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European Standardization of NDT within CEN/TC 138 - Answer to question about NDT performances
A. KOZLOWSKIChairman of CEN/TC138
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·Table of Contents ·Standardization | European Standardization of NDT within CEN/TC 138 - Answer to question about NDT performancesA. KOZLOWSKIChairman of CEN/TC138 Contact |
These codes as well as industrial practices propose different NDT methods for different situations. Such differences are justified by the environment in which these inspections are conducted and by the defects to be detected and evaluated.
Qualification of inspection procedures is a way of harmonising inspection requirements with the objective of being equally open to any inspection technology. Qualification based on performance standards allow the use of any method and technique which satisfies the inspection objectives in the considered environment. Demonstration of performance has obviously to be performed following well codified rules.
Qualification procedure of an inspection system should be based on precise inspection objectives or target to be defined prior to any qualification (component, environment, defects, requirements, safety, ....)
Qualification may be the key to the introduction of performant inspection methodes/techniques, new technologies in view of increased effectiveness and economy, elimination of non performant procedures, replacement of a particular technique by another or by a combination of techniques that would combine effectiveness in various situations, high performance and economy.
The importance and technical complexity of NDT is growing notably where new material or design methods are introduced (design margins are reduced to take advantage of developments in material and design methodologies) in order to monitor in-service performance, also life extension of power plant, air planes .... is increasingly important and dependant on reliable NDT.
The harmonised European standard is acknowledged as a cornerstone of this new policy, which unites all of the European Community into one great trading partnership. Technical standards cannot be written unless they are justified on a sound technical and scientific basis. The knowledge and expertise necessary to write such documents is derived from two sources :
The pressure equipment industry is very much dependent upon technical standards for all aspects of its business, from initial design to manufacture and safe use throughout the lifetime of the equipment. This dependence upon standards is reflected in the current programme of harmonised European Standards, which are now finalised or under preparation in support of the New approach Directive 97/23/EC concerning pressure equipment which was incorporated in member state's national laws on November 1999 and will become mandatory in May 2002.
Whilst incorporation in standard specification is often the most efficient form of technology transfer, appropriate action lies in the hand of producer or operational engineer.
It is recognised that these will cover a wide range of skills and abilities and that different applications will bring various demands and different levels of qualification and experience. In certain cases, it may be asked whether conventional undergraduate engineering courses do give their students sufficient practical guidance as how to reduce the incidence of failures.
Certainly the last years have shown an increase in the teaching of fracture mechanics in such courses, but in many cases this is seen primarily as a mathematical challenge rather than in a way of identifying the practical steps that can be taken to reduce the risk.
Perhaps, such courses should be incorporated into wider aspects of studies covering some historical examples relating to causes of failures, the role of non-destructive testings.
Another opportunity to participate in such technology transfer is by the organisation and participation in special courses for practising engineers.
Several such courses have been run and these have been widely recognised as having achieved a high standard in giving up to date information in a useful form.
Considering the case of different situations such as control after fabrication and in-service inspection, qualification is certainly a powerful tool for the promotion of additional and new techniques typical of one situation (e.g. fabrication control) to another (e.g. in-service inspection) and to facilitate the harmonisation of the inspection of a component from the first phase of its fabrication till it enters service. This aspect is important in view of the homogeneity of judgement of the Quality of a product in the different countries at different moments of its life particularly in the actual concept of globalisation of world trade where a lot of projects and products are multinational. Projects are designed in one country and build in others with equipment and materials produced around the world. Companies executing major projects need to call up standards and local certificated personnel to execute NDT.
EN 473/45013 certificated give a reasonable assurance for the basic competence of the operators but it is dangerous to waive other requirements.Only the employer can authorize the NDT operator for a specific job, such authorizations should include much more than EN 473 certification.
These additional requirements will be reviewed and motivated. Also in validation procedures all aspects relevant for the quality of NDT should be included.
Personnel certification as a verification of the capability of personnel to carry out NDT is a vital parameter insofar as standards procedures equipment controls cannot achieve quality if the practitioner carry out NDT is not adequately capable.
In the other hand an NDT skills certificate will not guarantee quality if the practitioner is expected to use inadequate equipment or to work in too difficult condition or under inordinate pressure or is asked to carry out tasks which are outside the scope of his certificate (there is probably a need today for a code of practice on employment conditions for NDT personnel engaged in quality critical activities, on the other hand it should be noted that the automation of equipments leads to a deresponsibility of the operator who has not the knowledge of their functioning and therefore is no more able to correctly practice the evaluation and validation of the result of the tests).
Standards for quality systems such as ISO 9000 require to establish quality systems to control all activities which affect quality. The quality systems must address each essential parameters to ensure that all appropriate tools are in place.
Organisations executing NDT have their quality systems and their personnel certified by an accredited certification body and the competence of their laboratories can be accredited to EN 45001. Inspection bodies themselves can be accredited to EN 45004.
The responsibility of the different elements remains with various organisations responsible for standards, certification and accreditation which are not concerned with the complete quality system.
Given the international nature of the market place for NDT CEN/TC138 appears as a fundamental actor for a global quality insofar as CEN/TC138 is responsible for the preparation of European standards on :
and including for each method :
and due to the fact that in Europe when the European Standards are published, the corresponding national standards shall be withdrawn.
On the basis of resolution N182 (1996) it was decided at the October 1997 meeting of CEN/TC138 to carry out an enquiry on the item "Methodology for qualification of non-destructive test".
As the result of this enquiry was in favour of the inscription of new work item in the CEN/TC138 programme a specific working group was created and the first meeting of this WG9 held on June 1999 in Petten, the Netherlands at the institute for advanced Materials, Joint Research Centre of the European Commission.
In order to determine the necessity for qualification, the following should be considered:
As detection and characterisation may be significantly different processes, this may imply that different techniques are used for detection and characterisation often more traditional NDT techniques only cover detection and location
The professional competence of NDT operators is an important parameter to reach the required quality of NDT.
The goal for this working group is explained in the following
The normal process of ensuring the adequacy of NDT is to use procedures developed from codes and standards by personnel with a certificated ability to write such documents. The procedures are then applied by staff with a certificated ability to carry out such inspections. This process has been used over many years and has proved to be perfectly adequate in most applications. However, there are a number of circumstances where it might be judged appropriate to augment the conventional approach. These arise first whenever the safety or economic consequences of inadequate NDT are particularly severe. There may also be a need for additional measures to assure NDT effectiveness when methods are to be used for which the conventional approach is inapplicable because the NDT method is a new one or is not covered by existing standards or certification arrangements. This process of providing additional confirmation of the effectiveness of NDT is known as NDT qualification.
Such a standardisation corresponds with the research of common solutions to common problems.
In confronting the experiences, in causing a large reflection and a collaboration between the partners, the standardisation far to be an 'uniformisation" form a privileged tool of exchanges and dialogues necessary to develop the industrial and trade strategies of the companies within the concept of the global quality.
For conventional control where the main objective is the survey of the production process the direct use of controls according to codes and standards seems really suited to the situation and economically reasonable insofar as such standards allows the evaluation of performance and quality of the tests.
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