1、PUBLISHED DOCUMENTPD CLC/TR 50427:2004Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation Guide ICS 13.230; 33.060.20g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55
2、g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58PD CLC/TR 50427:2004This Published Document was published under the authority of the Standards Policy and Strategy Committee on 28 April 2006 BSI 2006ISBN 0 580 45883 0National forewordThis Published Document is the official English language vers
3、ion of CLC/TR 50427:2004. It is envisaged that PD CLC/TR 50427:2004 will eventually replace BS 6656:2002 but for a transitional period both documents will be current in order for users of the standards to familiarize themselves with the contents of the new document.The UK participation in its prepar
4、ation was entrusted by Technical Committee GEL/31, Electrical apparatus for explosive atmospheres, to Subcommittee GEL/31/-/602, Radio-frequency radiation-induced ignition and detonation, which has the responsibility to:A list of organizations represented on this subcommittee can be obtained on requ
5、est to its secretary.Cross-referencesThe British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogueunder the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Elec
6、tronic Catalogue or of British Standards Online.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a Published Document does not of itself confer immunity from legal obligations. aid enquirers to
7、understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK.Summary of pagesThis document compr
8、ises a front cover, an inside front cover, the CLC/TR title page, pages 2 to 95 and a back cover.The BSI copyright notice displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd. No. Date CommentsTECHNICAL REPORT CLC/TR 50427RAPPORT TECHNIQUE TEC
9、HNISCHER BERICHT December 2004 CENELECEuropean Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels ICS 13.230; 33.060.20 English version Assessment o
10、f inadvertent ignition of flammable atmospheresby radio-frequency radiation GuideEvaluation des risques dinflammation des atmosphres inflammablespar des rayonnements de radiofrquence GuideLeitfaden zur Verhinderungder unbeabsichtigten Zndung explosionsfhiger Atmosphrendurch hochfrequente Strahlung T
11、his Technical Report was approved by CENELEC on 2004-08-28. CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,Latvia, Lithuania, Luxembourg, Malta, Netherlands
12、, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. CLC/TR 50427:2004 E PD CLC/TR 50427:2004 2 Foreword This Technical Report was prepare
13、d by the Technical Committee CENELEC TC 31, Electrical apparatus for explosive atmospheres - General requirements. The text of the draft was submitted to the formal vote and was approved by CENELEC as CLC/TR 50427 on 2004-08-28. _ 3 PD CLC/TR 50427:2004ContentsIntroduction 6 1 Scope72 Normative refe
14、rences .73 Terms and definitions.74 Symbols and abbreviations .94.1 Modulation codes94.2 Polarization codes.105 General considerations 105.1 Radio-frequency hazard105.2 Philosophy of systematic method of approach .11 5.3 Responsibility for making the hazard assessment116 Transmitters and transmitter
15、 output parameters 126.1 Types of transmitter 126.2 Frequency range.126.3 Transmitter output power126.4 Antenna gain.126.5 Modulation factors.126.5.1 General.126.5.2 Frequency modulation (FM).136.5.3 Amplitude modulation (AM)136.5.4 Single sideband (SSB) operation.136.5.5 Pulsed radar.137 Structures
16、 and spark-making mechanisms .147.1 Structures147.2 Loop-type structures .147.3 Vertical structures .167.4 Spark-making mechanisms.178 Ignition of flammable atmospheres.178.1 Flammable atmospheres 178.2 Ignition by radio-frequency discharges .178.3 Criteria for ignition.188.3.1 Effectively continuou
17、s transmissions .188.3.2 Radar transmissions 189 Practical measurements and tests199.1 Measurement of electromagnetic fields 199.2 Measurement of extractable power 199.3 Test transmissions 209.4 Incendivity tests 20PD CLC/TR 50427:2004 4 10 Methods of assessment for determining potential RF ignition
18、 hazards on a plantcontaining hazardous areas.2110.1 General .21 10.2 Basis of the theoretical assessments .2110.2.1 General.21 10.2.2 Initial assessment.22 10.2.3 Full assessment .2210.3 Initial assessments32 10.3.1 Initial assessment of the risk from a particular transmitter site32 10.3.2 Initial
19、assessment for a particular plant33 10.4 Full assessment procedure.34 10.4.1 Procedure.34 10.4.2 Information to be obtained .35 10.4.3 Calculation of effective field strengths .35 10.4.4 Calculation of extractable power or energy41 10.4.5 Comparison of the total extractable power or energy from the
20、structure with the threshold values detailed in Clause 8 43 10.5 Practical on-site tests46 10.5.1 Procedure.46 10.5.2 Plant and transmitter both in existence (Case 1 of Figure 3).46 10.5.3 Existing plant and proposed transmitter (Case 2 of Figure 3) .47 10.5.4 Existing transmitter and proposed plant
21、 (Case 3 of Figure 3) .48 11 Plant safety measures 49 11.1 General .49 11.2 Bonding.49 11.3 Insulation.50 11.4 Reducing the structure efficiency50 11.5 De-tuning of structures50 12 Special cases.51 12.1 Cranes.51 12.2 Mobile and portable transmitters.51 12.3 Ships .51 12.3.1 General.51 12.3.2 Ships
22、in harbour areas.52 12.3.3 Ships at sea .52 12.4 Offshore oil and gas installations53 12.4.1 General.53 12.4.2 Structures on offshore installations53 12.4.3 Assessment procedures.53 12.4.4 Radio frequency transmitters and vulnerable zones54 12.4.5 Safety measures and recommendation .55 5 PD CLC/TR 5
23、0427:2004Annex A (informative) Sources of information and addresses of some advisory bodies.57Annex B (informative) Electromagnetic radiated fields and examples of radiating antenna andunintended receiving antenna characteristics 59Annex C (informative) Subdivision of group II flammable gases and va
24、pours.67Annex D (normative) Measurement of electromagnetic fields .72Annex E (normative) Methods of measurement on structures (on-site tests)76Annex F (informative) Derivation of vulnerable zone distances for Table 5, Table 6 and Table 10 82Annex G (informative) Worked examples of full assessment pr
25、ocedure .83Annex H (informative) Ground-wave propagation (vertical polarization) - Calculation of field strength 92Bibliography94PD CLC/TR 50427:2004 6 IntroductionElectromagnetic waves produced by radio-frequency (RF) transmitters (e.g. radio, television and radar) will induce electric currents and
26、 voltages in any conducting structure on which they impinge. The magnitude of the induced current and voltages depends upon the shape and size of the structure relative to the wavelength of the transmitted signal and on the strength of the electromagnetic field. When parts of the structure normally
27、in contact are caused to break or separate momentarily (e.g. during maintenance or as a result of vibration) a spark may occur if the induced voltage and current is sufficiently large. If this happens in a location where a potentially flammable atmosphere may be present a hazardous situation can occ
28、ur. However, the possibility of ignition will depend on many factors including whether the spark can deliver sufficient energy to ignite a particular flammable atmosphere.This European Technical Report provides a systematic approach to assist transmitter operators, plant managers and all others conc
29、erned with a logical method for the assessment and elimination of RF induced ignition hazards.The assessment procedures recommended in this European Technical Report are based on measurements of the powers and energy that can be extracted from typical structures, including cranes, and measurements o
30、f the minimum powers and energy that are required to ignite various flammable atmosphere gas groups.The assessment procedures for probability of ignition recommended in this European Technical Report are based on the assumption that worst case conditions apply at all times. The critical features are
31、 the coincidence of the structure in resonance and the presence of the gas/air mixture in the optimum proportions for RF spark ignition. Deviation from these optimum conditions will result in significantly higher powers being required for ignition.NOTE 1 Several studies have been performed which ind
32、icate that the power could be twice as great for an assumed risk as detailed in reference 1, if due allowance is taken for probabilistic effects. In order to achieve a probability of ignition comparablewith other risks, it would be necessary for effective extractable power calculated to be twice the
33、 values determined according to this European Technical Report. The probabilistic elements could be taken into consideration following further research work and practical experience.NOTE 2 If allowances for probabilities are to be applied then expert advice should be sought. 7 PD CLC/TR 50427:20041
34、Scope This European Technical Report provides guidance on assessing the potential ignition hazard from the inadvertent extraction of energy from electromagnetic fields, propagated from communication, radar or other transmitting antennas to plant where a potentially flammable atmosphere may be presen
35、t. The frequency range covered by this European Technical Report is 9 kHz to 60 GHz. This European Technical Report does not apply to similar hazards arising from electromagnetic fields generated by other means, such as electric storms, electricity generating installations or other radiating electri
36、cal equipment, nor does it apply to any hazard arising within telecommunication or other electronic equipment.NOTE 1 The methods of assessment from 9 GHz to 60 GHz are based on extrapolation of data for frequencies below 9 GHz. NOTE 2 The ignition of dust is not covered in this European Technical Re
37、port. This European Technical Report also provides advice on how to mitigate the hazard in cases where the assessment indicates that a hazard may exist. This European Technical Report does not cover the hazards associated with the use of electro-explosive devices (EED) (see CLC/TR 50426), or the bio
38、logical hazards of exposure to RF fields. 2 Normative referencesThe 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 amendm
39、ents) applies. Publication Year TitleEN 60079-0 Electrical apparatus for explosive gas atmospheres Part 0: General requirements (IEC 60079-0) EN 50020 Electrical apparatus for potentially explosive atmospheres Intrinsic safety “i” EN 60079-10 Electrical apparatus for explosive gas atmospheres Part 1
40、0: Classification of hazardous areas (IEC 60079-10)3 Terms and definitions For the purposes of this European Technical Report the following terms and definitions apply. 3.1circuit factor, Qkperformance parameter for a structure acting as a receiving antenna (see 2)NOTE Assuming the structure to be t
41、uned to the transmission frequency ft, Qkis the ratio of ftto f, where f is the difference between those frequencies, one above and one below ft, at which the structure resonates when it is re-tuned so that the open circuit voltage at fthas fallen by 3 dB. Qkis closely related to the Q factor of a t
42、uned circuit. 3.2extractable power, Pmaxpower dissipated in a resistive load connected across a discontinuity in a structure acting as a receiving antennaNOTE The extractable power reaches its maximum when the structure is tuned to the frequency of the transmitter (under these conditions the impedan
43、ce of the structure presents a resistive value only, with no reactive components), and the load resistance is a value equal to that of the structure. 3.3modulus match power, Pmmmaximum value of extractable power that can be achieved with a resistive load at a frequency to which the structure is not
44、tuned (see 2) PD CLC/TR 50427:2004 8 3.4structure efficiencyratio of the extractable power that the structure can deliver to a matched load and the maximum extractable power delivered by a lossless short dipole in free space immersed in the same field 3.5thermal initiation timetime during which ener
45、gy deposited by the spark accumulates in a small volume of gas around it without significant thermal dissipationNOTE For times shorter than the thermal initiation time the total energy deposited by the spark will determine whether or not ignition occurs. For increasingly longer times, the power or r
46、ate at which energy is deposited becomes the determining factor forignition.3.6vulnerable zone region surrounding a transmitter in which a potential hazard could arise within a hazardous area of a plant 3.7far fieldregion, distant from the transmitter, in which the field strength is inversely propor
47、tional to distance in the absence of ground reflectionNOTE The inner limit of the far field is generally regarded as the distance d from the transmitter defined as follows. For frequencies up to and including 30 MHz, d = 8H2/O where H is the height of the top of the antenna above ground and O is the
48、 wavelength. At frequencies above 30 MHz, d = 2W2/O where W is the width of the antenna. 3.8near fieldregion close to the transmitter which lies within the far field regionNOTE In the near field region the dependence of the field strength on distance is complex and mutual coupling effects can also a
49、ffect the value of extractable power. 3.9flammable atmospheregas/air or vapour/air mixture capable of being ignited which can occur in a hazardous areaNOTE See EN 60079-10 for further information. 3.10equivalent isotropically radiated power (EIRP)product of the power supplied to the antenna and the antenna gain in a given direction relative to an isotropic antenna (absolute or isotropic gain) 3.11effective field strengthvalue of electric field strength due to a single transmitter which is derived from the transmitte
