NDT technicians are judged, qualified and may be certified in accordance with various program requirements.
In 2011, the American Society for Nondestructive Testing’s (ASNT) journal, Material Evaluation, pub-lished the 2011 ASNT Annual Business Meeting Minutes. As of this year ASNT is celebrating its 70th year as an organized society. ASNT published its first edition of a recommended practice in 1967 for the qualification and certification of nondestructive testing personnel. Currently, there are 5,726 indi-viduals holding 15,829 ASNT NDT Level III certificates.1 Employers have certified many thousands more in accordance with employer based written practices that meet ASNT’s recommended guidelines. Many other organizations have derived similar programs but with third party or central agency admini-stration. They all contain essentially the same six elements.
The six essential elements of nondestructive testing (NDT) qualification and certification programs are:
4. Written exams
5. Practical exams
6. Physical exams
Since the 1974 edition of SNT-TC-1A, a high school education has been the minimum desired education requirement. Eighth grade educations have been allowed but only with substantially increased training requirements. The most common education found in practitioners today is “some college” as evidenced by industry surveys (PQNDT Survey 2011).
All NDT is based on the principles of physics, such as penetrating radiation, mechanical vibration at low and high frequencies, capillary action, electromagnetic theory, physics of light, piezoelectric principles, physics of light and optics, and other principles of general physics. In order to calculate the variables of NDT, mathematics, general algebra and trigonometry would be needed as a minimum. In all cases, comfort is needed in working with scientific notations, units of measurement for distance, time and velocity.
English reading and comprehension would be necessary for all NDT methods in order to understand written instructions, procedures, standards and specifications enough to allow performance of NDT and reporting of results. Also of essential value more and more is the ability to navigate computer files, folders, menus, templates and general skills in the usage of word, data base, spreadsheet, graphics and project management programs. A basic inspector with a high school education candidate can seek qualification in visual testing, magnetic particle testing, liquid penetrant testing and ultrasonic testing for thickness. But high school math would barely suffice to perform these NDT entry-level NDT methods properly.
An intermediate inspector needs to master more difficult NDT methods such as radiographic testing or ultrasonic testing of welds needs to be very much at ease with Algebra I and II. Trigonometry and geometry are needed especially for ultrasonic testing of welds by shear wave or use of triangulation to locate defect depth by radiography (RT). The RT II examinations require calculations of source strength, distances to various level of radiation exposure, and time needed to get the exposure factors desired for an acceptable radiograph. The UT II examinations require mastery of dozens of formulae and significant understanding of principles of physics to map out and locate reflectors in materials.
Advanced NDT technicians who may work in specialty NDT Methods and state of the art applica-tions need to come into the NDT world with Associate Science or Bachelor of Science Technology de-grees. Computed Radiography, phased array ultrasonics, time of flight ultrasonics, acoustic emission testing, infrared thermography, and other new techniques require advance calculating capabilities.
The more difficult the NDT Method the more hours of training is required. For example, The Recom-mended Practice No. SNT-TC-1A – 2011edition requires 12 hours for liquid penetrant testing, 20 hours for magnetic particle testing, and 24 hours for visual testing and limited ultrasonic A-scan thickness measurement. More difficult NDT methods such as radiography, ultrasonics, eddy current and acoustic emission all require 80 hours training each. Special techniques require even more training on top of the common advanced NDT methods.
The major NDT methods since the 1960’s, have required less months of experience for the three NDT methods of visual testing (VT), liquid penetrant (PT), and magnetic particle testing (MT) than ultra-sonic testing (UT), radiographic testing (RT), and eddy current testing (ET). Three months for VT and PT and four months for MT have been converted in recent editions of SNT-TC-1A (2001, 2006 and 2011) into hours. Roughly the number of months times 175 hours per month times 40% roughly equates to the number of hours needed. For example; visual testing and liquid penetrant require 400 hours total NDT experience. Magnetic particle testing requires 530 total NDT hours. Radiography, computed radiography, ultrasonics, acoustic emission and eddy current all require 1600 total NDT hours of experience.
SNT-TC-1A and CP-189 require written exams with the following elements for the different levels of certification.
The NDT Level I performs NDT and the Level II can perform and evaluate results of NDT. There-fore, their exams include the: 1. General for principles and theory knowledge; 2. Specific for specific code, standard, specification and procedure requirements; and 3. Practical to demonstrate proficiency level of skills.
Their exams include:
1. Basic Examination covers knowledge of certification processes, materials and processes and gen-eral knowledge of other NDT test methods.
SNT-TC-1A- 2001, 2006 or 2011 editions and ASNT Standard, CP-189, 2006 & 2011 editions all require the NDT Level I/II to take a practical exam to demonstrate proficiency in performing NDT. This Practical includes the requirement for a 10 point checklist and examination/inspection of test samples containing known defects/reflectors/flaws.
Visual Acuity exams are the almost exclusive physical exam requirements. Color perception is also re-quired if the NDT methods needs it. Breathing apparatus, weight carrying capacity, lifting weight minimums, etc., have all been mention but not required for NDT certification the best of this author’s knowledge. Employment criteria may have some of these physical prerequisites. Generally, near dis-tance visual acuity of Jaeger 1 for CP-189 and Jaeger 2 for SNT-TC-1A is required.
In conclusion, this article is only a general introduction to the NDT qualification and certification guidelines and the essential elements to consider. If one wishes details then the contractually required codes, standards, specifications and resultant written practice details must be reviewed to get an accu-rate idea of job specific requirements. This function is typical performed by the company’s NDT Level III who interprets the required documents to determine the specifics of NDT personnel qualification and certification. These requirements need to be in the employer’s written practice for most United States of America contractual requirements regarding performance of NDT.
1. Materials Evaluation, March 2012, Vol. 70- No. 3, American Society for Nondestructive Testing
2. “Handbook of Nondestructive Evaluation”, Charles J. Hellier, McGraw-Hill, 2001
3. “SNT-TC-1A 40 Years of Employer Certification for NDT Personnel”, Stephen Lavener, Lavender International NDT Consultancy Services, Sheffield, United Kingdom, 5th International Conference on Certification and Standardization in NDT, 2007
4. “NAS 410 National Aerospace Standard”, PQT, http://www.pqt.net/nas-410.php, 2012
5. NDT Forum, Posted by: Nigel Armstrong, on October 29, 2008, ndt.net
6. “ISO 9712 International Standard for Nondestructive Testing Personnel Qualification and Certifi-cation”, PQT, http://www.pqt.net/iso9712.php, 2012