CLC/TR 50426:2004

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 the systematic method of approach
   5.3 Responsibility for making the hazard assessment
   5.4 Recommended practices for radio silence in offshore
        operations
6 Transmitters and transmitter output parameters
   6.1 Types of transmitters
   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 Circuits for blasting and well perforation
   7.1 General
   7.2 Typical blasting circuit layouts
        7.2.1 General
        7.2.2 Extended line blasts
        7.2.3 Benching or 3-dimensional blasts
        7.2.4 Multipattern blasts
        7.2.5 Shaft sinking
        7.2.6 Demolition work
   7.3 Circuits formed during well-perforating using wireline
8 Electro-explosive devices
   8.1 General
   8.2 Commercial EED
   8.3 EED hazard threshold
   8.4 Common mode operation
9 Methods of assessment for determining potential RF
   ignition hazards on a site where EED are used
   9.1 General
   9.2 Basis of the theoretical assessments for land sites
        9.2.1 General
   9.3 Initial assessment for land sites
        9.3.1 Initial assessment of the risk from a particular
              transmitter site
        9.3.2 Initial assessment for a particular site using EED
   9.4 Full assessment procedure for land sites
        9.4.1 Procedure
        9.4.2 Information to be obtained
        9.4.3 Calculation of effective field strength
   9.5 Safe field strength
        9.5.1 General
        9.5.2 Single EED
        9.5.3 Single EED with extended leading wires
        9.5.4 EED in typical quarry/demolition firing circuits
        9.5.5 EED in well-perforating drilling operations
   9.6 Multiple transmissions
        9.6.1 General
        9.6.2 Multiple-transmission assessments for quarry/demolition
              sites
        9.6.3 Multiple transmission assessments for well-perforating
              drilling operations
   9.7 Assessments for offshore drilling operations
10 Practical on-site testing
11 Safety procedures
   11.1 General procedures
   11.2 Alternative means of firing
12 Special applications
   12.1 Semi-permanent installations
   12.2 Flammable hazard situations
   12.3 Use of transmitters in mines and quarries
   12.4 Safety in transit
Annex A (informative) Extraction of energy from the
                      electromagnetic field
Annex B (informative) Measurement of electromagnetic fields
Annex C (informative) Sources of information and addresses of
                      advisory bodies - UK ONLY
Annex D (informative) Electromagnetic radiated fields and
                      examples of radiating antennas and
                      unintended receiving antenna characteristics
Annex E (informative) The effective resistance of the leading
                      wires of an EED
Annex F (informative) Derivation of minimum distances of safe
                      approach for Table 2 and Table 3
Annex G (informative) Ground-wave propagation (vertical polarization):
                      calculation of field strength
Annex H (informative) Worked examples to demonstrate the effects
                      of antenna gain
Annex I (informative) The effects of leading wire resistance,
                      safety resistors and the use of EED with
                      different characteristics
Annex J (informative) Derivation of Figure 12a) to Figure 12g)
                      for EED alone incorporating the
                      resistance of leading wires and safety
                      resistances
Bibliography

This standard provides guidance in assessing the potential ignition hazard from the inadvertent extraction of energy from electromagnetic fields, propagated from communication, radar or other transmitting aerials to plant where a potentially flammable atmosphere may be present. The standard is not concerned with similar hazards arising from electromagnetic fields generated by other means, such as electric storms, electricity generating installations or other radiating electrical equipment, nor is it concerned with any hazard arising within telecommunications or oter electronic equipment