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Shipboard firefighting manual.SOLAS: Fire Training Manual (Including Fire Safety Ops) - Amnautical
For maximum cooling, the water must come in direct contact with the burning material. A straight stream is best used to break up and penetrate materials. Keeping in mind the constant problem of excess water disposal, high volume water discharge should be used as little as possible, especially in situations below decks. For Navy All Purpose nozzles, the solid stream discharges greater flow than fog patterns. Do not use Navy All-Purpose nozzle fog applicator or straight stream water pattern on an energized electric source to avoid shock hazards.
Maintain a minimum standoff distance of four feet when applying water fog to an energized electric source. Water accumulation can provide a path for electrical shock to personnel. Straight stream water is the greatest conductor of electricity as opposed to the fog spray pattern and straight stream should not be used on electrical fires.
A straight stream of water is ineffective for extinguishing class B fires and can cause a violent fire reaction if the water stream atomizes the fuel into the air causing a greatly increased surface area.
However, a straight stream can be used to wash combustibles over the side in a weather deck fire. When washing combustibles over the side, it is imperative that the burning material is washed directly into the sea and not onto another deck or overhang.
Water in the form of water fog is very effective for firefighting purposes. However, the fog must be applied directly to the area to be cooled if its benefits are to be realized.
Additionally, water fog can provide protection to firefighters from both convective and radiant heat. Because of the cooling qualities of the finely divided water particles, water fog can be used successfully on fires involving fuels with flashpoints above F, such as Navy Distillate Fuel F Extinguishment occurs by cooling the flammable liquid below its flashpoint. Water fog should be used on flammable liquids only when AFFF is not available.
Danger of reflash exists until all of the fuel is cooled down below its flashpoint. Narrow angle fog concentrates the water at the fuel surface which increases its effectiveness. The wide angle fog pattern does not provide sufficient water concentration to extinguish a class B fire. AFFF is composed of synthetically produced materials similar to liquid detergents. These film forming agents are capable of forming water solution films on the surface of flammable liquids.
Nonmilitary specification commercial AFFF should not be used. AFFF concentrate is a clear to slightly amber colored liquid. The AFFF solution of water and concentrate possesses a low viscosity and is capable of quickly spreading over a surface. AFFF concentrate is nontoxic and biodegradable in diluted form.
AFFF concentrate may be stored indefinitely without degradation in characteristics. The concentrate will freeze if exposed to temperatures below 32F. If the frozen concentrate is thawed out it can be reused, but storage in heated areas is recommended.
AFFF, when proportioned with water provides three fire extinguishing advantages. First, an aqueous film is formed on the surface of the fuel which prevents the escape of the fuel vapors. Second, the layer of foam effectively excludes oxygen from the fuel surface. Third, the water content of the foam provides a cooling effect. The principle use of foam is to extinguish burning flammable or combustible liquid spill fires class B. AFFF shall be used to re-enter all compartment fires involving flammable liquids.
AFFF has excellent penetrating characteristics and is superior to water in extinguishing class A fires. AFFF is designated as an environmental pollutant. AFFF should not be discharged into any system which, when pierside, may feed into an ashore sewer treatment plant. AFFF may kill the bacteria that aids in sewer treatment and disrupt plant operation. A method of extinguishing fires by smothering is the use of the inert gas CO2.
CO2 is about 1. This makes CO2 a suitable extinguishing agent because it tends to settle and blanket the fire. CO2 is a dry, noncorrosive gas, which is inert when in contact with most substances and will not leave a residue and damage machinery or electrical equipment. In both, the gaseous state and the finely divided solid snow state, it is a nonconductor of electricity regardless of voltage, and can be safely used in fighting fires that would present the hazard of electric shock.
CO2 extinguishes the fire by diluting and displacing its oxygen supply. If gaseous CO2 is directed into a fire so that sufficient oxygen to support combustion is no longer available, the flames will die out. Depending on the fuel, this action will take place when the 21 percent oxygen content, normally present in air, is diluted with CO2 below 15 percent oxygen. Some ordinary combustible class A fires require that the oxygen content be reduced to less than 6 percent in order to extinguish glowing combustion smoldering fire.
CO2 has limited cooling capabilities, and may not cool the fuel below its ignition temperature and is more likely than other extinguishing agents to allow reflash. Therefore, the firefighter must remember to standby with additional backup extinguishers. The temperature of the burning substance and its surroundings must be lowered below its ignition temperature if the fire is to remain extinguished.
CO2 is not an effective extinguishing agent for fires in materials that produce their own oxygen supply such as aircraft parachute flares. Fires involving reactive metals, such as magnesium, sodium, potassium, lithium, or titanium cannot be extinguished with CO2. Because of the relatively high temperatures involved, these metal fuels decompose CO2 and continue to burn.
Halon is a halogenated hydrocarbon, which means that one or more of the hydrogen atoms in each hydrocarbon molecule have been replaced by one or more atoms from the halogen series fluorine, chlorine, bromine, or iodine. This substitution provides nonflammability and flame extinguishing properties. A Halon numbering system has been developed to provide a description of the various halogenated hydrocarbons.
The first digit in the number represents the number of carbon atoms in the molecule; the second digit, the number of fluorine atoms; the third digit, the number of chlorine atoms; the fourth digit, the number of bromine atoms; and the fifth digit, the number of iodine atoms, if any. In this system, terminal zero digits, if any, are not expressed. The two types of Halon used aboard Naval ships are Halon and Halon is the most commonly used type. Halon is only used in a limited number of special applications in portable fire extinguishers or in larger units with a hose line.
For shipboard installation, Halon is superpressurized, with nitrogen, and stored in gas cylinders as a liquid. When released, it vaporizes to a colorless, odorless gas with a density of approximately five times that of air. Halon is also colorless, and has a sweet smell. Halon is stored and shipped as a liquid and pressurized with nitrogen gas. Pressurization is necessary since the vapor pressure is too low to convey it properly to the fire area.
Halon is not used in total flooding systems. Its lower volatility, plus a high liquid density, permit the agent to be sprayed as a liquid and therefore propelled into the fire zone to a greater extent than is possible with other gaseous agents.
Halon is used in 20pound capacity portable fire extinguishers on air cushion landing craft LCAC and on mobile firefighting apparatus used on flight decks. Halon decomposes upon contact with flames or hot surfaces above F C.
Decomposition products are principally hydrogen fluoride and hydrogen bromide, which have a sharp irritating odor even at low concentrations. The short discharge time of Halon 10 seconds maximum keeps the thermal decomposition products well below lethal concentrations. The real hazard lies not in the by-products of the Halon, but rather in the products of combustion from the fire. Combustion products such as CO, combined with the oxygen depletion, heat and smoke pose a greater hazard to personnel.
Personnel should not remain in a space where Halon has been released to extinguish a fire unless a breathing apparatus is worn.
If Halon should inadvertently be released into a space where no fire exists, personnel can be exposed to 5 to 7 percent concentration of Halon for a period up to 10 minutes depending upon the individual without danger to health. Halon can be considered a nontoxic and nonsuffocating extinguishing agent in the normal 5 to 7 percent concentrations; however, spaces should be evacuated on Halon system discharge.
At Halon concentrations between 7 and 10 percent and Halon concentrations between 3 and 4 percent, personnel experienced dizziness and tingling of the extremities, indicative of mild anesthesia. At Halon concentrations above 10 percent and Halon concentrations above 4 percent the dizziness becomes pronounced, the subjects feel as if they will lose consciousness although none have , and physical and mental dexterity is reduced.
The discharge of Halon to extinguish a fire may create a hazard to personnel from the natural Halon itself and from the products of decomposition that result from the exposure of the agent to the fire or other hot surfaces.
Halon is colorless and has a faintly sweet odor prolonged exposure to concentrations greater than 4 percent carries with it the possible risk of unconsciousness and even death. Although Halon vapor has a low toxicity, its decomposition products can be hazardous. When using Halon in unventilated or confined spaces, operators and others should avoid breathing the gases, and should only use the agent needed to accomplish extinguishment. No significant adverse health effects have been reported from the use of Halon or as a fire extinguishing agent since their introduction into the marketplace 30 years ago.
Therefore, if the system is activated, personnel shall leave the space immediately. The liquid phase vaporizes rapidly during discharge and therefore limits this hazard to the immediate vicinity of the nozzle.
In humid atmospheres, reduction in visibility may occur due to condensation of water vapor in the air. Halon and Halon are severe ozone depleting substances. These agents should be used only against actual fires. Any Halon cylinder which may contain only a partial charge, or is being turned in, shall not be vented off for any reason. Halon will generally be replaced in future ship designs, such as the DD class and the LPD class, by new alternative non-ozone-depleting agents such as water mist or heptafluoropropane HFP.
Steam as an agent smothers a fire by reducing the concentration of oxygen or the gaseous phase of the fuel in the air to the point where the combustion stops. As long as the steam blanket is maintained, it will prevent reignition. Steam smothering systems are installed in boiler casings and catapult troughs. Additionally, steam condenses when the supply is shut off.
Its volume decreases rapidly and combustible vapors and air rush in to replace it. There is a very good chance that the fire can reflash if it has not been completely extinguished and cooled.
Also, steam is hazardous to personnel since it can inflict severe burns. Potassium bicarbonate PKP is a dry chemical principally used as a fire extinguishing agent for flammable liquid fires. It is used in portable extinguishers.
Various additives are mixed with the PKP base materials to improve their storage, flow, and water repellency characteristics. The most commonly used additives are silicones which coat the particles of PKP to make it freeflowing and resistant to the caking effects of moisture and vibration.
When PKP is applied to fire, the dry chemical extinguishes the flame by breaking the combustion chain. PKP does not have cooling capability. This cloud limits the amount of heat that can be radiated back to the heart of the fire.
Less fuel vapors are produced due to the reduced radiant heat. It is believed that PKP reduces the ability of the molecular fragments to recombine, therefore breaking the chain reaction.
PKP is highly effective in extinguishing flammable liquid class B fires. Although PKP can be used on electrical class C fires, it will leave a residue that may be hard to clean. PKP can also be used extensively in the galley for such items as the hood, ducts and cooking ranges. Like all other fire extinguishing agents, PKP is not effective on materials that contain their own oxygen.
PKP should not be used in electrical controllers or cabinets where relays and delicate electrical contacts are present. PKP is not effective on combustible metals and may cause a violent reaction. Where moisture is present, PKP may combine with it to corrode or stain surfaces on which it settles; when possible it should be removed from the surfaces.
PKP does not produce a lasting inert atmosphere above the surface of a flammable liquid; consequently, its use will not result in permanent extinguishment if ignition sources such as hot metal surfaces or persistent electrical arcing are present. PKP is not effective on fires involving ordinary combustibles class A. However, it can be used to knock down a flaming fire, keeping it under control, until hose lines are advanced to the scene.
The ingredients used in PKP are nontoxic. However, the discharge of large quantities may cause temporary breathing difficulty during and immediately after the discharge and may seriously interfere with visibility. Aqueous potassium carbonate APC, K2 CO3 is used on board Naval ships for extinguishing burning cooking oil and grease in deep fat fryers and galley ventilation exhaust ducts. Aqueous potassium carbonate APC solution consists of A technique often used in combating liquid grease fires involving unsaturated animal and vegetable oils and fats is the application of alkaline solutions such as APC which, upon contact with the burning surface, generate a soaplike froth that excludes air from the surface of the grease or oil, and the fire is extinguished.
Water mist is a fire extinguishing agent which replaces Halon in new ship designs such as the LPD, because use of Halon is an ozone-depleting substance which is harmful to the environment. Water mist for machinery spaces is a total-space fire extinguishing system which discharges high-pressure approximately psi fresh water as a fine mist from nozzles located in all levels except the bilge.
High-pressure water mist is effective at suppressing oil pool fires, oil spray fires and class A fire even if the fire is obstructed from the nozzles.
Water mist may not totally extinguish deep-seated class A fires, but will knock-down open flaming to a smoldering state and prevent fire spread of a class A fire. Actuation of the water mist system will automatically shut down ventilation in the affected space, but does not include a 30 second or 60 second actuation time delay needed for ventilation air-flow stoppage as with Halon or HFP systems.
Water mist may cause short circuits in energized electrical equipment. Note: 1 micron equals one millionth of a meter, so there are roughly 25, microns in one inch.
The Navys minimum discharge rate for high pressure water mist, 0. Low pressure water mist and medium pressure water mist systems found in some commercial ships have larger particle diameters and are less effective against obstructed class B fires.
Water mist is not toxic. However, the presence of toxic fire gases and reduction of oxygen by the fire will require evacuation of personnel without breathing protection even if water mist is operating.
Therefore, personnel without operating SCBAs shall immediately leave the space when water mist is actuated for a fire. Water mist in air is not electrically conductive; there is no risk from simply coming near an energized conductor. As mist droplets accumulate in electrical equipment, they can form a pool or film that is conductive; this conductive path can cause short circuits and hazardous conditions.
The time for mist to accumulate and cre-. During tests of VAC equipment, no dangerous leakage currents occurred in any equipment within the first five minutes of mist discharge. Lighting fixtures in machinery spaces are sealed and will not pose a shock hazard.
The electrical shock hazard from any electrical equipment will be minimized by installing and closing covers and accesses to electrical equipment, keeping the equipment clean, and ensuring the cabinets or exterior surfaces are grounded to the hull. Personnel should avoid contact with energized equipment during a water mist discharge.
Although the water mist system operates at psi, the nozzle discharge will not penetrate skin even at close range and does not pose a personnel hazard. HFP is the Navys term for a specific gaseous fire extinguishing agent which is an alternative to Halon in some new ships. HFP is a colorless, odorless and electrically non-conducting gas. HFP is clean and leaves no residue. HFP is stored in steel containers at PSIG at 70 oF 41 bars at 21 oC , as a liquified compressed gas, with nitrogen added to improve the discharge characteristics.
When discharged, HFP liquid vaporizes into a gas at the discharge nozzle and is uniformly distributed as it enters the fire space. HFP replaces Halon in some limited new ship design applications, such as fuel pump rooms and flammable liquid storerooms in CVN and engine enclosures and flammable liquid storerooms in the LPD Class. HFP extinguishes fire with a combination of physical and chemical mechanisms. Unlike Halon , HFP extinguishes primarily by physical mechanisms.
HFP is used in fire extinguishing systems for class B flammable liquid and combustible liquid pool fires and spray fires. It is installed where water mist is inappropriate, such as flammable liquid storerooms with low-flash point flammable liquids including alcohol, and where water mist was deemed less cost effective. Where water mist can be applied, water mist is the agent of choice over HFP due to its cooling capability and lack of acid gas production.
The HFP system is configured identical to a Halon system. Actuation of the HFP system will activate visual and audible alarms and automatically shut down space ventilation, including dampers where installed. NOTE If an accidental discharge of HFP system occurs, ventilation should be operated for at least 15 minutes, and the space certified gas free, before entry.
To avoid unnecessary and potentially adverse exposure to HFP, evacuate the space when the discharge warning sounds. With no fire present, HFP is nontoxic and non-suffocating. However, if HFP should be inadvertently actuated when no fire exists, personnel should be immediately evacuated to limit unnecessary exposure. In pump rooms, generator rooms, and diesel engine enclosures, unprotected personnel can be exposed to the 10 to Personnel exposure should not be permitted.
Symptoms similar to oxygen deprivation headache, nausea, dizziness may also result from inhalation of high concentrations of HFP. Definite eye, skin and upper respiratory track irritation. Moderate irritation of all body surfaces.
Moderate irritation of all body surfaces, escape impairing effects likely. Escape-impairing effects will occur; increasing concentrations can be lethal without medical intervention. Personnel must leave the space when the HFP system is actuated. Exposure to HF gas may have the following effects on humans: - Corrosive and irritating to the eyes. In addition to the usual fire combustion products such as CO, oxygen depletion, heat and smoke, the discharge of HFP to extinguish a fire will create a hazard to personnel from the products of decomposition that result from the exposure of HFP to fire or hot surfaces.
HFP decomposes upon contact with flames or very hot surfaces above F C. The predominant decomposition product is hydrogen fluoride HF acid gas. The chemical breakdown of HFP when exposed to fire or flames initially can produce very high concentrations of Hydrogen Fluoride HF acid gas, which can be hazardous even to personnel with breathing protection.
The design concentration of HFP and the short agent discharge time ten seconds maximum of Navy HFP systems are intended to provide rapid extinguishment and minimize the formation of HF. Nevertheless, the atmosphere in the compartment during and after discharge of the agent should be considered extremely toxic. If the fire reflashes, the remaining HFP which is exposed to flames will produce additional quantities of HF acid gas. Depending on the size of the fire in relation to the size of the space at time of discharge of the HFP agent, the level of HF acid gas may exceed ppm.
HF concentrations will reduce somewhat with time as the HF reacts with metal surfaces. Special precautions should be taken prior to reentry, such as setting smoke boundaries and establishing active desmoking, to preclude release of this toxic atmosphere to unaffected areas of the ship. Re-entry should not be made if the HF acid gas concentration is above 90 ppm, the maximum that can be detected with shipboard gas tube detectors. Extremely high concentrations of HF acid gas will cause skin burns through firefighters protective clothing and may damage breathing apparatus.
Determine if HF concentration is below 90 ppm just inside the space access before completely entering the space. Monitor HF acid gas levels during fire party re-entry. Assure personnel have adequate breathing protection in locations where HF gas may be present. The 90 ppm HF limit is the maximum that can be detected with shipboard gas tube detectors. Special precautions should be taken, such as setting smoke boundaries and establishing active desmoking, to preclude release of a toxic atmosphere to unaffected areas of the ship.
HFP should be used only against actual fires and should not be discharged for training or maintenance. HFP cylinders that may contain only a partial charge, or are being turned in, shall not be vented off. Undischarged HFP can be reclaimed and recycled. Main transverse watertight bulkheads and in some ships longitudinal watertight bulkheads , the shell, and the damage control deck uppermost deck to which watertight bulkheads are carried constitute the watertight envelope and subdivision which will enable a ship to maintain watertight integrity and survive underwater damage.
A fire zone boundary is a bulkhead or deck designed to limit the passage of flame and smoke. Fire zone boundaries confine a fire within a zone and provide protected staging areas for fire parties.
Fire zones are formed using selected main subdivision bulkheads and portions of decks where the subdivision is stepped. Exceptions are longitudinal bulkheads in tank wells on landing ships. Fire zone boundaries are designated FZ on damage control drawings. The minimum tightness for a fire zone boundary is fume tight.
The single-sided fire insulation system does not retard heat transfer from a fire on the uninsulated side. New ship designs LPD 17 will have fire zone boundaries fitted with fire insulation on both sides.
This dual-sided fire insulation system will be effective for a fire on either side. Specific locations and details are provided in the ships Damage Control Book. Some ships have additional fire insulation installed on bulkheads and overheads of selected hazardous spaces. The CG 47 class has fire insulation on the fire zone bulkhead and uptake spaces in the aluminum superstructure. The MCM 1 and MHC 51 classes have fire insulation in the overhead of each machinery space and other selected hazardous spaces.
At repair party leader discretion, manning of fire boundaries may be reduced where fire insulation is installed on the fire side. Periodic inspection by an investigator may be adequate.
The ventilation system consists largely of vent ducts of many sizes, which provide ventilation to various compartments throughout the ship. These vent ducts can also provide the means to spread fires, smoke and toxic gases to these compartments. It is the responsibility of the firefighter to ensure that the spread of the fire, smoke, toxic gases and flooding dangers are guarded against during the time of fire.
Recirculation systems and air conditioning systems should also be secured to avoid the spread of smoke and fire to surrounding compartments. The ventilating system is designed to supply fresh air or cooled air to the various compartments and to remove from these compartments the foul air and toxic gases.
These labels also indicate what compartments are served. Usually there is a supply and exhaust duct in each watertight compartment. When a naval ship is put in material condition ZEBRA for battle, most of the ventilating ducts are closed. At the time of fire, it may be advisable to close still others. The supply system, for instance, could be harmful because it might spread fumes to inboard areas.
It might spread the fire further by supplying air oxygen to smoldering embers or a small fire. The exhaust system likewise might be harmful, in that it could spread a fire if not secured and monitored. Firefighters shall have a working knowledge of the firemain piping system, its valves and its outlets. They should know the measures to be taken after battle damage to assure water supply for firefighting.
The firemain system is designed for maximum damage resistance with the following survivability features: a. Multiple, independent pumps b.
Redundant seawater paths c. Ability to segregate sections d. Separation of redundant components e. Resistance to shock f. Capability for remote operation The shipboard firemain system consists of fire pumps, piping consisting of vertical pump risers, longitudinal service mains, cross-connects, service risers, branch lines, and valves through which seawater is pumped to fire hose stations, Aqueous Film Forming Foam AFFF proportioners and sprinkler systems.
It also supplies water to flushing, emergency drainage, backup seawater service, machinery and electronic cooling systems. The type of firemain installed in a ship is determined by the ships function and physical characteristics. The following are specific types of firemains. Single Main System. The Single Main System extends fore and aft on the damage control deck see Figure It is located near the centerline of the ship and extends as far fore and aft as necessary to supply the The single main system provides little battle damage survivability and is not used in most current U.
Naval surface ships, however the MHC class and small craft such as the PC class use a single main design. Horizontal Loop System. The Horizontal Loop System consists of two single mains separated athwartship as far as practicable, extending fore and aft on the damage control deck. The two mains are connected at both ends to form a horizontal loop. Single mains may extend fore or aft of the horizontal loop as necessary for services see Figure Athwartship cross-connects are usually provided at each pump riser.
Ships such as the FFG class use a horizontal loop design. Vertical Offset Loop System. The Vertical Offset Loop consists of two single mains installed fore and aft in an oblique e. The lower main is located as low in the ship as practical on one side and the upper main is located on the damage control deck on the opposite side of the ship.
The DDG class uses a vertical offset loop fire main system. Composite System. The Composite System consists of two service mains installed on the damage control deck and separated athwartship, and a bypass main normally installed on a lower level near the centerline see Figure Fire Pumps are driven by either electric motors or steam turbines. Fire pumps are provided with suction and discharge cutout valves and a separate sea chest valve if more than one pump takes suction from a common sea chest and suction header see Figure In most installations each pump has its own suction piping and sea chest, which is not shared with any other service or any other fire pump.
These sea chests are separated fore and aft and athwartships. They are also located to preclude ingestion of air from hull masker systems, drainage eductors and from possible flammable fluid discharges. Valves permit isolation of the pumps from the sea and the firemain for damage control purposes, and permit pump maintenance. A check valve is installed in the discharge line for each fire pump to prevent back flow through the pump, to prevent the rotating assembly from rotating opposite of design and to prevent subsequent loss of firemain pressure in the event of pump failure or inadvertent pump shutdown.
To prevent overheating during low flow conditions, each fire pump is equipped with recirculation line which connects the pump discharge to either the pump suction line or overboard, and which includes an orifice sized to pass approximately 5 percent of the pumps rated capacity. Each fire pump is provided with a casing vent to alleviate air binding and a casing drain for maintenance. Fire pumps are required to be vented prior to startup.
Each discharge recirculation line for turbine driven centrifugal fire pumps is fitted with a relief valve set at percent of the firemains rated pressure. The number of fire pumps on Naval ships permit the largest fire demand, all vital continuous loads and the largest backup cooling or 10 percent of all backup cooling demand to be satisfied with only 75 percent of the installed pumps operational.
Pumps are usually installed in separated locations along the length of the ship. Electric motor driven pumps have normal and alternate independent power sources. The optimal design goal is to locate at least one fire pump in each fire zone or Collective Protection System CPS zone, with the pumps in the forward most and after most zones located as far forward and as far aft as possible.
Steam driven fire pumps should be near the steam supply and there should be a fire pump near the emergency generator, when installed. Pumps are typically located to bracket large hazards, which means they are located on either side of the hazard, and are located in each fire zone.
Pumps are located below the water line to provide a minimum positive static head of three 3 feet under all conditions of load and a list of up to fifteen 15 degrees. The Navy standard fire pump NSTFP is an electric motor driven centrifugal, close coupled pump of titanium construction. The standard configuration includes both the pump and a totally enclosed, fan cooled, energy efficient motor. The standard fire pump can be procured in horizontal configurations with six interchangeable impellers to achieve various pressure heads and flow capacities.
The six impellers are designed for the following head and capacity ratings: a. The pump zero flow, or shutoff head is limited to approximately 1. This causes extreme wear on pump parts. The ability to vary the speed and capacity of a turbine-driven fire pump provides a benefit on ships with large variable firemain loads i.
For firemains which have turbine driven fire pumps, steam supply is a backup to electric power for firemain supply. The mains of loop and composite configurations are cross-connected in each main traverse watertight subdivision.
Cross-connections, risers and branches are installed so they do not penetrate any main transverse watertight bulkhead below the tightness level.
Risers in horizontal loop systems generally are led from cross-connections. Risers in vertical loop and composite configurations are led from cross-connections and upward only from the upper mains as necessary to best supply services above the loop. Risers to the various services are led up to the main of a single main system. Fire pump risers discharge into the main of a single main system, and into the cross-connections of loop and composite configurations.
Branch lines are installed to distribute seawater from the main to the service. The number of connections to the main is kept to a minimum to improve the speed and ease of damage control actions, to reduce costs, to reduce the number of cutout valves and for simplicity. A single connection is made to the main for all services in the same vicinity. Connections are made such that closing a cutout valve for a nonvital system does not affect a vital system.
Branch lines are not permitted to cross main watertight boundaries. In general, a single connection of ample size is installed to supply services in the vicinity through a manifold, or to individual branches from the large branch, through Y fittings. Branches from the firemain for services below the watertight level are taken from within the same main transverse watertight subdivision.
Branches for essential battle services, such as fireplugs; sprinkling; water-curtains; foam proportioners; drainage eductors; and cooling water to diesel engines, compressors and similar auxiliaries are located so that the closing of cutout valves will deprive nonessential services of a supply of water, and maintain a supply to essential services. Connections to services in magazines are usually made in trunks or handling rooms to avoid locating valves in the magazines. Foreign substances, encrusted particles and marine growth accumulate inside the firemain system.
These substances are especially prevalent in the tropics. The flushing lines should be opened periodically to flush out any debris and prevent excessive pressure loss through the strainer. The strainers remove large particles and marine growth from the incoming seawater.
Valves in the firemain consist of cutout valves, check valves, pressure regulating valves and relief valves. Valves are controlled locally or remotely at various stations throughout the ship. Major segregation and cutout valves can be operated from the damage control deck. Each valve is assigned a damage control number in order to identify the location of the valve, should it become necessary to secure or isolate a portion of the system.
The cutout valves can be gate, ball, globe, or high performance butterfly valves. Cutout valves are installed in the main, and on each side of risers which lead to services provided by the firemain. The exceptions to this are valves used for sea chest service or where gate or ball valves are used to provide positive closure during damage control efforts due to more reliable seating, and the criticality of hull integrity valves.
Cutout valves that isolate portions of the firemain are provided with either manual, electrical or hydraulic remote control. Hydraulic remote control may also be used for fire pump suction valve operation. Check valves are installed to prevent return or back flow in pipes. These are automatically operated valves without handwheels or stems. They are also installed on the discharge side of centrifugal fire pumps, to prevent back flow and resultant reverse rotation of secured pumps.
Pressure regulating systems with cutout valves, cascade orifice restrictive device and pressure regulating valves are installed on some ships. When firemain pressure increases because of low demand from installed services, the pressure regulating valve will open to divert flow overboard.
This provides an artificial load for a pump which would otherwise operate in or near a no-flow condition. As firemain pressure drops due to additional services being energized, the flow overboard is reduced.
Relief valves are installed on the recirculation line downstream from turbine driven pumps. Downstream of the firemain cutout valve other relief valves are located on the service side of pressure reducing stations to protect equipment from reducing station failure. The firemain system for each ship is carefully planned by NAVSEA to determine the exact number of independent segregations which would be practical during battle.
Optimum segregation of the system will result in the minimum loss of available water for firefighting should damage be incurred and at the same time will insure an adequate water supply to meet the demands or other ships services. See NWP Temporary service can be restored by inserting hose adapters and connecting a length of firehose between the adapters.
Damage control hose-flange adapters are provided to repair parties so that such temporary connections or jumpers may be rigged. These hose-flange adapters can be bolted or clamped with C-clamps into place quickly and easily.
The damaged section of piping shall be repaired as quickly as possible. To describe in general terms the application of segregation of the firemain as to time, place and situation, the conditions described in the following paragraphs apply.
These conditions, however, are subject to authorized change. In condition X-RAY, the firemain normally is operated as a single system. All valves and fittings marked X are closed, and all valves and fittings marked Y, Z or W remain open.
Pressure is maintained on the firemain by a minimum number of pumps as service demands require. War cruising and other situations covered in NWP All valves and fittings in the firemain system designated by X and Y are closed. This sectionalization usually creates two or more separately operating firemain systems either forward and after systems, or port and starboard systems.
In certain ships condition Yoke provides almost complete sectionalization, allowing condition Zebra, the final stage, to be set quickly by closing a minimum number of additional valves and fittings.
Most ships achieve only partial sectionalization of the firemain system in condition Yoke because of the location of certain pumps, a possible heavy resultant electric load, a desire to have spare pumps available for repair and maintenance operations, or for various other reasons associated with the ships particular firemain installation.
Condition Zebra produces the maximum degree of segregation in the firemain system. It is required during General Quarters, collision, and other hazardous situations, as prescribed by NWP Some ships have their firemain system sectionalization into its ultimate number of sections during condition Yoke and continue this during condition Zebra. This is particularly true of smaller ships, but certain of the larger ships which maintain a quartered four section sectionalization in condition Yoke continue that sectionalization in condition Zebra.
Other larger ships advance from a two-section war cruising condition firemain sectionalization into as many as six separate and independent systems for battle. Various instruments, gages, and controls allow the system operator to monitor the firemain for routine conditions and for emergency situations. Gage boards, panels, or on newer ships, a centralized cabinet type control console in DC Central, Central Control Station, or mimic panel provide the watchstander the necessary displays and controls.
Control of the firemain valves may be as follows: a. Local - by handwheel or other manual device, as well as by a push-button control, governor, or regulating device. Remote - electrical push-button, hydraulic valve control, mechanical remote operating gear or other means not in the vicinity of the valve or pump. Automatic - self-regulating device, such as a pressure regulating system, pressure regulation valve or pump governor.
Automatic start of selected motor driven fire pumps initiated by flow to a sprinkler system or missile quench injection system, or low firemain pressure. Manual push-button control of electric motor driven valves. In general, electrical interlocks are provided to inhibit pump start up if fire pump suction valves are closed. Governor controls are available for steam turbine driven fire pumps to regulate speed and, therefore, control pressure or flow rate. The turbine is controlled locally.
A combination vacuum and pressure gage is installed on the suction piping of each fire pump. A pressure gage is installed on the discharge piping from each fire pump. The firemain system draws water from the sea and distributes it throughout the ship.
The firemain system is one of the critical auxiliary systems which may determine whether a ship survives battle damage. On most ships, the firemain also provides services critical for peacetime operation. It can operate in a degraded condition after battle damage. Depending on the details of a particular ship class, the following services may be provided by the firemain: a.
Fire suppression and extinguishment b. Countermeasure washdown of external ships surfaces c. Equipment cooling, either normal or emergency backup d. Dewatering Ballasting and list control f. Sanitary flushing g. Emergency shielding and cooling to nuclear reactors and reactor support equipment The number of fire pumps, the operating pressure, and the size of the firemain piping have all been selected to provide the required flows and pressures under extreme or casualty conditions.
On most ships, the largest design load is the operation of the Countermeasure Washdown System, with all zones flowing simultaneously. For wet-well amphibious ships, firemain fill to ballast tanks may be the largest design load, and on salvage ships, off-ship fire fighting or salvage requirements may be the largest design load. On most ships, the next largest design load is a major fire , either a vertical fire involving multiple decks or a horizontal fire involving adjacent spaces on one deck.
The system is sized with sufficient margin to supply vital cooling loads and the largest backup cooling load, and to account for 25 percent of the pumps out of commission while supplying the largest design load. For each ship class, the fire pump pressure rating was selected to ensure the most remote fire plug will receive its required pressure. Many services lower in the ship or closer to the fire pumps are protected against over pressurization by pressure regulating system, pressure regulating valves or by orifices.
The distribution piping will accommodate the largest design flow rate when supplied by the pumps most remote from the services. Operation from the DC Deck is needed for pumps and valves located in normally unmanned spaces which are difficult to access, such as pump rooms.
Remote operation from the DC Deck is also needed for pumps and valves in manned spaces which may be damaged or become inaccessible due to battle damage. Pumps and valves which survive the weapon effects must be capable of operation from outside the space to avoid breaking watertight integrity and because entry may be blocked.
The principal isolation and cutout valves will be on the DC Deck, or operable from the DC Deck by remote operating gear or by valve actuators controlled from the DC Deck. Even on ships with steam driven fire pumps, at least some fire pumps will be motor driven and controllable from the DC Deck. These design features provide the necessary flexibility for reconfiguring the firemain, or adding, shifting and securing pumps under battle conditions.
Reports regarding the operation of all pumps and services should be passed to them. Each ship must establish procedures to ensure the following events are reported, whether inport or underway. Start and stop of pumps, including the set point of the regulators for steam turbine driven pumps if installed b. Firemain pressure out of tolerance band c. Start and stop of firemain cooling water to ships machinery or combat systems equipment d. Start and stop of dewatering eductors e. Start and stop of ballasting which requires firemain f.
Casualties and repairs to firemain equipment g. Isolating a pump or firemain segment--because of casualty or maintenance tagout h. Setting or relaxing material conditions i. Alarm indications of fire emergency j. Complaints or other indication of inability to provide adequate seawater service to any user Operating in reaction mode creates vulnerabilities: A medium or small firemain break will be noticed by the as a drop in pressure, the same as would be caused by an intended service being placed on line.
The response will be to add one or more pumps. Over time, the tendency is to run more pumps than required, which causes high firemain pressure, premature fire pump failure, premature firemain system failure, and inefficient operation.
In the event of a large sudden firemain demand, there will be a delay until sufficient pumps can be brought on-line to satisfy the demand.
This is a prediction style process, and it means the system operator is in positive control of the system, and the system will be in the best condition to meet normal demands and respond to casualties.
To achieve this, each ship should develop a method for tracking the status of services and pumps, and develop a table or other tool that will show the expected firemain pressure under different combinations of pumps, services, and material condition.
This information, combined with experience, will allow the system operator to predict the number of pumps which ought to be sufficient at any given scenario, and the operator will therefore be able to determine when something is wrong in the system.
The firemain should be operated at the lowest pressure sufficient to meet the needs of the connected services. On most ships, minimum operating pressure is derived from the need to maintain pressure at the highest fire plug. The actual firemain pressure at any particular moment is determined by the available number of pumps on line and the services on line.
When the discharge pressure at a fire pump is higher than its design pressure rating, the flow from the pump is lower than its design flow rating. At low flows, the pump will vibrate, leading to stress on the bearings, seals, and pump mechanical seals.
The lower the flow from the pump, forcing the pump to not operate as designed, will result in more stress on the pump causing premature failure.
All portions of the firemain system are designed to withstand the maximum pressure produced by the pumps, but the less stress on seals, gaskets, and pressure reducing valves, the less maintenance will be required. To lower the firemain pressure and increase flow through operating pumps, reduce the number of pumps on line or place additional services on line without adding pumps.
Some ships are equipped with pressure regulating systems and pressure regulating valves, which will open during high pressure conditions and divert flow to the sea, thus increasing the flow rate through the operating pump or pumps and reaching design intentions.
Closing a main segregation or cutout valve can also cause high pressure, because the closed valve may block the flow of water from a pump to a service. When the flow from the pump is higher than its design flow rating the discharge pressure at a fire pump is lower than its design pressure rating. In this situation: a. The pressure at the highest fire plug may fall below its design pressure rating.
Power requirements of motor driven pumps will increase. For other pump and motor combinations, it may be possible to overload the motor at high flow rates. To determine this possibility, consult the curves of pump power and motor current in the pump technical manual. Motor driven pumps will operate nearer to their point of best efficiency, for pressures about 20 psi less than the design rating. To raise the firemain pressure, place additional pumps on line or secure services.
Correct load management by matching pump and system design characteristics is critical to lower life cycle maintenance. A firemain fault is sudden departure from expected operational limits, principally a sudden loss of pressure or flow. A sudden loss of firemain pressure means that not enough flow is getting to the connected services. This condition may be caused by: a. A large demand placed on line, such as a main eductor or large sprinkling system.
A pump problem, such as a mechanical failure in the pump or driver, a steam or electrical failure to the pump driver, or loss of pump suction by clogging or air ingestion. A pipe rupture somewhere in the system. A firemain load that is big enough to cause a significant drop in pressure should be accompanied by a system signal or watchstander report.
The automatic sprinkling systems are equipped with flow switches. There will be a watchstander report before connecting large loads such as emergency auxiliary cooling or a dewatering eductor. By maintaining positive control of the firemain, large intended demands will be identified and will not surprise the firemain system operator. Because a loss of firemain pressure can be caused by a failure of a pump, the firemain system operator should direct pump watchstanders to check all operating pumps.
After a rupture, a pressure pulse travels through the firemain system within tenths of a second, and the system will react by re-establishing an equilibrium. This change of equilibrium within the fire main will preclude the use of pressure gauges within the damaged area of the main to precisely locate a rupture.
Pipe ruptures must be located using all available information: a. Installed sensors, including pressure gages to determine the area of the main damaged , flooding alarms, and equipment status indicators. A loss of signal can indicate damage that may be linked to the firemain damage.
Reports from Combat Information Center or the bridge, regarding the location of general battle damage. Reports from watchstanders and damage control investigators. The following conditions must be met: a. There is no useful firemain pressure available. That is, no further harm will come from isolating undamaged portions of the firemain system. The firemain system operator must be able to open and close segregation and isolation valves in the main and riser piping. Personnel at the DC deck valve operating stations can do this, or central control of motorized valves may be available.
Determine the number of fire pumps that can be used to supply the portion of the firemain in which pressure cannot be maintained. Available electrical power may limit the number of pumps that can be operated.
Split the firemain into segments, one segment for each pump that can be operated. Start the pumps. If pressure cannot be maintained in a segment, there is a rupture somewhere in that segment. The pumps in segments that maintain pressure should be left operating.
For segments in which pressure cannot be maintained, close valves farthest from the pump and check to see if pressure is regained. If not, repeat. When pressure is regained, the rupture or ruptures will be downstream of the last valve closed. At this point, there may be portions of the firemain that are undamaged but isolated from any pump. To Caution is required because these isolated segments may be ruptured, but the damage was masked by a damaged segment that was closer to the pump.
If a pressure drop was caused by a large service that was intentionally placed on line, start one or more additional pumps to regain pressure, or secure other connected services. For pump problems, follow troubleshooting and recovery actions described in the ships engineering casualty control manual, the pump technical manual, or NSTM Chapter Since it may take several minutes for damage control personnel to locate the rupture and the nearest firemain cutout valves, it may be prudent to close the system isolation valves at the damage control boundaries established by the DCA.
This action will rapidly restore firemain pressure to the undamaged portions of the ship, including the staging areas from which the fire parties will advance on any fires. This action will also isolate undamaged portions of the firemain that are within the damage control boundaries.
If the firemain rupture has a caused a general loss of firemain pressure, no further harm will be caused by isolating the undamaged portion--there was no pressure available anyway. This course of action may be prudent if isolating the damage would also isolate vital services, such as cooling to ships combat systems, cooling to emergency generators, or fire fighting. This course of action will cause continued flooding, but the flooding may be a less immediate threat to the ships survival than continued enemy attack or a conflagration.
To implement this course of action, start additional fire pumps to regain system pressure. As time and resources permit, damage control personnel should continue their efforts to close cutout valves near the rupture, and secure non-vital services throughout the ship.
Table shows the time to flood a hypothetical compartment, under the assumptions shown. Notes: 1. Pipe sizes are based on copper-nickel pipe, MIL-T class The indicated flows are a worse case scenario assuming a clean break of the pipe.
Ruptured pipe flow assumes sufficient pump capacity is available. One common cause of firemain malfunction is fouling by marine growth which accumulates inside the piping. It will build up in a pipe, decreasing the pipes internal cross-section This growth will also accumulate on the valve seats, valve discs, and stems, preventing the valve from seating properly or the stem from working freely.
Rapid fouling of the firemains by marine growth is experienced in many ships, particularly ships operating in tropical waters. AFFF systems are installed on surface ships to protect machinery spaces, fueled vehicle stowage spaces, helicopter hangars, landing platforms, refueling stations, flight decks, hangar bays, fuel pump rooms and other compartments or areas where flammable liquid fires are likely to occur.
Balanced Pressure Proportioner. The balanced pressure proportioner see Figure does not inject a set amount of concentrate into the seawater but proportions the amount depending on the demand see paragraph Two Speed Pumps. These pumps inject rated capacity of AFFF concentrate for the speed selected. The speed at which the pump operates depends on the demand of the system. If only a hose line is needed, the low 27 gpm speed is actuated.
If AFFF for a sprinkler group is needed, the high speed 65 gpm mode is actuated. FP Proportioner. This proportioner is being replaced by balanced pressure proportioners, or fixed AFFF eductors for selected small demands see paragraph Single Speed Pump. Single speed pumps are rated at 27 and 60 gpm see Figure and paragraph AFFF station actuation is hydraulic or electrical.
Hydraulic actuation is accomplished by means of a manual control valve and electrical actuation by means of switches which energize a solenoid operated pilot valve SOPV. The sequence for activating an electrically operated AFFF station is described below see Figure The circled numbers on the figure correspond to the reference numbers in parenthesis: a.
All SOPVs master or service have four control line ports. One port is always connected to firemain supply pressure. A second port is always connected to a drain pipe. The other two control ports are connected by control lines to diaphragm operated control valves, or one will be plugged if not used. A separate service SOPV 2 allows flow through the distribution subsystem Powertrols to the individual demands served by the station.
This allows the Hycheck 3 to be forced open by the firemain pressure and allows the seawater to be mixed with the AFFF concentrate in the venturi 6. There are three types of high capacity AFFF systems installed on board navy ships; balanced pressure proportioners see Figure , electric two speed AFFF pumps see Figure , and high capacity single speed pumps see Figure The capacity of the tank is determined by the firefighting demands of the system it supplies.
An AFFF tank is located inside each station. The operation of the electric single speed pump, two speed pump, and balanced pressure proportioner with their associated stations is described in paragraphs This permitted the fire to gain considerable headway before water was applied. All of these were brought under control quickly by prompt action of fire-fighting parties. The fact that these fires were put out speaks for itself. They will also damage mains, fire plugs, nozzles, and fire extinguishers in the vicinity.
Fire-fighting equipment on exposed decks should be shielded as much as arrangements permit. Time is the very essence of effective action in combating a fire of this type, inasmuch as the fire will accelerate swiftly and quickly advance beyond control of any facilities which are practicable to install on a warship.
Those who failed to use them learned their lesson the hard way. Fragments 5 pierced the hangar deck, and fires were started in three planes. The sprinkler system and water curtains in the two after bays quickly extinguished the fire.
The presence of unessential inflammable material and the absence of adequate fire-fighting facilities prevented control of the fire. Clothing, bedding, linoleum, cork slab, and bulkhead paint burned in these spaces, producing a great deal of smoke.
The fire was difficult to control due to lack of access. Wrecked bunks and bins kept men from the seat of the fire. Insulation on cables The fires were under control in about twenty minutes. To permit the repair party to fight the fire, the smoke was vented topside by opening hatches on the second and main decks. Rescue breathing apparatus was used while fighting the flames in enclosed spaces and in making inspections of smoke-filled holds and engineering spaces.
During the fire-fighting operations on this ship, fog, solid stream, chemical, and mechanical foam were used. These fires were fed by excess clothing, upholstered furniture, and excess material in squadron ready rooms.
Dense smoke passed into the hangar where conditions were made extremely difficult for the repair parties. There was little if any fire in the crew's mess room where the bomb exploded because no combustible material was present. Fire in the upholstered furniture of these cabins was very difficult to extinguish. These fires created dense smoke which completely permeated the area.
It was finally extinguished by a handy billy set up on the main deck. Drainage of damage water, and obstacles encountered. There was confusion in getting started, and difficulty in getting submersible pumps in operation.
There was delay in getting electric submersible pumps and gasoline driven handy billies into operation, due to inability to find proper couplings for connecting up sections of hose. Further, the leads on the submersible pumps were not long enough to reach a power outlet, and had to be lengthened before the pumps could be used, power outlets in the vicinity of the damage being dead because electricity had been cut off in the damaged, fuel-oil filled areas as a precaution against fire.
One burned out and the other had a ground which required two hours to bake out. The latter then was used to clear AL of water. All compartments were flooded with oil making it impossible to use a handy billy. Such pumps should have large basket screens; these are being made on this ship. Engineering and electrical aspects.
This resulted in loss of cooling water to the lubricating system of the forced-draft blowers. This casualty apparently resulted when electrical faults appeared in the five-inch system which had locked circuit breakers. It is clearly evident that considerable effort was expended on the myriad details of maintenance, and that such efforts paid dividends.
It was kept in operation, however, by frequent changes of the watch. Operating personnel wore plenty of clothing for heat insulation. Tests showed other circuits to be shorted also.
The explosion also ruptured the air lines to the forward guns Damage-control organization and training. The success of damage-control measures indicates thorough preparation both in material readiness and training of personnel. Despite the radical reduction in fighting efficiency, this ship continued in action, engaged an enemy battleship, and sank an enemy destroyer the following morning.
This record is impressive, and is a tribute to the skill of her personnel. Fires, slight flooding, necessary shoring of bulkheads, removal of injured personnel, and necessary pumping and rigging of emergency electrical leads were all handled in a highly commendable fashion which showed the direct result of constant instruction and vigilant training. An obvious lesson is the danger of opening scuttles for visual observation of damaged spaces below.
Sounding tubes or air escapes should be utilized for this purpose, where installed. Air-test fittings can always be used. Under no circumstances should any hatch be opened where there is even a slight possibility of the space below being flooded. This was a noteworthy achievement, and was made possible by the prompt and effective damage-control measures taken by the crew. This could have occurred easily had the engineering force been less vigilant.
The remarkable, persistent, and skillful efforts of her entire crew not only saved her, but also most of her cargo, sorely needed at that time Minor fires caused by exploding 20 mm. As the fire main was ruptured, a jumper was rigged between two risers on either side of the break, thus putting the magazine sprinkling system back in operation.
It was gratifying to note the skill with which the repair parties operated. The damage-control party upon immediate investigation ascertained that there had been serious damage from the explosion, and repotted small scattered fires which were quickly brought under control.
It was realized by the damage-control party that electrical power in the after part of the ship could cause serious fires due to broken leads, and steps were taken to secure all electrical power in the damaged area. Inasmuch as power was required by the submersible pumps in case of flooding and for welding and cutting equipment in the damaged compartments, portable electric leads from the power casualty system were rigged, and were available almost immediately.
This fire was put out with foam, as there was no water pressure available. There were two subsequent fires in the same compartment that were extinguished by the same means. Compartment B-4 was not damaged, and the generator located there kept running. Under the leadership of the assistant engineer officer, the rigging of emergency power cables was commenced at once.
The repair party immediately began shoring the forward bulkhead located in compartment B The work of repair parties in evaluating and repairing damage and in the extinguishing of fires was outstanding. Before the hit was received speed was 15 knots. Just as the hit was received speed was increased to 25 knots for evasive purposes, but the port engine slowed momentarily until the plant could be cross-connected and both engines shifted to steaming on the forward fireroom.
The after fireroom was properly secured by the watch, and all action incident to the cross-connecting of the plant was carried out, despite rising water and escaping steam in the fireroom. The fireroom was flooded to a depth of approximately 12 feet. An exterior temporary patch of boiler plate, held in place by a turnbolt in the center of the plate and padded with mattresses and pillows was put into place.
After this the fireroom was pumped dry, using three submersible pumps in addition to the main drain. No further difficulty was experienced with flooding. Damage-control measures were instituted immediately. Mattresses backed with heavy shoring were used to block off the hole and the leakage was completely stopped. A wire strap was taken around one of the blades of the useless screw and secured to the deck. This prevented the screw from turning and banging against the ship's side while the ship was underway.
Further repairs were made later by ship's force, who welded a temporary patch on the hole in the engine room. An immediate inspection was made of the watertight integrity throughout the undamaged portion of the ship. C and R soundings were instituted immediately. The damaged area was inspected for possible points of weakness, and to see if the ship showed signs of breaking in two. Watches were posted adjacent to spaces where the damage was centered for the purpose of detecting fires and any breaking noises.
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