in a broad sense it refers to all forms of radiographic testing. Neutron radiography refers to radiographic testing using a stream of neutrons rather than electromagnetic radiation.

Uses

Industrial Radiography inspection is used to detect features of a component or assembly that exhibit a difference in thickness or physical density as compared to surrounding material. Large differences are more easily detected than small ones. In general, radiography can detect only those features that have an appreciable thickness in direction parallel to the radiation beam. This means that the ability of the process to detect planar discontinuities such as cracks depends on proper orientation of the test piece during testing. Discontinuities such as voids and inclusions, which have measurable thickness in all directions, can be detected as long as they are not too small in relation to section thickness. In general, features that exhibit a 2% or more difference in absorption compared to the surrounding material can be detected. Radiography is more effective when the flaws are not planar.

Gamma Ray Projector
X- Ray Machine

Levels of certification

Most NDT personnel certification schemes listed above specify three "levels" of qualification and/or certification, usually designated as Level 1, Level 2 and Level 3 . The roles and responsibilities of personnel in each level are generally as follows (there are slight differences or variations between different codes and standards.

Level 1 are technicians qualified to perform only specific calibrations and tests under close supervision and direction by higher level personnel. They can only report test results. Normally they work following specific work instructions for testing procedures and rejection criteria.

Level 2 are engineers or experienced technicians who are able to set up and calibrate testing equipment, conduct the inspection according to codes and standards (instead of following work instructions) and compile work instructions for Level 1 technicians. They are also authorized to report, interpret, evaluate and document testing results. They can also supervise and train Level 1 technicians. In addition to testing methods, they must be familiar with applicable codes and standards and have some knowledge of the manufacture and service of tested products.

Level 3 are usually specialized engineers or very experienced technicians. They can establish NDT techniques and procedures and interpret codes and standards. They also direct NDT laboratories and have central role in personnel certification. They are expected to have wider knowledge covering materials, fabrication and product technology.

OVERVIEW

The course is intended to provide through grounding in the principle of Radiographic Testing-RT and fundamentals of material and process such that the trainee would be able to

  • Identify suitability of RT for the material and inspection technique
  • Develop techniques and procedures that can be followed by a Level I operator
  • Analyze the test result and document the same
  • Be familiar with codes, standards and specifications for RT to evaluate results of the tests
  • Be conversant with all statutory and safety norms of the authorities under jurisdiction

COURSE CONTENTS


Level I course

  • Nuclear Physics-Interaction of Radiation with Matter
  • Shielding, Radiation Detectors, Biological Effects
  • Radiation Protection, Basic Rules & Techniques
  • Sources of Radiation and their characteristics
  • Film Radiography
  • Film Processing
  • Inspection Techniques and Procedures
  • Sensitivity & Definition, I.Q.I”s, Other Accessories
  • Types of Discontinuities
  • RT Level I Course : Min 5 Days. Practical 3 Days. Radiography of welds using X-ray and Gamma ray, RT Film processing

Level II course

  • Review of Level-I
  • Non-conventional Radiography
  • Techniques in radiography
  • Codes, standards and Procedures
  • Acceptance Standards
  • RT Level II Course:Min 5 Days. Practical 3 Days. Same as level-I + Interpretation, evaluation of Radiographs, recording of test results and preparation of test reports, NDT Request