Like It Or Not; It’s Here
Fighting LNG Ship Fires
Originally Published Sept 2007
First, let me state that this article is neither FOR nor AGAINST Liquid Natural Gas (LNG) in the USA. Its purpose is to understand what it is and how the vessels crew and Land-Based Firefighters and first responders can deal with emergencies. Opponents of LNG have come up with many false statements about the dangers of LNG while the LNG industry may lead us to believe there is absolutely no danger in handling LNG. We as firefighters (marine or land-based) and as the mariners who work with the LNG vessels must look at this issue in a more unbiased view. Anything is dangerous if used improperly. Even water has been found to be the culprit of many devastating oil tanker explosions when used under pressure to clean the vessels tanks. The static electric charge the water builds up can create a spark which can rip apart a huge oil tanker. We have also seen that water has caused many vessels to capsize and sink when too much of it has accumulated aboard a ship during firefighting operations.
My company, Marine Firefighting Inc., has been involved in providing informational seminars to the tug boat crews who have the task of escorting some of the large LNG ships into US waters. The tug boats being used are specially designed for this task. Each is equipped with state of the art firefighting equipment. MFI has been providing the familiarization with this new firefighting equipment and also familiarization with the properties of the LNG they will be working with.
Much controversy surrounds the Liquid Natural Gas (LNG) industry in the United States. A good deal of the criticism comes from the “Not in my back yard” syndrome. Most of us realize that our energy needs will soon outpace our supplies. With new emerging economies such as China and India the world’s existing oil reserves are going to be drawn upon much more than at any time in our history. LNG has been presented as one of the answers of bridging the eminent energy gap between users and suppliers. However, no one wants to live next door to an LNG plant.
What is LNG? Liquid Natural Gas (LNG) is a colorless, odorless, liquid which is natural gas in a liquid form. Previously, the world’s large supplies of natural gas have not been available to areas remote from these gas wells. The cost of shipping natural gas in its gaseous state was simply too expensive. Liquefying natural gas reduces its volume 600 times (see diagram left.). Because of this reduction in volume it became profitable to export natural gas in its liquid form (LNG). The process of liquefying natural gas differs from the liquefying of other gasses. The main difference is that LNG does not require pressurization to keep this gas in a liquid state as is the case with Liquid Petroleum Gases (LPG) such as Propane. (Marine transport of Propane may use refrigeration to reduce its pressure during transit.) LNG is formed by subjecting natural gas to extremely cold temperatures. At minus 260 degrees F (-161°C ) the gas becomes a liquid at atmospheric pressure. Liquids at these temperatures are considered “Cryogenic”.1
When the natural gas was first removed from the ground it was mostly methane, however, it also contained many impurities. Most of these impurities are removed in the liquefaction process. Because of this, LNG is almost pure methane. Therefore, when LNG vapor burns there is no visible smoke as there would be if an equal amount of gasoline vapor were burned. Note I said vapor. The actual liquid does not burn. A flammable liquid evaporates into a gas. It’s that gas that is burning when there is a fire.
The weight of LNG is also important. LNG weighs just 3.9 pounds (1.8 Kilograms) per gallon. This is important because the weight of a gallon of water is 8.3 pounds (3.8 Kilograms). That means that the LNG will float on the surface when spilled onto the water. And when it evaporates or burns off there is no environmental mess to clean up.
Regardless of your viewpoint on LNG it is something that already is a factor in the USA and will become a much greater factor in the very near future. Currently there are five operating regasification LNG facilities in the US. Just last year (2005) three new LNG terminal construction requests received the go-ahead and two existing terminals won approval to expand their operations. This makes 11-LNG projects currently under construction and there are 40 more applications before the Federal Energy Regulatory Commission (FERC).2
So, if LNG is already set to become a major part in the energy supply chain within the USA I feel it is time that we address some issues that first responders and mariners should become familiar with. Liquefied Natural Gas is not stored under pressure so some of the problems associated with pressurized gas containers will not apply to LNG.
Because LNG is stored at -260°F it does present the problem of instantly freezing anything that the liquid touches. Mariners or First Responders and their equipment would also be subject to this freezing if they come in direct contact with the liquid. Therefore, all personnel who might come in contact with the liquid at an LNG emergency should be provided with personal protective equipment (PPE) designed to protect against this hazard. Your equipment, fire apparatus, and emergency vessels are also subject to this cryogenic effect. When dealing with metal, such as the deck of a tug or fire boat, that metal might be subject to brittle fracture if the cryogenic liquid comes in contact with the deck.
As mentioned at the beginning of this article, most new LNG escort tug boats are equipped with Fi Fi 1 (Firefighting 1) safety equipment (click on Diagram to the left) . To obtain any Fi Fi category (1, 2, or 3) the vessel must have a certain level of firefighting equipment.
At all levels of Fi Fi categories the vessel must have a deluge system which will protect the vessel and crew from radiant heat. This deluge system is composed of a series of pipes all over the deck and pilot house of the tug boat. At several points sprinkler heads and deluge nozzles are inserted in the piping.
When water is started, it projects a protective curtain around the surface area of the tug. This water curtain helps to protect the vessel and crew from the effects of radiant heat. This would allow the vessel to escape the scene of a fire in order to reach an area of refuge or it might enable the vessel to enter an area of high heat to effect a rescue. (See photo left.)
But this water deluge serves another purpose when it comes to LNG. The vessels deck is continuously wet down and this water on the deck helps to protect the deck from the brittle fracture effects of the LNG. As the LNG hits the water surface it is immediately warmed and disbursed as a gas or washed over the side.
It must be remembered that LNG is just natural gas in a liquid form. Therefor, all the properties that we associate with natural gas will be present as the LNG boils off into a gas.
The flammability range of a gas is the mixture of gas and air that would be required for that gas to ignite and burn,
Luckily this gas is usually either too rich or too lean to burn. The LNG gas will only burn when it is in a concentration between 5% and 15% when mixed with air.
If it’s mixture with air is below 5% then it is too lean to burn. If the gas and air mixture is above 15% then it is too rich to burn. The illustration on the right gives a graphic representation of this flammable range.
If you have ever seen a demonstration of an LNG spill or leak you will remember seeing the white cloud that forms. Many mistakenly believe that this cloud is the gas. Remember, we said that LNG is colorless and odorless. You cannot see the actual gas. What you are looking at when that white cloud is present is water vapor in the air that is chilled by the extreme cold of the LNG to form a fog or even snowflakes. It is odorless because that’s the way natural gas is in its natural state. The odor we all associated with natural gas when it leaks from your cooking stove at home is an odorant called mercaptan and/or thiophane that is added by your local gas utility company. (This gives that rotten egg or rotting garbage smell.)
Because LNG is merely natural gas in a liquid state, when it returns to a gas it has all the properties of natural gas. If you enter the vapor cloud (and we now know that the white color is only chilled moisture in the air) you will be subjected to the asphyxiant properties of the gas. All first responders should be equipped with and ordered to wear self contained breathing apparatus (SCBA) until the air is tested and found safe.
Because LNG rapidly reverts back to a gas when heated, most small spills will have either evaporated and risen into the atmosphere or, if ignited, the fire will have consumed the LNG by the time municipal first responders arrive. If it is merely a spill with no ignition the on-scene action is usually limited to closing valves to stop the spill and insuring that any vapor cloud is dispersed with water spray and directed away from any source of ignition. If the vapor from this minor spill does reach a source of ignition and the gas concentration is within the 5% to 15% range the ensuing flame will burn back to its source at a slower rate than that of gasoline or propane vapor. If the spill is ignited initially, its vapors will burn off at the source until all the LNG has been vaporized. The on scene action at this fire will generally consist of not extinguishing the fire until the source of the leak has been shut and the flow stopped. Quite often the fire will then be allowed to burn until all LNG has been consumed. On scene first responders will be protecting any exposures which may be in danger and possibly using fog streams to divert the vapor cloud and quicken the warming of the vapor so it will rise and dissipate more rapidly.
If the fire is to be extinguished you do not use water. Much success has been accomplished with the use of a combination of firefighting foam and dry chemical agents. The foam of choice here is Hi-Expansion foam. It has been found that the foam both separates the LNG from sources of ignition and also allows the controlled regasification of the LNG through frozen tunnels which form in the foam. The foam must be applied in very large quantities in a very short time therefor newer high capacity foam generators have been invented.
I mentioned that you do not use water to extinguish an LNG fire. Water will react violently with the LNG and may cause the fire to flare up and intensify. Another possibility is that the water will cause a Rapid Phase Transition (RPT) of the LNG. LNG will turn to a gas at a normal rate when exposed to the air. When it comes into contact with water this transition from a liquid to a gas is greatly increased. (At times this may even be desirable under controlled circumstances) However, if the transition is speeded up too much the expansion of so much liquid into a gas in a small area will cause a RPT. “A large amount of energy is released during this rapid transition between phases and a physical explosion can occur. While there is no combustion, this physical explosion can be hazardous to any nearby person or buildings.”3
I have done much research on LNG over the past few years and I have come to believe that, if handled properly, LNG can be as safe if not safer than many of the petroleum based energy products currently in use. The LNG industry has a remarkable record when it comes to the marine shipment of Liquefied Natural Gas. If we as Firefighters and as Mariners take the safety precautions seriously we should be able to keep up the industry’s record.
This article is in no way intended to be a complete study of LNG. Anyone who is tasked with handling LNG or responding to an LNG incident should receive detailed information about the LNG and about operating at LNG emergencies. Please contact us for details about our LNG familiarization seminars.
Tom is a retired Lieutenant of the New York City Fire Department’s Marine Division. During his 34-year tenure with the FDNY he worked at structural firefighting in some of the busiest areas of New York City. In his last ten years he also acted in the capacity of Training Officer for the FDNY Marine Division. Tom held a US Coast Guard License as a Ships Master and has been certified as a Fire instructor both within New York State and Nationally in the USA.
He is currently a participating member of the Society of Naval Architects and Marine Engineers (SNAME) Fishing Vessel Operations and Safety panel and also their Small Working Vessel Operations and Safety panel. Tom is also a Principal Member of the NFPA Technical Committee on Merchant Vessels.
The Marine Firefighting Institute is available for Lectures, Seminars and Consulting. To find out more CLICK HERE
- “What are cryogenic liquids? Cryogenic liquids are liquefied gases that are kept in their liquid state at very low temperatures. The word “cryogenic” means “producing, or related to, low temperatures,” and all cryogenic liquids are extremely cold. Cryogenic liquids have boiling points below -150°C(- 238°F) (Carbon dioxide and nitrous oxide, which have slightly higher boiling points are sometimes included in this category). All cryogenic liquids are gases at normal temperatures and pressures. These gases must be cooled below room temperature before an increase in pressure can liquefy them. Different cryogens become liquids under different conditions of temperature and pressure, but all have two properties in common: they are extremely cold, and small amounts of liquid can expand into very large volumes of gas. ” Quote taken from the Canadian Centre for Occupational Health and Safety website.
- “Gassed Up”, Kahy Brgren Smith, Work Boat magazine, December 2006 edition. Pg. 50
- “California Energy Commission” web-site http://www.energy.ca.gov/lng/faq.html#1100