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Fire Extinguishing Agents: Making the Right Choice
Janine
Posted: Friday, October 7, 2011 5:29 PM
Joined: 02/05/2008
Posts: 392


You’re underway at sea when you hear, “Fire in the galley!”  What would be the correct extinguishing agent for this fire? Which extinguishing agent would be the wrong choice? By quickly identifying the type of material that is burning and knowing which extinguishing agent to apply, you should have a positive outcome.

Water
Water is a universal extinguishing agent, but it’s not the best choice for all types of fires. Water is the best choice for Class A (solid materials such as wood, cloth, rubber) fire extinguishment and for boundary cooling. Water affects the fire by removing the heat. The smaller the water droplets the more heat is absorbed; smaller water droplets create greater surface area than large water droplets. For cabin areas with large amounts of Class A material, water is the best extinguishing agent.

However, a primary concern when using water is a vessel’s stability condition. As water is applied to fight a fire, it is retained inside the vessel. Furniture and carpets retain water and the additional weight could affect stability. Also, large pools of water will affect stability because of the Free Surface Effect or unrestricted movement of liquid. As water moves around the vessel it constantly changes the ship’s stability. If enough water is retained, it could cause a negative stability condition.

Foam
Foam is the best choice for Class A & B fires (solid materials and flammable liquids or gases). Foam also can be used for fire prevention and protection. Applying foam to a flammable liquid spill greatly reduces the chances of a fire. Foam performs multiple actions on a fire while most other extinguishing agents perform only one. The three actions of foam are cooling, smothering and separating. Water is the largest component in foam and therefore cools the fire. The foam “blanket” smothers the fire. The foam separates the flammable vapors from mixing with oxygen, preventing the liquid from igniting.

Carbon Dioxide
Carbon Dioxide can be used for Class B & C fires (flammable liquids or gases, and electrical or energized devices). CO2 affects the fire by displacing the oxygen. CO2 is the first choice for an electrical fire because it does not destroy or damage equipment and it does not conduct electricity. When using CO2 on a flammable liquid fire, a concentration of 34 percent is needed for extinguishment. The use of CO2 has the greatest potential for re-flash because it only displaces the oxygen momentarily. When possible, the first action before electrical fire extinguishment is power isolation.  Electricity is most likely causing the fire. Once the power is isolated, there is a reduced risk of the fire re-flashing. The greatest hazard with CO2 is suffocation as it displaces oxygen in the body if inhaled in large amounts. This can occur when CO2 is discharged into small or confined spaces. This hazard also can be encountered if personnel are trapped in an Engine Room and the Total Flooding System is discharged. If the CO2 Total Flooding System has been discharged, anyone reentering the engine room should wear a Self -Contained Breathing Apparatus (SCBA)

Dry Chemical (Dry Powder)
Dry Chemical (or Dry Powder, depending on where you are from) can be used on multiple types of fires: Class A, B & C or B & C depending on the chemical makeup of the powder. A Multi-purpose Dry Chemical is appropriate for Class A, B & C fires, and Ordinary Dry Chemical is appropriate for  B & C fires. Dry Chemical affects the fire by breaking the chemical chain reaction, thereby preventing the fuel and oxygen molecules from bonding together. Dry Chemical is the second choice for flammable liquids, if foam is not available, and it is the second choice for electrical fires due to the corrosive nature of the powder. Dry Chemical will work on a Class A fire, but there is a risk of re-flash because it may not reach the deep-seated heat in a Class A fire.

Halon
Although it’s been banned from further production since 1994 for its effects on the ozone layer, Halon can still be found in extinguishers or Fixed Fire Suppression Systems. Halon affects fire by breaking the chemical chain reaction. There are three types of Halon; 1202, 1211, and 1301. Halon 1202 is the rarest. Halon 1211 is still common and can be found in extinguisher form; it’s best suited for Class B & C fires but should be used only for exterior fire fighting due to its toxicity.  Halon 1301 is still found in fixed fire suppression systems, such as Engine Room systems. FM 200, which is a Halon replacement, works on a similar principle as Halon by chemically extinguishing fire with the added benefit of cooling.

Dry Powder (Dry Chemical)
Dry Powder (or Dry Chemical, depending on where you are from) is a metal fire-extinguishing agent. Dry Powder will only work on certain types of metal fires. This extinguishing agent is not commonly carried on a luxury yacht. Magnesium flares would be the most likely source of a metal-based fire. In the event of a metal- based fire the best course of action is to jettison whatever is burning, if possible. If you cannot jettison the item, applying large amounts of water is the best course of action. Extreme caution must be taken as there will be an explosive reaction upon water application.

APC
APC or Aqueous Potassium Bicarbonate is commonly referred to as Wet Chemical. APC is the best choice for fire in grease fryers. APC has extinguishing properties similar to foam, and it also inhibits flames when mixed with grease. APC is fast acting but also potentially toxic. After the fire has been extinguished and sufficient cooling time has passed, use extreme caution and the correct protective clothing are for cleanup. If APC is carried on board, the MSDS (Material Safety Data Sheet) should be reviewed for the appropriate cleanup procedure. APC can be found in extinguisher form or in a fixed system. 

Now, back to fighting your shipboard galley fire emergency, a Class B fire in the grease fryer.  You that now know the differences between extinguishing agents, which is the correct agent to extinguish this fire? Water is the worst choice. Foam could work but you would still be applying water. CO2 would work but the fire will instantly re-flash due to heat retention in the grease and the surrounding metal components. Dry Chemical will work but the fire would re-flash. The best extinguishing agent is APC.

To prepare your crew for a fire emergency, conduct the following drill.  Have each crew member independently check to see what types of extinguishers are in the different areas of the vessel, and determine if the extinguisher and extinguishing agent are the best choice for a fire in that area.  

______

By Tom Jones, a Training Manager at Resolve Maritime Academy, 1510 S.E. 17 St., Suite 400, Ft. Lauderdale, Fl. 33316, Tel: 877-975-3473, info@ resolveacademy.com, www.resolveacademy.com

 


benjaminfisher
Posted: Sunday, October 9, 2011 6:09 PM
Joined: 10/05/2008
Posts: 21


Great information. Do you have any suggestions on the use of FM-200 and Halotron 1. Thanks
yellowcat
Posted: Monday, October 10, 2011 3:44 PM
Joined: 25/04/2010
Posts: 2


Near a beach ? collect dry and wet sand for possible fire extinguishing, we used that "expensive stuff" often when our "fiesta" fires became out of control. Yes it is heavy, but it can be used as ballast partly. Can put that technically advanced stuff on about anything, i did on a burning engine worked just fine. You can also used crushed ice from the ice box. All kitchen cooking areas must have swing down metal lids, no water on burning oils !
Captain Andy
Posted: Wednesday, October 12, 2011 3:34 PM
Joined: 17/09/2008
Posts: 93


Would be nice to have mentioned atomised water droplets: aka 'Hi Fog'!
Henning
Posted: Friday, October 14, 2011 8:21 PM
Joined: 01/06/2008
Posts: 1052


For a typical galley fire, you forgot the most useful extinguishing agent of all, a Fire Blanket. Most Galley fires are small grease fires. The blanket does a fine job of these and limits the spreading of the fire that a pressurized agent can cause by breaching the containment.

Minimise Fire Risks
Posted: Saturday, June 30, 2012 6:15 PM
Joined: 30/06/2012
Posts: 35


Tom love to discuss Flame Proofing Textiles with you.
 
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