BS 6656:2002
$215.11
Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation. Guide
| Published By | Publication Date | Number of Pages |
| BSI | 2002 | 92 |
This British Standard 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 present. The frequency range covered by this British Standard is 9 kHz to 60 GHz. This British Standard does not apply to similar hazards arising from electromagnetic fields generated by other means, such as electric storms, electricity generating installations or other radiating electrical 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 British Standard.
This British Standard also provides advice on how to mitigate the hazard in cases where the assessment indicates that a hazard may exist.
This British Standard does not cover the hazards associated with the use of electro-explosive devices (EED) (see BS 6657), or the biological hazards of exposure to RF fields.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 1 | BRITISH STANDARD |
| 2 | Committees responsible for this British�Standard |
| 3 | Contents |
| 7 | Introduction 1 Scope 2 Normative references |
| 8 | 3 Terms and definitions 3.1 circuit factor, 3.2 extractable power, 3.3 modulus match power, 3.4 structure efficiency 3.5 thermal initiation time 3.6 vulnerable zone 3.7 far field 3.8 near field 3.9 flammable atmosphere |
| 9 | 3.10 equivalent isotropically radiated power (EIRP) 3.11 effective field strength 3.12 antenna gain 3.13 hazard 3.14 safe distance 4 Symbols and abbreviations 4.1 Modulation codes |
| 10 | 4.2 Polarization codes 5 General considerations 5.1 Radio-frequency hazard 5.2 Philosophy of systematic method of approach |
| 11 | 5.3 Responsibility for making the hazard assessment 6 Transmitters and transmitter output parameters 6.1 Types of transmitter |
| 12 | 6.2 Frequency range 6.3 Transmitter output power 6.4 Antenna gain 6.5 Modulation factors |
| 13 | 7 Structures and spark-making mechanisms 7.1 Structures |
| 14 | 7.2 Loop-type structures |
| 15 | Figure 1 Typical loop-type structures |
| 16 | Figure 1 Typical loop-type structures (continued) |
| 17 | 7.3 Vertical structures 7.4 Spark-making mechanisms 8 Ignition of flammable atmospheres 8.1 Flammable atmospheres |
| 18 | Table 1 Representative gases for gas groups 8.2 Ignition by radio-frequency discharges 8.3 Criteria for ignition Table 2 Radio-frequency power thresholds |
| 19 | Table 3 Radio-frequency energy thresholds 9 Practical measurements and tests 9.1 Measurement of electromagnetic fields |
| 20 | 9.2 Measurement of extractable power 9.3 Test transmissions 9.4 Incendivity tests Table 4 Representative gases for gas groups and the most easily ignited mixture (%�volume with air) |
| 21 | 10 Methods of assessment for determining potential RF ignition hazards on a plant containing haza… 10.1 General |
| 22 | 10.2 Basis of the theoretical assessments |
| 23 | Figure 2 Assessment procedure flow chart |
| 24 | Table 5 On-site test procedure flow chart [see |
| 25 | Radii of vulnerable zones |
| 32 | Figure 4 Safe threshold field strength versus frequency for single unmodulated transmissions |
| 33 | 10.3 Initial assessments |
| 34 | Table 6 Radii of vulnerable zones for small structures at frequencies up to and including 30�MHz |
| 35 | Table 7 Maximum radii of vulnerable zones 10.4 Full assessment procedure |
| 37 | Table 8 Modulation factors |
| 39 | Figure 5 Field strength versus distance from the transmitter (land path) |
| 40 | Figure 6 Field strength versus distance from the transmitter (sea path) |
| 45 | Figure 7 Modulus match powers for |
| 47 | 10.5 Practical on-site tests |
| 49 | 11 Plant safety measures 11.1 General 11.2 Bonding |
| 50 | 11.3 Insulation 11.4 Reducing the structure efficiency Figure 8 Example of reduction of structure efficiency 11.5 De-tuning of structures |
| 51 | 12 Special cases 12.1 Cranes 12.2 Mobile and portable transmitters 12.3 Ships |
| 53 | Table 9 Maximum radii of vulnerable zones for ships’ transmitters 12.4 Offshore oil and gas installations |
| 54 | Table 10 Radio frequency transmitters on offshore mobile and fixed installations (Gas Group IIA, threshold… |
| 57 | Annex A (informative) Sources of information and addresses of some advisory bodies (informative) Sources of information and addresses of some advisory bodies Table A.1 Advisory bodies |
| 58 | Annex B (informative) Electromagnetic radiated fields and examples of radiating antenna and unintended re… (informative) Electromagnetic radiated fields and examples of radiating antenna and unintended re… B.1 Nature of the field B.2 Units of measurement |
| 59 | B.3 Examples of antenna characteristics Table B.1 Antennas for vertical polarization, for frequencies up to and including 30�MHz Table B.2 Antennas for horizontal polarization, for frequencies up to and including 30�MHz Table B.3 Antennas for frequencies above 30�MHz |
| 60 | Figure B.1 Typical antenna installations (physical characteristics of transmitting�antennas) |
| 61 | Figure B.1 Typical antenna installations (physical characteristics of transmitting�antennas) (continued) |
| 62 | B.4 Derivation of field strength expressions |
| 63 | Figure B.2 Definition of angles |
| 65 | B.5 Power extracted from structures |
| 66 | Annex C (informative) Subdivision of group II flammable gases and vapours (informative) Subdivision of group II flammable gases and vapours Table C.1 Subdivision of gases and vapours according to their maximum experimental safe gaps and minimum ig… |
| 71 | Annex D (normative) Measurement of electromagnetic fields (normative) Measurement of electromagnetic fields D.1 Range of measurement D.2 Mode of measurement D.3 Validity of measurement D.3.1 Far field region D.3.2 Near field region D.3.3 Circular and elliptical polarization D.3.4 Measurement errors |
| 72 | D.4 Method of measurement |
| 73 | D.6 Characteristics of measuring instruments D.6.1 Field strength measuring receivers D.6.2 Broad-band detectors Annex E (normative) Methods of measurement on structures (on-site tests) (normative) Methods of measurement on structures (on-site tests) E.1 General E.2 Measurement of extractable power |
| 75 | Figure E.1 Test arrangements for measurement of extractable power |
| 76 | E.3 Test transmissions |
| 77 | E.4 Ignition tests Table E.1 Current in calibration circuit |
| 78 | Test arrangement for incendivity tests Annex F (informative) Derivation of vulnerable zone distances for (informative) Derivation of vulnerable zone distances for |
| 79 | Annex G (informative) Worked examples of full assessment procedure (informative) Worked examples of full assessment procedure G.1 Example 1: Single frequency assessment Table G.1 Transmitter data (Example 1) |
| 80 | Table G.2 Plant data (Example 1) |
| 81 | G.2 Example 2: Assessment of multiple effectively continuous sources Tablle G.3 Transmitter data (Example 2) Table G.4 Plant data (Example 2) |
| 82 | Table G.5 Effective field strength for station transmitters (Example 2) Table G.6 Maximum extractable power from station transmissions (Example 2) |
| 84 | Figure G.1 Modulus match powers for structure resonated at 1,1 MHz |
| 85 | Table G.7 Total extractable power at Table G.8 Total extractable power at Table G.9 Total extractable power at |
| 86 | G.3 Example 3: Assessment of two radar transmitters situated 500�m and 200�m respectively from ethyle… Table G.10 Transmitter data (Example 3) Table G.11 Plant data (Example 3) |
| 87 | Table G.12 Peak field strength for radar transmitters (Example 3) Table G.13 Energy in structure from pulse transmissions (Example 3) Annex H (informative) Ground-wave propagation (vertical polarization) — Calculation of field strength (informative) Ground-wave propagation (vertical polarization) — Calculation of field strength H.1 General |
| 88 | H.2 Field strength calculation H.3 Limitation |
| 89 | H.4 Ground conditions |
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