Non-destructive testing (NDT) laboratories play a vital role in assessing the integrity and safety of materials and structures without causing any damage. Adhering to ISO/IEC 17025:2017, especially clause 7.7, is essential for NDT laboratories to ensure the validity of their test results. This standard emphasizes the need for consistent monitoring and validation of testing methods to maintain accuracy and reliability.
Use of Reference Materials or Quality Control Materials: NDT labs might use reference blocks or samples with known flaws or characteristics for calibrating equipment like ultrasonic flaw detectors. For example, a reference block with predefined defects can be used to calibrate an ultrasonic testing device, ensuring that it correctly identifies and sizes flaws in materials being tested.
Use of Calibrated Instrumentation: Instruments such as radiographic testing equipment need regular calibration against traceable standards. This ensures that the equipment can accurately measure the density or thickness of materials, which is crucial for identifying potential weaknesses or faults.
Functional Checks of Equipment: Regular checks are vital for equipment like magnetic particle inspection units. For instance, a daily check of the magnetizing force ensures that the equipment is functioning at the necessary level to detect surface and near-surface discontinuities in ferromagnetic materials.
Use of Control Charts: Control charts can be implemented in processes like dye penetrant inspection. Parameters such as dwell time, wash time, and developer application are monitored to detect any deviations that could impact the test’s sensitivity and reliability.
Replicate Testing: To validate results, a lab might perform repeated radiographic tests on a weld joint using different angles or exposures. Consistent findings across these tests reinforce the confidence in the result’s accuracy.
Retesting or Recalibration: If an eddy current test on a batch of aerospace components yields unexpected results, retesting with recalibrated equipment or an alternative method, like ultrasonic testing, may be necessary to confirm the findings.
Intralaboratory Comparisons: The same component might be tested using both visual inspection and liquid penetrant inspection by different technicians to ensure consistency in the detection of surface flaws.
Proficiency Testing: Participation in proficiency testing allows NDT labs to compare their results with those from other laboratories, ensuring external validity, especially in critical testing scenarios.
Interlaboratory Comparisons: Engaging in collaborative studies, such as comparing phased array ultrasonic testing techniques across different labs, helps to validate methodologies and foster best practices.
Use of Alternative Instrumentation: An NDT lab might utilize various types of ultrasonic testing equipment to assess material integrity. By comparing results from phased array ultrasonic testing (PAUT) and traditional ultrasonic flaw detectors, the laboratory can validate the consistency and accuracy of its findings.
Intermediate Checks on Measuring Equipment: Regular intermediate checks of instruments such as radiographic testing equipment are essential. For instance, verifying the output of an X-ray machine against a known standard regularly helps maintain its accuracy for flaw detection in welds.
Correlation of Results: In the case of assessing a structure for corrosion, an NDT lab might use both eddy current testing and magnetic particle inspection. Correlating the findings from these methods can enhance the confidence in the test results, ensuring that both surface and sub-surface flaws are accurately identified.
Review of Reported Results: Each NDT report, whether it pertains to dye penetrant inspection or visual inspection, undergoes a thorough review. This step ensures that the results align with the observed indications and that all applicable standards and procedures have been followed.
Testing of Blind Samples: The NDT lab might include blind samples, such as a piece of metal with known but undisclosed internal flaws, in their testing workflow. Successfully identifying and characterizing these flaws validates the effectiveness and accuracy of the testing techniques.
NDT labs implementing ISO/IEC 17025:2017’s requirements ensure that their testing processes are not only reliable and repeatable but also continually improved for accuracy and efficiency. This adherence is crucial in industries where safety and material integrity are paramount.
About the Author
Dr. Sambhu Chakraborty is a distinguished consultant in quality accreditation for laboratories and hospitals. With a leadership portfolio that includes directorial roles in two laboratory organizations and a consulting firm, as well as chairman of IOL ( An ILAC stakeholder organisation), Dr. Chakraborty is a respected voice in the field. For further engagement or inquiries, Dr. Chakraborty can be contacted through email at director@iaqmconsultants.com and info@sambhuchakraborty.com. Additional resources and contact information are available on his websites,https://www.quality-pathshala.com and https://www.sambhuchakraborty.com or via WhatsApp at +919830051583.