CLC/TR 50427:2004

Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation - Guide

This standard provides guidance in assessing the possibility of inadvertent extraction of energy from an electromagnetic field propagated from communication, radar or other transmitter aerials and the coupling of this energy to an EED in a manner capable of causing initiation. It does not cover the similar hazard arising from electromagnetic fields generated by other means, for example electrical storms, electricity generating plant or power transmission lines, nor does it cover the potential hazards that may arise in oil and gas exploration and production operations

Leitfaden zur Verhinderung der unbeabsichtigten Zündung explosionsfähiger Atmosphären durch hochfrequente Strahlung

Evaluation des risques d'inflammation des atmosphères inflammables par des rayonnements de radiofréquence - Guide

Ugotavljanje nenamernega vžiga vnetljivih atmosfer z radiofrekvenčnim sevanjem - Vodilo

General Information

• Status: Published
• Publication Date: 13-Dec-2004
• ICS: 13.230 - Explosion protection
• ICS: 33.060.20 - Receiving and transmitting equipment
• Technical Committee: CLC/TC 31 - Electrical apparatus for explosive atmospheres - General requirements
• Drafting Committee: IEC/TC 31 - Electrical apparatus for potentially explosive atmospheres
• Parallel Committee: IEC/TC 31 - Electrical apparatus for potentially explosive atmospheres
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 14-Dec-2004
• Completion Date: 14-Dec-2004
• Ref Project: SIST-TP CLC/TR 50427:2005 - Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation - Guide

Standards Content (Sample)

SLOVENSKI STANDARD
01-april-2005
8JRWDYOMDQMHQHQDPHUQHJDYåLJDYQHWOMLYLKDWPRVIHU]UDGLRIUHNYHQþQLPVHYDQMHP
9RGLOR
Assessment of inadvertent ignition of flammable atmospheres by radio-frequency
radiation - Guide
Leitfaden zur Verhinderung der unbeabsichtigten Zündung explosionsfähiger
Atmosphären durch hochfrequente Strahlung
Evaluation des risques d'inflammation des atmosphères inflammables par des
rayonnements de radiofréquence - Guide
Ta slovenski standard je istoveten z: CLC/TR 50427:2004
ICS:
13.230 Varstvo pred eksplozijo Explosion protection
13.280 Varstvo pred sevanjem Radiation protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT CLC/TR 50427
RAPPORT TECHNIQUE
TECHNISCHER BERICHT December 2004

ICS 13.230; 33.060.20
English version
Assessment of inadvertent ignition of flammable atmospheres
by radio-frequency radiation –
Guide
Evaluation des risques d'inflammation Leitfaden zur Verhinderung
des atmosphères inflammables der unbeabsichtigten Zündung
par des rayonnements de explosionsfähiger Atmosphären
radiofréquence – durch hochfrequente Strahlung
Guide
This 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, Norway, Poland, Portugal, Slovakia, Slovenia,
Spain, Sweden, Switzerland and 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 - 1050 Brussels

© 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
Foreword
This Technical Report was prepared 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 – CLC/TR 50427:2004
Contents
Introduction .6
1 Scope.7
2 Normative references.7
3 Terms and definitions.7
4 Symbols and abbreviations .9
4.1 Modulation codes.9
4.2 Polarization codes.10
5 General considerations .10
5.1 Radio-frequency hazard.10
5.2 Philosophy of systematic method of approach .11
5.3 Responsibility for making the hazard assessment.11
6 Transmitters and transmitter output parameters .12
6.1 Types of transmitter .12
6.2 Frequency range.12
6.3 Transmitter output power .12
6.4 Antenna gain.12
6.5 Modulation factors.12
6.5.1 General.12
6.5.2 Frequency modulation (FM).13
6.5.3 Amplitude modulation (AM).13
6.5.4 Single sideband (SSB) operation.13
6.5.5 Pulsed radar.13
7 Structures and spark-making mechanisms .14
7.1 Structures.14
7.2 Loop-type structures .14
7.3 Vertical structures .16
7.4 Spark-making mechanisms.17
8 Ignition of flammable atmospheres.17
8.1 Flammable atmospheres .17
8.2 Ignition by radio-frequency discharges .17
8.3 Criteria for ignition.18
8.3.1 Effectively continuous transmissions .18
8.3.2 Radar transmissions .18
9 Practical measurements and tests.19
9.1 Measurement of electromagnetic fields .19
9.2 Measurement of extractable power.19
9.3 Test transmissions .20
9.4 Incendivity tests.20

10 Methods of assessment for determining potential RF ignition hazards on a plant
containing hazardous areas.21
10.1 General.21
10.2 Basis of the theoretical assessments .21
10.2.1 General.21
10.2.2 Initial assessment.22
10.2.3 Full assessment .22
10.3 Initial assessments.32
10.3.1 Initial assessment of the risk from a particular transmitter site.32
10.3.2 Initial assessment for a particular plant.33
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 energy.41
10.4.5 Comparison of the total extractable power or energy from the structure with the
threshold values detailed in Clause 8 .43
10.5 Practical on-site tests.46
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 (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 efficiency.50
11.5 De-tuning of structures.50
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 in harbour areas.52
12.3.3 Ships at sea .52
12.4 Offshore oil and gas installations.53
12.4.1 General.53
12.4.2 Structures on offshore installations.53
12.4.3 Assessment procedures.53
12.4.4 Radio frequency transmitters and vulnerable zones.54
12.4.5 Safety measures and recommendation .55

– 5 – CLC/TR 50427:2004
Annex A (informative) Sources of information and addresses of some advisory bodies.59
Annex B (informative) Electromagnetic radiated fields and examples of radiating antenna and
unintended receiving antenna characteristics .61
Annex C (informative) Subdivision of group II flammable gases and vapours.69
Annex D (normative) Measurement of electromagnetic fields .74
Annex E (normative) Methods of measurement on structures (on-site tests).78
Annex F (informative) Derivation of vulnerable zone distances for Table 5, Table 6 and Table 10 .84
Annex G (informative) Worked examples of full assessment procedure .85
Annex H (informative) Ground-wave propagation (vertical polarization) -
Calculation of field strength .94
Bibliography.96

Introduction
Electromagnetic waves produced by radio-frequency (RF) transmitters (e.g. radio, television and radar)
will induce electric currents
...