SINCE2011 Singapore International NDT Conference & Exhibition, 3-4 November 2011 Break down of traceability or Quality Chain in Non Destructive Testing to International Standards Sajeesh Kumar BABU * 1, Muthuramalingam Balakrishnan 2 *1 WENS Quality Assurance (SIN) Pte. Ltd., 758095 SINGAPORE, Singapore e-mail: skbabu@wensgroup.com, Phone: 91110635 2 Non - Destructive Testing Society (Singapore), Singapore Email: muthunaveenam@gmail.com Abstract: This Paper would reveiw the quality assured methods to conduct non destructive test to international standards including American standards & European standards. The paper enlighten the practioners to take necessary measures to comply the standards in whole while conducting various NDT test methods such as ultrasonic test or radiographic test. The paper would be a useful tool for the non destructive testing laboratories seeking accreditation for multiple standards to understand the requirement of resources. Quality Chain in Non Destructive Testing There are three important factors to achieve the necessary quality and reliability of inspection:- 1. The responsible engineer must specify his requirements very clearly in terms of the regions to be inspected and the types of flaws or deterioration to be looked for (all-encompassing combinations would be prohibitively expensive). 2. The NDT methods, equipment and personnel must be capable of the purpose for which they are being employed. 3. The selected NDT process must be implemented thoroughly. Within the second criteria the below block diagram represents a simple sub quality chain of operating effectively a Non - Destructive testing, In order to obtain the quality testing results we shall employ right personnel, appropriate equipment & proper testing methodology, if one of the elements goes wrong the quality chain is broken. The common practice in testing companies is using multiple standards for various product /customer needs. In order to achieve a quality test results, the laboratory & testing firm shall group the testing standards. It won t be practical to adopt one procedure for all international Personnel Equipment Testing Methodology standards. Page 1
Let us look into the first element - Personnel Personnel for Non Destructive Testing: In the field of personnel certification there are two types of standards: those which cover central, independent certification and those for in-house certification. Central independent certification as defined in standards such as the International Standard ISO 9712 and its European equivalent EN 473 is increasingly being accepted internationally, Recently the ISO & CEN committee working together to release a new standard which EN ISO 9712 which sets out as one universal standard for training & certification. For in-house qualification and approval (certification, by definition, involves a third party certification body ) the American ASNT document SNT-TC-1A is widely used in place of a standard in, for example, the pressure equipment sector, where ASME codes are often applicable. In the aerospace sector, there are sector specific standards, such as EN 4179 and AIA NAS 410 for the qualification and approval of personnel by the employer. The most common one in Asia is ASNT written practice SNT-TC-1A or third party certified programs such as ACCP of ASNT, PCN of BINDT, CSWIP of TWI, An ASME pressure vessel manufacturer to Section VIII would allow NDT personnel qualified to employers written practice or to a third party certification. While a structural steel welding done to BS 5950 or Eurocode 3 would require NDT personnel certified to EN 473: 2008 or ISO 9712:2005, In most cases companies carrying out Non- destructive test doesn t fulfill the standard requirement in this aspect which is critical breakdown of traceability in quality chain. An endorsed report issued in Asia would not be accepted in European counterpart due to this aspect although an MRA between two countries exist. End users, stakeholders shall deeply take into consideration while fabricating their components meant for export to this European standards. Improvement for Personnel Competence: Employment and performance history on previous projects shall be considered Evaluation of individual personnel competency and capability shall be made available Acceptance criteria and specific standard / specification and contract requirements shall be considered during evaluation of personnel Discipline specialists shall be consulted where this is recognized to be a requirement. Competence evaluation shall be performed periodically Reliable In-house Training In additions to third party training and certification program, more reliable in-house training in line with specific product / compound / configuration, etc., shall be established for the reasonable and reliable inspection method and increase the confidence of our client and public safety. Equipment: The other aspect of the trio would be Equipment; NDT Testing equipment s are produced globally and available at various cost & quality. It is the responsibility of the testing
laboratories to employ the adequate equipment for the application needs. It s often the case equipment s are not calibrated to the appropriate standards, validation of the equipment s are not carried out at reasonable intervals. In general ultrasonic flaw detectors are calibrated as a combined equipment rather than individual equipment, New standards for measuring the electronic characteristics of the pulse echo flaw detector are available such as ASTM E1324-2011 Standard Guide for Measuring Some Electronic Characteristics of Ultrasonic Testing Instruments or the BS EN 12668-1:2010 Non-destructive testing - Characterization and verification of ultrasonic examination equipment. Instruments, Testing laboratories shall prepare their equipment for calibrating electronic characteristic s to keep reproducibility error at minimum. Appropriate Calibration blocks shall be selected to set the sensitivity to meet various application such as flat bottom hole block for a plate lamination scanning, distance amplitude block for a weld scanning, an API piping calibration block for curved surfaces. The blocks shall be adequately calibrated by a primary laboratory or an accredited laboratory. Testing Methodology Although there are no differences in Physics on both sides of the world, but basic application and standards adopted are different. This is due to the historical development and national specialties. Here with reproduced some basic differences between European and American standards for radiographic testing EN 444 General rules(r) ISO 5579 EN 1435 Welding pren 12681 Foundry (Casting) The idea behind these standards is: Standards shall guarantee a minimum image quality by 'Minimum Requirements' while using the testing procedure. This is basically: Contrast- opt. Density, IQI-values, max. X-ray energies, Wall thickness limits for gamma sources Film system classes-definition of film system classes in dependence on energy and wall thickness Unsharpness- minimum focus-object-distances Handling- Radiation geometries, Filter, Shielding, Masking, Marking The radiographic techniques are subdivided in Europe into two classes: Class A: basic technique; Class B: improved technique. Class B technique will be used when class A may be insufficiently sensitive. All test tasks
shall be preferably performed by class A or class B testing. ASTM standards (E 94, E 1742, E 1032, E 1030) do not require testing classes. The quality of testing is basically defined through the Image Quality Indicator (IQI).This IQI's are mostly step hole type penetrameters accordance to to E 1025. ASTM issued a standard for wire type IQI's, E747, which corresponds to the old British standard but, does not comparable to European E 462. The ASTM standards mainly describe the method and workmanship. No minimum requirements have been set other than Geometric un sharpness. For each application a written procedure shall define the needed IQI perceptibility and geometric un-sharpness. The standard is the broad basic for all testing tasks. Qualified personnel shall carry out the radiography with a quality corresponding to the requirements. Now a days, software are being used and playing a vital role in the NDE inspection and its methods. It should be considered and trouble free, well trained personnel and fewer break down, more reliable system shall be selected and delivered with economic manner. Similarly for Magnetic Particle Testing, frequency of the lifting capacity of Yokes to ASTM standard shall be performed every 6 months while for European standard, no requirements has been spelt out for the frequency to verify the lifting force & most contracts would require a daily functional check prior to the test. Visible Inspection requirements; Most of the inspection after test is performed under illuminated conditions at site either natural or artificial source, laboratory shall have the practice of determining the minimum illumination requirement as required by most of the standard as 1000Lux for visible inspection. Environmental Factors: Due to global warming and changes in the climate and environmental effect shall be considered for any type of NDE inspection system, availabilities, location of the work, logistic support, delivering support / back-up system, spare parts manufacturing time, its delivery to project site, etc., shall be considered and taken in to account. Recording of Test Results: It is often a practice at sites, testing operators doesn t use worksheets to record the test results, in most of the cases a final report is produced without preliminary results, this action clearly break down the requirement of traceability. The NDT test results shall be broadly classified into acceptable & Rejectable, when operators have acceptable test results there are certain discontinuities revealed during the course of testing & might be within the limits of acceptance level, such indications or discontinuities are required to be recorded. This practice would give the clients, stake holders a tool for preventive maintenance & use the data s for condition monitoring of equipment s /structure under serviceability. The current technology development is helping some extend to use the suitable recording media
for the inspection system / methods / trained personnel, availabilities at project site. The cost and areas for the storage / media shall be considered and international user / customer has to approve and conformable such usage of the recording media. Conclusion: Laboratories / testing organization shall review application standard with the testing personnel and shall have specific training on various standards to communicate the requirements prior to the test, appropriate tools & equipment as required by the standard shall be available in order to carry out the test effectively. Such best practices will put the standard of Non Destructive testing into better heights & reliability of test results is possible. Keywords: Quality Chain, Non Destructive Testing, Traceability, Reliability References: 1. EFNDT Guidelines Overall NDT Quality System 2. Radiographic Testing - A comparison of Standards for Classical and Digital Industrial Radiology- Uwe Ewert, Uwe Zscherpel, BAM-Berlin, Germany