Here's an interesting paragraph with respect to VT and CP-189... This is from a paper submitted for the15th World Conference on Non-Destructive Testing 15-21 October 2000 in Rome:
"I think that you will agree training would be beneficial for visual test applications, but is certification necessary? Certain codes mandate certification this is exemplified by the application of ASME XI. Certification is required in accordance with CP189 to categories segregated as VT1, VT2 and VT3. Each category specifies visual applications and is available at levels 1 or 2 with specific criteria pertaining to eligibility of trainers and prospective level 3 persons. Not all code or standards require certification but how else do you assess the competence of test personnel? An age-old phrase of justification is that of "continued satisfactory performance" but what does this mean? Is this a quantifiable value or a misnomer of accuracy? Surely by virtue of demonstrating continuous performance by an internal or external means of assessment, automatically achieves traceability and quantification. But this approach is little short of the certification process advocated by many as costly and unnecessary. Certification schemes are available to operate as company internal quality measures with internal or external moderation. Quality control documents typified by written practices based around SNT-TC-1A, CP189, NAS410 or prEN4179 are used globally for internal certification being moderated by internal or independent external examiners. Certification in accordance with EN473 and ISO9712 is differs from those previous by classification as central certification in a similar vein to college examination bodies. Although both routes to certification have attributes and detriments they do ensure adequate coverage of all industrial needs with flexible options to address specific requirements.
Should you require any further guidance on any of the points mentioned in this paper please contact Lavender International NDT Ltd. via email at Stephen@lavender.demon.co.uk or phone 44 (0) 1226 765769 addressing enquiry's to Tim Armitt."
Here's the link to the page:
http://www.ndt.net/article/wcndt00/papers/idn006/idn006.htmIn 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.
A brief list of some of the major differences below:
1.)
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.
2.)
Vision Requirements - The vision requirements for near vision acuity are more stringent in CP 189 requiring acuity to read the Jaeger # 1 instead of Jaegar # 2.
3.)
Levels of qualification - There are 5 levels of qualification instead of 3 the additional 2 being "Instructor" and "Trainee".
4.)
Minimum training hours - 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).
5.) 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"...
So basically there's no requirement from ASNT to use one system over the other because that decision is up to the contractor to make and the subcontractor to follow... However, the owner, customer should be aware of the differences between a set of recommended guidelines and an actual ANSI approved by consensus American National standard in order to make the right choice in choosing between the 2 parallel certification schemes offered by ASNT...
The Nuclear industry does prefer to use ASNT CP-189 but they also allow limited use of SNT-TC-1A also and the military has there own standards that is based on the ASNT CP189 certification scheme with very few additional criteria to establish the differences between the 2 also....
ASME does require that the VT personnel be certified to ASNT CP-189as well as other methods too... The bottom line is that one (CP-189) is stricter in it's certification and education requirements because it is a orderly formal standard compared to ASNT SNT-TC-1A which is not, but the choice between the 2 to be applied to a project is decided by either the OR,or EOR, or the customer/client and followed according to the specifications found in the contract documentation. Clear as Oktoberfest Beer eh?
Respectfully,
Henry