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:
- 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.
- gas emissions such as hydrogen sulfide (H2S) or ammonia are a concern.
- 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.
- 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.
- 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.
Various Other Research
Several studies have been conducted throughout the years to determine the safety and dangers associated with LNG. The safety of LNG tankers (ocean going ships) was a major focus of several of these studies, which were conducted since these vessels carry significant amounts of LNG and visit ocean ports that may be in close proximity to inhabited areas. One example of such research can be found in the 2012 Report to Congress on Liquefied Natural Gas Safety Research published by the United States Department of Energy (DOE). The Liquefied Natural Gas (LNG) Import Terminals: Siting, Safety, and Regulation research conducted by the Congressional Research Service, for example. This study focuses emphasis on the safety of LNG terminals and related infrastructure. These and other publications cover the physical threats posed by LNG, such as pool fires, flammable vapor clouds, fire, and cryogenic implications, as well as the environmental consequences. Some studies also include ship safety, terminal safety, liquefaction plant safety, and security, among other topics.
Locating LNG import terminals, as well as ensuring their safety and compliance with regulations
Liquefied natural gas (LNG) is a hazardous fuel that is transported to U.S. ports by big tankers from foreign ports. While LNG has traditionally represented a modest proportion of natural gas supply in the United States, growing price volatility and the risk of domestic shortages have resulted in a considerable rise in LNG demand. Several energy corporations have proposed additional LNG import facilities along the United States’ eastern seaboard in order to accommodate the growing demand. Many of these terminals would be constructed on land, close to densely inhabited regions.
Under the Natural Gas Act of 1938 and the Energy Policy Act of 2005, the Government Energy Regulatory Commission (FERC) awards federal permission for the siting of new onshore LNG plants (P.L. 109-58). This clearance procedure integrates the Department of Transportation’s basic safety criteria for LNG, which were set earlier this year. Since its inception 45 years ago, LNG has maintained a high level of safety, with no LNG ship or land-based facility having been targeted by terrorists. Nonetheless proposed new LNG terminal facilities have sparked widespread public anxiety. Some community organizations and government authorities are concerned that LNG terminals may expose individuals in the surrounding area to unacceptable risks. Because of ongoing public concern about LNG safety, Congress has focused attention on a number of issues, including the exclusivity of FERC’s LNG siting authority, proposals for a regional LNG siting process, the lack of “remote” siting requirements in FERC regulations, state permitting requirements under the Clean Water Act and the Coastal Zone Management Act, the attractiveness of LNG to terrorists, the adequacy of Coast Guard security resources, and a number of other concerns.
LNG terminals have a direct impact on the safety of communities in the states and congressional districts where they are located, and they may have an impact on energy prices throughout the country. Against the backdrop of an unclear national demand for further LNG imports and continuing public concerns about LNG safety, some members of Congress have suggested revisions to safety safeguards in federal LNG site selection regulations. A number of bills introduced in the 110th Congress addressed issues such as Coast Guard LNG resources, the Federal Energy Regulatory Commission’s exclusive siting authority, state concurrence in federal LNG siting decisions, and agency coordination under the Coastal Zone Management Act, among other things. According to provisions in the Coast Guard Authorization Act of 2010 (H.R. 3619), which was enacted by the House on October 23, 2009, new waterway suitability notification requirements in LNG siting studies by the Federal Energy Regulatory Commission (FERC) (Sec. 1117). Maritime Hazardous Cargo Security Act (S. 1385), proposed by Senator Lautenberg and three co-sponsors on June 25, 2009, would mandate a national study to be conducted in order to find steps to strengthen the security of liquefied natural gas transportation by sea (Sec. 6).
The United States Congress may propose further LNG safety-related legislation, or it may use its oversight power in other ways to influence the approval of new LNG terminals if it determines that new LNG terminals as presently controlled would represent an unacceptable danger to public safety. Alternatively, Congress may examine various modifications to existing energy policy laws in the United States in order to lower the nation’s demand for natural gas or to enhance supply of North American natural gas, hence reducing the need for new LNG infrastructure in the United States.
LNG-related safety concerns
LNG is natural gas that has been cryogenically chilled and liquefied in order to minimize the volume for transportation and storage. A common storage temperature for the liquid is between -162 and -155°C, at which point the saturation vapor pressure will range between 1 and 10 bar. LNG is mostly composed of methane, although it may also include up to 10% ethane and propane.
As previously stated, natural gas is combustible when mixed with air at concentrations ranging from 5 to 12 percent. If LNG is freed from its containment vessel and begins to evaporate, the natural gas vapor cloud that results may catch fire, causing a large explosion. In this aspect, LNG is no different from other commonly used petroleum fuels such as gasoline, kerosene, and LPG in terms of combustion characteristics. LNG, on the other hand, will vanish entirely if no ignition source is present since it is lighter than air. LNG is very unlikely to ignite when in its liquid condition.
The fact that LNG is a cryogenic liquid increases the danger of cold burns when it comes into contact with the skin. In order to ensure safe storage, transportation, and handling of LNG, cryogenic equipment that complies with relevant standards and regulations should be used. Personnel engaged in transfer operations should be outfitted with personal protective equipment (PPE) in order to further reduce the hazards (i.e., filling an LNG road tanker or truck). In this way, the risks associated with LNG handling are quite comparable to those associated with other popular industrial gases such as liquid Nitrogen (LIN), liquid Argon (LAR), and oxygen (O2) (LOX).
Finally, if an LNG vapor cloud is allowed to accumulate in a confined place, it may pose a threat to human health. Because LNG may be used to replace oxygen in a restricted area, there is a danger of asphyxiation in such an environment. Installations should be built to prevent the building of LNG vapor clouds in order to avoid such dangers. Furthermore, while working with LNG, employees should be equipped with gas detectors or explosimeters.
Personal protection equipment (PPE) for LNG process
When working with cryogenic gases and liquids, it is recommended that you use the following personal protective equipment (PPE):
- LNG overalls with long sleeves (NEN-EN 342:2004/C1:2008 cold) are available.
- Safety Goggles or a face shield are recommended (NEN-EN-166 Eye protection)
- Shoes for safety (NEN-EN-ISO 20345) Safety shoes (e.g., Gate >=S2) are required.
- Gloves made of cryogenic liquid (EN511 protective gloves against cold)
- Helmet (NEN-EN 397 with A1 visor) Safety helmet (which is most effective when used in conjunction with neck protection)
- Detector for gas
LNG Material Safety Data Sheet
A material safety data sheet (MSDS) is a critical component of product stewardship, safety and health, and spill-handling processes and protocols. The Material Safety Data Sheet (MSDS) is used to store information on chemicals, chemical compounds, and chemical mixes. In addition, MSDS information may contain directions for the safe use of a specific material or product, as well as information on possible risks connected with that material or product. The Material Safety Data Sheet (MSDS) should be readily accessible for reference in the location where the chemicals are kept or used. Furthermore, the MSDS contains labeling standards that are based on the dangers to human health and the environment. Labels may incorporate hazard symbols, such as those used by the European Union to identify danger zones. Due to the fact that the same product might have various formulas depending on the country in which it is sold, it is essential to utilize an MSDS that is unique to both the nation and the provider.