Definition of Visual Testing
1. Visual testing might be called the foundation of all NDT.
2. Looking at a technical component during and after manufacturing to check if it serves the intended
purpose was one of the first attempts to perform quality control (QC).
3. Subsequently, the search for discontinuities became part of visual quality control.
4. Later on, many companies regarded the visual search for discontinuities as an NDT method: visual
testing (VT) or visual examination (VE).
5. VT was added to Recommended Practice No. SNT-TC-1A: Personnel Qualification and Certification in
Nondestructive Testing at an ASNT conference in Charlotte, NC, in 1988.
6. As an NDT method with certification, VT stayed a US specialty until the European Committee for
Standardization (CEN) incorporated VT in its certification standard, EN 473 (2001).
7. Once the standard was publicly available, industry started to demand certification of VT technicians.
8. One aspect of a direct visual test that differentiates VT from other NDT methods is that the
discontinuities that the inspectors look for are visible.
9. This makes VT unique because all other NDT methods look at indications of discontinuities and never
show the discontinuities directly.
10. However, the use of optoelectronic devices and charge-coupled device (CCD) cameras in visual testing
may blur categorization with image enhancement techniques since inspectors do not look at the object
directly.
History of Visual Testing
1. Boiler inspection in the late 1800s and early 1900s was an early application of visual testing in the United
States.
2. The first edition of the ASME Boiler &Pressure Vessel Code (1915) clearly states visual acceptance
criteria for a casting: “free from blemishes, scale or shrinkage cracks.”
3. The history of borescopy started, however, outside the industry, in medicine.
1
Introduction to Visual Testing
Lesson 1
1. Visual testing might be called the foundation of all NDT.
2. Looking at a technical component during and after manufacturing to check if it serves the intended
purpose was one of the first attempts to perform quality control (QC).
3. Subsequently, the search for discontinuities became part of visual quality control.
4. Later on, many companies regarded the visual search for discontinuities as an NDT method: visual
testing (VT) or visual examination (VE).
5. VT was added to Recommended Practice No. SNT-TC-1A: Personnel Qualification and Certification in
Nondestructive Testing at an ASNT conference in Charlotte, NC, in 1988.
6. As an NDT method with certification, VT stayed a US specialty until the European Committee for
Standardization (CEN) incorporated VT in its certification standard, EN 473 (2001).
7. Once the standard was publicly available, industry started to demand certification of VT technicians.
8. One aspect of a direct visual test that differentiates VT from other NDT methods is that the
discontinuities that the inspectors look for are visible.
9. This makes VT unique because all other NDT methods look at indications of discontinuities and never
show the discontinuities directly.
10. However, the use of optoelectronic devices and charge-coupled device (CCD) cameras in visual testing
may blur categorization with image enhancement techniques since inspectors do not look at the object
directly.
History of Visual Testing
1. Boiler inspection in the late 1800s and early 1900s was an early application of visual testing in the United
States.
2. The first edition of the ASME Boiler &Pressure Vessel Code (1915) clearly states visual acceptance
criteria for a casting: “free from blemishes, scale or shrinkage cracks.”
3. The history of borescopy started, however, outside the industry, in medicine.
1
Introduction to Visual Testing
Lesson 1