When it comes to maintaining the safety of LNG facilities, what are the gas and fire detection requirements?
The world interest for energy and cleaner fuels is growing and liquefied natural gas (LNG) plays an important role in meeting these needs. Scale and expansion of LNG demand raise fundamental questions concerning safe handling and use. Some LNG infrastructures, especially vehicle fuelling stations, are located within public areas and many countries now require installation of both gas and flame detectors to address public safety concerns. In Europe, several LNG facility safety standards have been adopted. EN 13645 Standard for the design and construction of onshore stationary LNG installations, with a storage capacity between 5t and 200t, stipulates in clause 6, “Consideration shall be given to the installation of fixed leak detection systems with executive action to stop the leak source, to isolate relevant sections of plant and shutdown sources of ignition in the vicinity.” The newest ISO 16924 specifies the design, construction, operation, maintenance and inspection of stations for fuelling LNG to vehicles, including equipment, safety and control devices, indicating that offloading area shall be equipped with leak detection systems. EN 1473 Standard for larger installation and equipment for liquefied natural gas specifies in clause 5.3, “A detection system shall be provided to give warning of any leakage of LNG or natural gas and also to give warning in the event of fire.”
Considering these requirements, practical deployment of fire and gas detectors that maximise detection efficiency is vital. This approach is based upon the notion that any single detection technique cannot respond to all hazardous events and consequently, risk of detection system failure is reduced by deploying detection instruments that deliver complementary strengths while minimising traditional technology limitations.
Improved safety through gas detection system diversity
Hazards associated with LNG include cryogenic temperature of constantly boiling liquid, vapour expansion and dispersion characteristics making it highly flammable. Although a combination of hazards occurs in most instances, the primary one is leakage of a flammable mixture that can lead to fire or explosion. As LNG’s minimum ignition energy at atmospheric pressure is around 0.28mJ, it can readily be ignited.
The first step in fire escalation and detonation is loss of gas containment. When released at temperatures below -110°C LNG vapour is heavier than air and the vapour blankets the ground, with clouds travelling in the wind direction. As soon as the temperature is above -110°C, the LNG vapour becomes lighter than air and will rise when sufficiently warmed by ambient air.