Demonstration Of NDE Procedures Why, What And How?

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1 National Seminar & Exhibition on Non-Destructive Evaluation, NDE 2014, Pune, December 4-6, 2014 (NDE-India 2014) Vol.20 No.6 (June 2015) - The e-journal of Nondestructive Testing - ISSN Demonstration Of NDE Procedures Why, What And How? Prakash D. Tamhankar 1,a, Pradeep Kumar 2,b and Monish Vadhavkar 3,c 1,2,3 Insight Quality Services, 507/508, Siddharth Towers, S. No. 12/3 B, Kothrud, Pune , India a prakash.tamhankar@iqs-ndt.org, b pradeep.kumar@iqs-ndt.org, c monish.vadhavkar@iqs-ndt.org Abstract Non-destructive Examination (NDE) is carried out as per a written procedure. The procedure is a must as per most codes. Procedures give assurance of quality to customers. Procedures give confidence of repeatable consistent results. A procedure is incomplete without its qualification. Qualification is done through demonstration of the procedure. Demonstration validates the procedure. Codes, and many times customers, specify demonstration. Demonstration requirements may vary. ASME codes refer to their Section V Article 1 for general demonstration requirements. Clause T-150 is important. Other parts of this code may specify other requirements. For example, Radiographic examination procedure demonstration in Section VIII Division 1 talks about a very simple method. Methodology of demonstration is important but may vary. Use of calibrated equipment is essential. Consumables used need to have certificates as specified by the code. Personnel performing demonstration shall be as specified in the procedure. Test pieces used in demonstration are very important. They represent the material and jobs specified in the scope of the procedure. The samples have to be with flaws. They need to qualify the range specified as per the procedure. Naturally flawed samples are preferred. Quantity to be tested may be specified by the code. Documentation of demonstration is critical. Equipment calibration certificates, consumable certificates, qualification certificates of personnel, master reports of the samples, reports of demonstration and summaries, and other supporting documents for all these are required. These are to be well controlled and are auditable during ASME audits. The Level III controlling and supervising the demonstration, and the Inspector witnessing the demonstration, play important roles in the demonstration of procedures. Keywords: Procedure, Demonstration, Qualification, Demonstration requirements, Equipment, Personnel, Test specimens or samples, Documentation.

2 A successful Nondestructive Examination requires basically three things; approved / qualified procedures, calibrated equipments and qualified personnel. This paper discusses the requirements for qualifying a procedure. Methodology of demonstration is important but may vary. When carrying out demonstration there are some prerequisites which need to be considered. These are 1) Approved procedure- All NDE procedure used on the job shall be approved by NDE Level III. NDE Level III shall select a suitable technique according to the job requirement. All essential and non essential variables shall be mentioned on the procedures. Some values in the procedure may have to be changed after the demonstration. 2) All instruments used in the procedure needs to be calibrated preferably traceable to the national standard. Calibration certificates shall be made available to the review of NDE Level III and Authorized Inspector. 3) All personnel performing and evaluating NDE shall be qualified and certified in accordance with the requirements of the code accepted Editionof ASNT SNT-TC-1A or CP 189 or as acceptable to the code. The personnel performing NDE shall be competent in the applicable method /Technique. 4) Flawed Sample Test specimens used in demonstration are very important. They represent the material and jobs specified in the scope of the procedure. There should be a flawed sample which shall be approved by NDE Level III. These flaws may be artificial or Natural. Usually natural flaws are preferred. When selecting the sample NDE Level III should select in such a way that it should resemble the expected flaw in the actual job base on process like welding and forming. Test specimen having flaws whose size; location, orientation; quantity and characterization have been determined prior to demonstration should be known only to the supervising Level III Examiner. The referencing Code Section shall be consulted for the following specific detailed requirements: (a) (b) (c) (d) (e) (f) Personnel certification requirements or prerequisites for qualification under the requirements of this Article Examination planning, including the extent of examination Acceptance criteria for evaluating flaws identified during examination Level of rigor required for qualification Examination sensitivity, such as probability of detection and sizing accuracy Records, and record retention requirements In deciding the NDE requirements for a job, there are various factors to be considered like whether the requirements of any NDE are given by the referencing code, and if the referencing code requires NDE according to a particular standard. In general, most codes and most methods will prescribe a written procedure requirement. There are certain exceptions, like Radiographic examination as per Section VIII Div. 1 of ASME B & PV code, where a procedure is exempted. ASME B & PV code requires the procedures to be demonstrated and qualified before use. The demonstration has to be done to the satisfaction of the Inspector. Procedure demonstration is defined in article 1 of section V as: A written procedure is demonstrated, to the satisfaction of the Inspector, by applying the examination method using the employer s written nondestructive examination procedure to display compliance with the requirements of this Section.

3 Procedure qualification is defined as: A written nondestructive examination procedure is qualified in accordance with the detailed requirements of the referencing Code Section. When we go through the various requirements of section V, we understand that a number of variables are involved in all examinations. Most of the times, these variables are listed in the articles. The variables, as the name goes, have full potential to change the results of the examinations, and therefore, need to be controlled. The code differentiates the variables as essential and non-essential. A common misconception about non-essential variables is that they need not be included in the written procedure. Actually, they need to be very much there in the procedure. The word non-essential is related to their significance. When there is a change in any non-essential variable, the procedure has to be revised, but need not be redemonstrated and requalified. Whereas, a change in essential variable needs the procedure to be revised, redemonstrated and requalified. Now controlling the variables means not letting the variables go off beyond or under certain limits. The limits are specified in the codes. But what is the confidence that a written procedure will run well and give the desired results? How to ascertain that particular discontinuities will be identified by this procedure? One way is to actually perform the examination as per the procedure, and prove it. But what shall we do with the variables when performing this examination? Obviously, we will be performing with some fixed values of the variables. The best practice is to do various examinations during the demonstration, using the limiting values of the variables, so that we are able to establish that the procedure will still work with any value within these limits. This is called establishing a range of variables. With such demonstration, we are giving the confidence to the Inspector and to the customer that the procedure works well. It is the responsibility of the Manufacturer, fabricator, or installer to establish non-destructive examination procedures and personnel qualification and certification procedures conforming to the referenced requirements. As per article 1 of section V, when required by the referencing Code Section, a personnel demonstration may be usedto verify the ability of the person to apply the examination procedure. When Article 1 is directly referenced, the qualification of the person can be as per SNT-TC-1A or ANSI/ASNT CP-189. Other National or international central certification programs may be used. When the referencing Code Section does not specify qualifications or does not refer to Article 1 directly, in such cases qualification may involve a personnel demonstration to show the competency of the personnel performing the examinations. This means that sometimes the demonstration is not only to ensure that the procedure is technically correct to identify discontinuities, but it also proves the ability of the performer. The demonstration shall be performed under the control and supervision of a Level III Examiner who is qualified and certified for performing the examination method and technique specified by the procedure, and shall be witnessed by the Inspector. The supervising Level III may be an employee of the qualifying organization or a subcontractor organization. The Level III will monitor the demonstration, and guide regarding all the aspects. It is his responsibility to ensure that the finer points of the examination are not missed out and carried out so as to give a clear result of the demonstration. In actual job, the same way we need to ensure that the finer points are not missed. At least one specimen having flaws whose size, location, orientation, quantity, and characterization have been determined prior to the demonstration and are known only by the supervising Level III Examiner shall be tested. The Level III preferably shall carry out the examination on the specimen himself to get the details of the flaws. Care must be exercised by the Level III to keep the master reports only to himself, which is important. Demonstrations can be done on flawed specimens purchased from renowned suppliers. In such cases, full reports are available with the specimens.

4 The Level III shall be extra careful in such case, as the report can be easily available to others from other sources, and the same samples may be used many times in other demonstrations. The maintenance of these samples is also equally important. The demonstration has to be done by a Level II or Level III Examiner, other than the supervising Level III, who is qualified and certified to perform the examination method and technique specified by the written procedure. The demonstrator shall have a good knowledge of the procedure and technique to be performed. He/she should be conversant with the requirements and the variables. The knowledge of the demonstrator gives a good confidence to the Inspector and customer even on the procedure. In the same manner, we have to ensure that the detection of discontinuity is not missed in the job. As per section VIII division 1, a procedure for Radiographic examination is not essential. Hence the requirement of demonstration is also diluted. Demonstration of density and penetrameter image requirements is considered to comply with Section V requirements. This is so because when density and sensitivity requirements are met, it means that the radiograph is interpretable, and the technique employed was correct. The defect catching capacity is hence proved. Ultrasonic examination demonstration is required when working as per Section VIII div 2. This is critical, and good samples are a must. Penetrant examination demonstration is critical. The demonstration has numerous variables. The techniques could be more than one, and demonstration is required for every technique. For example, procedure may be for solvent removable and water washable penetrants. The scope of the procedure could be for welds, ground welds, machined parts etc. This means we have to demonstrate on each such specimen. The timings between steps are variables. M inimum and maximum time after precleaning, after excess penetrant removal, minimum penetrant dwell time, and start and limiting timings for interpretation all have to be demonstrated. This makes the demonstration a long one, but takes care of all variables in practice. Care must be taken in water washable technique not to repeat tests on the same specimen a number of times. The indications may get weaker and weaker in such a case. Magnetic particle examination demonstration, when compared to penetrant examination demonstration, is simpler. The equipment used is yoke most of the times. It could be AC, DC or permanent magnet yoke. Specimens may differ as per the scope of the procedure. Calibration of the yoke with regards to lifting power is a must. The variables regarding timings are absent, and hence the demonstration is quicker. In both penetrant examination and Magnetic particle examination, light demonstration is a must. White light requirement for both is the same, and one common demonstration is sufficient. Calibration of the lux meter is important. When done with a lamp, care should be taken to consider the ambient light falling on the luxmeter, or the demonstration shall be done in dark space. Most of the codes require procedure demonstration to be witnessed by Authorized Inspector. Customer also may witness the procedure demonstration. Documents relating to the procedure needs to be properly prepared satisfying all the code requirements and shall be properly maintained. It will be helpful in convincing the customer that the procedure is adequate enough to identify the discontinuities in the job.

5 Documentation of the procedure demonstration shall include the following: (a) (b) (c) (d) (e) The technical justification document NDE procedures, including the essential variables applied Description of the equipment used, including the calibration records Description of the specimens used to perform the demonstration Certification of acceptable completion of the performance demonstration. The certification may be issued separately for the equipment/procedure and the individual. So all the NDE Procedures should be demonstrated with a flawed specimen with the approval of NDE Level III and also should be controlled by NDE Level III. Procedure is always incomplete unless we demonstrate or qualify it. The actual testing on the job is always incomplete unless we implement the demonstrated procedure effectively. References: [1] ASME BPVC Section VIII Division I, Edition 2013 [2] ASME BPVC Section V, Edition 2013 [3] SNT-TC-1A Edition 2006