LNG Plant Safety

The use of natural gas as a cleaner-burning alternative to other fossil fuels is becoming more popular as the globe works toward decarbonization. Natural gas may be converted to liquefied natural gas (LNG) for storage and transportation purposes, which is safer. Facilities that handle LNG, such as liquefaction plants, regasification plants, and storage facilities, are still connected with the possibility of injury or death from the gas. Understanding these dangers is critical to putting in place the required preventative and mitigation measures to protect people and property.

When it comes to LNG plants, an uncontrolled leak of a cryogenic, poisonous, or combustible fluid is a major concern. Releases of this kind might originate in a variety of locations within the industrial system. When these releases occur, the consequences are determined by what they expose and whether or not they are ignited. For the sake of simplicity, the most significant LNG plant risks may be divided into seven categories.

Natural gas liquids (LNG) take up just 1/600th of the volume of natural gas in its gaseous condition, but they maintain all of the energy potential. As a result, the energy potential of a certain volume of LNG is much larger than the energy potential of a same amount of natural gas in its gaseous condition. The intrinsic features of LNG, as well as the design and operation of LNG facilities and transportation modes, are all taken into consideration when addressing the safety of LNG facilities.

Land-based LNG facilities use impoundment structures surrounding LNG tanks and pipes, which are intended to limit the spread of LNG in the event of an accidental leak. When a release occurs, fire and vapor suppression devices are installed in order to limit the repercussions of the event. Automated fire suppression and vapor suppression systems are activated by gas detectors, fire detectors, temperature sensors, and other sensors. Firefighters may employ water spray to cool heat-affected exposures, or high-expansion foam to lessen the effect of radiant heat on certain exposures in the case of a fire. Vapor fences are constructed at certain sites to prevent fumes from escaping and spreading to neighboring property boundaries. In addition, vacuum jacketed pipe offers an extra layer of protection in the event that the inner pipe ruptures. When operating parameters exceed the usual range, emergency shutdown mechanisms are activated to prevent further damage. The operator of an LNG plant must establish and adhere to thorough maintenance protocols in order to maintain the integrity of the facility’s different safety measures.

Prior to beginning operations, the LNG plant operator must develop precise operating procedures that outline the usual operating parameters for all of the facility’s machinery. Any time a piece of equipment is upgraded or replaced, all associated processes must be examined and, if required, adjusted in order to maintain the system’s integrity. All staff are required to undergo training in operations and maintenance, security, and firefighting before they may begin working. Coordination with local authority and informing them of the sorts of fire control devices accessible inside the facility are essential tasks for an owner or operator. Aside from that, federal requirements need a high level of security for the facility, which includes access control systems, communications systems, enclosure monitoring, and patrolling.

Risks associated with LNG installations include:

Temperature

      - It is possible to have cryogenic liquid releases that induce embrittlement if they come into contact with materials that are not intended to manage such releases, and freeze burns if they come into contact with persons.

      - Turbines, boilers, and engines generate electricity and heat by releasing hot vapor into the atmosphere.

Toxic

      - gas emissions such as hydrogen sulfide (H2S) or ammonia are a concern.

Asphyxiation

      - Releases of nitrogen oxide, carbon monoxide, carbon dioxide, or sulfur dioxide that replace oxygen in an area and may result in asphyxiation are classified as asphyxiation.

Pool Fire

      - Liquid discharges that collect in a pool on the ground or in water and ignite, resulting in a pool fire that might burn for hours or days.

Jet fire

      - Pressurized gas or liquid is released and ignites, resulting in a high heat flux jet fire with a fast rate of spread.

Vapor dispersion/flash fire

      - Gas or liquid discharges that cause a flammable cloud to build in an open area and then ignite, resulting in a brief and powerful flash fire that is hazardous to the surrounding environment.

Explosion of a vapor cloud (VCE)

      - An explosion and pressure wave are caused by the discharge of gas or liquid, which causes a flammable cloud to build in a crowded or confined region and then ignites.

Research and Studies about LNG Safety

Through its Pipeline Safety Research and Development programs, the Federal Highway Administration (PHMSA) sponsors LNG research. The following LNG projects are underway: 

      - DTRS56-04-T-0005, Modeling and Assessing a Spectrum of Accidental Fires and Risks in an LNG Facility.

      - DTPH5615T00005, Comparison of Exclusion Zone Calculations and Vapor Dispersion Modeling Tools.

      - DTRS56-04-T-0005, Modeling and Assessing a Spectrum of Accidental Fires and Risks in an LNG Facility.

      - DTPH5615T00008, Statistical Review and Gap Analysis of LNG Failure Rate Table (Statistical Review and Gap Analysis of LNG Failure Rate Table)

An Overview of the History of Vapor Cloud Explosions (VCE)

The recent availability of domestic shale gas has resulted in the construction of LNG export facilities that will be able to liquefy massive amounts of natural gas. When it comes to liquefying natural gas, these facilities need substantially bigger volumes of refrigerants than are generally required in peak shaving or small-scale operations. ethane, propane, ethylene, and iso-butane are among the heavy hydrocarbons found in most refrigerants gases and mixes used in export facilities, and they are referred to as heavy hydrocarbons. These gases are comparable to gases that have caused VCEs at petrochemical sites in the past. However, the Pipeline and Hazardous Materials Safety Administration (PHMSA) is not aware of any valid reports of outdoor natural gas vapor cloud explosions and does not think that there is a danger of vapor cloud explosions (VCEs) owing to the emission of methane in an open area.

The Review of Vapor Cloud Explosion Incidents report was sponsored by the Pipeline and Hazardous Materials Safety Administration (PHMSA) with the primary goal of improving scientific understanding of vapor cloud development and explosion in order to more reliably assess hazards at large liquid natural gas (LNG) export facilities. We must emphasize that the LNG export facilities in operation today have several levels of security in place that were not in place at the sites described in the study. Many of the lessons learnt from these incidents have resulted in the implementation of safety measures that are now needed in LNG installations. Specifically, the purpose of reviewing the specific incidents in this report is to examine the extensive forensic evidence that is available, which provides the information necessary to investigate how the vapor cloud formed and ignited, the amount of overpressure exerted, and other information about the mechanism of VCE.

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