Since the end of World War II, the world’s navies have thousands of major accidents, resulting in dozens of ship sinkings, hundreds of explosions and fires, costly repairs and early vessel retirements, and major loss of life
Naval accidents occur in a unique environment. The oceans can be violent and unrelenting. The nature of naval operations, maneuvering in close quarters in a borderless medium, the presence of explosives and other combustible materials, the fact that ships are dangerous places, full of moving machinery and electrical equipment increases the potential for accidents, whether brought on by “acts of God” or human error.
Accidents and naval disasters are also a byproduct of the use of naval forces in gunboat diplomacy or open warfare. The nature of the navies of the superpowers and most NATO members, particularly the global mobility of modern blue-water navies, facilitates the deliberate placement of combatants and support ships in areas where there are ongoing conflicts.
Fires are by far the most prevalent cause of ship damage, according to official Navy statistics, from 1973 to 1983 there were an average of 148 fires per year on U.S. ships or at shore bases. There have been 267 documented major fires aboard ships, although many more are suspected as having taken place. In addition, hundreds of minor fires have occurred at sea, during ship construction and overhauls.
In the maritime sector, fires are known by being a critical risk for the safety on board specially on passenger ships as the number of passengers on board is directly proportional to the potential life loss.
In the last six years more than 25 people have been killed in Naval accidents. The highest number of casualties was when 18 saliors died when a blast took place at the torpedo compartment of INS Sindhurakshak. In 2018, INS Betwa that was being docked at the Mumbai Dock yard tipped over, two Naval soldiers lost their lives in the incident and 14 others were injured.
A lieutenant commander lost his life while attempting to snuff out an accidental fire that broke out on India’s only aircraft carrier INS VIKRAMADITYA near the INS Kadamba Naval Base in Karwar in Apr 2019. Though the crew was able to bring the fire under control immediately, lieutenant commander DS Chauhan lost consciousness inhaling the fumes during the firefight. He was rushed to the INHS Patanjali hospital near the base, but breathed his last while undergoing treatment.
Naval Fire Accidents
The analysis of maritime accidents is crucial for evaluating the risk and to identify the main causes, contributions and organizational factors that will eventually result in the accidents.
There is a wide range of accident types. The types of accidents that may occur include collision, fire, explosion, capsizing, grounding, among others. Grounding and fire on board are the main types of maritime accidents.
Accidents are processes that involve a number of errors, failures and uncontrolled environmental impacts. This set of events is called accidental events, and each event is characterized by the following attributes: hazardous material, environmental effects, equipment failure, human error and other agent or ship.
The ever-increasing number of electrical appliances used during everyday life means that the number of potential ignition sources within the accommodation area of a ship may have greatly increased since it was first built. As a result, the use of multi-gang extension leads is commonplace. These are often used to compensate for the fact that there are not sufficient socket outlets available within cabins.
Another area where fires commonly occur on a vessel is within the engine room. Over 50% of fires within the engine room are caused by fuel/lubricating oil leakage onto hot surfaces.
The human error is the leading cause of the accidental events. As regards human factors, non-detection of technical failures is the main cause of accidents. Lack of knowledge and operating and emergency procedures is important contributor. Regarding daily operations, the supervision is the most common causal factor whereas issues related to emergency procedures, under the management and resources classification, occur frequently in the accidents analyzed.
A modern ship is required by SOLAS, national and classification society rules to be built with an integral fire-fighting system. The main objective of the SOLAS Convention is to specify the minimum requirements for the construction, equipment and operation of ships (SOLAS, 2014). For the prevention of fires on board, there is the International Code for Fire Safety Systems, hereinafter FSS Code, that aims to provide international standards of intrinsic engineering specifications for fire safety systems required by chapter II-2 of SOLAS and became mandatory after 1 July 2002.
Unlike a land based fire, a ship’s crew are not able to walk away from a fire at sea and rely upon the local Fire Department to extinguish it. Therefore, the safety of the vessel and its crew is dependent upon adequate fire prevention measures to avoid the occurrence of such incidents in the first place.
Breaking out of fire in a place where no fire exist is called “ignition”, whereas “flash” is a term used for fire eruption in a new place as a result of flames from an existing fire in a nearby place (the ignition source). Fires on board ships can be prevented by finding and rectifying leakages of fuel oil, lubricating oil, and exhaust gases.
In a ship’s generator room, the biggest danger of fire is from a leaky high pressure fuel pipe. Oil leaking from such pipe can fall on high temperature exhaust manifold or on indicator cocks, which are sensitive points for catching fire.
These days fuel high pressure pipes are sheathed and the leakage finds its way to a small tank at the bottom of the engine known as fuel leak off tank. It is imperative to keep this system in good order by regularly testing the tank alarm – fuel leak off tank high level alarm.
Fires can be largely prevented by providing effective laggings to hot surfaces such as generator turbocharger bellows, main engine exhaust uptakes after the turbocharger, various steam pipes and pipes carrying hot oil. Laggings can be done by ship staff but these days specialist contractors are available to carry out this work more aesthetically. Also, whenever lagging is removed, a habit should be cultivated to put it back after the work is finished.
Some of the main types of detectors used on ships are:
Light produced by a flame has a characteristic flicker frequency of about 25Hz. The spectrum in the infra red or ultra violet range can be monitored to give an alarm. Oil fires generally do not give off much smoke and this type of sensor is preferred, especially near fuel handling equipment or boilers to give an early warning.
Heat detectors are of various types such as rate of rise type, which has bi-metallic type detecting elements – a thick strip and a thin strip. The thin strip is more sensitive to temperature rise than the thicker one. If there is a sudden rise in temperature, the thin one bends faster than the thicker one, bringing both of them in contact.
During normal temperature rise both strips will deflect about the same amount and thus show no reaction. Normally if rate of rise is less than 10 deg C in half an hour, the detector will not give any alarm. If the rate should rise to 75 degree Celsius, or more, the two strips come in contact, thus triggering the alarm.
There are two main types of smoke detectors used
1) Light obscuration type
2) Ionization type Liquid or gas fires may not give off smoke initially but will catch fire spontaneously. Thus smoke detectors are not effective for such fires. These detectors are mostly used in accommodation areas.
Fighting fire on ships is done in several ways and can involve automatic systems releasing water or fire suppressant gases or by manual means using fire hoses and hand-held extinguishers, buckets and sand.
There are six different types of hand-held extinguishers with each type intended for dealing with one or more of the different types of fires and completely unsuited for others:-
- Powder fire extinguishers are ideal for use in mixed risk environments. They are the only effective solution for fires involving flammable gases.
- Foam fire extinguishers are ideal for use on fire involving solid combustible materials and are highly effective on flammable liquid fires. The layer of foam applied by these extinguishers helps to prevent re-ignition after the fire has been extinguished.
- CO2 fire extinguishers are suitable for use on flammable liquid fires and are extremely effective at extinguishing fire involving electrical equipment.
- Water fire extinguishers are suitable for use in environments containing solid combustible materials such as wood, paper and textiles. They should not be used around electrical equipment (unless water extinguishers with additive are used).
- Wet chemical fire extinguishers are usually supplied with a special application lance. They are intended for tackling large burning oil fires and are ideally suited to the kitchen/galley environment. * Water mist works on the basis of cooling fire, suffocating it and then cooling the burning media to prevent re-ignition using microscopic particles of water. Water mists extinguishers are ideal for covering areas where multiple fire risks can be found.
Navy Researchers Look For Safer Firefighting Foams
Firefighting foams — called aqueous film-forming foams — are used by the military to rapidly extinguish liquid fuel fires on airplanes and ships.
These foams contain fluorine in the form of per- and polyfluoroalkyl substances, or PFAS. PFAS chemicals work as a surfactant — they lower the surface tension of water, allowing the foam to more effectively cut off the oxygen that feeds a fuel fire.
According to the Environmental Protection Agency, PFAS is found in many products, such as clothing, carpets, fabrics for furniture, adhesives, paper packaging for food, and heat-resistant and non-stick cookware. PFAS chemicals are persistent in the environment and in the human body — meaning they don’t break down and they can accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects, the EPA says.
Naval Research Lab scientists routinely test fluorine-free foams at Chesapeake Beach as part of their effort to find a replacement firefighting foam that meets military requirements.
They also test foams that contain fluorine, because the military still uses them to fight real liquid fuel fires. The military no longer uses these foams for training. John Farley, director of fire test operations at the lab, demonstrated a test in the facility’s 28-square-foot fire tank.
First, workers put an inch of water into the tank. Next, they added two gallons of ethanol-free gasoline, which floats on top of the water. The water helps to protect the test pan and ensures the test area is completely covered with fuel.
A worker then ignites the fuel, which produces a 5-megawatt fire. Farley said researchers then wait 10 seconds before attempting to extinguish the blaze with the foam, so the fire maintains a consistent burn.
The foam comes out of a nitrogen-pressurized nozzle at a set rate, so test results are consistent, he said.
During the test, Farley pushes the foam around the pool of fire to separate the vapor from the pool of gas. He said the gas in the pool doesn’t burn, just the vapor. Also, the foam barrier minimizes radiant heat going back into the fuel.
The military’s standard for a successful product, called MIL-SPEC, requires that a fire of the size of the test fire must be extinguished within 30 seconds.
Since the foam used contained fluorine, it met the MIL-SPEC with an extinction time of 27 seconds, Farley said.
After the fire was extinguished, a foam layer floats over the fuel and water. At this point, researchers perform a second test — called a burn back — in which a bucket of gasoline is set in the middle of the tank and ignited.
The purpose of the burn back test is to measure how long it takes the foam to degrade and the fire to reignite over the pool.
After the test is over, Farley said a sample of the foam is measured by a dynamic foam analyzer, which computes the geometric structure of the foam. If an effective firefighting foam is developed, the structure of the foam will be informative, particularly, since commercially developed foam makers don’t disclose their ingredients, he said.
Farley said the lab also conducts tests using the fluorine-free commercial foams. In a recent test, one foam being tested took 47 seconds to extinguish the fire, and the other took nearly one minute. Since neither met the MIL-SPEC of 30 seconds, they both failed.
After each test, workers wash the foam down with water and collect it inside a tank for incineration for safe disposal.
During all testing, the Annapolis, Maryland, fire marshal is present to ensure the tests are conducted safely. Farley said each type of foam is tested 23 times — 22 in the 28-square-foot tank and once in the lab’s 58-square-foot tank. He said he’s confident that a safe and effective firefighting foam will be developed in the years ahead.