Protection against inadvertent ignition of explosive atmospheres by radio-frequency radiation at onshore hazardous installations
Summary
This document provides guidance on the expected standard for protection against inadvertent ignition of explosive atmospheres by radio-frequency radiation at hazardous installations.
Introduction
Ignition-capable sparks can occur when electric currents and voltages are induced in conducting structures by electromagnetic waves produced by radio-frequency (RF) transmitters (eg radio, television and radar).
Although this is a recognised phenomenon, research suggests that the probability of it leading to ignition of an explosive atmosphere is low, therefore Inspectors must act proportionately to focus on major hazard installations where reasonably foreseeable risk remains.
Action
Inspectors should:
- use the high level process described in Figure 1 of Appendix 1 and the accompanying notes to verify, or otherwise, that relevant good practice has been applied;
- refer Duty Holders to the high level process described in Figure 1 of Appendix 1 and the accompanying notes so that recognised engineered measures can be applied to relevant structures before assessment of risk from first principles is considered.
Background
For the purpose of the Enforcement Management Model, this guidance is an interpretative standard.
Relevant good practice is provided by PD CLC/TR 50427, Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation - Guide. It provides a process for identifying and analysing structures that are vulnerable to the ignition-capable effects of radio-frequency radiation and provides guidance on how risk can be managed. In parts, it is a technical standard that requires a deep engineering knowledge, however, such engineering need only be applied where the assessment of risk deems it necessary.
The following research has been carried out into ignition probabilities:
- Research Report 226 - Development of a method for the determination of on-site ignition probabilities
- Contract Research Report 203/1998 - A model for the ignition probabilities of flammable gases Phase 2
- Contract Research Report 226/1997 - Ignition probabilities of flammable gases
The research suggests that radio-frequency sources present negligible likelihood of ignition, however, publically available information, for example from OSHA, suggests that electrical discharges from structures close to radio broadcast transmitters have been observed.
Organisation
Targeting
Onshore major hazard installations.
Timing
Ongoing.
Resources
To be used by HID EC&I Specialist Inspectors during established intervention processes.
Recording & Reporting
No special requirements.
Health & Safety
No special requirements.
Diversity
No special requirements.
Further References
Relevant Acts and Regulations
- Health and Safety at Work etc Act 1974 (as amended)
- Control of Major Accident Hazards Regulations 1999 (as amended)
- Management of Health and Safety at Work Regulations 1999 (as amended)
- The Dangerous Substances and Explosive Atmospheres Regulations 2002
Relevant Good Practice
- PD CLC/TR 50427 – Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation - Guide
- BS 6656:2002 Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation — Guide (current, superseded)
- SGOTT: International Safety Guide for Oil Tankers and Terminals, International Chamber of Shipping
Contacts
HID Chemicals, Explosives and Microbiological Hazards Division 2E Electrical, Control and Instrumentation Team