A Deep Dive into NDT Standards
Two nondestructive testing experts explain the standards process.
Standards make up the backbone of quality assurance in manufacturing. In addition to providing guides for the appropriate methods and techniques used in the testing, measurement, inspection, and evaluation of materials, standards indicate whether or not a material is of the right quality, and by extension, the utmost suitability and safety for its intended use.
In the field of nondestructive testing (NDT), several organizations are involved in the development and application of standards, including the American Society for Nondestructive Testing (ASNT); ASTM International, formerly known as the American Society for Testing and Materials (ASTM); and the International Organization for Standardization (ISO). But what are these organizations doing to not only ensure that their standards are being effectively and appropriately implemented in the industries that they serve, but also to maintain an open dialogue with other industry professionals who wish to be a part of the decision-making process?
Quality spoke to two experts on the subject — Charles “Chuck” Hellier, former national president of both ASNT and the Nondestructive Testing Management Association (NDTMA), as well as the founder and former president of HELLIER Technical Training and Consulting; and James W. Houf, senior manager of the ASNT Technical Services Department — for insight into how and why these standards are working for NDT-related industries today.
Chuck Hellier: There’s been a lot of misuse of the terms and misunderstanding of the terms, like “standard,” “code,” and “specification.” The most common term is “standard.” There have been a number of different definitions, but in my own words, I believe a good definition is that a standard is an established norm. Standards also could be considered as requirements regarding technical processes like NDT or technical systems. So it is something that has been established, typically by standard writing organizations.
Another term that is used quite a bit in NDT is the term “practice,” which is a traditional way of doing things, or a standardized method. It is different than a "standard." Standards are established by standard writing organizations, whereas practices are too, but they are more like guidelines than requirements, although they can be referenced and they can be followed.
Then there is the term “Recommended Practice,” which is not a code and not a specification. It is really a set of recommendations or guidelines that can be used if a company or individuals want to. For example, the most widely used certification program, I would say at least in the U.S., is a Recommended Practice: SNT-TC-1A. That is an ASNT program, but it is a set of recommendations that is available for employers to use to develop their own, in-house certification procedures.
A “specification” is more of a detailed description, an assessment of a requirement, and it applies to specific materials and components. Specifications are usually specified in contracts and purchase orders when there is a need to tell an organization what actually has to be done.
A “code” is probably the most demanding of all of the different standards and practices. The “code” is more like a collection of laws, rules, and regulations. For example, the American Society for Mechanical Engineering (ASME) has a code that refers to boilers and pressure vessels used worldwide. That code is law; it contains minimum requirements that are mandatory. So you can see that there is a different flavor for each of these different terms that apply to NDT applications and practices.
By the way, a good reference for all of these terms is an ASTM standard, E1316-13. That is a standard that actually contains the standard terminology for NDT.
James Houf: ASTM, which was founded in 1898 as the International Association for Testing Materials (IATM), approved the first AITM standard, "Structural Steel for Bridges" in 1901, changed their name to the American Society for Testing Materials in 1902, and has been developing process standards ever since. In 2002 the name was changed to ASTM International to reflect their worldwide acceptance as a standards developer. The first ASME Boiler & Pressure Vessel Code was published in 1915 (1914 edition) and was one 5" x 8" book with 114 pages. Today there are 12 Sections (books) with well over 16,000.00 8" x 11" pages.
In the late 1950s, industry members approached the Society for Nondestructive Testing ("American" was added to the name in 1968) with a request to develop standardized guidelines for the certification of NDT personnel. At that time there were no certification requirements and the quality of inspection work was suffering from a lack of qualified personnel. SNT responded, and in 1996 published the first edition of Recommended Practice No SNT-TC-1A. The document name came from SNT (the Society initials), TC (Technical Committee), and 1A (the first document developed), and was never changed. Revisions were made in 1968, 1971, 1975, and 1980. It was then revised at four-year intervals until 1996, when the next revision was published in 2001. SNT-TC-1A was then revised at five-year intervals, to align with our American National Standards. The current edition is 2011 and the 2016 revision is in progress at this time.
Internationally, the ISO NDT central certification standard, ISO 9712, was first published in May 1992 and the European equivalent, EN 472, was published in 1993. The latest edition of ISO 9712 is 2012, and EN 473 was replaced with EN ISO 9712:2012. ISO 9712:2012 and EN ISO 9712:2012 have identical requirements but the EN version is published by CEN.
World War II brought the need for NDT to the forefront due to the need to construct huge numbers of ships and aircraft in a short period of time, and the need for quality welds and fabrication was epitomized by the problems found in Liberty ships, which often broke up and sank due to poor weld quality. NDT equipment at that time was fairly primitive due to the need for many large electronic tubes, heavy cables, and a lack of portability. As time went on, transistors started replacing tubes, and later, circuit boards replaced transistors so equipment sizes decreased, outputs were increased, and the equipment became much more portable. Hand-held electronic equipment today can perform inspections that operators in the 1940s and 1950s could not even dream of.
With the refinement in equipment, inspections became much more sensitive, allowing much smaller discontinuities to be found and evaluated. Research was (and is being) done on additional testing techniques, and it is now possible to steer multiple ultrasonic sound beams, vary their phase, and adjust the frequency so that inspection can be done over relatively long lengths of pipe, with or without insulation removal, and radiographic ("x-ray") techniques now incorporate digital radiography (as opposed to using film), computed radiography, and computed tomography to provide 3-D images of solid materials. As noted above, new techniques are being developed [in ultrasonic testing] to increase sensitivity and reliability.
Chuck Hellier: The process starts out as either a need or an idea. New materials may come along, and there has to be some type of way to make sure that the proper tests are specified and the proper procedures are used.
Then it goes through what we call an “approval process.” A committee would be developed, and the committee that will work on this standard should consist of personnel that are specialized in the particular methodology that is being developed. Most of these standards organizations [consist of] groups of volunteers; there are not a lot of paid people that are involved with the development of standards. So the most logical way to develop a standard is to get a group of specialists that are really qualified in the particular subject, Then the group working together would come up with what we call a “draft standard,” and this is done in the committees, sub-committees, or working groups.
And if it’s going to be an American National Standards Institute (ANSI) standard, then it has to go out for a “peer review,” meaning it has to be sent out to other groups, organizations, and people who are familiar or involved with that particular industry for comments. So the comments come in; and after a certain period of time, all of the comments are addressed and either discarded or will, in many cases, cause changes to occur with the draft standard.
And then it goes to some type of board. Depending on the organization, the structure will be different, but there will be a final board and an approval process before the standard is actually published. Then once it is published, it is subject to periodic review and revision. In the interim, if there is a major reason for changes, they will also be put out in the form of code changes. This is just a glimpse into how the standards writing process works today.
James Houf: The standards development process nationally and internationally is essentially the same; a standard must go through a consensus process which requires that the content of a prospective standard be developed, reviewed, and approved by a group of materially interested personnel. The international standards development body is ISO, located in Geneva, Switzerland. Made up of representatives from 160+ countries, ISO publishes international standards. In the European Union, the standards developing body is the European Committee for Standardization (CEN), which is an association that brings together the National Standardization Bodies of 33 European countries. Standards in the EU are called "norms.”
In the United States, ANSI promotes and facilitates voluntary consensus standards and ensures their integrity by providing all interested U.S. parties a neutral venue to come together and work towards common agreements. Standards that have gone through the ANSI standards development process and have been approved are designated American National Standards (ANSs). ANSI is also the U.S. member body to ISO, which gives the U.S. a vote when international standards are being developed. All of these standards, international and domestic, are voluntary consensus standards.
ASME is also an ASD and they publish the ASME Boiler & Pressure Vessel Code, along with many other standards that describe how pressure-retaining vessels are fabricated and maintained. The ASME standards cover power boilers, unfired pressure vessels, nuclear and fossil fuel power plants, and many of the pressure vessels used by the petro-chemical industry's refining processes.
Before going into how standards are developed in the U.S., let me make a clarification: ASNT publishes NDT certification documents and ASTM International (astm.org) publishes NDT "process" standards which describe how the NDT methods and techniques should be applied. All of the ASNT and ASTM standards are American National Standards, which means they have been developed using a consensus process approved by ANSI. Both ASNT and ASTM are accredited by ANSI as ANSI-approved Standards Developers (ASDs) and have their standards development processes audited at five-year intervals by ANSI. ASNT publishes four ANSs, has a fifth draft standard in process, and has one Recommended Practice — Recommended Practice No SNT-TC-1A — which is not a standard, but has guidelines for NDT certification by employers. ASTM has in excess of 200 standards addressing NDT processes and these can be found in the Annual Book of ASTM Standards, Volume 03.03.
Under ANSI rules, anyone can write a standard but the approval of that document must go through an ANSI-approved consensus process. Under this process, a "consensus body" made up of industry volunteers with a material interest in the document's subject matter must review and approve a draft standard, or a revision to an existing standard. Once they are satisfied with the content, the draft is sent to ANSI to be sent out for public review for 30, 45, or 60 days, with the time depending on how the draft document can be accessed by the public. The announcement of the public review period is posted on ANSI's weekly Standards Action web page.
Following the public review period, the consensus body addresses any comments that were a result of that review, then sends the document back to ANSI with documentation of the development and revision process for final approval. If the ANSI Board of Standards Review (or their designated representative) finds that the process has met the ANSI consensus requirements, the document is approved and the developer can publish it as an ANS. At five-year intervals each ANS must be reviewed by the ASD and revised, reaffirmed without revision, or withdrawn. This ensures that the content stays up-to-date and relevant.
All of these standards, international and domestic, are voluntary consensus standards (i.e. use of these standards is not mandatory), but may be made mandatory when “incorporated by reference,” which is the act of referencing one standard within another by only mentioning the second standard in the primary document. When incorporated by reference, a standard becomes mandatory for anyone working under the primary document.
James Houf: Advances in technology will drive the NDT industry to become more and more specialized. Where it was once possible for an NDT technician to be certified in all techniques under a single test method certification, the diversification and specialization of new techniques may soon make this impossible. This will require a restructuring of the certification process and will most likely require multiple certifications in specific techniques.
Chuck Hellier: I think the format for how standards will be developed and applied is not going to change that much. Of course there is new technology all the time, with ultrasonic testing, for example, and radiography. We are using digital radiography, rather than using film, and we are getting much better resolution and sensitivity. So one of the changes that I see is additional development for the new technological changes that we have in NDT; that will be ongoing.
But on top of it all, I sense a greater move towards globalization and harmonization with international standards. I think that makes a lot of sense: rather than having different standards for every country, to have solid and usable standards that apply for the same products regardless of which country is involved. For example, Germany has a wonderful certification program, and all of Europe now has basically complied with the ISO 9712 standard. In the U.S., we don’t really have an ISO 9712 compliant program. What this means is that for our NDT practitioners to do examinations on products that are going to be shipped to Europe, or to Japan, or to the far East, they are going to have to comply with the certification requirements of ISO 9712; the U.S. program does not comply with it. So you can see the benefit of trying to merge these programs together into one good one; it would save a lot of money and a lot of time.
For the future, I see us working to become much more harmonized with the international community, so that we can work with these international standards and make them more uniform. This is where our focus should be.