Defence Standard Part 1. Issue 3 Date: 21 June Requirements for Non-Destructive Examination Methods Part 1: Radiographic

Transcription

1 Defence Standard Part 1 Issue 3 Date: 21 June 2013 Requirements for Non-Destructive Examination Methods Part 1: Radiographic

2 Contents Foreword...iii 1 Scope Warning Normative References Definitions Acceptance Standards Inspection Approval Requirements Surface Preparation Radiation Sources Production Radiography Storage of Radiographs and Radiographic Records Darkroom Facilities Film Viewing Facilities Interpretation of Radiographs Image Quality Indicators IQI Location Welds with Overlay Cladding Simultaneous Exposures Radiography of Pipe Welds Radiography of Small Parts Radiography of Repair Welds Radiography of Castings...20 Figures Figure 1 Example of a Radiographic Report data sheet...6 Figure 2 Minimum Focus/Source-to-Film Distance v Effective Source Size...7 Figure 3 Recommended X-ray voltages and radioisotope sources for use with steels and similar alloys 2% sensitivity level...8 Figure 4 Recommended x-ray voltages and radioisotope sources for use with copper base and similar alloys 2% sensitivity level...9 Figure 5 Selection of IQI wire number for percentage sensitivity: WIRE TYPE BS EN Figure 6 Method of marking welds for radiography...16 Tables Table 1 Material Grouping For Radiographic Procedures...4 Table 2 Screens and Filters...12 Table 3 Source to film distance for the radiography of pipe welds using gamma rays and double-wall double-image technique...13 Table 4 IQI Location for Circumferential Welds...18 ii

3 Foreword AMENDMENT RECORD Amd No Date Text Affected Signature and Date REVISION NOTE This standard is raised to Issue 3 to update its content. HISTORICAL RECORD This standard supersedes the following: Def Stan Part 1 Issue 2, Dated 14 th July 2006 Def Stan Part 1 Issue 1, Dated 1 st April 2000 a) This standard provides requirements and guidance for the management and production of Defence Standards. b) This standard has been produced on behalf of the Ministry of Defence (MOD) by UK Defence Standardization (DStan). c) This standard has been reached following broad consensus amongst the authorities concerned with its use and is intended to be used whenever relevant in all future designs, contracts, orders etc. and whenever practicable by amendment to those already in existence. If any difficulty arises which prevents application of the Defence Standard, DStan shall be informed so that a remedy may be sought. d) Please address any enquiries regarding the use of this standard in relation to an invitation to tender or to a contract in which it is incorporated, to the responsible technical or supervising authority named in the invitation to tender or contract. e) Compliance with this Defence Standard shall not in itself relieve any person from any legal obligations imposed upon them. f) This standard has been devised solely for the use of the MOD and its contractors in the execution of contracts for the MOD. To the extent permitted by law, the MOD hereby excludes all liability whatsoever and howsoever arising (including, but without limitation, liability resulting from negligence) for any loss or damage however caused when the standard is used for any other purpose. iii

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5 Requirements for Non-Destructive Examination Methods Part 1: Radiographic 1 Scope 1.1 This part of Defence Standard covers the minimum requirements for the radiographic examination method used to detect internal discontinuities in welded joints and metallic materials including castings, pipes and fabrication. It applies to all items for which specifications, standards, drawings, or refit / repair instructions require radiographic examination, by X-ray or gamma ray techniques. 1.2 The Defence Standard (Def Stan) also covers the Quality Assessment of Examining Authorities who performs radiographic examination. The extent to which radiographic examination is required is not included herein but will be found in the relevant Contract Documents. The Critical Test Regions and Test Regions for the radiographic examination of castings are contained within Def Stan Clause 4.2 (Steels) and Def Stan Clause 6.2 (Cu-Ni Alloys). 1.3 The Def Stan does not contain acceptance criteria for defects and does not apply to the examination of nuclear plant and machinery. 2 Warning 2.1 The Ministry of Defence (MOD), like its contractors, is subject to both United Kingdom and European laws regarding Health and Safety at Work. Many Defence Standards set out processes and procedures that could be injurious to health if adequate precautions are not taken. Adherence to those processes and procedures in no way absolves users from complying with legal requirements relating to Health and Safety at Work. 2.2 Exposure to ionizing radiation; X-rays or gamma-rays, can be highly injurious to health. All local, national or international safety precautions and all appropriate legal requirements are to be applied and adhered to when using ionizing radiation. 3 Normative References 3.1 The publications shown below are referred to in the text of this standard. Publications are grouped and listed in alpha-numeric order. BS BS 2737 BS EN BS EN 1435 BS EN BS EN BS EN ISO 9712 Welding terms and symbols Part 1: Glossary for welding, brazing and thermal cutting Terminology of internal defects in castings as revealed by radiography Non-destructive testing. Image quality of radiographs Part 1: Image quality indicators (wire type). Determination of image quality value Non-destructive examination of welds. Radiographic examination of welded joints Non-destructive testing. Terminology Part 3: Terms used in industrial radiographic testing Welded, brazed and soldered joints. Symbolic representation on drawings Non-destructive testing Qualification and certification of NDT personnel General principles 1

6 Def Stan Def Stan Def Stan Def Stan Requirements for non-destructive examination methods Part 2: Magnetic particle Part 3: Eddy current Part 4: Liquid penetrant Part 5: Ultrasonic Classification, inspection requirements and acceptance standards for castings Minimum non-destructive examination acceptance standards for welds in HM submarines and surface ships not in class Requirements for the classification, dimensions, tolerances and general standards of acceptance for copper and nickel alloy castings 3.2 Reference in this Standard to any normative references means in any Invitation to Tender or contract the edition and all amendments current at the date of such tender or contract unless a specific edition is indicated. Care should be taken when referring out to specific portions of other standards to ensure that they remain easily identifiable where subsequent amendments and supersession s might be made. For some standards the most recent editions shall always apply due to safety and regulatory requirements. 3.3 In consideration of clause 3.2 above, users shall be fully aware of the issue, amendment status and application of all normative references, particularly when forming part of an Invitation to Tender or contract. Correct application of standards is as defined in the ITT or contract. 3.4 DStan can advise regarding where to obtain normative referenced documents. Requests for such information can be made to the DStan Helpdesk. Details of how to contact the helpdesk are shown on the outside rear cover of Defence Standards. 4 Definitions For the purpose of this standard definitions contained in BS and BS EN are to apply to the relevant terms used in this Def Stan. The following additional definitions are also to apply: 4.1 Design Authority The body that has overall responsibility for the system concerned. 4.2 Examining Authority The Company, Organisation, Establishment or Naval Base that carries out the radiographic examination within the scope of this Part. 4.3 Multiple Film Technique A procedure in which two or more films of the same or different speed with the relevant intensifying screens are used in the same film holder. 4.4 Material Thickness The thickness of the material presented for radiographic examination. 4.5 Maximum Effective Radiation The maximum source or focal dimension projected on the Source Dimension centre of the radiographic film. 5 Acceptance Standards The standards for acceptance of defect indications detected by radiographic examination are to be specified in the Contract; where not specified therein, Def Stan , Def Stan or Def Stan is to apply as appropriate. 2

7 6 Inspection a) It is not the intent of this part of Def Stan to exclude proven radiographic inspection procedures which can be demonstrated to meet the quality requirements. However, prior Design Authority approval is to be obtained before such procedures are used. b) Unless otherwise specified in the Contract, acceptance radiography is to be performed after final heat treatment. c) The material thickness at final acceptance radiography is not to exceed the finished thickness of the section under examination by more than 20% or 6 mm whichever is the greater. 7 Approval Requirements 7.1 Personnel Qualification a) The Examining Authority is to ensure that all personnel associated with radiographic examination have been adequately trained to the levels (Level 1, 2 and 3) appropriate to their responsibilities and maintain records accordingly; personnel should have a certificate from a nationally or internationally accredited scheme in accordance with BS EN ISO 9712, e.g. PCN or equivalent. b) Personnel performing and interpreting radiographic examinations are to be able to carry out an operational test radiograph using the test method or technique to be used in production. The Examining Authority is to be able to interpret the results and be familiar with the standards to which they are working. Personnel are to be considered qualified when they have demonstrated their ability to meet the requirements of the approved procedure. c) Level 1 operatives must have demonstrated their competence to carry out NDT according to written instructions and under supervision of a Level 2 or Level 3 personnel. Within the scope of the competence defined on the certificate, Level 1 personnel may be authorised by the employer to setup the equipment, perform the tests, record and classify the results in terms of written criteria, report the results. Level 1 personnel shall not however be responsible for the choice of test method or technique to be used, nor the assessment of the test results. d) Level 2 operatives must have demonstrated their competence to carry out NDT according to established or recognised procedures. Within the scope of the competence defined on the certificate, Level 2 personnel may be authorised by the employer to the same as a Level 1 operative but additionally to; select the NDT technique, define the limitations of the test method, translate NDT standards, setup and verify equipment settings, perform and supervise tests, prepare written instructions, carry out and supervise all tasks at or below Level 2, provide guidance for personnel at or below Level 2, organise and report the results of tests. e) Level 3 operatives are qualified to direct any NDT for which they are certificated and may be authorised by the employer to undertake all Level 1 and Level 2 duties, and additionally to; take full responsibility for a test facility and staff, establish and review NDT written instructions and procedures, designate test methods and techniques, interpret codes, standards and specifications, provide guidance and supervision at all levels. Level 3 personnel are to have demonstrated their competence to interpret and evaluate test results in terms of existing standards and specifications, and to possess the required level of knowledge in materials, fabrication and product technology to enable the appropriate selection of NDT methods and techniques, to assist the establishment of non-standard NDT test criteria and procedures. f) A register of approved personnel shall be kept by the Examining Authority. 3

8 7.2 Radiographic Procedures a) Design Authority approval of radiographic procedures is to be obtained prior to radiographic examination of production items. Radiographic and film processing procedures are to form a part of the standard procedure approval. b) Separate procedures are to cover the requirements for the radiographic examination of structural welding, castings, forgings and pipe welds. c) The relevant Contract Documents are to define the extent of the radiographic examination; the number of areas and items to be radiographed; the stage in fabrication when this is to be performed (if different from that stated in 6b); the quality level of inspection and the appropriate acceptance standards that are to be applied. d) Materials are to be grouped in accordance with Table 1. For materials having substantially different radiographic absorption characteristics from those in Groups 1, 2 and 3 (see Table 1) procedure approval is to be related to reference samples simulating production requirements. Table 1 Material Grouping For Radiographic Procedures Group No 1 Typical Metals/Alloys Carbon, low alloy, high alloy steels, including stainless steels; nickel chromium iron alloys; nickel aluminium bronze 2 Copper; copper nickel alloys; gun metal; nickel copper alloys 3 Light metals, e.g. aluminium, magnesium 4 Titanium and titanium alloys e) Radiographic procedures are to reference all relevant document, specification and acceptance standards. The procedures are to be recorded and maintained by the Examining Authority for audit purposes. f) Radiographic procedures are to cover all pre-requisites and technical requirements associated with the relevant application and are to contain specific guidance information included the following: 1) Type of production item, e.g. welds, castings etc 2) Material group; 3) material; 4) method of marking radiographic and production items; 5) X-ray equipment information: i) focal spot size; ii) tube voltage (expressed as kv); iii) tube current (expressed as ma); 6) isotope information: i) type of isotope; ii) source dimensions; 7) type of film cassettes and type of film; 8) type and thickness of intensifying screens; 9) type of IQI, location and required film sensitivity; 4

9 10) object to film distance FSD or FFD; 11) radiation direction and film disposition; 12) film image density; 13) film processing technique; 14) film viewing facilities. g) All radiographic examinations are to be recorded in a radiographic report in which the following information is to be recorded. An example of a radiographic report data sheet, showing the typical information to be recorded, is illustrated in Figure 1. 1) relevant radiographic procedure; 2) name(s) of qualified operators; 3) description of the component, location, material and thickness; 4) contractual details; 5) radiographic technical details; 6) film coverage; 7) date, place and time of examination. h) The radiographic procedure is to be re-approved in accordance with 7.2a to 7.2g if; 1) the Design Authority has reason to believe that: the Examining Authority cannot meet the required radiographic quality levels in production radiography using the previously approved procedure; 2) an isotope of larger physical size, or X-ray tube of larger focal spot size, than that used in the approved procedure is to be used, unless the source-to-film distance (SFD) or focus-to-film distance (FFD) is maintained within the limits of Figure 2; 3) there is a change in the type of isotope source used; 4) the X-ray equipment voltage is greater than that used during initial qualification and greater than the maximum value permissible in Figures 3 and 4 for the material thickness under examination; 5) there is a change in the type of film; 6) there is a reduction of the FFD or SFD below the minimum shown in Figure 2 unless inaccessibility prevents compliance; (in the latter case, the Examining Authority is to verify that the greatest possible FFD/SFD is used and that the radiographic record shows that accessibility limits the FFD or SFD); 7) there is an increase in the thickness of intensifying screens beyond the thickness qualified and beyond the maximum permitted by Table 2; 8) there is a change in the type of intensifying screen material used. 7.3 Radiographic Equipment Qualification Radiographic test equipment is to be capable of consistently producing radiographs to the required Quality in accordance with this Def Stan and an approved written procedure. 8 Surface Preparation Accessible surfaces of castings and welds to be radiographed are to be dressed as necessary to prevent the occurrence of indications on the radiographs resulting from weld beads, ripples, slag, scale and other surface irregularities which could interfere with the interpretation of the radiographs. Such dressing is to be in accordance with limitations in Def Stan and Def Stan for casting surfaces and Def Stan for weld surfaces. 5

10 Procedure No Issue No Date Company Procedure drafted by Approved by Radiographed by COMPONENT DESCRIPTION Title Drg No Material Spec No Location TECHNIQUE DETAILS 1. Radiation Source X-ray KiloVoltage Anode current Effective source-size Exposure time Equipment manufacturer Radiographic Report No Contract Order No Material Casting/Forging/Weld/Other Thickness Gamma-ray Isotope ma/source strength mm x mm Model or Type 2. Geometry Source film distance mm Principal beam angulation to normal Area examined size mm x mm IQI Type Location Required sensitivity % Sensitivity achieved % 3. Photographic Details Film: Make Type Size mm x mm Screens Type Thickness Backscatter control Block medium Processing: Type Time Temp Density required Density achieved 4. Coverage No of films Marking system etc, shown separately in attached sketch 5. Acceptance Standard Specification 6. Other information 7. Results of examination Shooting sketches to be added as necessary. Figure 1 Example of a Radiographic Report data sheet 6

11 FFD/SFD per mm source size Material Thickness (mm) Figure 2 Minimum Focus/Source-to-Film Distance v Effective Source Size 9 Radiation Sources 9.1 Gamma-Ray Isotopes a) The following gamma-ray isotopes may be used: 1) Thulium (Tm) 170 2) Iridium (Ir) 192 3) Caesium (Cs) 137 4) Cobalt (Co) 60 5) Ytterbium (Yb) 169 6) Selenium (Se) 75 The use of any other gamma radiation sources requires specific Design Authority approval. 7

12 9.2 X-Ray Sources X-ray sources may be used providing the values of the kilovolts against material type and thickness complies with those recommended in Figures 3 and 4. SELENIUM 75 Figure 3 Recommended X-ray voltages and radioisotope sources for use with steels and similar alloys 2% sensitivity level 9.3 Thickness Limitations Guidance regarding X-ray voltage and gamma-ray sources to be used with various specimen thicknesses for optimum radiographic results is given in Figures 3 and 4 is not to be taken to imply that on these thicknesses the flaw sensitivity with gamma-rays is equivalent to that with X-rays. In general, any gamma-ray technique will be less sensitive than an X-ray technique for material thickness of less than 50 mm. On material thickness 50 mm and greater the difference in sensitivity is less marked and is dependent upon the actual gamma ray technique used. 8

13 Figure 4 Recommended x-ray voltages and radioisotope sources for use with copper base and similar alloys 2% sensitivity level 9.4 Source Dimensions A cylindrical isotope source whose length is greater than its diameter will have a greater effective radiation sources dimension when orientated coaxially in the centre of a pipe for a panoramic exposure than when the axis of the source is positioned at right angles to the pipe. For a focal spot projected as a square image the diagonal of the square is to be used for calculation. 9

14 10 Production Radiography 10.1 Direction of Radiation Whenever appropriate, the radiation beam is to be directed perpendicular to the external surface and/or axis of the section under examination. Beam angling is, however, permissible where required to determine the type, location and/or dimensions of a defect Image Quality Level Radiography is to be performed with a technique, which will distinguish the acceptable Image Quality Indicator, (IQI) (see Section 14). Radiography quality level is to be determined by using one or more of the IQIs referred to in Figure 5. Unless otherwise specified, 2% IQI sensitivity is to be used as a standard for evaluating radiography quality for materials up to and including 50 mm thick, and 1% above this thickness. NOTE For a particular thickness the IQI sensitivity provides a means by which the quality of radiographic techniques may be compared Screens and Filters Radiographic procedures that use either a gamma source, or an X-ray source of 120 kv or greater, are to include front and back screens in accordance with Table 2 and the notes that are applicable. Screen surfaces are to be free of blemishes which may produce spurious indications in the resultant radiograph Film Whenever gamma radiography is used radiographs are to be made on fine grain or ultra-fine grain, high contrast, safety base film Film Quality Radiographs presented for interpretation are to be free from blemishes or film defects which might mask, or be confused with, defects in the material being examined. If doubt exists concerning the true nature of an indication on the film, the radiograph is to be rejected. Typical blemishes are as follows: a) fogging caused by light leaks in the processing room or cassettes, or by defective safelights or marks caused by improper processing, or by use of old film; b) mechanical processing defects such as streaking, air bubbles or water marks or chemical stains; c) pressure or lead marks, scratches, gouges, finger marks, crimp marks or static electricity marks; d) loss of detail caused by poor film-to-screen contact in localised areas Cassettes a) Cassettes may be rigid or flexible types with the exception of Ytterbium 169 technique. They are to be light tight and able to maintain close film-to-screen contact. b) For Ytterbium 169 radioisotope sources only, plastic cassettes/film holders are to be used. Vacuum loading techniques are preferred to ensure positive screen to film contact. 10

15 SPECIMEN THICKNESS WIRE NUMBER NOTE Where a sensitivity value for a given thickness falls between two wire numbers the smaller number is to be used. Figure 5 Selection of IQI wire number for percentage sensitivity: WIRE TYPE BS EN

16 Table 2 Screens and Filters Radiation Screen Material Screen Thickness Front (mm) Back (mm) X-rays below 120 kv Lead none 0.1 minimum X-rays 120 to 250 kv Lead to minimum X-rays 250 to 400 kv Lead 0.05 to minimum X-rays 1 to 8 MeV Lead or Copper 1 to to 1.6 X-rays above 8 MeV Lead, Tantalum or Tungsten 1 to 1.6 None Gamma-rays Ir 192 & Cs 137 Lead 0.05 to minimum Gamma-rays Co 60 Lead, Steel or Copper 0.5 to to 1.0 Gamma-rays Tm 170 Lead 0.05 to minimum Gamma-rays Yb 169 Lead NOTE 1 Intensifying Screens. Intimate contact between the screens and the film is to be maintained during exposure. The use of fluorescent screens requires specific approval of the Design Authority. NOTE 2 Back Filters. Lead filters are to be used behind the film holder to prevent scattered radiation from the floor, walls, air or surrounding objects from fogging the film. Each film holder is to have a lead letter 'B', a minimum of 12 mm high and a minimum of 1.5 mm thick, fastened to the back of the film holder within the area of film to be read. The image of this letter B showing a light image on a darker background is to be cause for rejection of the radiograph. NOTE 3 For Cobalt 60 the use of copper or steel screens produces the best flaw sensitivity but a longer exposure time is required than with lead screens (in the order of 2 to 1). NOTE 4 Below 5 mm material thickness, image quality is improved by the omission of lead screens 10.7 Film Density The optical density of individual films is normally to be between 2.0 and 3.0 in the area being examined. Densities in excess of 3.0 may be accepted for viewing only if adequate high intensity viewing facilities are available Multiple-Film Technique When the thickness of the part varies considerably in the area under examination, two or more films, of either equal or different speeds as employed during procedure qualification may be exposed simultaneously in the same film holder and the resultant radiographs submitted for interpretation as single films. This technique is to employ the use of a centre screen placed between the films to be exposed in addition to the required front and back screens Filmless Techniques The use of filmless techniques is to be limited to 'in process' inspection and is to be subject to the prior approval of the Design Authority Focus/Source to Film Distance a) The minimum focus or source-to-film distance (FFD or SFD) is to be in accordance with Figure 2 which is applicable to all techniques except double-wall double-image radiography of pipe welds using gamma-rays to which Table 3 applies. 12

17 b) The geometric image unsharpness (Ug) assumes greater importance as the distance between defect and film increases and therefore this distance is to be kept at a minimum for optimum assessment of defect. Further exposures may also be required for this purpose. The use of longer SFD may improve definition. The Ug value is not to exceed the inherent unsharpness of the film-screen combination for the type of radiation used, as defined in BS EN c) The FFD or SFD is to be compatible with the minimum sharpness value obtainable and any practical limitations that prevent the latter being achieved are to be indicated in the radiographic procedure as submitted for approval. Table 3 Source to film distance for the radiography of pipe welds using gamma rays and double-wall double-image technique Outside Dia. of Pipe mm NOTE 1 NOTE 2 Source-To-Film Distance As A Multiple Of The Outside Diameter Cylindrical Source Size And Orientation Used 0.5 mm x 0.5 mm 1 mm x 1 mm 1.3 mm x 1.3 mm 2 mm x 2 mm End on Side on End on Side on End on Side on End on Side on Cut-off point for double-wall double-image technique The figures in the above table are based on geometric unsharpness values not exceeding 0.25 mm. Wherever possible the longer source-to-film distance is used. d) The following factors are also to be taken into account in SFD calculations: 1) the film is to be located as close to the item being examined as possible; 2) where a gap unavoidably exists between the film and the item the maximum gap width is to be added to the specimen thickness for the calculation of the SFD; 3) all calculations are to be based on the maximum effective source dimensions. For a focal spot or source projected as a rectangle the effective dimension is the length of the diagonal of the rectangle, i.e. effective dimension = X² + Y² mm where X and Y are lengths of rectangle sides; 4) the effective dimension for a focal spot projection consisting of divided images is the diameter of the smallest circle circumscribing both images; 5) the effective size of the focal spot for each X-ray tube is to be established using the pinhole method and checked at least once per year throughout its working life; 6) for double-wall single-image radiography the material thickness to be used for the calculation of the minimum SFD is the thickness of the wall to be examined plus the thickness of the backing strip if featured; 7) for double-wall double-image radiography the material thickness to be used for the calculation of the minimum SFD is the maximum dimensions between the specimen surface and the film, i.e. the outside diameter of the pipe irrespective of the pipe wall thickness; 8) for steel greater than 50 mm in thickness reference is to be made to BS EN

18 10.11 Diagnostic Film Length a) The diagnostic film length of the weld or part under examination is to be such that the thickness of the material at the extremities of the exposed area measured in the direction of the incident beam at that point does not exceed the actual thickness (T) at that point by more than the relevant value stated below: 1) X-ray techniques with ultra-fine grain and fine grain high contrast direct-type film i) maximum incident thickness = T + 6% 2) X-ray techniques with medium speed direct-type film i) maximum incident thickness = T + 10% 3) Gamma-ray techniques with ultra-fine grain and fine grain high contrast direct-type film i) maximum incident thickness = T + 10% b) The diagnostic film length for pipe welds, pipes and castings of small radius and with thickness variation will generally determine the number of exposures required for full coverage of the weld examined Radiograph Location Markers The images of the location markers used to correlate the part with the film are to confirm complete coverage without interfering with the interpretation. Marker positions are to be marked on the part and maintained on the part throughout radiography. When radiographing a weld, the edge of the marker image is to be approximately 3 mm from the edge of the weld wherever possible Film Identification A system of positive identification of the film and the IQI type used is to be provided. a) The following information is to appear on each radiograph: 1) identification of the organisation making the radiograph; 2) identification code letters related to b.1 where space permits; 3) a unique identification number; 4) a suffix letter R to denote a repair radiograph where applicable followed by the number of the repair, e.g. R2, R3 etc. b) The above information is also to appear in the records that accompany each radiograph together with: 1) identification of the item, part, component or system, and where applicable, the weld joint; 2) details of the radiographic technique used and date of exposure. 11 Storage of Radiographs and Radiographic Records a) Radiographs and radiographic records are to be retained for seven years from completion of a fixed term contract. Where work is performed under a continuing contract, or on other than a contractual basis, these are to be retained for seven years from the date on which the work was performed. Technique details including radiographic inspection location sketches, evaluation and disposition sheets are to be included in the records retained. At the end of the seven-year period, the organisation is to ask the relevant MOD project team for instructions on disposal or further storage and act accordingly. b) Should radiography be performed by a subcontractor to the Prime Contractor, in addition to supplying the QA documentation required by the Prime Contractor s order, the subcontractor is to provide those radiographs and radiographic records, including technique details; radiographic inspection location sketches; evaluation and disposition sheets. 14

19 c) All radiographs and radiographic records are to be made available to the Design Authority on request. No radiographs or radiographic records are to be disposed of without the written authorisation of the Design Authority. 12 Darkroom Facilities Darkroom facilities, including equipment and materials, are to be capable of producing uniform, blemish-free radiographs and of controlling film processing procedures in accordance with the recommendations of the manufacturers. Records are to be maintained for the purpose of assuring control of the life and quality of the photographic solutions and the effectiveness of the safelight conditions. 13 Film Viewing Facilities a) Radiographs are to be examined by diffused light in a darkened room or cubicle that is suitable for this purpose. b) Viewing facilities and background lighting are to minimise reflection on the radiographs. c) Equipment used for radiographic interpretation is to include the following minimum requirements: 1) controllable light source of sufficient maximum intensity to allow the selection of optimum intensities for viewing the ranges of film densities specified in The light enclosure is to be so designed as to provide a uniform level of illumination over the entire viewing surface. The required light intensity for viewing film densities over 3.0 may be provided by the use of a separate high intensity viewing port. Film damaged owing to exposure to heat is to be rejected and repeat radiography carried out; 2) the provision of a suitable fan or blower or other cooling device, and limitation of the time of contact of the film with the viewing port in order to avoid film damage caused by excess heat at the viewing port of high intensity viewers; 3) masking facilities to suit the sizes of radiographs to be viewed; 4) densitometers to ensure compliance with the film density requirements of Interpretation of Radiographs a) To assist in the proper interpretation of radiographs a sketch or drawing and written technique or equivalent record, as per 7.2g, is to be prepared to show the arrangement used to make each radiograph. This information is to accompany each relevant radiograph, or group of radiographs. Reference to a standard arrangement is to be acceptable if details of the standard arrangements are made available. The required information is to include, where applicable: 1) number of films; 2) location of each film on the radiographed item. The film position is to be recorded relative to the film centre marker and some fixed datum; 3) orientation of location markers. The preferred arrangement for weldments is shown in Figure 6; 4) location of radiation source, including source-to-film distance and angle of beam; 5) type of weld and weld history; 6) whether original weld or repair; 7) part and drawing number; 8) details of visible surface imperfections. 15

20 NOTE 1 The IQI is to be placed at one or both ends of each section to be radiographed. The wires are to lie transversely across the weld with the thinnest wire remote from the centre of the radiation beam. NOTE 2 Marker arrows that denote the length of weld under examination may also be used to point to the appropriate IQI wire corresponding to the sensitivity value required. NOTE 3 Wherever possible the minimum overlap of radiograph is to be 35 mm. For pipe welds adequate coverage is to be demonstrated. Figure 6 Method of marking welds for radiography b) Interpretation of radiographs is to be carried out only by personnel with the necessary qualifications and experience to do so (see 7.1a). Radiographs are to be examined and interpreted by the Examining Authority to assure compliance with the requirements of this Def Stan. The terminology used in the report of interpretation of weld defects is to be that recommended in BS 499 Part 1 and BS EN The terminology for internal defects in castings is to be that recommended in BS Image Quality Indicators 15.1 General Wire type IQIs complying with BS EN are to be used to assist in determining the quality level of all radiographs (see Figure 5). 16

21 15.2 IQI Materials Selection of IQI material is to be made as follows: a) materials are grouped in accordance with Table 1, the correct IQI series for each material group under examination is given below and is to be used wherever possible. If the correct IQI is not available, then an IQI of a lower absorption coefficient, at the lowest energy level to be used, may be substituted provided the same measured quality level is attained; Material Group IQI Series 1 FE 2 CU 3 AL 4 TI b) for radiography of a material not covered by Table 1, an IQI may be used which is either manufactured from the same material or from another material whose radiographic absorption coefficient, at the lowest energy level to be used, is within 15% of that of the material under examination; c) for welds made between dissimilar metals in a single group per Table 1, the IQI for that group is to be used as in 15.2.a) above; d) for welds made between dissimilar metals not of the same group per Table 1, one IQI corresponding to the relevant group or of a lower absorption coefficient as in 15.2.a) is to be placed on each side of the joint; e) for welds with weld metal of a different group for the base material(s), an additional IQI corresponding to the weld metal composition or of a lower absorption coefficient as in 15.2.a) is to be used Wire Type IQI complying with BS EN Each material group is covered by four IQI models which together contain a series of 19 wires. Each IQI model contains seven wires numbered respectively 1-7, 6-12, and Wire diameters range from 3.2 mm (wire No 1) to 0.05 mm (wire No 19) IQI Identification IQIs are identified by a combination of symbols, which appear on the radiograph, e.g. 1 FE EN, 6 FE EN, 10 FE EN, 13 FE EN. The symbol denotes the number of the thickest wire, the material type and EN specification. 16 IQI Location a) One IQI is to represent an area within which radiographic densities do not vary more than +30% to 15% from the density measured adjacent to the IQI. At least one IQI per radiograph is to be used except as specified in When the firm density variation is more than above, two IQIs used as follows will be satisfactory; if one IQI shows an acceptable sensitivity at the most dense portion of the radiograph and the second IQI, placed in accordance with the other required of the Def Stan, shows an acceptable sensitivity at the least dense portion of the radiograph, these two IQIs are to serve to qualify the radiograph within these density limits. b) The IQI is to be located on the source side of the section being examined wherever possible. c) For weld examination the IQI is to be placed at one or both ends of each length to be radiographed. The wires are to lie transversely across the weld with the thinnest wire remote from the centre beam. 17

22 d) For double-wall, double-image exposures (e.g. on pipe welds) the IQI is, where practicable, to be placed on the outside of the pipe across the weld nearest to the source of radiation. The selected wire is to be placed over the centre line of the weld. e) For double-wall, single-image exposures in which only the portion of the weld next to the film is viewed, the radiographic technique is to be demonstrated on a similar test section with the applicable IQI placed on the inside compared with an IQI placed on the film side. The demonstrated radiographs are to be identified and included with the production radiographs when these are presented for interpretation. f) Where a gap necessarily exists between the item under examination and the film, the IQI is to be placed on that part of the item furthest from the film. g) For circumferential pipe welds, the number and location of IQIs are to be in accordance with Table 4. h) For longitudinal pipe welds, one IQI is to be placed at each extremity of each film along the weld, and only the weld image that appears between the thinnest visible wires of the IQIs is to be assessed. Table 4 IQI Location for Circumferential Welds Radiation Passes Through One Wall Only Pipe Diameter Number Of Walls Viewed For Acceptance Number And Location Of IQIs 100 mm up to but not incl. 250 mm 250 mm and over 1 Radiation Passes Through Two Walls Under 100 mm 1 or mm up to but not incl. 250 mm 250 mm and over One IQI on the outside surface of the pipe on the source side, along the centre line of the pipe. If the length to be inspected is less than 125 mm, one IQI. If over 125 mm, two IQIs one at each extremity of the area to be inspected or one at the centre of the radiation beam and one at an extremity of the area to be inspected. One IQI on the outside surface of the pipe on the source side along the centre line of the pipe. See clause 16d. The IQI is to lie along the centre line of the pipe. Two IQIs, one at each extremity of the area to be inspected or one at the centre of the radiation beam and one at an extremity of the area to be inspected. 17 Welds with Overlay Cladding Radiography is to be performed on the completed base metal weld prior to cladding. 18 Simultaneous Exposures When a single film or series of films is exposed in a 360-degree radiation beam on a single component, a minimum of one IQI is to be located in each Quadrant. If multiple components or parts are exposed simultaneously, at least one IQI is to be required on each film plus where relevant, additional IQIs as required by 16g. 18

23 19 Radiography of Pipe Welds 19.1 Single-Wall Technique Exposures are to be made through a single-wall wherever practicable. The radiation beam is to be directed at the centre of the weld and normal to the pipe surface at that point. Additional beam directions may, however, be necessary to detect weld fusion face defects. The SFD is to be based on the single-wall thickness in accordance with Figure Double-Wall Single-Image Technique Exposures are made for the examination of the weld closest to the film. The radiation beam is to be directed through the centre of the section being examined and offset from the plane through the weld by the minimum distance necessary to avoid superimposing images. The film is to be placed diametrically opposite the radiation source in close contact with the weld. The SFD is to be in accordance with 10.10d6) and Figure 2. The IQI sensitivity is to be calculated relative to the single-wall thickness Double-Wall Double-Image Technique a) Exposures are made for the examination of both walls when double-wall single-image exposures are not practicable. The centre line of the radiation beam is to be directed through the centre of the pipe in the plane of the weld. The source of radiation is to be offset only by the minimum amount necessary to avoid superimposing images. The SFD is to be in accordance with 10.11a and Table 3. The IQI sensitivity is to be calculated relative to the double-wall thickness. At least three exposures will be required to cover a pipe butt joint in normal practice by this method, except where restricted access precludes compliance. b) Offset is not to be employed in the radiography of consumable root inserts. c) Generally, for pipework radiography, the recommendations in BS EN 1435 are to apply. Double-wall double-image exposures are to be restricted to pipes not exceeding 90 mm outside diameter unless otherwise specifically approved by the Design Authority 20 Radiography of Small Parts At the discretion of the Design Authority, IQIs may not be required on each film when radiographing small parts, or limited areas of larger parts, when location of the IQI on the part would obscure part or all of the area of interest and where it would not be practicable to place the IQI on a test section adjacent to the part. However, an initial technique, shot, with the applicable IQI on the part, is to demonstrate the specified IQI sensitivity. Subsequent exposure without an IQI is to be made only if exposed in the same manner as the technique shot. Whenever the arrangement is changed, additional technique shots are to be made in proper sequence to ensure that the process is being properly controlled. The technique shots are to accompany the subsequently exposed film when presented for interpretation. 21 Radiography of Repair Welds When weld repairs to welded joints and metallic materials including castings or forgings have been made, weld repair details are to accompany the radiographs when offered for review. The original radiographs of the previously defective area are also to be made available for review with the final acceptance radiographs. 19

24 22 Radiography of Castings In addition to the information required in 7.2g and Figure 1, casting radiographic reports are to include a suitable sketch or drawing which includes the following information: a) the classification of the casting and its unique identification; b) Critical Test Regions and Test Regions in accordance with Def Stan and Def Stan ; c) number of films and type; d) location of each film on the casting; e) location of markers; f) location of radiation source including angle and source-to-film distance relative to each film position; g) voltage or isotope type and strength; h) details of visible surface imperfections Techniques Radiography of Critical Test Regions is to be limited to single-wall techniques unless this is demonstrated to be impracticable and a double-wall technique is necessary. Test Regions may be examined by double-wall single-image and double-wall double-image techniques. Defects shown by double-wall exposures may require additional radiography to establish the severity of the defects relative to single-wall thickness Technique Shot Films The production of films on the first casting, are to be used to demonstrate the adequacy of the radiographic technique. The Design Authority or contractor as agreed is to approve the procedure when satisfactory quality is obtained on all films and the extent of coverage required by the applicable specification or drawings has been obtained. 20

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26 Crown Copyright 2013 Copying Only as Agreed with DStan Defence Standards are published by and obtainable from: Defence Equipment and Support UK Defence Standardization Kentigern House 65 Brown Street GLASGOW G2 8EX DStan Helpdesk Tel: 44 (0) /2 Fax: 44 (0) Internet File Reference The DStan file reference relating to work on this standard is D/DStan/69/2/729/1. Contract Requirements When Defence Standards are incorporated into contracts users are responsible for their correct application and for complying with contractual and statutory requirements. Compliance with a Defence Standard does not in itself confer immunity from legal obligations. Revision of Defence Standards Defence Standards are revised as necessary by an up issue or amendment. It is important that users of Defence Standards should ascertain that they are in possession of the latest issue or amendment. Information on all Defence Standards can be found on the DStan Website updated weekly and supplemented regularly by Standards in Defence News (SID News). Any person who, when making use of a Defence Standard encounters an inaccuracy or ambiguity is requested to notify UK Defence Standardization (DStan) without delay in order that the matter may be investigated and appropriate action taken. Sponsors and authors shall refer to Def Stan before proceeding with any standards work.