EN 12681-2-2017 Founding - Radiographic testing - Part 2 Techniques with digital detectors.pdf

《EN 12681-2-2017 Founding - Radiographic testing - Part 2 Techniques with digital detectors.pdf》由会员分享，可在线阅读，更多相关《EN 12681-2-2017 Founding - Radiographic testing - Part 2 Techniques with digital detectors.pdf（68页珍藏版）》请在麦多课文档分享上搜索。

1、BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06Founding Radiographic testingPart 2: Techniques with digital detectorsBS EN 12681-2:2017EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12681-2 November 2017 ICS 77.040.20 English Version Founding - Radiographic te

2、sting - Part 2: Techniques with digital detectors Fonderie - Contrle par radiographie - Partie 2 : Techniques laide de dtecteurs numriques Gieereiwesen - Durchstrahlungsprfung - Teil 2: Technik mit digitalen Detektoren This European Standard was approved by CEN on 16 July 2017. CEN members are bound

3、 to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN

4、-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre ha

5、s the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Lu

6、xembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-

7、1000 Brussels 2017 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12681-2:2017 ENational forewordThis British Standard is the UK implementation of EN 12681-2:2017. Together with BS EN 12681-1:2017 it supersedes BS EN 12681:2003, w

8、hich is withdrawn.The UK participation in its preparation was entrusted to Technical Committee ISE/111, Steel Castings and Forgings.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisi

9、ons of a contract. Users are responsible for its correct application. The British Standards Institution 2018 Published by BSI Standards Limited 2018ISBN 978 0 580 93114 7ICS 77.040.20Compliance with a British Standard cannot confer immunity from legal obligations. This British Standard was published

10、 under the authority of the Standards Policy and Strategy Committee on 31 January 2018.Amendments/corrigenda issued since publicationDate Text affectedBRITISH STANDARDBS EN 12681-2:2017EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12681-2 November 2017 ICS 77.040.20 English Version Founding -

11、 Radiographic testing - Part 2: Techniques with digital detectors Fonderie - Contrle par radiographie - Partie 2 : Techniques laide de dtecteurs numriques Gieereiwesen - Durchstrahlungsprfung - Teil 2: Technik mit digitalen Detektoren This European Standard was approved by CEN on 16 July 2017. CEN m

12、embers are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on applic

13、ation to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Mana

14、gement Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvi

15、a, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Aven

16、ue Marnix 17, B-1000 Brussels 2017 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12681-2:2017 EBS EN 12681-2:2017EN 12681-2:2017 (E) 2 Contents Page European foreword . 4 Introduction 5 1 Scope 6 2 Normative references 6 3 Terms

17、and definitions . 7 4 Symbols and abbreviations 13 5 Classification of radiographic techniques and compensation principles 14 5.1 Classification 14 5.2 Compensation principles 14 6 General preparations and requirements 15 6.1 Protection against ionizing radiation . 15 6.2 Surface preparation and sta

18、ge of manufacture . 15 6.3 Agreements 15 6.4 Personnel qualification 16 7 Test arrangements . 16 7.1 General . 16 7.2 Single wall radiography of plane areas 16 7.3 Single wall radiography of curved areas . 16 7.4 Double wall radiography of plane and curved areas 17 7.5 Choice of test arrangements fo

19、r complex geometries 17 7.6 Acceptable test area dimensions 17 8 Choice of tube voltage and radiation source 21 8.1 X-ray devices up to 1 000 kV 21 8.2 Other radiation sources . 23 9 Metal screens for IPs and shielding . 23 10 Reduction of scattered radiation 25 10.1 Metal filters and collimators 25

20、 10.2 Interception of backscattered radiation 26 11 Source object and detector position 26 11.1 General . 26 11.2 Source-to-object distance for magnification 1,4). Because of the better sensitivity compared to class A, the casting may be regarded as being examined to class B, if the correct IQI sens

21、itivity is achieved. This does not apply if the special SDD reduction as specified in Clause 11 for test arrangements Figure 3 and Figure 4 are used. 5.2 Compensation principles Three rules to be applied in this standard for radiography with digital detectors to achieve sufficient contrast sensitivi

22、ty. This requires achieving a minimum contrast-to-noise ratio, normalized to the detector basic spatial resolution (CNRN) per detectable material thickness difference w. If the required normalized contrast-to-noise ratio (CNRNper w) cannot be achieved due to an insufficient value of one of the follo

23、wing parameters, this can be compensated by an increase in the signal to noise ratio (SNR): CP I: Compensation for reduced contrast (e.g. by increased tube voltage) by increased SNR (e.g. by increased tube current or exposure time). CP II: Compensation for insufficient detector sharpness (the value

24、of SRbimagehigher than specified) by increased SNR (increase in the single IQI wire or step hole value for each missing duplex wire pair value). CP III: Compensation for increased local interpolation unsharpness, due to bad pixel correction for DDAs, by increased SNR. BS EN 12681-2:2017EN 12681-2:20

25、17 (E) 15These compensation principles are based on the following approximation for small discontinuity sizes (w 50 kV to 150 kV 70 120 0 to 0,1 (Pb) X-ray potentialsa 150 kV to 250 kV 70 100 0 to 0,1 (Pb) X-ray potentialsa 250 kV to 350 kV 50 70 100 0 to 0,3 (Pb) 50 70 70 0 to 0,3 (Pb) X-ray potent

26、ialsa 350 kV to 1 000 kV 50 70 100 0 to 0,3 (Pb) 50 70 70 0 to 0,3 (Pb) Ir 192a, Se 75a 50 70 100 0 to 0,3 (Pb) 50 70 70 0,1 to 0,4 (Pb) BS EN 12681-2:2017EN 12681-2:2017 (E) 25Radiation source Penetrated material thickness w mm Minimum SNRNType and thickness of metal front screens mm Class A Class

27、B Co 60 X-ray potentialsb,c 1 to 5 MV 100 70 100 0,3 to 0,8 (Fe or Cu) 0,6 to 2 (Pb) 100 70 70 X-ray potentialsb,c 5 MV 100 70 100 0,6 to 4 (Fe, Cu or Pb) 100 70 70 aPb screens may be replaced completely or partially by Fe or Cu screens. The equivalent thickness for Fe or Cu screens is 3 times the P

28、b thickness. bIn the case of multiple screens (Fe + Pb) the steel screen shall be located between the IP and the lead screen. cInstead of Fe or Fe + Pb also copper, tantalum or tungsten screens may be used if the image quality can be proven. Table 4 Minimum SNRNvalues (CR and DDA) and metal front sc

29、reens (screens for CR only) for the digital radiography of aluminium, magnesium and zinc Radiation source Minimum SNRNType and thickness of metal front screens mm Class A Class B X-ray potentials 150 kV 70 120 0,03 (Pb) X-ray potentials 150 kV to 250 kV 70 100 0,2 (Pb)aX-ray potentials 250 kV to 500

30、 kV 70 100 0,2 (Pb)aSe 75 70 100 0,3 (Pb)aaInstead of 0,2 mm lead, a 0,1 mm screen with an additional filter of 0,1 mm may be used outside of the cassette. 10 Reduction of scattered radiation 10.1 Metal filters and collimators In order to reduce the effect of scattered radiation, direct radiation sh

31、all be collimated as much as possible to the section under examination. With Se 75, Ir 192, Co 60 radiation sources or X-ray potentials above 120 kV, or in the case of edge scatter, a sheet of lead can be used as a filter of low energy scattered radiation between the test object and the cassette or

32、DDA. The thickness of this sheet is 0,5 mm to 2 mm in accordance with the penetrated thickness. A thin steel or copper screen should be positioned between the lead sheet and the detector. BS EN 12681-2:2017EN 12681-2:2017 (E) 26 10.2 Interception of backscattered radiation It shall be ensured that t

33、he effect of backscattered radiation is minimized. The presence of backscattered radiation shall be checked for each new CR test arrangement by means of a lead letter B (with a minimum height of 10 mm and a minimum thickness of 1,5 mm) placed immediately behind each cassette. If the image of this sy

34、mbol records as a lighter image on the digital image (negative presentation, i.e. decreased linearized grey value), it shall be rejected. If the symbol is darker (increased linearized grey value), or invisible, the digital image is acceptable and demonstrates good protection against backscattered ra

35、diation. If necessary, the detector shall be shielded from backscattered radiation by a sheet of lead of at least 1 mm thickness or a sheet of tin of at least 1,5 mm thickness, placed behind the detector. An additional shielding of steel or copper (about 0,5 mm thickness) shall be applied between th

36、e lead shield and the detector to reduce the influence of lead X-ray fluorescence radiation. No lead screens shall be used in contact with the back side of the detector for radiation energies above 80 keV. 11 Source object and detector position 11.1 General The minimum source-to-object distance fmin

37、depends on the source size or focal spot size d and on the object-to-detector distance b. The source size or focal spot size d shall be in accordance with EN 12543 or EN 12679. When the source size or focal spot size is specified by two dimensions, the larger shall be used. 11.2 Source-to-object dis

38、tance for magnification 1,5 For exposure geometries, except for those in Figures 2 b) and 3 b), the distance f shall be chosen so that the ratio of this distance to the source size d, i.e. f/d, is not below the values given by the Formulae (2) and (3): for class A: ( )2/37,5fbd(2) for class B: ( )2/

39、315fbd(3) where b is the distance given in millimetres (mm). If the distance b is less than 1,5 t, the dimension b in Formulae (2) and (3) and Figure 14 shall be replaced by the wall thickness t. For determination of the source-to-object distance fminthe nomogram in Figure 14 may be used. The nomogr

40、am is based on Formulae (2) and (3). For exposure geometries set on the basis of Figures 2 b) and 3 b), the distance f shall be chosen so that the ratio of this distance to the source size d, i.e. f/d, is not below the values given by Formulae (4) and (5): for class A: BS EN 12681-2:2017EN 12681-2:2

41、017 (E) 2737,5fbd t(4) for class B: 315fbd t(5) where t is the wall thickness to test, in millimetres (mm); b is the object-to-detector distance, in millimetres (mm). If the radiation source could be placed inside the test object to be radiographed (techniques shown in Figure 3) to achieve a more su

42、itable direction of exposition and when a double wall technique (see Figures 5 to 7) is avoided this method should be preferred. The reduction in minimum source-to-object distance should not be greater than 40 %. When the source is located centrally inside the test object and detector outside (panor

43、amic technique as shown in Figure 4) and provided that the IQI requirements are met, this percentage may be increased. However, the reduction in minimum source-to-object distance shall not be greater than 50 %. NOTE Both the inherent unsharpness (ui= 2 SRbdetector) of a digital detector system and t

44、he geometric unsharpness (uG) contribute to the total unsharpness (uT) in the image if not corrected by means of geometric magnification see Formula (6): 22T Giu uu= +(6) Therefore, it is recommended that the distance fminis increased to compensate for any additional unsharpness of the detector syst

45、em. BS EN 12681-2:2017EN 12681-2:2017 (E) 28 Class B Class A Key b object-to-detector distance in mm d source size in mm fminminimum source-to-object distance in mm NOTE This Nomogram does not apply for exposure geometries as shown in Figures 2 b) and 3 b). Figure 14 Nomogram for the determination o

46、f minimum source-to-object distance fminin relation to object-to-detector distance b and the source size d 11.3 Conditions for magnification 1,5 An obstacle to the application of CR and DDA systems for casting radiography is the large ( 50 m) pixel size of most digital detector arrays and most IP-sc

47、anner systems compared with the small grain size in film (which leads to film having very high spatial resolution). This difficulty can be circumvented by taking advantage of the unique property of DDAs to increase the SNRNcompensation principle II (CP II) in the image and/or the geometric magnification if needed. BS EN 12681-2:2017