A Comparative Study Of ISO 9712:2012 And SNT-TC-1A:2011
Release date:2018-03-14


The effectiveness of Non Destructive Testing is primarily dependent upon the capabilities of the NDT Personnel. Hence, Qualification and Certification of NDT Personnel is of great importance for the enforcement of Quality. ‘Non-destructive Examination (NDE) is an important tool in most of the industries today. The application of NDE has to be done by skilled personnel. Various codes will demand qualified and certified individuals doing this job.

Qualification and Certification of NDE Personnel is based on these five basic factors:

  1. Training Requirements
  2. Experience in the given NDE method
  3. Vision Requirements
  4. Basic Educational Qualification
  5. Examination Requirements

Out of the many schemes for Qualification and Certification of NDT Personnel, two prominent ones are SNT-TC-1A [1] and ISO 9712 [2].

For the purpose of this paper, the term SNT-TC-1A will refer to Recommended Practice SNT-TC- 1A 2011 and ISO 9712 will be used for Standard ISO 9712 : 2012.

When referred together in this paper, the term‘standard’ is used for both SNT-TC-1A and ISO 9712.

ISO 9712 is an international standard from the International Organization for Standardization, and SNT-TC-1A is published by The American Society for Nondestructive Testing, Inc., as a recommended practice.

ISO 9712 is titled Non-destructive testing – Qualification and Certification of NDT personnel. SNT- TC-1A is titled Personnel Qualification and Certification in Nondestructive Testing.SNT-TC-1A was first published in 1966, and ISO 9712 in 1992.

Both have basically the same intention.

Various qualification and certification programs can be classified as either employer based or central. The employer based programs are to be monitored by some employer, with full responsibility of qualification and certification resting with the employer. Whereas the central programs are controlled and monitored by a central agency. The examinations of the central programs are independent of any employer.

SNT-TC-1A, being a recommended practice, provides guidelines for establishing a Written Practice, which will be a base document for the qualification and certification of NDE personnel for a particular company. A Written Practice will define responsibilities of each level of certification, as expected by the company (or employer of the NDE personnel), experience requirements and examination requirements for each level. This makes SNT-TC-1A, a Company (or employer) based scheme. So to sum up, if a candidate wishes to join another company, his NDE certificate remains no longer valid, as it was made to suit the requirements of the previous company, and may not be effective in this next employment. SNT-TC-1A is not a strict specification, but a recommended practice. The purchaser and supplier can agree upon acceptance of an employer’s program.

ISO 9712 being a standard provides defined requirements, and does not require a Written Practice. The requirements for responsibilities, experience, training and examination need to be documented as per the requirements in the ISO standard. This makes ISO 9712 a Central Certification scheme. The examination as per ISO9712 is conducted by a body which is independent of the employer.

The training, education, experience requirements are adhering to a standard, and hence, the certificate remains valid even if there is a change in employment. Though ISO 9712 is meant for certification as required in standards / codes, wherever freedom provided, the certification body can determine specific requirements. The certification body administers the procedures for certification according to ISO 9712, and can authorize a qualification body to prepare and administer qualification examinations.

ISO 9712 specifies requirements for third party assessment scheme, but allows appropriate requirements to be referred to in first or second party assessment schemes.

SNT-TC-1A specifies guidelines and allows the employer for modifications in these to meet particular needs in case not appropriate. This is of great importance. The program is basically for the employer, to be run by the employer. So the flexibility is to be used with discretion by the employer, to the benefit of the organization. In no way can this be taken as a means of diluting the essence of the scheme.

ISO 9712 covers 10 methods of NDT, allowing application to other NDT methods / techniques under certain conditions.

SNT-TC-1A mentions 15 NDT methods, with no direct reference of applicability to other methods.

Actually, all normally used methods are covered.

Both schemes have three levels of qualification – level I or 1, level II or 2 and level III or 3.For the sake of simplicity, when referred to both standards together, the terminology used in this paper is level 1, level 2 and level 3.

SNT-TC-1A allows subdivision of these levels where additional levels are deemed necessary for specific skills and responsibilities. This can be used advantageously by certain employers, especially when they want to involve good operators who may be lacking in formal education in the program.

ISO 9712 is silent on any changes in the qualification level structure. This is justified as it is a central program.

ISO 9712 requires near vision acuity of reading Jaeger number 1 chart, whereas SNT-TC-1A requires Jaeger number 2 chart to be read. Certain standards require Jaeger number 1 to be read in the method of Visual Testing. The logic applied by ISO 9712 is that visual testing forms the base of interpreting indications of all other methods as well. SNT-TC-1A requires color contrast differentiation examination to be conducted every five years after initial certification. Previous editions of SNT-TC-1A required color contrast differentiation examination to be conducted only once, assuming that this condition of the eye is hereditary. Later, it transpired that this condition can be acquired too. Hence this requirement of examination every 5 years. ISO 9712 is silent on re- examination for color contrast differentiation.

Both the documents refer to training requirements for NDE Personnel.

Prior training requirement is tabulated in number of training hours for Level 1, 2 and 3 in ISO 9712. As per ISO 9712, the candidate must complete a course of theoretical and practical training recognized by the certification body. Training requirements may also vary depending on the number of sectors opted by the candidate.

In SNT-TC-1A, only Level I and Level II training requirement is mentioned. The requirement for Level III training after having trained for Level I and II, in SNT-TC-1A, is left to the discretion of the employer. SNT-TC-1A states that all the training programs must be approved by the responsible Level III. Apart from instructor led training, SNT-TC-1A also talks about virtual instructor led training, self-study, computer based training or web based training. But inclusion of such methods is left to the discretion of the employer (or the company’s written practice). 

ISO 9712 is silent on this aspect.

The requirement for training is comparatively more demanding in ISO 9712 as compared to SNT- TC-1A, especially for Level 2 and 3. Conditions for reduction in training hours exist in both the documents. The concept of direct access to level II or level III is similar in both standards. One has to complete the requirements of the lower level/s too.

Recommended training course outlines can be obtained from ANSI/ASNT CP-105 when developing training courses as per SNT-TC-1A.

As referred in ISO 9712, ISO/TR 25108 gives guidelines to the training organizations, and ISO/TR 25107 gives detailed syllabi for the NDT methods. The syllabi are much focused and in details, and form a solid foundation of the success of the program.

A major difference in the two standards is the sector wise approach in ISO 9712. ISO 9712 defines product sectors and industrial sectors. This is the unique feature of the standard, which aims at making specialists in particular sectors.

The product sectors defined are: castings, forgings, welds, tubes and pipes, wrought products and composite materials. A number of product sectors can be combined to form an industrial sectors. Some industrial sectors defined are manufacturing, pre and in-service testing, railway maintenance and aerospace. The certifying body is given the freedom of creating additional sectors, with well- defined scope. Certification in any method, at any of the three levels, can be for specific sectors. The examinations, of course will be sector specific.

The experience requirement is given in ISO 9712 method-wise, but it should be noted that this is actually duration of experience required in the sector. Level III experience requirement is tabulated, but is applicable after specific educational qualification. SNT-TC-1A does not mention method- wise level III experience requirement, after having completed the method-wise level II experience requirement.

The pattern of examination for Level I and II is the same in both standards – general, specific and practical.

Specific and practical examinations in ISO 9712 are required to be sector specific. The standard is clear about identification, master report, number of areas or volumes to be tested, types of discontinuities within the specimen and the timings allowed for the examination. Number of specimens for practical examination are detailed sector-wise in a table. The specimens used for the examination must have master reports, against which the candidates’ performance is graded. ISO 9712 also requires the Level 2 candidate to be able to draft a written instruction suitable for level 1. As per ISO 9712, the Subjects and weighting factors for grading Practical Examinations are tabulated. The number of questions for specific examination depend upon the number of sectors opted by the candidate. All this ensures a certain degree of firmness in the practical examination.

As per SNT-TC-1A, the practical examinations are evaluated on the basis of 10 checkpoints as per the employers’ procedural requirements. The specific examination is based on the codes / standards used in the employers’ NDT procedures. SNT-TC-1A is silent on the requirements of master report and the maximum allowable timings. It is expected that the employer and his level III take care of all the smaller points.

ISO 9712 requires a level III candidate to take only basic and method examination. But prior to this, he should have passed the practical examination for level 2 in the relevant sector and method. A candidate who is already level 2 in the same method and sector need not repeat this practical exam. This is a good point to ensure that the candidate has done or is capable of doing hands-on work, and is better than a written testimony of the experience.

Level III examination as per SNT-TC-1A requires Basic, Method and Specific examination. A Company Level III can be appointed by the employer based on examination as per written practice. A current ASNT NDT Level III or ACCP Professional Level III need not take basic and method exam. He/she may be qualified as meeting the company requirements if he/she qualifies the specific examination only. The specific examination may be waived off by the employer for such candidates if the required experience is evidenced. There is no practical examination for level III.

The specific examination as per SNT-TC-1A is related to the employer’s product(s) and methods employed. This is so because the concept of sector is not strictly outlined in SNT-TC-1A.

In ISO 9712, the main method examination stresses on application of the method in the concerned sector, and hence no separate specific examination is required. ISO 9712 method examination also requires drafting of NDT procedures.

In ISO 9712, a person already certified to Level 1 or 2 and wanting to add another sector is required to take only the specific and practical examination in that sector. Similarly, a certified Level 3 wanting to add a sector need not take the basic examination and the level 3 knowledge related part of the method examination.

The passing of Level I, II and III examinations as per SNT-TC-1A requires a passing grade of 70 percent in each examination, with a composite grade of at least 80 per cent. But in ISO 9712, for passing Level 1 and Level 2 examinations, a minimum grade of 70 per cent is required in general, specific, for each specimen tested in practical examination, and in written NDT instruction. For passing Level 3, a minimum grade of 70 per cent is required in each part of the basic examination (A- Material science and process technology, B- Certification body’s qualification and certification scheme based on ISO 9712, C- General knowledge of at least four chosen NDT methods), and a minimum grade of 70 per cent is required in each part of the method examination (D – Level 3 knowledge, E – Application of the method in the sector, including codes, standards etc., F – Drafting of NDT procedure in the sector). Thus, in a way, SNT-TC-1A is stricter as they are demanding an aggregate of 80 per cent. But ISO 9712 seems to apply the stringency in asking 70 per cent in every part of the examination.

The grading of the practical examination in ISO 9712 is to be done using weighting factors. SNT- TC-1A does not specify any such factors, but talks about a minimum ten checkpoints to be included in the examination.

A candidate failing the examination as per ISO 9712 has to may retake the examination twice more. The re-examination can be only in the failed part. SNT-TC-1A does not mention the number of attempts and is silent on whether full examination is to be repeated, or part. Both standards require the candidate to wait 30 days or one month before the re-examination, or receive additional training otherwise. ISO 9712 puts an outer limit of 2 years on re-examination. Unethical behavior is also addressed in ISO 9712, where the candidate has to wait for 12 months before reapplying. Hence, it is seen that ISO 9712 is giving more clarity on re-examination. This does not mean the employer can be lenient when applying SNT-TC-1A. It would be a good practice to incorporate all rules of re- examination in the written practice.

Certification records in both standards vary to the extent of a central scheme and an employer based scheme. ISO 9712 mentions a wallet card and a digital certificate as an option.

Both standards mention a maximum recertification / revalidation period of 5 years.

The certificate as per ISO 9712 may be renewed for all levels at the end of the first 5 years period, and every 10 years thereafter, based on visual acuity examination and evidence of continued satisfactory work. At the end of first 10 years and every 10 years after that, recertification for 5 years may be done based on visual acuity examination, evidence of continued satisfactory work and practical examination for level 1 / practical and instruction writing examination for level 2.

A level 3 may be recertified either by a written examination or an evidenced credit system based collection of points.

In SNT-TC-1A, the appointed Level III is very important. Numerous responsibilities like approving the written practice, approving the training programs, administering and grading the examinations are given to him. In a way, he plays the role of monitoring the program.

SNT-TC-1A, being an American program, is most used in countries following the American codes. In India too, SNT-TC-1A is used most.

SNT-TC-1A, in spite of the specific examinations, appears to make the certificate holder a person knowing all. ISO 9712 appears to make the certificate holder a specialist in that sector.

ISO 9712 is an effort to harmonize the qualification and certification program throughout the world. In India, the related standard for qualification and certification of NDT personnel is also making a shift towards ISO 9712.


  1. Recommended Practice No. SNT-TC-1A 2011 Edition - Personnel Qualification and Certification in Nondestructive Testing.
  2. International Standard ISO 9712 : 2012 Edition – Nondestructive Testing – Qualification and Certification of NDT Personnel.
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