BS M 34-1970 Method of preparation and use of radiographic techniques《X光射线照相技术的准备工作和使用方法》.pdf

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1、BRITISH STANDARD AEROSPACE SERIES BS M 34:1970 Incorporating Amendment No. 1 Method of preparation and use of radiographic techniques ICS 49.020 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS M 34:1970 This British Standard, having been prepared under the direction of the A

2、erospace Industry Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 13 December 2001 BSI 13 December 2001 The following BSI references relate to the work on this British Standard: Committee reference ACE/56 Draft for comment 68/

3、22114 DC ISBN 0 580 05699 6 Amendments issued since publication Amd. No. Date Comments 13184 13 December 2001 Indicated by a sidelineBS M 34:1970 BSI 13 December 2001 i Contents Page Foreword ii 1 General requirements 1 2C a s t i n g s 3 3 Welding and brazing 5 4 Aircraft structures and sub-assembl

4、ies 6 5 Other applications 7 Appendix A Technique sheet 7 Appendix B Compensation for image unsharpness 9 Figure 1 Typical technique sheet 8 Figure 2 Diagram of image unsharpness geometrical factors 9BS M 34:1970 ii BSI 13 December 2001 Foreword This British Standard, prepared at the request of the

5、Aerospace Industry Committee, is one of a series within the Aerospace series on the non-destructive testing and inspection of aerospace materials, components and structures. Its objective is to provide a standardized approach to the devising, presentation and application of radiographic techniques.

6、Other standards in the series will cover magnetic particle, ultrasonic, etch and penetrant inspection techniques. The SI system of physical units has been adopted as standard. Equivalent imperial or C.G.S units are quoted in parenthesis. NOTE Information concerning SI units is given in BS 350, Conve

7、rsion factors and tables and also PD 5686, The use of SI units. This standard makes reference to the following British Standards: BS 2737, Terminology of internal defects in castings as revealed by radiography; BS 4000-1, Sizes of paper and board Part 1: Specification for A and B series of trimmed s

8、izes of writing paper and certain classes of printed matters; BS 4727-5:Group 01, Glossary of electrotechnical power, telecommunication, electronics, lighting and colour terms Part 5: Terms particular to electromedical equipment Group 01: Radiology and radiological physics terminology; BS EN 462-1,

9、Non-destructive testing Image quality of radiographs Part 1: Image quality indicators (wire type) Determination of image quality value; BS EN 462-2, Non-destructive testing Image quality of radiographs Part 2: Image quality indicators (step/hole type) Determination of image quality value; BS EN 462-

10、3, Non-destructive testing Image quality of radiographs Part 3: Image quality classes of ferrous metal; BS EN 462-5, Non-destructive testing Image quality of radiographs Part 5: Image quality indicators (duplex wire type), determination of image quality value; BS EN 1330-3, Non-destructive testing T

11、erminology Part 3: Terms used in industrial radiographic testing. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity

12、 from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 9 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Sidelining in this document indicates the most recen

13、t changes by amendment.BS M 34:1970 BSI 13 December 2001 1 1 General requirements 1.1 Scope All factors affecting the accurate repetition of a radiographic technique for the examination of a succession of similar material samples, components or structures are considered. A recommended standard forma

14、t for all techniques is given. For the various broad fields of radiography, viz, castings, welds, structures and other applications, specific requirements are laid down as appropriate to each case. Finally, consideration is given to the environmental and physiological conditions affecting the effici

15、ency of film interpretation by operators, and certain minimum conditions recommended. 1.2 Definitions For the purposes of this British Standard the definitions given in BS 4727-5:Group 01 and BS EN 1330-3 apply. 1.3 Identification of technique The radiographic technique shall be stipulated on the re

16、levant drawing or document by calling up “Radiograph to BS M 34 and technique No . . . ”. 1.4 Preparation of technique 1.4.1 The technique shall comprise sample radiographs accompanied by a technique sheet complying with the requirements of Appendix A. The technique sheet shall state the following c

17、onditions used to obtain the sample radiographs. 1) Apparatus used, type of radiation, source size. 2) Positions of source of radiation, component under examination and film, suitably illustrated by photographs or sketches. 3) Relating angles of 2). 4) Source-to-film distance (s.f.d.). 5) Kilo-volta

18、ge or isotope used. 6) Tube current or source strength. 7) Exposure time. 8) Thickness and material of filter used. 9) Thickness and material of intensifying screens. 10) Geometric unsharpness Ug. 11) Film used. 12) Size of film. 13) Processing conditions. 14) Specific requirements as applicable fro

19、m the relevant Section 1 to Section 5 of this British Standard. 1.4.2 The technique, once established, shall not be altered in any way other than by that which does not detract from the quality of the resultant radiograph. When an alteration is made to the technique the following points shall be con

20、sidered. 1) A change in film size may prejudice the value of the shot due to a change in angle of the beam at the extremities of the film. This may also apply when a change in s.f.d. is made. 2) When a change in source size is noted, the s.f.d. may have to be altered to compensate for the image unsh

21、arpness as indicated in Appendix B. 3) When a change of type of apparatus is made (e.g. half wave self-rectified to constant potential) it could give rise to a detrimental change of contrast for the same nominal kV. 4) If a film of alternative manufacture is used, the type should remain constant.BS

22、M 34:1970 2 BSI 13 December 2001 1.5 Identification 1.5.1 Each radiograph shall bear the radiograph number as given in the technique and such other details as will enable it to be fully identified (see Section 2, Section 3, Section 4 and Section 5). 1.5.2 Wherever practicable and necessary, markers,

23、 whose image will appear on the film, shall be placed on the surface of the component under examination and their locations shall be accurately marked on the component, in order that the orientation of the film may be established and any flaws appearing on the film may be precisely located. 1.5.3 Ca

24、re shall be taken that any marking on the component does not detract from the function of that component and that markers do not affect the interpretation of the radiograph. 1.6 Location of film The film shall be accurately located in accordance with the technique for the duration of the exposure. 1

25、.7 Image quality indicators Image quality indicators used shall comply with the requirements of BS EN 462-1, BS EN 462-2, BS EN 462-3 and BS EN 462-5 and shall be located in accordance with the technique. 1.8 Control of scattered radiation In all techniques the possibility of scattered radiation hav

26、ing an adverse effect on radiographs should be borne in mind and steps taken where necessary to eliminate or reduce this effect. Common methods of achieving this object are by the use of lead backing behind the film, lead masking and the use of tube cones or diaphragms. 1.9 Processing The processing

27、 used in the execution of the technique shall give similar contrast, densities and graininess (see Appendix B) to those on the radiographs supplied in the technique. 1.10 Artefacts Radiographs shall be free from artefacts that are prejudicial to their interpretation. 1.11 Viewing 1.11.1 Viewing shal

28、l be carried out in a room with subdued ambient light, the light not reaching the eye of the viewer either directly or by reflection from the radiograph. 1.11.2 The viewing room shall not be subjected to traffic or unnecessary noise that will disturb the concentration of the person viewing. 1.11.3 E

29、quipment used for viewing radiographs shall include the following minimum features. 1) Light sources of sufficient intensity, and suitably controlled to allow the selection of optimum intensities for discriminating the variations in film density on the sample radiographs. 2) A light enclosure so des

30、igned as to provide a uniform level of illumination over the viewing area. 3) Masking facilities to suit the areas of the radiographs to be viewed. 4) Densitometers to ensure compliance with the radiograph density requirements. 1.12 Interpretation of radiographs The method of manufacture of the obje

31、ct under examination and types of defects anticipated should be appreciated by all persons viewing the radiographs.BS M 34:1970 BSI 13 December 2001 3 1.13 Personnel 1.13.1 Visual requirements. It is essential that the eyesight of any person engaged on viewing radiographs is satisfactory for the tas

32、k. 1.13.2 Fatigue. Persons viewing who work steadily at the interpretation of radiographs will become fatigued due to the sustained concentration that is required. The length of time before a viewer suffers from fatigue will depend on numerous factors such as whether the person was mentally alert wh

33、en he started work and the viewing room condition, i.e. temperature, background lighting, freshness of the air and extraneous noises. It is therefore recommended that the following may be used as a basis for suitable conditions for the critical viewing of radiographs. 1) Mental and visual acclimatiz

34、ation of the person viewing to his environment. 2) Continuous viewing of radiographs, not more than 90 mins. 3) 30 min to 60 min rest from continuous viewing but doing other associated work, away from the viewing area. This cycle may be repeated such that not more than 6 h viewing is completed in on

35、e day. To obtain the best results, it is essential that the viewer should start fresh. 2 Castings 2.1 Information The radiographic technique for the examination of a casting shall record the following information. 1) Material and specification, from which the casting has been made. 2) Method of manu

36、facture, i.e. sand, gravity die, shell mould, etc. 3) Location of any “cast-in” inserts, machining lugs or tie bars, which the casting may contain. 4) Existence of any plates or plugs which may have been welded on after casting. 5) Existence of any cored jackets or oilways etc., which may be prone t

37、o obstruction or may require to be free from sand or flash. 6) Location of image quality indicators when these are required. This shall be shown on sample radiographs. 7) Details of any standards relating to the radiological acceptance of the casting, and an indication of any areas to which special

38、standards may apply. 2.2 Preparation of specimen Prior to radiographic examination, runners and risers and excessive flash should be removed from the casting, and any sand or dirt removed from the surface by abrasive blasting. Care shall be taken that all sand is removed from any cored pipes or pass

39、ages, and that these are finally left free from shot or other cleaning medium. Castings shall be dry and free from oil or grease. It may be necessary to fettle and polish the castings so as to remove surface irregularities, the images of which might tend to mask such effects as micro-porosity on the

40、 radiographs. Care shall be taken to avoid leak pick-up as particles may adhere to the castings, and give misleading indications on the radiograph. 2.3 Identification When several films are required for the examination of a large casting and if a casting is to be examined all over, there shall be ad

41、equate overlap between films. When overlap of adjacent radiographs is not self-evident from surface features on the casting, lead markers shall be positioned in accordance with 1.5.2 to verify that overlap has been obtained. Similarly when several small castings are examined on one film, it must eas

42、ily be possible to identify each casting from the radiograph. 2.4 Coverage Complete coverage shall be obtained on the entire casting or those areas of the casting that are required to be examined. The number of radiographs required for this purpose will depend upon size, complexity and variation in

43、section thickness.BS M 34:1970 4 BSI 13 December 2001 2.5 Radiographic sensitivity An IQI sensitivity of 2 % over all sections must be maintained, unless otherwise stated in the relevant technique. 2.6 Density An optimum density of 2 5 shall apply to sections of uniform thickness. Where changes of s

44、ection occur a density range of 1 to 4 is acceptable. 2.7 Use of a lead screens Lead screens having thicknesses in accordance with Table 1, shall normally be used for all exposures carried out at 120 kV or more, and may also be used to advantage at lower energies in reducing scatter. In this latter

45、case the front screen thickness should not exceed 0 05 mm (0 002 in). Table 1 Front lead screen thicknesses In general, all exposures at 120 kV or more should be made with lead intensifying screens, or with other metal foil screens giving similar results. 2.7.1 In all instances intimate contact must

46、 be maintained between screen and film. 2.8 Use of double films Subjects having a wide variation in section thickness may be examined by employing double films. Two films having different speeds are employed and the exposure conditions adjusted on that the thicker sections are recorded on the faster

47、 film and the thinner sections simultaneously on the slower film. The kilovoltage used will be determined by the thickest section to be covered, and for this reason the thickness range should not be too great or the contrast on the thinner sections may be too low. Intensifying screens may be used as

48、 recommended in 2.7 by employing an intermediate screen. One film is then loaded between the front and intermediate screen, and the other between the intermediate screen and back screen. The relative positions of the fast and slow films may be varied according to the result required, and in some cas

49、es one film only is enclosed between a pair of screens, the other film being placed nearer the source. Care must be taken to maintain intimate contact between screens and films, especially when they are enclosed in flexible cassettes 2.9 Filtration Filtration may be used provided the requirements of 2.5 are maintained. 2.10 Interpretation The information given in 2.1 should be considered when interpreting all radiographs, and the nomenclature for internal flaws in coatings, as given in BS 2737 shall be employed. Radiation