English version. Central Secretariat: rue de Stassart 35, B Brussels

Transcription

1 Annex 1 EN 50445

2 EUROPEAN STANDARD EN NORME EUROPÉENNE EUROPÄISCHE NORM February 2008 ICS ; English version Product family standard to demonstrate compliance of equipment for resistance welding, arc welding and allied processes with the basic restrictions related to human exposure to electromagnetic fields (0 Hz GHz) Norme de famille de produit pour démontrer la conformité d un équipement pour le soudage par résistance, le soudage à l arc et les techniques connexes avec les restrictions de base concernant l'exposition des personnes aux champs électromagnétiques (0 Hz GHz) Produktfamiliennorm zur Konformitätsprüfung von Einrichtungen zum Widerstandsschweißen, Lichtbogenschweißen und artverwandten Prozessen in Bezug auf die bei der Exposition durch elektromagnetische Felder anzuwendenden Basisgrenzwerte (0 Hz GHz) This European Standard was approved by CENELEC on CENELEC members 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 application to the Central Secretariat or to any CENELEC 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 CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B Brussels 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 50445:2008 E

3 EN 50445: Foreword This European Standard was prepared by the Technical Committee CENELEC TC 26A, Electric arc welding equipment. The text of the draft was submitted to the formal vote and was approved by CENELEC as EN on The following dates were fixed: latest date by which the EN has to be implemented at national level by p ublication of an identical national standard or by endorsement (dop) latest date by which the national standards conflicting with the EN have to be withdrawn (dow) s This European Standard is to be read in conjunction with EN and EN The latter was prepared by the Technical Committee CENELEC TC 26B, Electric resistance welding. This European Standard has been prepared under mandates M/305 and M/351 given to CENELEC by the European Commission and the European Free Trade Association.

4 3 EN 50445:2008 Contents 1 Scope Normative references Terms and definitions Compliance criteria and exposure limits Background Equipment for use by the general public Equipment for occupational use Equipment for occupational use in a public area Exposure of persons wearing cardiac pacemakers or other medical implants Projectile risk Touch currents Compliance assessment General Measurement and calculation Time averaging Spatial averaging Assessment of equipment with pulsed or non-sinusoidal welding current Assessment of equipment with multiple welding current waveforms Assessment of EMF General considerations Electric field Magnetic field measurements to show compliance with reference levels Calculations to show compliance with reference levels Calculations to show compliance with basic restrictions Information to be supplied with the apparatus Marking Uncertainty of assessment Using uncertainty for comparison with limits Permissible expanded uncertainties...12 Annex A (informative) General public basic restrictions and reference levels...13 Annex B (informative) Occupational basic restrictions and reference levels...15 Annex C (informative) Example for general EMF information...17 Bibliography...18 Tables Table 1 Summation parameters...9 Table 2 Permissible expanded uncertainties...12 Table A.1 General public basic restrictions for electric, magnetic and electromagnetic fields...13 Table A.2 General public reference levels for electric, magnetic and electromagnetic fields...14 Table B.1 Occupational basic restrictions for electric, magnetic and electromagnetic fields...15 Table B.2 Occupational reference levels for time varying electric and magnetic fields...16

5 EN 50445: Scope This product family standard applies to equipment for resistance welding, arc welding and allied processes designed for use in industrial or domestic environments, including welding power sources, wire feeders and ancillary equipment, e.g. torches, liquid cooling systems and arc striking and stabilising devices. NOTE 1 Allied processes are for example resistance hard and soft soldering, resistance heating by means comparable to resistance welding equipment, electric arc cutting and arc spraying. The frequency range covered is 0 Hz to 300 GHz. This product family standard may be used to demonstrate compliance with the requirements of Directive 2006/95/EC [1] (needed for placing electric welding equipment on the European market), with regard to the limitation of human exposure to electromagnetic fields (EMF). There are additional requirements in the Directive, which are not included in this product family standard. NOTE 2 The Directive 2006/95/EC [1], Article 2, stipulates that the Member States take all appropriate measures to ensure that electrical equipment may be placed on the market only if, having been constructed in accordance with good engineering practice in safety matters in force in the Community. This product family standard may also be used for assessment regarding the requirements of Directive 2004/40/EC [3] on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (electromagnetic fields) or Recommendation 1999/519/EC [2] on the limitation of exposure of the general public to electromagnetic fields, provided that no other relevant field sources are present in close proximity. If other relevant field sources are present, additional assessment is necessary. NOTE 3 It should be noted that the supplier of specific equipment might not know the overall exposure environment in which the equipment is being used. This product family standard can only be used to assess human exposure from the specific equipment under evaluation when being used in accordance with the suppliers guidelines. NOTE 4 Assessment procedures for workplaces with multiple field-sources may be found in EN [7]. Other standards may apply to products covered by this product family standard. In particular this standard can not be used to demonstrate electromagnetic compatibility with other equipment; nor does it specify any product safety requirements other than those specifically related to human exposure to electromagnetic fields. NOTE 5 Procedures to demonstrate compliance are not specified for the whole frequency range. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN Generic standard to demonstrate the compliance of electronic and electrical apparatus with the basic restrictions related to human exposure to electromagnetic fields (0 Hz 300 GHz) EN Basic standard for the evaluation of human exposure to electromagnetic fields from equipment for arc welding and allied processes EN Basic standard for the evaluation of human exposure to electromagnetic fields from equipment for resistance welding and allied processes EN Arc welding equipment Part 1: Welding power sources (IEC ) EN Arc welding equipment Part 6: Limited duty manual metal arc welding power sources (IEC )

6 5 EN 50445: Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 action values magnitude of directly measurable parameters at which one or more of the specified measures in Directive 2004/40/EC [3] must be undertaken 3.2 arc welding power source equipment for supplying current and voltage and having the required characteristics suitable for arc welding and allied processes NOTE 1 An arc welding power source may also supply services to other equipment and auxiliaries e.g. auxiliary power, cooling liquid, consumable arc welding electrode and gas to shield the arc and the welding area. NOTE 2 In the following text, the term welding power source is used. 3.3 basic restrictions exposure limit values restrictions on exposure to electric, magnetic and electromagnetic fields that are based directly on established health effects and biological considerations 3.4 compliance boundary spatial border outside which any point of investigation is deemed to be compliant 3.5 EMF electric, magnetic or electromagnetic field 3.6 expert competent person skilled person person who can judge the work assigned and recognize possible hazards on the basis of professional training, knowledge, experience and knowledge of the relevant equipment NOTE Several years of practice in the relevant technical field may be taken into consideration in assessment of professional training. 3.7 induced current density (J) electromagnetic field induced current per unit area inside the body 3.8 industrial and professional use use intended only for experts or instructed persons 3.9 instructed person person informed about the tasks assigned and about the possible hazards involved in neglectful behaviour NOTE If necessary, the person has undergone some training.

7 EN 50445: magnetic flux density (B) magnitude of a field vector that is equal to the magnetic field strength H multiplied by the permeability µ of the medium B = µ H 3.11 point of investigation (POI) location in space at which the value of the E-field, H-field or power density is evaluated NOTE This location is defined in cartesian, cylindrical or spherical co-ordinates relative to the reference point on the EUT reference levels directly measurable quantities, derived from basic restrictions, provided for practical exposure assessment purposes NOTE Respect of the reference levels will ensure respect of the relevant basic restriction. If the reference levels are exceeded, it does not necessarily follow that the basic restriction will be exceeded resistance welding equipment equipment for supplying current and voltage and having the required characteristics suitable for resistance welding and allied processes 4 Compliance criteria and exposure limits 4.1 Background Reference levels are provided for practical exposure assessment purposes to determine whether the basic restrictions are likely to be exceeded. If the measured value exceeds the reference level, it does not necessarily follow that the basic restriction will be exceeded. In some situations, it may be necessary to show compliance with the basic restrictions directly, but it may also be possible to derive compliance criteria that allow a simple measurement or calculation to demonstrate compliance with the basic restriction. Often these compliance criteria can be derived using realistic assumptions about conditions under which exposures from a device may occur, rather than the conservative assumptions that underlie the reference levels. NOTE 1 The limit is the basic restriction. The exposure assessment results for the points of investigation specified in the basic standards EN and EN shall be below the relevant limits. For equipment designed exclusively for mechanized or robotic applications the points of investigation (reflecting the normal operator position for manual welding) defined in the basic standards EN and EN are not applicable. The manufacturer of this type of equipment shall define specific points of investigation. As the highest exposure from equipment covered by the scope of this standard is to be expected in the inductive near-field, summation effects of maximum exposure levels of various pieces of equipment, e.g. in the same factory, are unlikely to be significant. However, in the presence of other strong magnetic fields (from large transformers, large electrolytic cells, etc.), in situ measurements to evaluate summation effects at medium distances (a few metres) might be appropriate. Such additional measurements are not a requirement of this standard, but may be required by other national or international regulations. NOTE 2 Further guidance may be found in EN [7]. As there are different limits for general public or occupational exposure, the equipment documentation shall clearly state the intended use.

8 7 EN 50445: Equipment for use by the general public The manufacturer shall specify if the equipment is intended to be used by the general public. Arc welding equipment built in accordance with to EN shall be assessed for such use. Any equipment assessed for general public use may also be used in an occupational environment. If the environment in which the equipment is intended to be used is unknown, or not clear, the equipment shall be assessed for general public use. The basis for assessment shall be the values of basic restrictions or reference levels from the Recommendation 1999/519/EC [2]. It must be noted that the tables of values referred to in the following sections are explained and rationalised in the text of the Recommendation 1999/519/EC [2] and the associated notes adjoining the tables. The basic restrictions on the current density only apply to central nervous system tissues in the head and trunk. These exposure limit values may permit higher current densities in body tissues other than the central nervous system under the same exposure conditions. 4.3 Equipment for occupational use The manufacturer shall specify if the equipment is intended to be used only in an occupational environment (where the general public access is prohibited or regulated in such a way as to be similar to occupational use) by an expert or an instructed person. Arc welding equipment built in accordance with EN and resistance welding equipment can be assessed for such use. The basis for assessment shall be the exposure limit values or action values from Directive 2004/40/EC [3]. It must be noted that the tables of values referred to in the following sections are explained and rationalised in the text of the Directive 2004/40/EC [3] and the associated notes adjoining the tables. The exposure limit values on the current density only apply to central nervous system tissues in the head and trunk. These exposure limit values may permit higher current densities in body tissues other than the central nervous system under the same exposure conditions. If the limits specified above can not be complied with for some or all points of investigation, additional measures shall be defined which allow compliance (e.g. definition of a compliance boundary for occupational exposure, the use of protection devices, restrictions for manual use, etc.). If such special conditions are established, they shall be clearly stated in the instruction manual. 4.4 Equipment for occupational use in a public area If equipment could be used under occupational conditions, but in an area where also the general public may be exposed, then the exposure shall additionally be assessed against the general public requirements under the conditions expected for that exposure situation (e.g. at usual safety distances) or, alternatively, the conditions necessary for compliance shall be established during assessment. If special conditions (such as the definition of a compliance boundary for the general public) are established, these shall be clearly stated in the instruction manual. 4.5 Exposure of persons wearing cardiac pacemakers or other medical implants As the immunity of different types of pacemakers or other implants varies considerably, a risk assessment involving a responsible medical expert is necessary for every single case of user exposure. This risk assessment is not within the scope of this product family standard. A warning statement regarding this matter shall be included in the instruction manual. 4.6 Projectile risk The projectile risk from ferromagnetic objects in static magnetic fields shall be considered in the instruction manual if there is a magnetic flux density greater than 3 mt.

9 EN 50445: Touch currents The risk of touch currents generated by voltages induced in conducting structures at the workplace by electromagnetic fields due to the welding current is avoided by the application of general safety rules for electric welding, e.g. equipotential bonding and other measures, therefore no further evaluation is required. 5 Compliance assessment 5.1 General Measurement and calculation The measurements and/or calculations to demonstrate equipment compliance shall be made in accordance with the basic standards EN and EN Time averaging For occupational exposure the d.c. components of the magnetic flux density or field strength values should be averaged over a time interval of 8 h, taking into account the duty cycle of the equipment and the welding current sequence, as applicable [4]. For exposure to time-varying magnetic fields up to 10 MHz no averaging of induced current densities over time intervals is allowed. At frequencies below 100 khz no averaging is allowed for H and B values, at frequencies between 100 khz and 10 GHz averaging over any six-minute period is permissible, provided that the peak restrictions given in the notes to Table 2 of Recommendation 1999/519/EC [2] and Table 2 of Directive 2004/40/EC [3] are not exceeded Spatial averaging Generally the reference levels are intended to be spatially averaged values over the entire body of the exposed individual, but with the important proviso that the basic restrictions on localized exposure are not exceeded. This product family standard is used to assess mainly the exposure generated from the welding circuit, creating stimulation effects. The maximum exposure is localized on the part of the body nearest to the source. In this type of situation an approach based on the spatial averaging of non uniform field distributions underestimates the exposure and is not suitable to ensure that the localized exposure does not lead to exceeding the basic restrictions for induced current densities. Therefore spatial averaging shall not be applied to reference level based exposure assessment of stimulation effects due to fields generated by the welding circuit. For evaluation of exposure generated from sources other than the welding circuit (for example from microprocessors, radio communication systems, ancillary equipment) and assessment of thermal effects, spatial averaging of the field may be appropriate. For homogeneous models, induced current density values shall be averaged over any area of 1 cm 2. In the case of induced current density values obtained by numerical simulation using high resolution anatomic body models this area shall be limited to central nervous system tissues and shall not include other types of tissue. Therefore the resulting averaging area for heterogeneous models shall be smaller than or equal to 1 cm 2. For all 3D models the averaging area shall be perpendicular to the induced current flow.

10 9 EN 50445: Assessment of equipment with pulsed or non-sinusoidal welding current Assessment shall be made in accordance with the basic standards EN and EN If summation procedures are applied, the parameters given in Table 1 shall be used, as applicable. Table 1 Summation parameters General public exposure Occupational exposure ϕ I below ƒ coc RAD ϕ I above ƒ coc RAD ƒ coc Hz ƒ sco khz for B & H for J for B & H for J for B & H for J for B & H for H A m -1 b for B µt for H A m -1 d for B µt pi/ pi/ ,2 6,25 0,73/ƒ 0,92/ƒ pi/ pi/ ,4 30,7 where ϕ i is the phase angle of the weighting function; ƒ coc is the cut off frequency of the modelled (e.g. by RC circuit) frequency response of nervous cells; ƒ sco is the summation cut off frequency; b is the value to relate frequency components above ƒ sco to for stimulation considerations; d is the value to relate frequency components below ƒ sco to for thermal considerations; ƒ is the frequency of the spectral component to be summed, given in MHz. NOTE These values are taken from the Recommendation 1999/519/EC [2] and ICNIRP documents [5] and [6]. Alternatively the limits, reference levels and phases of the weighting functions for summation of spectral components can be approximated by first order filters, as specified in documents defining procedures to assess non-sinusoidal and pulsed signals [6]. Details and examples are given in the basic standards EN and EN The first order filter approach is applicable to both analytical and numerical methods as well as for field measurements Assessment of equipment with multiple welding current waveforms This type of equipment shall be evaluated in all relevant operation modes, e.g. arc welding equipment such as a MIG standard / pulse power source with constant d.c. and pulsed output current or an a.c. / d.c. MMA power source with constant d.c. and a.c. output current. The selection of relevant operation modes, as far as applicable, and test parameters shall be made in accordance with the basic standards EN and EN Assessment of EMF General considerations The EMF shall be assessed using one of the following methods. It is not necessary to demonstrate compliance using more than one method. However, if multiple operation modes have to be tested, different methods may be applied for these modes, e.g. measurements to show compliance with reference levels for d.c. mode and numerical simulation to show compliance with the basic restrictions for pulsed mode. Selection criteria for appropriate application of assessment methods are given in the basic standards EN and EN

11 EN 50445: Electric field In general, electric fields around electric welding equipment shall be taken into account. However, for most equipment the electric field strength can be considered to comply, without testing. This shall be verified by analysis of the technology used. If, by this analysis, electric fields are found to be significant, tests in accordance with generic standards or to the manufacturers own specifications shall be made Magnetic field measurements to show compliance with reference levels Measurements shall be made in accordance with the basic standards EN and EN For general public exposure, the basis for assessment of static and time-varying fields shall be the values provided in Table 2 of Recommendation 1999/519/EC [2]. For occupational exposure, the basis for assessment of static and time-varying fields shall be the values provided in Table 2 of Directive 2004/40/EC [3] Calculations to show compliance with reference levels Analytical and numerical calculations shall be based on welding current parameters and other data (e.g. equipment configuration and geometries). Assessment shall be made in accordance with the basic standards EN and EN For general public exposure, the basis for assessment of static and time-varying fields shall be the values provided in Table 2 of Recommendation 1999/519/EC [2]. For occupational exposure, the basis for assessment of static and time-varying fields shall be the values provided in Table 2 of Directive 2004/40/EC [3] Calculations to show compliance with basic restrictions Analytical and numerical calculations shall be based on calculated or measured field strengths. Assessment shall be made in accordance with the basic standards EN and EN The results used for induced current density assessment shall be those derived for central nervous system tissue in the head and trunk. For general public exposure, the basis for assessment of static and time-varying fields shall be the values provided in Table 1 of Recommendation 1999/519/EC [2]. For occupational exposure, the basis for assessment of time-varying fields shall be the values provided in Table 1 of Directive 2004/40/EC [3]. NOTE The basic restrictions for static fields in Table 1 of Recommendation 1999/519/EC [2] are magnetic flux density limits, therefore evaluation may also be performed by measurement. 6 Information to be supplied with the apparatus The manufacturer shall provide all necessary information with the product with regard to minimizing exposure. This shall include recommendations for correct installation, welding cable layout, minimum safety distances from the power source, the welding circuit, resistance welding guns and arc welding torches to the body and other relevant information such as special precautions which may be needed during maintenance and repair. The distance from the equipment, at which the assessment was carried out shall be given in the instruction manual.

12 11 EN 50445:2008 The distance from the equipment to a point beyond which the exposure value is less than 20 % of the permissible value shall be given in metres. NOTE Standards for workplace evaluation are under consideration in CENELEC TC 106X, which may require additional information, for example exposure quotients, to be provided for the user in the future. The instruction manual shall include general information for the user about EMF. An example is given in Annex C. If equipment is intended for professional use only, the instruction manual shall contain a warning that this equipment shall not be used by the general public as the EMF limits for the general public might be exceeded during welding. If there is a static magnetic flux density greater than 3 mt, a warning shall be given regarding the projectile risk from ferromagnetic objects. Users shall be informed of specific compliance boundaries, which deviate from normal use (represented by the points of investigations defined in the basic standards EN and EN 50505) and are established during the assessment process. In this case the manufacturer shall provide a document describing these specific compliance boundaries. Information on restrictions for use shall be made available to the user prior to purchase. 7 Marking If there is a risk that the basic restrictions could be exceeded, welding equipment shall be marked with appropriate safety symbols regarding hazards due to EMF. 8 Uncertainty of assessment 8.1 Using uncertainty for comparison with limits The concept of shared uncertainty budget shall apply to the assessment (both measurements and calculations). This means that the actual measured or calculated values shall be used for comparison with the permissible values, based on the relevant exposure guidelines. Uncertainty values shall be recorded but shall not be included in the comparison, provided that the expanded assessment uncertainty is less than or equal to that specified in Table 2, or if the assessment is proven to always overestimate the exposure (i.e. conservative result). The uncertainty of the assessment method applied shall be calculated as defined in the basic standards EN and EN If the expanded uncertainty is higher than the value specified in Table 2 and the assessment is not proven to always overestimate the exposure, the procedure given in the generic standard EN shall be applied. This method defines uncertainty penalties for the applicable limits which are calculated in accordance with Equation (1). m 1 L U p U m L (1) where L m is the assessed value; L is the applicable limit without consideration of assessment uncertainty; U p is the permissible expanded uncertainty, given in %, as defined in Table 2; U m is the expanded uncertainty of the assessment method applied, given in %.

13 EN 50445: NOTE If, for example, the permissible expanded assessment uncertainty is ± 40 % and the actual calculated expanded uncertainty of the applied assessment method is ± 50 %, the assessment results shall be compared to the applicable limits reduced by a factor of 0,91. In all cases, the assessment shall be made based on a representative sample of the equipment. 8.2 Permissible expanded uncertainties The expanded uncertainty of the assessment should be less than the values given in Table 2 except where it can be shown that because of the nature of the measurement environment, a higher uncertainty is appropriate. In this case the higher uncertainty shall be quoted and justified. Table 2 Permissible expanded uncertainties Frequency range Measurement Calculation < 10 khz + 58 %, - 37 % (± 4 db) ± 50 % 10 khz 1 MHz + 41 %, - 30 % (± 3 db) ± 50 % 1 MHz 30 MHz + 41 %, - 30 % (± 3 db) ± 40 % 30 MHz 1 GHz %, - 50 % (± 6 db) ± 40 % 1 GHz 30 GHz %, - 50 % (± 6 db) ± 50% When the uncertainties specified in Table 2 are asymmetric (e.g %, - 37 %) the values for possible underestimation shall be used for comparison. For combined assessment procedures, the higher value of permissible uncertainty shall apply.

14 13 EN 50445:2008 Annex A (informative) General public basic restrictions and reference levels The values of basic restrictions and reference levels, as specified in the Recommendation 1999/519/EC [2], Tables 1 and 2, on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz) are given in Tables A.1 and A.2 for information. Table A.1 General public basic restrictions for electric, magnetic and electromagnetic fields (0 Hz to 300 GHz) Source: Recommendation 1999/519/EC [2], Table 1 Frequency range Magnetic flux density Current density r.m.s. Whole-body average SAR Localized SAR (head and trunk) Localized SAR (limbs) Power density S mt ma m -2 W kg -1 W kg -1 W kg -1 W m -2 0 Hz 40 > 0 Hz 1 Hz 8 1 Hz 4 Hz 8/ƒ 4 Hz Hz Hz 100 khz ƒ/ khz 10 MHz ƒ/500 0, MHz 10 GHz 0, GHz 300 GHz 10 NOTE 1 ƒ is the frequency in Hz. NOTE 2 The basic restriction on the current density is intended to protect against acute exposure effects on central nervous system tissues in the head and trunk of the body and includes a safety factor. The basic restrictions for ELF fields are based on established adverse effects on the central nervous system. Such acute effects are essentially instantaneous and there is no scientific justification to modify the basic restrictions for exposure of short duration. However, since the basic restriction refers to adverse effects on the central nervous system, this basic restriction may permit higher current densities in body tissues other than the central nervous system under the same exposure conditions. NOTE 3 Because of electrical inhomogeneity of the body, current densities should be averaged over a cross section of 1 cm² perpendicular to the current direction. NOTE 4 For frequencies up to 100 khz, peak current density values can be obtained by multiplying the r.m.s. value by 2 (~1,414). For pulses of duration t p the equivalent frequency to apply in the basic restrictions should be calculated as ƒ = 1/(2t p). NOTE 5 For frequencies up to 100 khz and for pulsed magnetic fields, the maximum current density associated with the pulses can be calculated from the rise/fall times and the maximum rate of change of magnetic flux density. The induced current density can then be compared with the appropriate basic restriction. NOTE 6 All SAR values are to be averaged over any six-minute period. NOTE 7 Localised SAR averaging mass is any 10 g of contiguous tissue; the maximum SAR so obtained should be the value used for the estimation of exposure. These 10 g of tissue are intended to be a mass of contiguous tissue with nearly homogeneous electrical properties. In specifying a contiguous mass of tissue, it is recognised that this concept can be used in computational dosimetry but may present difficulties for direct physical measurements. A simple geometry such as cubic tissue mass can be used provided that the calculated dosimetric quantities have conservative values relative to the exposure guidelines. NOTE 8 For pulses of duration t p the equivalent frequency to apply in the basic restrictions should be calculated as ƒ = 1/(2t p). Additionally, for pulsed exposures, in the frequency range 0,3 GHz to 10 GHz and for localised exposure of the head, in order to limit and avoid auditory effects caused by thermoelastic expansion, an additional basic restriction is recommended. This is that the SA should not exceed 2 mj kg -1 averaged over 10 g of tissue.

15 EN 50445: Table A.2 General public reference levels for electric, magnetic and electromagnetic fields (0 Hz to 300 GHz, unperturbed r.m.s. values) Source: Recommendation 1999/519/EC [2], Table 2 Frequency range Electric field strength E V m -1 Magnetic field strength H A m -1 Magnetic flux density B µt Equivalent plane wave power density S eq W m -2 0 Hz 1 Hz 1 Hz 8 Hz 8 Hz 25 Hz 0,025 khz 0,8 khz 0,8 khz 3 khz 3 khz 150 khz 0,15 MHz 1 MHz 1 MHz 10 MHz 10 MHz 400 MHz 400 MHz MHz 2 GHz 300 GHz /ƒ 250/ƒ /ƒ 1/2 28 1,375 ƒ 1/2 3,2 x x ƒ/ ,2 x 10 4 /ƒ 2 4 x 10 4 /ƒ /ƒ 4/ƒ 5 5 0,73/ƒ 0,73/ƒ 0,073 0,003 7 ƒ 1/2 0, /ƒ 5/ƒ 6,25 6,25 0,92/ƒ 0,92/ƒ 0,092 0,004 6 ƒ 1/2 0,20 61 NOTE 1 ƒ as indicated in the frequency range column. NOTE 2 For frequencies between 100 khz and 10 GHz, S eq, E 2, H 2, and B 2 are to be averaged over any six-minute period. NOTE 3 For frequencies exceeding 10 GHz, S eq, E 2, H 2, and B 2 are to be averaged over any 68/ƒ 1,05 -minute period (ƒ in GHz). NOTE 4 No E-field value is provided for frequencies < 1 Hz, which are effectively static electric fields. For most people the annoying perception of surface electric charges will not occur at field strengths less than 25 kv m -1. Spark discharges causing stress or annoyance should be avoided. NOTE 1 No higher reference levels on exposure to ELF fields are provided when exposures are of short duration (see Note 2 of Table A.1). In many cases, where the measured values exceed the reference level, it does not necessarily follow that the basic restriction will be exceeded. Provided that adverse health impacts of indirect effects of exposure (such as micro shocks) can be avoided, it is recognised that the general public reference levels can be exceeded provided that the basic restriction on the current density is not surpassed. In many practical exposure situations external ELF fields at the reference levels will induce current densities in central nervous-system tissues that are below the basic restrictions. Also it is recognised that a number of common devices emit localised fields in excess of the reference levels. However, this generally occurs under conditions of exposure where the basic restrictions are not exceeded because of weak coupling between the field and the body. NOTE 2 For peak values, the following reference levels apply to the E-field strength (V m -1 ), H-field strength (A m -1 ) and the B-field (µt): for frequencies up to 100 khz, peak reference values are obtained by multiplying the corresponding r.m.s. values by 2 (= 1,414). For pulses of duration tp the equivalent frequency to apply should be calculated as ƒ = 1 /(2tp); for frequencies between 100 khz and 10 MHz peak reference values are obtained by multiplying the corresponding r.m.s. values by 10 a, where a = (0,665 log(ƒ/10 5 ) + 0,176), ƒ in Hz; for frequencies between 10 MHz and 300 GHz peak reference values are obtained by multiplying the corresponding r.m.s. values by 32. NOTE 3 Generally, with regard to pulsed and/or transient fields at low frequencies, there are frequency-dependent basic restrictions and reference levels from which a hazard assessment and exposure guidelines on pulsed and/or transient sources can be derived. A conservative approach involves representing a pulsed or transient EMF signal as a Fourier spectrum of its components in each frequency range, which can then be compared with the reference levels for those frequencies. The summation formulae for simultaneous exposure to multiple frequency fields can also be applied for the purposes of determining compliance with the basic restrictions. Although little information is available on the relation between biological effects and peak values of pulsed fields, it is suggested that, for frequencies exceeding 10 MHz, S eq as averaged over the pulse width should not exceed times the reference levels or that field strengths should not exceed 32 times the fields strength reference levels. For frequencies between about 0,3 GHz and several GHz and for localised exposure of the head, in order to limit or avoid auditory effects caused by thermoelastic expansion, the specific absorption from pulses must be limited. In this frequency range, the threshold SA of 4 mj kg mj kg -1 for producing this effect corresponds, for 30 µs pulses, to peak SAR values of 130 W kg W kg -1 in the brain. Between 100 khz and 10 MHz, peak values for the fields strengths are obtained by interpolation from the 1,5-fold peak at 100 khz to the 32-fold peak at 10 MHz.

16 15 EN 50445:2008 Annex B (informative) Occupational basic restrictions and reference levels The values of basic restrictions and reference levels, as specified in Table 1 (exposure limit values) and Table 2 (action values) of Directive 2004/40/EC [3] on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (electromagnetic fields) are given in Tables B.1 and B.2 for information. Table B.1 Occupational basic restrictions for electric, magnetic and electromagnetic fields (0 Hz to 300 GHz, all conditions to be satisfied) Source: Directive 2004/40/EC [3], Table 1, Exposure limit values Frequency range r.m.s. current density for head and trunk J Whole body average SAR Localised (head and trunk) SAR Localised (limbs) SAR Power density S ma m -2 W kg -1 W kg -1 W kg -1 W m -2 Up to 1 Hz 40 1 Hz 4 Hz 40/ƒ 4 Hz Hz Hz 100 khz ƒ/ khz 10 MHz ƒ/100 0, MHz 10 GHz 0, GHz 300 GHz 50 NOTE 1 ƒ is the frequency in Hz. NOTE 2 The exposure limit values on the current density are intended to protect against acute exposure effects on central nervous system tissues in the head and trunk of the body. The exposure limit values in the frequency range 1 Hz to 10 MHz are based on established adverse effects on the central nervous system. Such acute effects are essentially instantaneous and there is no scientific justification to modify the exposure limit values for exposure of short duration. However, since the exposure limit values refer to adverse effects on the central nervous system, these exposure limit values may permit higher current densities in body tissues other than the central nervous system under the same exposure conditions. NOTE 3 Because of the electrical inhomogeneity of the body, current densities should be calculated as averages over a crosssection of 1 cm² perpendicular to the current direction. NOTE 4 For frequencies up to 100 khz, peak current density values can be obtained by multiplying the r.m.s. value by 2 ½. NOTE 5 For frequencies up to 100 khz and for pulsed magnetic fields, the maximum current density associated with the pulses can be calculated from the rise/fall times and the maximum rate of change of magnetic flux density. The induced current density can then be compared with the appropriate exposure limit value. For pulses of duration t p, the equivalent frequency to apply for the exposure limit values should be calculated as ƒ = 1/(2t p). NOTE 6 All SAR values are to be averaged over any six-minute period. NOTE 7 Localised SAR averaging mass is any 10 g of contiguous tissue; the maximum SAR so obtained should be the value used for estimating exposure. These 10 g of tissue are intended to be a mass of contiguous tissue with nearly homogeneous electrical properties. In specifying a contiguous mass of tissue, it is recognised that this concept can be used in computational dosimetry but may present difficulties for direct physical measurements. A simple geometry such as cubic tissue mass can be used provided that the calculated dosimetric quantities have conservative values relative to the exposure guidelines. NOTE 8 For pulsed exposures in the frequency range 0,3 GHz to 10 GHz and for localised exposure of the head, in order to limit and avoid auditory effects caused by thermoelastic expansion, an additional exposure limit value is recommended. This is that the SA should not exceed 10 mj kg -1 averaged over 10 g of tissue. NOTE 9 Power densities are to be averaged over any 20 cm² of exposed area and any 68/ƒ 1,05 -minute period (where ƒ is in GHz) to compensate for progressively shorter penetration depth as the frequency increases. Spatial maximum power densities averaged over 1 cm² should not exceed 20 times the value of 50 W m -2. NOTE 10 With regard to pulsed or transient electromagnetic fields, or generally with regard to simultaneous exposure to multiple frequency fields, appropriate methods of assessment, measurement and/or calculation capable of analysing the characteristics of the waveforms and nature of biological interactions have to be applied, taking account of European harmonised Standards developed by CENELEC.

17 EN 50445: Table B.2 Occupational reference levels for time varying electric and magnetic fields (0 Hz to 300 GHz, unperturbed r.m.s. values) Source: Directive 2004/40/EC [3], Table 2, Action values Frequency range Electric field strength E V m -1 Magnetic field strength H A m -1 Magnetic flux density B µt Equivalent plane wave power density S eq W m -2 Contact current I C ma Limb induced current I L ma 0 Hz 1 Hz 1,63 x x ,0 1 Hz 8 Hz ,63 x 10 5 /ƒ 2 2 x 10 5 /ƒ 2 1,0 8 Hz 25 Hz x 10 4 /ƒ 2,5 x 10 4 /ƒ 1,0 0,025 khz 0,82 khz 500/ƒ 20/ƒ 25/ƒ 1,0 0,82 khz 2,5 khz ,4 30,7 1,0 2,5 khz 65 khz ,4 30,7 0,4/ƒ 65 khz 100 khz /ƒ 2 000/ƒ 0,4/ƒ 0,1 MHz 1 MHz 610 1,6/ƒ 2/ƒ 40 1 MHz 10 MHz 610/ƒ 1,6/ƒ 2/ƒ MHz 110 MHz 61 0,16 0, MHz 400 MHz 61 0,16 0, MHz MHz 3 ƒ 1/2 0,008 ƒ 1/2 0,01 ƒ 1/2 ƒ/40 2 GHz 300 GHz 137 0,36 0,45 50 NOTE 1 ƒ is the frequency in the units indicated in the frequency range column. NOTE 2 For frequencies between 100 khz and 10 GHz, S eq, E 2, H 2, B 2 and I L 2 are to be averaged over any six-minute period. NOTE 3 For frequencies exceeding 10 GHz, S eq, E 2, H 2 and B 2 are to be averaged over any 68/ƒ 1,05 -minute period (ƒ in GHz). NOTE 4 For frequencies up to 100 khz, peak action values for the field strengths can be obtained by multiplying the r.m.s. value by 2 ½. For pulses of duration t p, the equivalent frequency to apply for the action values should be calculated as ƒ = 1/(2t p). For frequencies between 100 khz and 10 MHz, peak action values for the field strengths are calculated by multiplying the relevant r.m.s. values by 10 a, where a = (0,665 log (ƒ/10 5 ) + 0,176), ƒ in Hz. For frequencies between 10 MHz and 300 GHz, peak action values are calculated by multiplying the corresponding r.m.s. values by 32 for the field strengths and by for the equivalent plane wave power density. NOTE 5 With regard to pulsed or transient electromagnetic fields, or generally with regard to simultaneous exposure to multiple frequency fields, appropriate methods of assessment, measurement and/or calculation capable of analysing the characteristics of the waveforms and nature of biological interactions have to be applied, taking account of harmonised European Standards developed by CENELEC. NOTE 6 For peak values of pulsed modulated electromagnetic fields, it is also suggested that, for carrier frequencies exceeding 10 MHz, S eq as averaged over the pulse width should not exceed times the S eq action values or that the field strength should not exceed 32 times the field strength action values for the carrier frequency.

18 17 EN 50445:2008 Annex C (informative) Example for general EMF information The instruction manual should include general information for the user about EMF as given below: Electric current flowing through any conductor causes localized electric and magnetic fields (EMF). Welding current creates an EMF field around the welding circuit and welding equipment. EMF fields may interfere with some medical implants, e.g. pacemakers. Protective measures for persons wearing medical implants have to be taken. For example, access restrictions for passers-by or individual risk assessment for welders. All welders should use the following procedures in order to minimize exposure to EMF fields from the welding circuit: route the welding cables together secure them with tape when possible; place your torso and head as far away as possible from the welding circuit; never coil welding cables around your body; do not place your body between welding cables. Keep both welding cables on the same side of your body; connect the return cable to the work piece as close as possible to the area being welded; do not work next to, sit or lean on the welding power source; do not weld whilst carrying the welding power source or wire feeder.

19 EN 50445: Bibliography [1] Directive 2006/95/EC of the European Parliament and of the Council of 12 December 2006 on the harmonisation of the laws of Member States relating to electrical equipment designed for use within certain voltage limits (codified version), Official Journal L 374, , p [2] Council Recommendation 1999/519/EC of 12 July 1999 on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz), Official Journal L 199, , p [3] Directive 2004/40/EC of the European Parliament and of the Council of 29 April 2004 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (electromagnetic fields) (18th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC), Official Journal L 159, , p [4] International Commission on Non-Ionising Radiation Protection, Guidelines on Limits of Exposure to Static Magnetic Fields, Health Physics, Volume 66, Number 1, 1994, p [5] International Commission on Non-Ionising Radiation Protection, Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic and Electromagnetic Fields (up to 300 GHz), Health Physics, Volume 74, Number 4, April 1998, p [6] International Commission on Non-Ionising Radiation Protection, Guidance on Determining Compliance of Exposure to Pulsed and Complex Non-Sinusoidal Waveforms below 100 khz with ICNIRP Guidelines, Health Physics, Volume 84, Number 3, March 2003, p [7] EN ), Determination of workers exposure to electromagnetic fields 1) At draft stage.

20 Annex 2 Chinese proposal on The Critiria for the Evaluation of Welder Exposure to Electromagnetic Field of Welding Equipment

21 1 CHINA NC The Critiria for the Evaluation of Welder Exposure to Electromagnetic Field of Welding Equipment CONTENTS Clause Page 1 Scope Terms and definitions Exposure limiting value Exposure limiting value Basic limiting value The Exposure in the Electric Field Comprehensive evaluation Method Test and Evaluation Procedure The Measurement of Electromagnetic Field in Welding Environment The Quality Assurance of Field Monitoring of Electromagnetic Radiation Measurement Equipment The evaluation scheme for the welding electromagnetic exposure...7 Annex A (normative) The electromagnetic field exposure limiting value and the evaluation limiting value for the welding operation personnel... 9 Annex B (informative) General information for welding EMF protection...13 Figure 1 the welding electromagnetic field exposure evaluation system flow chart....8 Figure A.1 Biological effects of induced current densities in the frequency range 1Hz to 100kHz...11 Table 1-Basic restrictions for the welding operation personnel exposure to electromagnetic fields Table A.1 Basic restrictions for the welding operation personnel exposure to electromagnetic fields for frequencies up to 10 GHz... 9 Table A.2 Reference levels for for the welding operation personnel exposure to electromagnetic fields ( r.m.s values)...11

22 2 CHINA NC 1 Scope The Critiria for the Evaluation of Welder Exposure to Electromagnetic Field of Welding Equipment This standard provides a suitable evaluation method of the potential effect of the electromagnetic field produced by welding equipment and auxiliary devices in normal welding conditions on the on-site operating personnel. This standard applies to the welding equipment and auxiliary devices. This standard shall not involve the electromagnetic compatibility evaluation of the welding equipment. NOTE 1 The welding equipment contained in this standard mainly refers to electric arc welding, cutting and arc spray equipment, electric resistance welding equipment and peripheral auxiliary equipment, including source of welding current, wire feed device, water cooling box, output cable, welding torch, arc strike, arc stabilizer, etc. NOTE 2 This standard does not contain the detection and evaluation of the electromagnetic environment of all known welding equipments. 2 Terms and Definitions The following terms and definitions are applicable to this standard. 2.1 basic limit the physical limiting values of the electric field, magnetic field and the electromagnetic field exposed to the open air which directly are based on the certain health effects and established by taking preventive principle for uncertain health effects. In this standard, the physical quantities of the basic limiting values are current density (J), specific absorption rate (SAR) and power density (S) according to field frequency. The physical quantities of the basic limiting values ares usually difficult to be measured directly. 2.2 reference limit the derived limiting value is used to assess whether the basic limit may be exceeded in actual condition of exposure to the open air. The derived limiting values indicate the maximum coupling condition of the electric field, magnetic field, electromagnetic field and explosure unit. It is deduced by the mathematical model of the basic limiting values and the test research results at certain frequency. The basic limiting value is expressed by physical quantities, such as the electric field intensity (E), the magnetic field intensity (H), the magnetic flux density (B), the pulse field specific absorbption eneragy (SA), the power density (S), etc. The basic limiting value is easy to be directly measured; so it is usually used to compare with the actual and to make safety assessment. When the actual measured value is lower than the limiting value; but it does not exceed the basic limiting value; when the actual measured value exeeds the derived limiting value; then it does not indicate that it exceeds the basic limiting value and a detailed evaluation shall be taken to the basic limiting value. Thus the most effective protection may be provided. 2.3 whole-body Exposure the exposure that the whole body is in the electromagnetic field.

23 3 CHINA NC 2.4 partial Exposure the exposure that some certain part of human body surface are in the electromagnetic field. 2.5 Electric Field the constituent component of the electromagnetic field characterized by electric field intensity and electric flux density. 2.6 magnetic Field the constituent component of the electromagnetic field characterized by magnetic field intensity and magnetic flux density. 2.7 electromagnetic Fields the field which is determined by four interrelated vectors and indicates the medium and the condition of electricity and magnetism in empty space together with current density and density of volume charges. 2.8 electric Field Strength the size of the quantity of electric vector field determines the electric field force on electrostatic charge, which may be expressed as follows:. NOTE The unit of electric field intensity is volts per meter (V/m). 2.9 magnetic Field Strength the size of the quantity of magnetic intensity vector field is related to the vector of magnetic flux density, the relationship of which may be expressed specifically as follows: where m r represent the relative magnetic conductivity of medium; m represent the free space magnetic conductivity. At fixed-location, it is the result of magnetic 0 flux density divided by magnetic constants and minus intensity of magnetization. NOTE the unit of magnetic field intensity is Amperes per meter (A/m) magnetic induction Strength the force of the vector field quantity B on the charged particle with certain speed is the product of the speed, vector field quantity B and particle charge, whose unit is in T. In the air, the magnetic induction intensity is the product of magnetic field intensity and magnetic conductivity m 0, which is B= m 0 H current Density (J) the current density indicates the physical quantity of the current intensity flowing through unit area or the current intensity of electromagnetic field inducing the unit area of human body. The unit is A/m environmental Field of Energy Consumption

24 4 CHINA NC the electric or magnetic field produced by welding equipment and the value measured when human body does not exist measurement of Electromagnetic Field according to the provisions in the relevant international standards, the electric field intensity and the magnetic field intensity in the operating area shall be measured, respectively, when the operation frequency of the radiation source is lower than 300MHz coupling Factor K the coupling factor is used to assess the the exposure of the complex electromagnetic field where human body is, such as the nonuniform magnetic field or disturbance electric field. NOTE 1 Coupling factor K has different physical interpretations and depends on the degree of association between the electric magnetic field exposure and it. NOTE 2 the size of the coupling factor K depends on the applied field source model and human body model. For example, the precise value of the coupling factor may be directly determined in a production standard and used in similar production standards when the exposure condition is certain. 3 Exposure limiting value 3.1 Exposure limiting value The judgment basis of the exposure limiting value is the derived limiting value. When it is not suitable to measure on the basis of derived limiting value, the basic limiting value shall be considered as the judgment basis. 3.2 Basic limiting value Different basic limiting values for different frequencies may be listed as follows: - as for the frequency lower than 100 khz, the basic limiting value is the current density (J); - as for the frequency from 100 khz to 10 MHz, the basic limiting values are the specific absorption rate (SAR) and the current density (J); - as for the frequency from 10MHz to 10GHz, the basic limiting value is the specific absorption rate (SAR). 3.3 The Exposure in the Electric Field For the alternating electric field whose partial electric field intensity is approximately 100V/m, its intensity is lower than the safety level. In this exposure case, the calculation of inductive current is not necessary. 3.4 Comprehensive evaluation Method When the electromagnetic field is stacked by several frequencies, the multiple physical quantities shall be measured, respectively. The force of electric field and magnetic field of different frequencies to human body has the accumulative effect. For the safety evaluation low-frequency electromagnetic exposure, the evaluation shall comply with the following measurement conditions under the frequency below 10MHz:

25 5 CHINA NC B + Bj 1 b 65kHz 10MHz j å å B j= 1Hz L, j j> 65kHz Where: B represents the magnetic flux density when the frequency of the measured location is j. B L, represents the derived limiting value of magnetic flux density when the frequency is j. For the occupational exposure, b is 30.7 µt (as shown in Table 1). As for the welding current of pulse or non-sinusoidal (including the DC component), it s DC and AC components shall be evaluated, respectively. The AC component shall be evaluated according to the limit condition of varying field and the DC component shall be evaluated according to the limiting value of the static field. The AC component may contain a series of frequency spectrum components, especially the fundamental wave components (such as the pulse repetition rate in the process of pulse MIG or contra variant wielding) and harmonic wave components. Table 1 shows the reference limiting value for the electromagnetic exposure of any occupational personnel. The reference limiting value is the spatial average value of the exposure body, which indicates the maximum coupling conditions of electric field, magnetic field and electromagnetic field. Therefore, the effective protection may be provided. The basic limiting value and the referece limiting value of the electromagnetic exposure are given in Table 1. Table 1 Basic restrictions for the welding operation personnel exposure to electromagnetic fields Basic limit Reference limit Frequency range Current density for head and trunk ma/m 2 Frequency range Electric Field Strength E V/m Magnetic Field Strength H A/m Magnetic induction Strength B µt To 1Hz 40 To 1Hz Hz~4Hz 40/f 1 Hz~8Hz /f /f 2 4 Hz~1000Hz 10 8 Hz~25Hz /f /f 1kHz~100kHz f/100 25Hz~0.82kHz 500/f 20/f 25/f 0.1MHz~10MHz f/ kH~65kHz kHz~1MHz /f 2.0/f NOTE 1 f is the frequency in hertz. NOTE 2 Because of electrical in homogeneity of the body, current densities should be averaged over a cross section of 1 cm² perpendicular to the current direction. NOTE 3 For frequencies up to 100 khz, peak current density values can be obtained by multiplying the r.m.s. value by 2 (~1,414).

26 6 CHINA NC 4. Test and Evaluation Procedure 4.1 The Measurement of Electromagnetic Field in Welding Environment Before any test, the nature and propagation characteristics of radiation source shall be understood as can as possible to properly select the measurement instrument and to measure accurately. - the radiation source type and power; - the number of radiation sources. If there are several radiation sources, it should be determined whether the existing radiation sources are of the same kinds and whether they may be superposed. - relevant time-domain and frequency-domain characteristics for choosing corresponding probe type; - the distance from the radiation source to the measured location. The measurement site shall be the welding operation site and the measurement shall be carried out during the normal equipment operating period. At the same time, the impact of the electromagnetic field on the various parts of human body shall be taken into account. For the welding equipment (arc welding equipment and welding resistance equipment) and the magnetic field produced in the welding process, the actual welding circumstance of welding site shall be simulated as soon as possible in the measurement process and the typical operating locations neighboring welding torch, cable and electrode shall be selected to accurately evaluate the impact of magnetic field on the safety and health of the operating personnel. In this way, the size of magnetic field where the operating personnel are may be truly reflected. The output cable connected by welding torch is closest to the human body and the magnetic field produces the most powerful impact on human body. The welding personnel are usually very close to the welding object. The selection of measurement location neighboring cables to measure the magnetic flux density may be used tosimulate the circumstance where the cable is close to human body. The welding power itself is radiation source. The external chassis of the power supply may play a certain role of magnetic screening, but the existence of factors such as any improper selection of screening materials and the unreasonable desigh of chassis certainly will reduce the screening funtion. The electromagnetic radiation produced directly acts on the human body and threatens to the personal safety. The measurement of the comprehensive values of the magnetic flux density at different distances from the welding power may be used to simulate the situations where the welding workerpersonnel is near the welding power. The current through the eletrode of the resistance welding equipment is relatively high and may reach tens of thousands of amperes. Therefore, a great magnetic field may be produced around the electrode. The welding personnel are very close to the electrode while welding; the electromagnetic radiation produced will directly effect on human head, chest and arms. The magnetic field intensity around the electrode may exceed the measurement range of the equipment. For ensuring the safety of the measurement equipment and measurement personnel,

27 7 CHINA NC the method of approaching the electrode gradually from the distance shall be employed in the measurement process for using the welding resistance equipment. 4.2 The Quality Assurance of Field Monitoring of Electromagnetic Radiation As for any electromagnetic radiation monitoring, the measurement program and implementation plan established beforehand shall be provided. As for selecting the monitoring locations, it shall be considered to make the measurement results representative. Different monitoring programs shall be aplied to different monitoring purposes. The monitoring instrument must correspond to the measured object in the aspects of frequency, measurement range, response time, etc. so as to ensure the real measurement results shall be obtained. The interference shall be avoided or reduced as can as possible during the measurement process. And the maximum error in the measurement results being possiblely produced by any unavoidable interference shall be estimated. Sufficient data shall be obtained during the measurement process to ensure the statistic precision of the measurement results. The monitoring instrument and devices (including any antenna or probe) must be regularly calibrated. As for accepting or cancelation of abnormal data in the monitoring process and the data processing of measurement results, the statistic principle shall be applied. As for any electromagnetic radiation monitoring, the complete documents shall established. The calibration specifications of instrument, monitoring program, monitoring locations figure, measurement original data, statistical processing procedures and so on must be reserved for review. All the measurement results on file or to be reported shall have been reviewed. And the reviewers shall be professional personnel who are not directly involved in the job and be familiar with the contents of this standard. 4.3 Measurement Equipment The electromagnetic field measurement is to convert the magnetic foux density at a certain location into electricity quantity (such as the current or voltage) by using the isotropic magnetic field probe. The electricity quantity is converted into the discrete digital signals via acquisition system. These discrete digital signals may be converted into the frequency spectrum of the magnetic flux density via FFT conversion; and it may be evaluated whether the electromagnetic pollution of the welding environment exceeds the standard value by comparing the measured value with derived limiting value. A typical measurement and evaluating equipment of the distribution of the welding electromagnetic field shall contain: the isotropus probe, the data acquisition module and the analysis software and so on; and the evaluating function of whether the electromagnetic field of the measured welding environment exceeds the standard value shall be provided. 4.4 The evaluation scheme for the welding electromagnetic exposure The welding electromagnetism exposure evaluation involves the welding equipment and its surrounding environment. The electromagnetic exposure for the different welding power sources may be varied in different circumstances. The evaluation scheme diagram is shown in Figure 1, in

28 8 CHINA NC which the contents in the two dotted frame boxes are the obtaining method for the information of the welding electromagnetic field, namely, the spatial distribution situation of the electromagnetic field produced by the welding current. This process may be obtained by using the two methods (measurement and simulation). The premise for the simulation shall be the explicit parameters of the welding current. By appling the welding current to the electromagnetic module of the welding power supply, the electromagnetic field intensity produced by current may be calculated. On the other hand, the measurement is to obtain the electromagnetic field intensity value by measuring the electromagnetic field generated due to the actual operation welding power source by using the low-frequency electromagnetic field measurement instrument. The welding electromagnetic exposure evaluation and analysis software may be used to compare the magnetic field intensity measurement values at various frequencies with the derived limiting values for determining the promote for exceeding the standard value or not. While the component magnetic fields in different frequencies do not exceed the standard value, it shall be determined whether the comprehnsive magnetic exposure calculated by using the evaluation equation exceeds the standard value. The attention shall be paid to the following questions during the welding electromagnetic field evaluation process: the electromagnetic field source is mainly the welding current, whose amplitude may influence the most greatly the electromagnetic field exposure; therefore, the evaluation of the electromagnetic field exposure shall be carried out based on the above parameters; and the welding circuit characteristics and structure, the test distance, the operation state and other relevant parameters should be described in detail. Besides the electromagnetic field exposure being evaluated by using the measurement method, the evaluation of the welding electromagnetic field may be carried out by utilizing the numerical simulation method, through which the welding power structure and welding parameters may be calculated and evaluated and which may be suitable for the electromagnetic exposure evaluation to the welding power source during the ex-factory inspection process. Figure 1 the welding electromagnetic field exposure evaluation system flow chart

29 9 CHINA NC Appendix A (Normative Appendix) The electromagnetic field exposure limiting value and the evaluation limiting value for the welding operation personnel The electromagnetic safety and health problems for the welding operation personnel involved in this standard is put forward based on the determined short-term effect. These adverse effects to any human body are resulted due to the induction current and the energy absorption acted to any human body. At the same time, the health damage caused due to the long-term electromagnetic field exposure has not been included in this standard. The measurement, calculation and evaluation to the welding environment electromagnetic field shall be periodically carried out by the specialized personnel according to the plan schedule. The data obtained in the various links shall be stored in some specific form for future reference. Two categories of exposure limiting values have been stipulated in this standard, respectively, which are called as the basic limiting values and the derived limiting values; the former is relevant to the frequency of the welding environment electromagnetic field and are put forward according to the biological effects directly relevant to the human boby health status; and the electromagnetic field exposure for any welding operation personnel shall exceed the values in no circumstances; they may be given with the current density within the low frequency range and they may be described with the specific absorption rate (SAR) within the high frequency range (more than 100kHz). The basic limiting values shall be obeyed to ensure any human body from any risk form the determined harmful effects. The electromagnetic exposure basic limiting values related to the frequency are given in Table A.1. Table A.1 Basic restrictions for the welding operation personnel exposure to electromagnetic fields for frequencies up to 10 GHz Frequency range Current density for head and trunk Whole body average SAR Localised SAR (head and trunk) Localised SAR (limbs) ma/m 2 W/kg W/kg W/kg Up to 1Hz 40 1Hz~4Hz 40/f 4Hz~1000Hz 10 1kHz~100kHz f/ MHz~10MHz f/ GHz~10GHz NOTE 1 f is the frequency in hertz. NOTE 2 Because of electrical inhomogeneity of the body, current densities should be averaged over a cross section of 1 cm² perpendicular to the current direction. NOTE 3 For frequencies up to 100 khz, peak current density values can be obtained by multiplying the r.m.s. value by 2 (~1,414). For pulses of duration tp the equivalent frequency to apply in the basic restrictions should be calculated as ƒ = 1/(2tp). NOTE 4 All SAR values are to be averaged over any six-minute period. NOTE 5 Localised SAR averaging mass is any 10 g of contiguous tissue.

30 10 CHINA NC The basic limiting values for various frequencies within the range of 1Hz~100kHz are given with the current densities. Figure A.1 shows the biological effect of the low-frequency electromagnetic field induction current density so that the adverse impact may be prevented to the cardiovascular and central nervous systems and so on. Within the frequency band of 1Hz~10MHz, the current density limiting value severs to protect the central nervous system function. While the frequecy is more than 100kHz, the stipulated specific absorption rate (SAR whose unit in W/kg) limiting value is to prevent the human body temperature being too high; on the other hand, the current density limiting value is to prevent the tissues in the central nervous system in the human head and trunk section from any intense stimulation. Therefore, the mean value method is used for the specific absorption rate measurement within 6 minutes; on the other hand, the mean value method may not be used for the current density measurement. The more strict calculation method shall be obeyed for the evaluation of the complex pulse conditions. The SAR value is proportional to the square of the body induced electric field. The mean SAR value and the human body SAR distribution may be obtained by using the experiment measurement method and the numerical calculation method. Moreover, the SAR value is related to the following factors: a) the radiated field parameters such as the frequency, intensity, near field region or far-field region; b) the exposure body characteristic parameters such as the human body appearance, geometry size, and dielectric properties of different tissues and so on; c) the screening effect and reflection effect from the bodies around the exposure body. Under the simultaneous exposure conditions in different frequencies, it is very important whether the exposure under these frequencies shall be taken into account comprehensively. The multiple physical quantities shall be measured, respectively. As for the exposure condition under the assumption of there being multi-source field, the following equation may be used. 10GHz SARi å 1 SAR i= 100kHz L where SARi represents the exposure SAR value due to the frequency I ; SAR L represents the SAR limiting value given in Table A.1. The limiting value is derived to be in comparison with the actual measurement physical value. Generally speaking, the derived limiting value may ensure the exposure limiting value shall not be more than the standard value. If the measurement value is more than the derived limiting value, it does not mean that the exposure limiting value is also more than the derived limiting value at the same time; as shall be determined through the further analysis. As for the actual exposure environment with the welding operation personnel, the direct measurement physical quantities for the safety evaluation are the electric intensity E, the magnetic field intensity H and the magnetic induction intensity B. In addition, the derived limiting values for various frequency bands are given in Table A.2.

31 11 CHINA NC Table A.2 Reference levels for for the welding operation personnel exposure to electromagnetic fields ( r.m.s values) Frequency range Electric Field Strength E V/m Magnetic Field Strength H A/m Magnetic induction Strength B µt Power density S W/m 2 至 1Hz Hz~8Hz /f /f 2 8Hz~25Hz /f /f 0.025kHz~0.82kHz 500/f 20/f 25/f 0.82kHz~65kHz MHz~1MHz /f 2.0/f 1MHz~10MHz 610/f 1.6/f 2.0/f 10MHz~400MHz MHz~2000MHz 3f 1/ f 1/2 0.01f 1/2 f/40 NOTE 1 ƒ is the frequency in Hz. NOTE 2 No EMF value is provided for frequencies < 1 Hz, which are effectively static electric fields. NOTE 3 For peak values at frequencies exceeding 100 khz see Figs. 1 and 2. Between 100 khz and 10 MHz, peak values for the field strengths are obtained by interpolation from the 1.5-fold peak at 100 khz to the 32-fold peak at 10 MHz. NOTE P established range of the perception threshold L established range of the let-go threshold F established range of the threshold for irreversible cardiac fibrillation all ranges are given from 0,5% to 99,5% probability a widely accepted limit-line for induced current density invoccupational exposure situations is indicated in orange up to 100 khz. Figure A.1 Biological effects of induced current densities in the frequency range 1Hz to 100kHz

32 12 CHINA NC As for the high frequency electromagnetic radiation, the measurement parameters are the electric field intensity, the magnetic field intensity and the electromagnetic field power flux density, respectively. The different types of instruments shall be selected for the different measurement modes so as to obtain the best measurement results. The measurement instruments may be divided into the non-frequency selection type broadband radiation measurement instrument and the frequency selection type broadband radiation measurement instrument according to the measurement purposes; no matter what type the measurement instrument is, the basic structure is composed of two parts, namely, the antenna (sensor) and the main machine system. As for the measurement of any electromagnetic radiation source, its near field region electromagnetic radiation intensity shall be mainly monitored because the electromagnetic radiation intensity is very large in the near field region and the contribution from other electromagnetic radiation sources in the relatively far field region may be negligible. Therefore, the comprehensive field intensity shall be selected for the near field region electromagnetic radiation intensity. As for the measurement of any high frequency electromagnetic radiation source, the following aspects shall be carried out: a) The environmental conditions: the measurement instruments at the environmental conditions shall be in operation according to the prescribed usage conditions and the environment temperature and the relative humidity shall be filled in the measurement record form. b) Measurement instrument: the broadband radiation meter with the isotropic response or directional electric field probe or magnetic field probe may be selected. While any directional probe is selected, the probe direction shall be adjusted at the measurement location so as to measure the maximum radiation level at the measurement location. The operating band of the measurement instrument shall conform to the requirements of the site to be tested. c) Measurement period: any measurement shall be carried out within the normal operating period of the electromagnetic radiation source; and the measurement shall be carried out for three times as for each measurement location and every measurement period shall not be less than 15 seconds; moreover, the maximum values shall be recorded at the stable states. While there is any relatively large deviation between the measurement readings, the measurement period shall be extended appropriately. d) The measurement locations: the personnel operating location, the horizontal distance from the ground level, the abdomen, waist and chest sections shall be taken as the measurement locations. e) Data processing: the average electric field intensity for each measurement site shall be solved (while there being several readings); and the RMS average value shall be solved at best.

33 13 CHINA NC Annex B (informative) General information for welding EMF protection The instruction manual should include general information for the user about EMF as given below: a) Electric current flowing through any conductor causes localized electric and magnetic fields (EMF). Welding current creates an EMF field around the welding circuit and welding equipment. b) EMF fields may interfere with some medical implants, e.g. pacemakers. Protective measures for persons wearing medical implants have to be taken. For example, access restrictions for passers-by or individual risk assessment for welders. c) All welders should use the following procedures in order to minimize exposure to EMF fields from the welding circuit. - route the welding cables together secure them with tape when possible; - place your torso and head as far away as possible from the welding circuit; - never coil welding cables around your body; - do not place your body between welding cables. Keep both welding cables on the same side of your body; - connect the return cable to the work piece as close as possible to the area being welded; - do not work next to, sit or lean on the welding power source; - do not weld whilst carrying the welding power source or wire feeder.