Fighting LNG and LPG fires is not a simple task. Completely extinguishing these fires could leave a pool of liquid which will continue to release gas that could reignite in a much more intensive and violent fire. The most important first step is to cool any surrounding areas, tanks or pipes that contain these or other flammable liquids and cool the spaces that contain critical machinery. In this article we’ll discuss ideas and methods surrounding liquefied gasses using state of the art equipment and updated techniques.
As we watch the industry expand the production of LNG and LPG and now transporting these products by land and sea, we often wonder what to do in the event of a leak whether it be small or large. As firefighters, we know what to do based on our training using LPG in many scenarios, but how many of us have actually ever dealt with LNG? Both are liquefied gasses, however LNG reacts much differently when exposed to water than LPG when pooled. LNG itself is not flammable, however it off gases constantly, producing Natural Gas which is highly flammable. In its liquid state, LNG is about -162 Celsius (-259 Fahrenheit). LPG in its liquid state is about -44 Celsius (-48) Fahrenheit). When medium or high expansion foam is applied it can still off gas, thus the potential for re-ignition is still there. There are many factors to be considered with both of these types of gasses however LPG is much more stable and resistant to reaction with water than that of LNG.
When we talk about responding to incidents involving LNG and LPG we must take into consideration several factors. Location of the leak is your first priority. With LNG, a leak that has not ignited can do just as much damage due to the intense cold it impinges on what it comes in contact with. Something not many people are aware. That being said, a leak that has not pooled can be mitigated by large quantities of spraying water to disperse the vapors. Both LNG and LPG can be handled in this manner. If there is a significant leak, which is now beginning to pool in low lying areas, the response will change. Water can still be utilized for vapor dispersion, however careful consideration needs to be made by preventing the water to come in contact with the pooling liquid, especially in the case of LNG. Pooling will only occur if the leak has not ignited. Violent reactions occur with water comes in contact with the cold LNG pool and can create much larger vapor clouds that have a better chance of finding an ignition source as they expand and evolve through the explosive range.
As companies continue to develop their product base, some manufacturers have taken note of the extreme volume of required water needed to mitigate larger incidents. Water is just one tool in the toolbox when it comes to mitigation for these types of incidents. Other firefighting media that can be utilized is dry chemical powders, foam agents and inert gases along with Carbon Dioxide. All have a use in extinguishing fires of LNG and LPG, however as mentioned earlier, some have limitations and drawbacks, namely when used to extinguish LNG.
Manufacturers have many tools that provide good application however, rates of flow in water, foam solution and dry chemical all play a role in successful mitigation. Water, usually plentiful, is your best resource. Getting water to the incident can sometimes be a task in itself. Manufacturers are constantly providing innovative ways to move water further and at higher pressures. As you’ll see in the photo above left.
Ferrara Fire Apparatus Inc. and US Fire Pump LLC in Louisiana, United States, demonstrate water delivery using an elevated master stream with capability of more than 5,000 US GPM (18,927 lpm) keeping responders at a safe distance from the hazard.
Selecting the right tools to use for these emergencies can vary based on several factors. Some of these factors include past practices, previous training methods, geographical location, and/or policies and procedures dictated by a company, business practice, or an AHJ (Authority Having Jurisdiction). No matter what the tools selected are, successful incident mitigation outcome with no injuries and limited to no property damage is what we all like to see. As we look at innovation throughout the years, medium and high expansion finished foam has gotten better and can be used where previously had difficulties suppressing the high vapor pressure. Using foam for spilled and pooling LNG, when applied correctly, can create a frozen layer on top of the liquid to minimize the vapors and off gassing. Having the water needed available is where many manufactures have excelled in providing the proper tools. Large diameter hose along with pumps and submersible systems where lift height can pose a problem are more readily available and perform much better than their predecessors. Foam generators combined with proper training and support equipment allows for the best chance of preventing vapor explosions when the water sets on the pooling liquid.
Other tools used in vapor mitigation are large portable or fixed monitors. Using portable equipment allows for the equipment to be mobile and used in various ways. Having portable equipment puts the deployment in the hands of the responders and allows for the delivery devices to be spotted uphill and/or upwind of the emergency. Having this flexibility allows the responders to mitigate at a safer distance and use Mother Nature to their advantage. All while being cognizant of the reactivity LNG can pose. LNG reacts with humid air and produces moisture as it converts to Natural Gas. More water, if not enough, can create the same situation as the LNG boils off. When in ambient conditions it passes through its flammable range as it expands creating an explosive atmosphere if any ignition sources are nearby.
Understanding the properties of these two products can assist with the response tactics and provide personnel the means to mitigate and apply the tactic best suited.
Applying copious amounts of water and foam solution is your safest mitigation until the liquid evaporates. In fixed installations, there may be systems engineered to apply an adequate formation to reduce and stop the vapor emission, but what if they’re damaged or destroyed from the leak or explosion and fire. Having portable equipment prevents your eggs in one basket approach.
With the flammable range of LNG being 5%-15% in air and LPG having a flammable range of 2.1%-9.5%, the upper and lower explosive limits are narrow. Both will not burn as liquids and will boil when exposed to ambient air and humidity. They boil more rapidly when exposed to water. Selecting the proper tool to reduce and quickly change the time they pass through their flammable range is important.
We have talked about the properties of these fuels and how they differ, but more so, we discussed the need for responders to utilize the tools that will best suit the situation at hand. Training is paramount to help understand the response as well as selecting the tools and placing them in service to achieve a successful mitigation. As we continue to see more and more of these products being transported via rail, road and water, we must be ever vigilant in maintaining our knowledge, but more so, having the right equipment to handle the situation. Something we haven’t yet discussed, is mutual aid partners. Mutual aid allows teams of responders to request resources from surrounding agencies, both private and public, bringing apparatus and equipment if varying degrees to the table. Some of these items may be unique in design while others may be costly. As Mutual Aid partnerships grow around the world, some agencies have formed organizations that agencies can join providing key components. This allows for specialized equipment to be purchased and made available by each participating agency reducing the financial burden on any one agency. For example, on the east coast of the USA, there are partnerships between municipal agencies and private sector companies to aid in providing the needed equipment for a large scale incident, whether it be a bulk storage tank incident or de-watering after a major weather event, such as a hurricane. Another example is a partnership of several industrial companies, municipalities and government agencies in a non-profit organization combining the fire-fighting, rescue, hazardous material handling and emergency medical capabilities for the refining and petrochemical industry near the Gulf of Mexico. Mutual Aid can be a key to success as it provides much more assistance to the initial responders.
In closing I’d like to express that there are many ways to go about the mitigation of these types of emergencies. Proper training and having the right tools in your “toolbox” are paramount to a successful outcome. We all know that every fire goes out, but having the ability to safely and quickly mitigate the emergency is what will save lives and property… Stay Safe!
For more information, go to www.ferrarafire.com