Vessel designs, better agents aid firefighting
A depiction of one of the 140-foot fireboats Robert Allan Ltd. is designing for New York with a pumping capacity of 50,000 gpm. (Courtesy Robert Allan Ltd.)
When a ship fire breaks out and seconds count, the latest vessel designs, equipment and agents increase the chances for a fast, effective response. Increasingly vessels that serve primarily in support roles now also are expected to have significant firefighting capabilities. Driving this trend is growth in the offshore oil and gas industry, as drilling moves farther offshore and proposals are made for new and expanded LNG terminals, some of them to be located offshore. As a result, anchor handling vessels, supply vessels and different types of tugs with firefighting capabilities can safely perform the role of early responder.
The three FiFi (Fire Fighting) vessel classes define their firefighting equipment capabilities. FiFi 1 is the lowest category, and the minimum requirements include two monitors, one to two fire pumps and water pumping capacity of 10,569 gpm. The FiFi 2 rating requires two to four monitors, up to four fire pumps and total pumping capacity of 31,704 gpm. FiFi 3 vessels must have three to four monitors and two to four fire pumps capable of supplying a total 42,272 gpm.
In each FiFi class, other fire suppression specifications also apply. According to Firefighting Systems AS, in Moss, Norway, additional firefighting equipment often includes water deluge spraying systems for FiFi 1 vessels, high-expansion foam generators for FiFi 2 and FiFi 3 vessels and foam monitors for FiFi 3.
The newest escort tugs built primarily for ship-assist work at major LNG terminals by Washburn & Doughty in East Boothbay, Maine, are also designed to meet the requirements of FiFi 1. They meet the ABS Maltese Cross A1 Firefighting Vessel, Class 1 and ABS Maltese Cross A1 Towing, Maltese Cross AMS with Escort Notation, and Towing Service class requirements.
For Moran Towing Corp., ship assist is the primary service it provides for the LNG tankers carrying up to 24 million gallons of LNG to the terminals at Cove Point on Chesapeake Bay near Baltimore and to Elba Island near Savannah, Ga. The tankers, which exceed 900 feet in length, are served by teams of 5,000-hp z-drive tractor tugs with specially trained crews. Kaye E. Moran and James R. Moran, two of the latest additions to Moran’s fleet, are classed as FiFi 1. During unloading, which takes up to 24 hours, the tugs provide emergency stand-by service.
“The attending tugs lie moored at specially placed buoys, enabling the tugs to be promptly available if the tanker needs attention during her discharge. One tug in the group will stand by ready to provide assistance within just a few moments call up time,” said Moran.
The primary firefighting equipment aboard the FiFi 1 class tug Eleanor F. Moran, delivered to Moran Towing in March 2007 by Washburn & Doughty, includes two remote-controlled FiFi monitors, each capable of delivering 5,280 gpm of water for a distance of 394 feet and reaching a height of 148 feet. The tug has eight fire stations along the main deck and a deluge sprinkler system to protect the tug and crew with a protective, cooling water mist that allows the tug to work safely closer to a fire source. Water supply is provided by two Caterpillar 3412C engines putting out 900 hp at 2,100 rpm and driving Nijhuis HGTFI-1-250.500 pumps in the engine room. Per class requirements, the new FiFi boats can sustain firefighting operations for 24 hours.
Dedicated fireboats traditionally provided the highest levels of marine firefighting capability, and those capabilities have steadily increased. One example is the Los Angeles fireboat built by Nichols Brothers Boat Builders in 2003. It is equipped with 10 fire monitors supplied by six water pumps and four foam pumps with a output of 31,704 gpm.
High-performance fireboats are being designed by Robert Allan Ltd. in Vancouver, British Columbia, for New York City. “They will have a very flexible pump system that will allow them to deal with anything from the smallest pleasure craft to the largest cruise ship,” explained Robert Allan, president.
Since municipal fireboats are called on not only for ship and pier fires but also to support land-based firefighting, the design provides 50,000 gpm total pumping capacity at 150 psi when connected to a system of hoses capable of supplying water up to five miles inland.
“There are a lot of oil refineries and chemical plants around the waterfront that pose unique hazards, and this vessel is designed to deal with all of those,” he said.
The 140-foot-long fireboats will have a beam of 36 feet and a maximum draft of 9 feet. “We have a fairly conventional semi-displacement hull form but with a slight tunnel stern in order to accommodate a draft constraint, and the engines are as low in the boast as possible,” Allan explained. The low-wake vessels have a response speed of 17.4 knots.
Deluge sprinkler systems for firefighting vessels are a classification society requirement, Allan noted, but his designers opted not to use a fixed-pipe system with deluge heads for the New York boats, since the smaller water monitors provided capacity for the wet-down operation, and reduced piping would minimize long-term corrosion problems. “This vessel will do it with directional nozzles, and using the small monitors it will have the ability to put up an umbrella of water to wet down the outer parts of the vessel accomplishing what is necessary, ” Allan said.
The firefighting equipment includes a crane fitted with telescoping ladder for high-level water stream and access to the decks of ships. For delivery of the firefighting agents, the fireboats will be equipped with one water-only monitor producing 17,000 gpm, four water-only smaller monitors with capacities of 2,000 gpm each and six water/foam monitors with capacities of 5,300 gpm each.
Selecting the appropriate agent to combat maritime fires depends on a fire’s location and source of fuel. Fixed-system water mist and CO2 dry chemical systems have proven successful for engine room fires. Although Halon 1301 gas is no longer allowed for new shipboard fire-suppression systems, it is still permitted for existing systems. Several replacement clean-agent gases are available.
One upcoming replacement agent for Halon 1301 is Ansul’s Sapphire System using Novex 1230 as the gaseous fire-smothering clean agent for machinery rooms, pump rooms, electrical switch boards, diesel generators or control rooms.
Anthony Gee, Tyco Safety Products’ (Ansul) marine systems manager, noted that this fire-suppression technology has been installed on some vessels, including U.S. Coast Guard ships.
“What makes the Sapphire System unique is the agent is stored in liquid form, but when it is discharged from pressurized cylinders and comes out of the nozzles, it flashes into a gas, filling the space. It is a smothering gas, but people in the space can safely breathe. So if there is a discharge in an occupied space, it is not harmful to people but is effective against fire,” Gee explained.
If a ship carries extra quantities of the Novex 1230 agent in its liquid form and a source of nitrogen is available, any discharged cylinders can be refilled on board by using the refill kit.
The Sapphire System was selected by Teekay Shipping Corp. for the machinery rooms of its Q-Flex LNG megacarriers.
Gee said that the most effective agent for extinguishing an LNG fire is CO2 dry chemical. High-expansion foam can be used as a secondary system. Foam generators built in various sizes have outputs ranging from 3,000 to more than 30,000 cubic feet per minute. The foam generator consists of an enclosure containing an electric or water-powered motor driving a fan and a series of nozzles that spray a water/foam mixture against a circular screen. As the air forces the mixture through the screen, millions of small bubbles are created that cool the area of the fire area and cut off oxygen to smother it.
LNG is a liquid formed by supercooling natural gas. “If there is a spill, it is not the liquid that burns but rather the vapor that is boiling off of the liquid and that vapor has to reach a certain concentration before it becomes flammable,” Gee explained. “The high expansion foam makes it difficult for the boiling off vapor to reach the point of the flammability concentration. Vapors will eventually penetrate through the bubble barrier, but not as if the foam was not there.”
Water sprays are not used against spilled LNG pools but can be effective in wetting down the vapor cloud and attempting to move it from the ship.
During a fire, the sprays or direct water streams from fireboats are also used to wet down and cool LNG containment tanks, piping and the ship’s structure to further reduce the fire risk.Â Â Â â€¢