CLC/TR 50427:2004

Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
   4.1 Modulation codes
   4.2 Polarization codes
5 General considerations
   5.1 Radio-frequency hazard
   5.2 Philosophy of systematic method of approach
   5.3 Responsibility for making the hazard assessment
6 Transmitters and transmitter output parameters
   6.1 Types of transmitter
   6.2 Frequency range
   6.3 Transmitter output power
   6.4 Antenna gain
   6.5 Modulation factors
        6.5.1 General
        6.5.2 Frequency modulation (FM)
        6.5.3 Amplitude modulation (AM)
        6.5.4 Single sideband (SSB) operation
        6.5.5 Pulsed radar
7 Structures and spark-making mechanisms
   7.1 Structures
   7.2 Loop-type structures
   7.3 Vertical structures
   7.4 Spark-making mechanisms
8 Ignition of flammable atmospheres
   8.1 Flammable atmospheres
   8.2 Ignition by radio-frequency discharges
   8.3 Criteria for ignition
        8.3.1 Effectively continuous transmissions
        8.3.2 Radar transmissions
9 Practical measurements and tests
   9.1 Measurement of electromagnetic fields
   9.2 Measurement of extractable power
   9.3 Test transmissions
   9.4 Incendivity tests
10 Methods of assessment for determining potential RF ignition
   hazards on a plant containing hazardous areas
   10.1 General
   10.2 Basis of the theoretical assessments
        10.2.1 General
        10.2.2 Initial assessment
        10.2.3 Full assessment
   10.3 Initial assessments
        10.3.1 Initial assessment of the risk from a particular
               transmitter site
        10.3.2 Initial assessment for a particular plant
   10.4 Full assessment procedure
        10.4.1 Procedure
        10.4.2 Information to be obtained
        10.4.3 Calculation of effective field strengths
        10.4.4 Calculation of extractable power or energy
        10.4.5 Comparison of the total extractable power or
               energy from the structure with the threshold
               values detailed in Clause 8
   10.5 Practical on-site tests
        10.5.1 Procedure
        10.5.2 Plant and transmitter both in existence
        10.5.3 Existing plant and proposed transmitter
        10.5.4 Existing transmitter and proposed plant
11 Plant safety measures
   11.1 General
   11.2 Bonding
   11.3 Insulation
   11.4 Reducing the structure efficiency
   11.5 De-tuning of structures
12 Special cases
   12.1 Cranes
   12.2 Mobile and portable transmitters
   12.3 Ships
        12.3.1 General
        12.3.2 Ships in harbour areas
        12.3.3 Ships at sea
   12.4 Offshore oil and gas installations
        12.4.1 General
        12.4.2 Structures on offshore installations
        12.4.3 Assessment procedures
        12.4.4 Radio frequency transmitters and vulnerable zones
        12.4.5 Safety measures and recommendation
Annex A (informative) Sources of information and addresses of
                      some advisory bodies
Annex B (informative) Electromagnetic radiated fields and
                      examples of radiating antenna and
                      unintended receiving antenna characteristics
Annex C (informative) Subdivision of group II flammable gases
                      and vapours
Annex D (normative) Measurement of electromagnetic fields
Annex E (normative) Methods of measurement on structures
                      (on-site tests)
Annex F (informative) Derivation of vulnerable zone distances
                      for Table 5, Table 6 and Table 10
Annex G (informative) Worked examples of full assessment procedure
Annex H (informative) Ground-wave propagation (vertical
                      polarization) - Calculation of field strength
Bibliography

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