We constantly hear about nuclear plants being a safety concern. On the other hand, natural gas never seems to get a second thought. As more gas power plants are built, more gas pipelines installed and gas consumption rises, few give much thought to the safety. After all, isn’t it “clean, safe and economical,” as the gas companies say?
Of course, the truth is that natural gas fires and explosions are fairly rare and when properly used, natural gas is reasonably safe, but not nearly as safe as something like nuclear energy. Natural gas facilities don’t go BOOM very often, but they do certainly do so on occasion. Natural gas is not an inherently safe fuel and the fact that it only explodes on occasion is due primarily to the engineering that goes into gas systems.
Many will point out that gas can’t burn or explode as long as it’s isolated from air. That’s certainly true, but once it does get lose and mixes with air, watch out!
That’s not to say that natural gas is not an important fuel and feedstock, but nobody should be under the illusion that it’s inherently safe or that it does not need to be treated with extreme caution. It can and will explode and kill people. That is the price of using natural gas. At the very least, this should be taken into account whenever natural gas is considered as a power source. Is it really necessary to accept this danger? Is there a safer alternative, such as nuclear fission?
Sometimes the answer is no. For small, load-following power plants, production of hydrocarbon-based chemicals, structure heating and other applications, gas may be the best option of reasonable economy, and the dangers it carries must be accepted, but can never be ignored.
Why flammable gases are especially dangerous:
- They are stored and distributed at high pressure pressure - gases have low density and in order to get enough to the end user, they must be compressed, or in some cases, liquefied. This means that the pipelines and tanks that store gas are always at much greater pressure than the atmosphere. If breached, they will not simply release gas slowly, it will rush out, sometimes violently. Mechanical stress to a tank or a pipeline can result in an explosion from the pressure alone.
- They easily and immediately mix with air – for a flammable material to become an explosive material, it must be thoroughly mixed with an oxidizer, such that all particles can rapidly combust due to the distribution of the oxidizer. This oxidizer can simply be the oxygen in the air if the material is thoroughly mixed with air to form a fuel-air cloud. In solids, this can be accomplished if they are pulverized into a dust and kicked up into a cloud. In liquids, this may happen if the liquid has been turned into a fine mist, but in gases it happens whenever the gas is released into the air. The two mix and produce a potentially explosive fuel-air bomb.
- They tend to ignite easily – Since flammable gases mix with the atmosphere easily and due to their low density, they tend to be very easy to ignite, when compared to other flammable substances. In the case of natural gas, it can ignite at concentrations as low as 5%
- It’s invisible and difficult to tell whether it has dispersed or not - Most gasses are invisible. Natural gas and LPG are also orderless in their native state, although a chemical is added to give them a distinct smell. The limits of human smell make it difficult to tell how much gas is present and whether or not it has been dispersed. It can be very difficult to determine whether a gas cloud has dispersed or lingers and to what degree. Natural gas tends to float upward, but when released from a compressed vessel, it may do the opposite until it reaches the temperature of the surrounding air (cold gasses tend to be heavier and pressure reduction makes the gas cold.) Gas can get trapped under overhangs or may linger if atmospheric moisture is high and winds are still.
- Long pipelines and high pressure mean that gas can continue to flow to an area after a fire – It can be very difficult to turn off the flow of gas from a pipeline. In some cases, the nearest valves are far enough away to make the effect of shutting off the gas take hours. If the gas is coming from a local tank, it may be difficult or impossible to reach cutoff points, and if it is coming directly from a well head, there may be no way of stopping it. Even after an initial explosion, a major gas leak may continue to burn as a “flaming geyser” or “gas volcano” that can’t easily be stopped. In many circumstances, the most dangerous part of fighting a gas fire is after the fire has been extinguished. At this point, the gas must be stopped, such as by capping a well head or leak. At any time during this procedure, it can reignite.
Natural gas explosion types:
- Boiling Liquid Expanding Vapor Explosion – This type of explosion occurs in liquid natural gas vessels, typically when a fire starts outside the main vessel, such as might occur if a leak catches fire. The heat causes the tank temperature to rise and the liquid to boil. Eventually the tank ruptures and the liquid inside flash evaporates and catches fire to explode. (Known as a BLEVE) BLEVE explosions are more common with LPG than natural gas, but can happen in liquid natural gas storage facilities.
- Combustion within gas container or pipeline - This type of explosion is relatively rare. It occurs when improper procedure or equipment malfunction allows air to enter a gas storage tank or pipeline. Normally gas cannot burn in such circumstances, as there is no oxygen. The most common cause of this is when an empty gas tank is open to the atmosphere and then later filled with gas without first being purged of oxygen. In enclosed systems like a tank or pipeline, it does not take very much to set off an explosion.
- Gas contained within a structure - This occurs when a gas leak allows natural gas to enter a building or other structure, where it mixes with air and is contained, not allowed to disperse. Since the structure contains the natural gas, only a small leak is required to build up a huge volume of gas, given enough time. As natural gas is lighter than air, it will often tend to build up at ceiling level and as more and more gas fills the structure, the level will slowly move down. The explosion can occur if the level of the gas eventually reaches that of an ignition source such as a pilot light or if another source, such as an electrical switch, static electricity or friction causes it to ignite. This type of explosion is common in vacant structures.
- Gas cloud explosion – This occurs when a large volume of gas is released from a leak, purge or other operation. The time that the gas lingers can depend on a number of factors, including temperature, winds, structures and the temperature of the gas. A large cloud of lingering gas can easily ignite and explode.
- Tank rupture and explosion – This occurs when a tank or pipe containing compressed gas explodes due to the internal pressure. The reason for the failure may be corrosion, materials fatigue or defects in the vessel. It can also happen if the pressure is too high and exceeds the design specs of the tank or pipe. The rupture can be violent and send pieces of the tank flying. The gas does not always ignite when a tank bursts, but it often does due to the violence of the rupture producing sparks.
2010 – Chandler, Oklahoma, USA
Type: Regional Natural Gas Pipeline Explosion
Result: Explosion reportedly enormous but luckily it occurred in a remote area. No injuries and only damage sustained was to pipeline.
2010 – Kleen Energy Power Plant, Middletown, Connecticut, USA
Type: Combined Cycle Gas Power Plant Explosion During Gas Purging
Result: 6 deaths, at least 24 injuries, extensive damage to power plant, by some estimates over half a billion dollars in damage, also caused damage to other local structures.
2009 – Siberia Russia
Type: Local Service Pipeline Explosion
Result: At least 8 deaths, unknown injuries, at least one apartment building destroyed, others damaged
2009 – Northern Ontario, Canada
Type: Pipeline Explosion of Major Continental Transmission Pipeline
Result: Some interruption to serve and severe pipeline damage, but no serious injuries due to remoteness of site. Explosion was described as “massive.”
2009 – ConAgra Foods Plant, Garner, North Carolina, USA
Type: Industrial User of Natural Gas Explosion During Gas Purging
Result: 4 deaths, 40 serious injuries, including severe burns, severe damage to plant resulting in the ultimate closure of the plant with severe local economic impacts.
2008 – Appomattox, Virginia, USA
Type: Natural Gas Transmission Pipeline Rupture Explosion and Fire
Result: Five injuries, many residents evacuated from homes. Two homes were destroyed and dozens only narrowly escaped being destroyed.
2007 – St Petersburg, Russia
Type: Explosion at Pumping Facility at Pipeline Supplying Power Plant
Result: Damage reported extensive, but official reports say no deaths. Temporary interruption of natural gas supply to Finland.
2004 – Ghislenghien, Belgium
Type: Major Natural Gas Pipeline Rupture and Explosion
Result: 24 Killed, 124 seriously injured, extreme local damage totaling many millions of Euro.
2004 – Stockline Plastics Factory, Glasglow, UK
Type: Industrial User of Natural Gas, Pipe Rupture and Explosion
Result: 9 deaths, 37 total reported injuries, 15 considered seriously injured, much of the factory destroyed
2004 – Arkhangelsk, Russia
Type: Local Service Pipeline Explosion
Result: 52 deaths, unknown injuries (probably hundreds), several buildings severely damaged or destroyed, many left homeless
2003 – Gao Qiao, Chongqing, China
Type: Well head blowout and mass release of “sour gas” containing large amounts of toxic hydrogen sulfide
Result: 243 deaths, at least 9000 injured, some seriously. Many of those injured will experience life-long respiratory complications and reduced lifespan. Over 64,000 had to be evacuated. Localized humanitarian disaster with catastrophic localized economic impact.
2000 – Carlsbad, New Mexico, USA
Type: Natural Gas Pipeline Rupture, Explosion and Fire
Result: Twelve Killed, several vehicles destroyed
1999 – Bridgeport, Alabama, USA
Type: Natural Gas Service Pipeline Rupture and Explosion
Result: Three killed, many structures severely damaged, four buildings destroyed or damaged beyond repair.
1999 – Wytheville Virginia, USA
Type: Natural Gas Pressure/Pump Station Explosion
Result: Two buildings destroyed (One home and one buisiness), others heavily damaged. The family that lived in a home that was destroyed were not in the house at the time. They would have been killed had they been home.
1998 – St. Cloud, Minnesota, USA
Type: Local Service Pipeline Explosion
Result: 2 Deaths, 11 serious injuries, six buildings destroyed
1998 – Esso Longford Facility, Australia
Type: Natural Gas Processing Facility and Oil Refinery
Result: 2 Deaths, 8 serious injuries, severe damage to facility and disruption to local gas supply
1997 – Indianapolis, Indiana, USA
Type: Natural Gas Pipeline Rupture and Explosion
Result: 1 Death, 1 serious injury, in excess of 2 million US Dollars in property damage
1994 – Edison, New Jersey, USA
Type: Regional Pipeline Explosion
Result: 1 Death, 100 left homeless, 14 buildings severely damaged or destroyed, tens of millions of dollars of damage
1988 – Piper Alpha Platform, North Sea
Type: Offshore Oil and Natural Gas Facility, Leak and Explosion
Result: 169 Deaths (including two rescue workers killed), 59 survivors, many of whom were injured in the explosion or suffered severe hypothermia, $3.4 billion in economic losses, platform destroyed
1984 – Abbystead, Lancashire, UK
Type: Natural Accumulation of Methane Gas at Water Valvehouse and Explosion
Result: 16 Deaths, 12 serous injuries, severe structural damage and economic claims over four million GBP.
1968 -Ronan Point, East London, UK
Type: Interior gas plumbing leak and explosion
Result: 5 deaths, unknown number of injuries (probably over 100), 23 story residential building heavily damaged
1968 – Richmond, Indiana, USA
Type: Local Service Pipeline Leak and Explosion
Result: 41 deaths, 150 injuries (officially reported), extreme damage to a large area of downtown district – many tens of millions of dollars total economic loss.
1965 – Natchitoches, Louisiana, USA
Type: Transmission Pipeline Rupture and Explosion
Result: 17 deaths, at least 9 serious injuries, many more moderate injuries, many buildings destroyed, many millions of dollars in damage.
1965 – La Salle, Quebec Canada
Type: Natural Gas Leak Within Structure and Explosion
Result: 28 dead. Apartment complex destroyed
1944 – Cleveland, Ohio, USA
Type: Liquefied Natural Gas Storage Tank Vapor Leak Leading to Fuel Air Cloud And Subsequent Explosion
Result: 130 deaths, hundreds injured, extreme damage to dozens of structures. Extreme financial losses. Local disaster.
1937 – New London School, New London, Texas, USA
Type: Natural Gas Leak Within Structure and Explosion
Result: At least 295 students and teachers killed (by some accounts many more), school building completely destroyed. Worst disaster to occur at a school in US history.
Additional dangers and incidents:
- Explosions at well heads and well head blowouts occur fairly frequently and are occasionally fatal.
- Small buildings and homes are destroyed by contained natural gas from an internal leak many times a year.
- “Sour gas” is natural gas with high in hydrogen sulfide. This is removed during refinement, but sour gas may be pumped significant distances from gas fields to refineries by pipelines. The gas is toxic even if it does not explode and can cause serious injury or death if released in quantity. These pipelines may be especially subject to corrosion. Several sour gas pipeline explosions have occurred.
- Natural gas storage locations and pipelines are known terrorist targets with potential for extremely catastrophic results. Several attacks have been made on pipelines in Canada, thankfully only minor damage has been caused and no fatalities. A massive explosion was caused by an attack by Kurdish separatists on a pipeline connecting Turkey and Iran and cutting off regional gas service until the pipeline could be repaired. No fatalities occurred, because the enormous explosion was in a very remote area.
This entry was posted on Tuesday, March 23rd, 2010 at 2:51 pm and is filed under Bad Science, Enviornment, Good Science, History, Misc. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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