Fireboat

Overview

A fireboat is a self-propelled vessel built to fight fires on other ships, on offshore structures, and on waterfront property that land appliances cannot reach. It carries its own water source, the sea or harbor around it, so unlike a land fire engine it never runs out of supply. The two defining features are very high pump capacity, often 15,000 to 30,000 cubic meters per hour total, and remote-controlled Water/Foam Monitor cannons that throw water or foam more than a hundred meters. The boat is built around a welded Hull and Superstructure, driven by a twin-engine Propulsion System train, and supplied by a redundant Fire Pump System. A Foam Proportioning System handles fuel fires, a Self-Protection Drencher protects the boat from radiant heat, and an Electrical and Control System system runs everything from the wheelhouse.

Hull and Propulsion

The Hull and Superstructure is a welded marine-grade steel monohull, with Hull Shell Plating of 8 to 12 mm divided by Watertight Bulkhead into watertight compartments so a single breach does not sink the boat. The Keel and Frame Structure carries the structural loads, and a continuous rubber Hull Fendering band protects the shell when the boat works alongside a burning vessel or a quay wall. An aluminum Wheelhouse sits above the deck with all-round Wheelhouse Glazing glazing so the crew can see the fire and aim the monitors. The wheelhouse also carries the Navigation Electronics, including a Radar Scanner for navigating in smoke and a VHF Marine Radio for incident communications, since fires often happen at night or in poor visibility.

Propulsion is usually twin Marine Diesel Main Engine diesels of 600 to 1000 kW each, each fed by a common-rail Fuel Injection System system and cooled by a seawater Engine Cooling Circuit circuit. Each engine turns a Marine Gearbox and a bronze Fixed-Pitch Propeller through a Propeller Shaft, drawing diesel from a baffled Fuel Tank. A Bow Thruster gives sideways thrust so the boat can hold position close to a fire while the monitors push back against it. The Ballast Tank system trims the boat and helps counter the reaction force of the jets, which can run to several tonnes when all monitors fire at once. On some designs the propulsion engines also drive the fire pumps through a power take-off, while on others each pump has a fully independent driver.

Pumps and Monitors

The Fire Pump System is the heart of the vessel. Two or three Centrifugal Fire Pump centrifugal pumps draw seawater through a hull Sea Chest and raise it to 10 to 16 bar. Each Pump Impeller runs inside a Pump Casing volute that converts velocity into pressure. On many designs each pump has its own Pump Driver Engine diesel so the loss of one engine does not cut the firefighting output. Pumped water passes through a Discharge Manifold to the monitors, the deck hydrants, and the shore-supply connections, with a Pump Pressure Gauge at each stage.

Each Water/Foam Monitor is a remote cannon with a variable-pattern Monitor Nozzle that adjusts from a long solid jet for reach to a wide fog for cooling. A Monitor Swivel Base base allows 360 degree train, driven by Monitor Actuator units, and the operator aims it with a Monitor Control Unit joystick. Roof-mounted monitors give the longest throw, while lower deck monitors reach below decks and into the waterline of a casualty.

Foam and Self-Protection

Burning oil, fuel, and chemicals cannot be put out with plain water, so the Foam Proportioning System injects concentrate from a Foam Concentrate Tank into the water stream. A Foam Metering Pump meters the concentrate, and a Foam Proportioner mixes it at one to six percent through a Foam Ratio Valve, producing a blanket that smothers the fuel surface and cuts off oxygen.

To approach an intense fire the boat protects itself with the Self-Protection Drencher. A ring of open Drencher Nozzle sprays fed by the Drencher Ring Main wets the whole superstructure with seawater, so the boat can sit inside radiant heat that would otherwise blister paint and crack glass. The crew opens the Drencher Valve from the wheelhouse before closing in.

Materials and Electrical

The hull uses marine-grade steel for strength and fire resistance, the wheelhouse uses aluminum to save topweight, and pump wetted parts use bronze and stainless steel to resist seawater corrosion. The Electrical and Control System system runs on Diesel Generator Set sets feeding a Main Switchboard, with a Pump and Monitor Controller coordinating pump start, monitor aiming, and alarms.

Use and Variants

Fireboats range from harbor launches around 20 m to large port and offshore craft of 40 m carrying Fi-Fi class society notation. Beyond firefighting they tow disabled vessels using the Mooring Bollard fittings, run rescue operations with a Rescue Boat Davit and fast boat, and pump out flooded hulls. Boarding crews draw hoses and breathing sets from the Equipment Locker and connect to a Deck Hydrant to fight fires inside a casualty.