When NDT was first introduced as an inspection tool most of the early users were either self taught or had simple instructions from the equipment manufacturers in operating principles.
Within the larger corporations and in military applications several internal training programs and operator qualification procedures were developed.
In the early and mid 60's the "Society for Nondestructive Testing" decided to take the bull by the horns and tasked a technical committee to develop a set of guidelines which could be used by employers to develop their own "In -house" employer based training, qualification and certification programs.
• This set of guidelines was not a mandatory set of rules, but a set of "Guidelines" which could be changed by the employer to suit their particular requirements.
• This set of guidelines was first printed in 1966 and was called SNT - TC -1A (which was an abbreviation for Society for Nondestructive Testing - Technical Council - the first document published, hence 1A).
• This form of employer based certification has been widely accepted throughout the USA as the mainstream form of NDT certification.
This is an internal company procedure which details how employees are trained, qualified and certified to perform NDT functions for the company.
Within the Written Practice are found details of:
• NDT "methods" and "techniques" used. (A method is an overall concept of inspection, such as Radiography or Ultrasonic or Penetrant Testing).
• (A technique is how the method is used, e.g. "water washable, fluorescent" is a "technique" of applying thePenetrant "Method" of NDT).
• Levels of qualification and responsibilities assigned to each level. Usually there are 3 levels of certification.
Level I is basically an operator, capable of performing specific tasks to written instructions under supervision and reporting the results.
Level II personnel have more responsibility and are capable of performing independent equipment "set - up" and "calibrations" and can also interpret the results of inspections in accordance with codes and specifications. Level II workers can also perform on the job training and guidance of Level 1 personnel and trainees.
Level III personnel can establish or approve procedures and techniques and interpret paperwork necessary to meet customer requirements. Assistance in developing acceptance criteria may also be given by the Level III. The Level III is usually responsible for the NDT operations at the facility.
• Level III's should also have a sound knowledge of other NDT methods and manufacturing processes. (The duties of the Level III may be subcontracted to an outside agency).
• The exact duties of the various levels may be altered to suit the companies' applications.
• Details of "Training", "experience", and "examination" requirements for company based certification.
• The "Written Practice" should be maintained on file and it is necessary to have a "Written Practice" before any certification is granted.
The structured training program(s) meeting the requirements of Table 1. and the guidelines of SNT-TC-1A should be successfully completed. (To successfully complete a training program, sufficient examinations must be passed to ensure that the necessary information has been comprehended).
Employees cannot be certified until they have achieved the minimum experience level detailed in the "Written Practice". This experience must be documented and kept in the certification records file.
The Level III(s) responsibilities include approval / grading of examinations administered for certification purposes. The actual administration of written examinations can be subcontracted to a designee of the Level III.
• A physical exam of the near vision acuity and color response of the candidates eyes.
• A written "General" examination to test the candidates knowledge of the methods basic principles.
• A "Specific" examination will be based on the equipment, procedures (including the "Written Practice" and the techniques used in the performance of their job).
• The minimum recommended numbers of questions for the specific examination are twenty.
• A "Practical" assessment of performing typical inspection work is also necessary. This evaluation should be performed to an audible criteria (at least a 10 point checklist).
With the exception of the vision examination, at least 70% must be scored in each part of the qualification examinations and an "average" score of at least 80% must be achieved.
Providing that all of the previously detailed criteria have been satisfied and documented evidence exists of satisfactorily completing each task the candidate can be certified by the "Certifying Authority" (a person(s) designated in writing in the "Written Practice" ) to sic-in a letter of certification.
SNT-TC-1A was developed and issued with the intent of providing a level of uniformity across the NDT profession. It has achieved this to a large degree, however, the facility to change the recommendations of SNT-TC-1A to meet employer requirements is often abused. This results in some employer base certification programs being somewhat lower in achievement than the intent. Unfortunately there are no ASNT auditors performing evaluations of the interpretations applied to individual company "Written Practices". The only auditors are the customers quality representatives, who in many instances are not familiar with the intent of SNT-TC-1A.
In an attempt to produce a more rigid uniformity, ASNT re-visited the intent of SNT-TC-1A and produced a new document which was designed from the outset to be a "national standard" rather than simply guidelines. This new document was offered as an alternative to SNT-TC-1A. Both exist as parallel programs available for a contractor to specify and a sub contractor to adopt. The overall structure is very similar to SNT - TC - lA in terms of training, experience, examinations, etc. It differs significantly in several areas.
Written Practice - instead of a "Written Practice" as detailed in SNT-TC-1A, a "Certification Procedure" is required for CP 189.This cannot be reduced in rigidity to suit company requirements dictated by CP 189. Again it must be approved by the Level III. The vision requirements for near vision acuity are more stringent in CP 189 requiring acuity to read the Jaeger # 1 instead of Jaegar # 2. There are 5 levels of qualification instead of 3 the additional 2 being "Instructor" and "Trainee". The minimum training hours are not reduced for having a 2 year degree, as is the case for MT, PT, and NRT for SNT-TC-1A. The training requirements for ET Level 1 are less stringent than the recommendations of SNT-TC-1A being only 12 hours instead of 40 (based on a High School education).
Level III certification for CP 189 also requires an ASNT Level III certificate in the method as a pre-requisite. A "Basic" exam is not required, holding a current ASNT Level III certificate satisfies this requirement. Level III examinations also require a procedure be prepared for the practical exam.
Again this is not a comprehensive list of the differences, but simply the "major" fundamental differences in the concepts. By far the most important fundamental difference is in the concept that CP 189 is a national standard and must be treated as a minimum requirement not simply a set of guidelines which may be altered. This is reflected throughout the 2 documents by the choice of verbs used. CP 189 uses "shall "throughout to emphasize a mandatory requirement", whereas SNT - TC - lA uses the verb "should" to emphasize a recommendation".
Military Standard - Nondestructive Testing Personnel Qualification and Certification. For companies or personnel employing NDT for the Inspection of products used on Military or Government contracts MIL-STD-410E was the governing document until January 1 st 1998. (It was then replaced by NAS 410). Like CP-189, MIL-STD-410E was a "standard" and not simply a "recommendation". It also had the same 5 levels of qualification as CP-189 (these are not levels of certification). Near vision acuity requirements were Jaeger # 1. A 'Certification Procedure" was required rather than a Written Practice. The procedure shall, as a minimum satisfy all of the requirements of MIL-STD-410E. Level III examinations required the writing of a procedure to fulfil the practical examination. Level III certification did not have a pre-requisite of holding an ASNT Level III certificate in the method, however, possession of a current ASNT Level III certificate did satisfy the requirements of the "General" examination. A waiver was given in this event. Level III examinations did not have a separate "Basic" examination. Instead, Level II type questions of other NDT methods were incorporated into the "General" examination.
"National Aerospace Standard 410, NAS Certification and Qualification of Nondestructive Test Personnel".
The "Aerospace Industries Association" approved NAS 410 as an Industry standard in 1996. With effect from December 31 1997 it replaced MIL-STD-410E for all DOD contracts. Again like CP-189 and the MIL-STD-410E that it replaced it is a "minimum standard" to be complied with, not a "recommended guideline" like SNT-TC-1A.
• Two additional levels of qualification added to the existing 5. The new levels being "Auditor" and "Limited level 1".
• The levels of "Certification " are 4 and levels of "Qualification" are 7.
• A "Certification procedure" is still required.
• Possession of an ASNT Level III is not mandated, it does, however, offer a waiver of the "General" examination.
• A procedure preparation examination is required for Level III certification.
• The number of examination questions required for the "Specific" examination is a minimum of 30 for each method.
• As of February 2003, a new Revision 2 was approved which specifies a change in the minimum hours of formal training required for Magnetic Particle and Penetrant methods for Levels I and 2 of 16 hours for Level I and 16 hours for Level 2 (with Level I experience) or 32 hours direct access (without Level I experience). That is an increase of 16 hours for Penetrant and 12 hours for Magnetic Particle Level II inspectors.
• Also, the re-certification period for Level I and II has been changed from 3 years to 5 years.
"Guidelines for Training and Qualifying Personnel in Nondestructive Testing Methods".
The Air Transport Association of America (ATA) and in particular representatives from American Airlines, Eastern Airlines, Trans World Airlines, United Airlines and US Air developed this document to provide more uniformity to the training of NDT Inspectors following the FAA sponsored "Aging Aircraft Conference" held in June 1988. It provides a "guideline" for training personnel to be certified under the existing framework of the airlines certification program. It was intended to compliment the knowledge and experience gained while attending airframe and powerplant technical schools. The scope of the specification claims equivalent competency to SNT-TC- 1A and MIL-STD-410E.
This is questionable on several issues as follows:
No additional training (classroom) is required for Level 2 certification. The total classroom training for Level 2 UT, RT and ET is in most instances only 50% of the requirement for each of the other training programs mentioned. See Table 3 for details.
|Classroom training hours
|Experience level 1 hours/months
|Experience level 2 hours/months