Ship Fire Main & Emergency Fire Pump System

1. Fire Main Purpose & General Principles

The fire main is a system consisting of sea-water inlet(s), suction piping, fire pumps and a distributed piping system supplying fire hydrants, hoses and nozzles located throughout the vessel. Its purpose is to provide a readily available source of water to any point throughout the vessel which can be used to combat a fire, and it is considered the backbone of the fire-fighting systems on board.

Through the fire main the firefighter gets a reliable and versatile system offering several methods of attack: water can be supplied as a straight stream (jet) for deep-seated fires, as a spray for combustible-liquid fires where cooling and minimum agitation is desired, or as a means to protect personnel where cooling is the primary effect desired.

• 2.6 kJ/g — Heat Absorption to Steam
• 1600× — Steam Volume Expansion
• 2 × 12 m — Mandatory Jet Throw
• 3.5 kg/cm² — Top Hydrant Working Pressure

Extinguishing capabilities of water:

Sensible & Latent Heat Absorption

Heating water from ambient to 100 °C and converting it into steam absorbs 2.6 kJ/g (1117 BTU/lb). This massive thermal sink drops the combustion zone temperature below the fuel's auto-ignition point.

1600× Smothering Steam Blanket

Upon vaporisation at atmospheric pressure, 1 m³ of liquid water expands into 1600 m³ of steam vapour, rapidly displacing ambient oxygen around the flame envelope and suffocating the combustion.

Versatile Jet & Spray Delivery

Applied as a solid high-velocity jet for deep-seated Class-A embers, a wide-angle mist fog for cooling Class-B oil spills without fuel splashing, and water curtains for boundary cooling of adjacent bulkheads.

Distributed Ring Architecture

Supplied by at least 2 independent main pumps plus 1 emergency fire pump outside machinery spaces, serving distributed deck hydrants equipped with instantaneous couplings and dual-purpose nozzles.

How to answer in viva. For "what is the purpose of the fire main?", say: backbone of firefighting — sea inlet to hydrants everywhere — cooling plus 1600× steam smothering at 2.6 kJ/g — applied as jet, spray and boundary cooling.

2. Emergency Fire Pump Regulation

Apart from the main fire pumps, an emergency fire pump is provided for emergencies such as CO2 flooding or main fire pumps dysfunctional. For "give the emergency-pump regulation", give position, drive, suction and figures together:

Main fails — backup runs: Place outside E/R; Drive own power; Throw two jets.

Emergency Fire Pump Statutory Requirements (SOLAS Ch. II-2 Reg. 10 & FSS Code):

The emergency fire pump is the vessel's ultimate firefighting lifeline should a major fire, total blackout, or flooding knock out the main engine room fire pumps. Surveyors and PSC inspectors verify its operational readiness, priming ability, and discharge pressure during almost every inspection.

• 40% — Main Pumps Total Capacity
• ≥ 25 m³/h — Min Cargo ≥2000 GT & Pax
• ≥ 15 m³/h — Min Cargo <2000 GT
• ≥ 0.27 N/mm² — Min Hydrant Working Pressure

Statutory Location & Access

Must be situated outside Category-A machinery spaces (typically installed in the steering gear compartment, shaft tunnel, forward pump room, or emergency generator flat). Access must not be compromised by smoke, fire, or heat from the engine room. If access requires passing through the engine room, it must be protected by an airlock with two self-closing A-60 steel fire doors.

Prime Mover & Cold Starting

Driven by an independent compression-ignition diesel engine OR a dedicated electric motor powered exclusively from the Emergency Switchboard (ESB). The diesel engine must be capable of starting from cold down to 0 °C by hand cranking or power starting, and down to −15 °C with preheating aids (glow plugs/jacket heaters). Two independent energy sources must be provided (e.g. primary electric battery starter plus secondary manual hydraulic or spring accumulator starter).

Fuel Oil Supply & Endurance

The diesel engine must have an independent service fuel tank containing sufficient fuel with flash point ≥ 43 °C to run the pump at full load for at least 3 hours. A reserve stock of fuel stored outside the machinery space must ensure full operation for a further 15 hours (total 18 hours endurance).

Suction Lift & Priming Mechanism

Must have an independent sea chest. The total suction head must not exceed 4.5 metres (statutory maximum 6 metres) at the vessel's lightest seagoing ballast waterline under any condition of list (15°) or trim (10°). Must be fitted with an independent automatic priming device (water-ring liquid pump, compressed air ejector, or vacuum primer). If suction piping traverses machinery spaces, it must feature ≥ 11 mm wall thickness, all-welded joints without flanges, and A-60 fire insulation.

Discharge Pressure & Jet Delivery

When discharging through any two adjacent hydrants fitted with standard 12 mm (or 16 mm / 19 mm) nozzles, the pump must maintain a minimum working pressure of 0.27 N/mm² (2.8 kg/cm² / 2.7 bar) at the third hydrant, throwing two powerful, coherent water jets with a horizontal throw of not less than 12 metres each.

External Isolating Valve

A screw-down non-return or stop fire main isolating valve must be positioned on the fire main pipework outside the machinery space in an easily accessible position. Shutting this valve isolates the engine-room fire main from the deck fire main, ensuring that a pipe rupture inside a burning engine room cannot depressurize the deck hydrants supplied by the emergency fire pump.

Memory hook for viva. Recite: 40% — 25 — 15 — 0.27 N/mm² — 2 × 12 m: 40% of main capacity, 25 or 15 m³/h minimum, maintaining 0.27 N/mm² while throwing two 12-metre jets — from outside the machinery space with independent sea suction and 3+15 h fuel reserve.

3. Hoses, Nozzles & Hydrant Pressures

Hoses and nozzles carry the water from the hydrant to the fire — surveyors test construction, stowage, lengths, couplings and pressures closely.

• 18 m / 64 mm — Hose Length & Diameter
• 15 / 20 / 25 m — ER / Deck / Wide Decks
• 17 / 24 bar — Working / Test Pressure
• 12 / 16 / 19 mm — Dual Nozzle Orifices

Fire Hose Construction & Testing

Made from synthetic woven textiles, lined with smooth synthetic rubber and coated with PVC. Highly resistant to rot, mildew, marine climate, and hydrocarbons. Tested annually to 50% above working pressure (17 bar WP → 24 bar TP).

Dual-Purpose Nozzle Function

Approved type incorporating solid jet, wide-angle spray, and complete shut-off in one twist assembly. Orifices: 12 mm, 16 mm, and 19 mm (accommodation restricted strictly to 12 mm). Delivers average ≥ 5 L/m²/min.

Two-Jet Coverage Mandate

Hydrant positions must allow at least two jets of water from separate hydrants (one from a single length of hose) to reach any normally accessible area on board, including cargo spaces when empty.

SOLAS Hydrant Working Pressures

• With 2 main pumps running: 3.5 kg/cm² (50 psi) at top two hydrants.
• Passenger Ships: ≥4000 GT: 0.40 N/mm² | <4000 GT: 0.30 N/mm²
• Cargo Ships: ≥6000 GT: 0.27 N/mm² | <6000 GT: 0.25 N/mm².

4. Relief, Drain & Isolating Valves

Valves keep the main alive when part of the ship is on fire, and protect the pumps and the main itself.

Isolate — drain — relief: Isolate cut section; Drain frost clear; Relief lift at set.

Spring-Loaded Pressure Relief Valve

Fitted on pump discharge headers. Automatically lifts if pumps exceed pipework design pressure. Crucially protects ship pipework and hydrants from excessive pressure during shore supply connection in dry dock.

Low-Point Anti-Freezing Drain Valves

Fitted at all low points along weather deck and exposed fire mains. Drains standing water when the system is idle, preventing catastrophic pipe ruptures caused by water freezing in sub-zero polar latitudes.

Machinery Space Isolating Valve

Fitted in an easily accessible and tenable position outside the engine room. When closed, keeps the entire deck and accommodation fire main pressurised via the emergency pump even if the engine room is flooded or ablaze.

Tanker Poop Front & 40 m Deck Valves

On oil/chemical tankers: one screw-down isolation valve sits in a protected position at the poop front bulkhead, plus additional valves along the tank deck at intervals of not more than 40 metres to isolate ruptured sections.

Tanker oral-exam rule. On tankers the isolating valve sits at the poop front in a protected position with tank-deck isolations at not more than 40 m intervals — quote both figures together.

5. Main Diameter & Fire-Main Sketch Points

For "draw the fire-main system" (Q24) and "what is the diameter of the fire main?" (Q24d), give the sizing rule and the sketch contents:

• 2 Pumps — Simultaneous Maximum Discharge
• 140 m³/h — Cargo Ship Main Capacity
• ≤ 40 m — Tanker Deck Valve Spacing
• Anti-Clockwise — Hydrant Valve Opening

Main Diameter Sizing Rule

Pipe diameter is dimensioned for effective distribution of maximum combined discharge from two main fire pumps operating simultaneously. On cargo ships, diameter need only be sufficient to carry 140 m³/h.

Sketch Checklist: What to Draw

1. Open sea chests → 2 main pumps with NR valves
2. Relief valve overboard
3. Machinery space isolating valve
4. Emergency pump outside ER
5. Poop front & 40 m deck valves
6. Hydrants, hoses & dual nozzles
7. International shore connection.

6. Q24 Oral-Exam Recap & Figure Table

For "draw the fire-main system" (Q24) plus sub-questions Q24a–Q24e, answer in this order — purpose, pumps, emergency pump, hoses and nozzles, pressures, valves, diameter:

Q24 main-system rapid answers:

• Composition: sea-water inlets, suction piping, 2 fire-main pumps, distributed main, hydrants, hoses and nozzles — the backbone giving water at every point.
• Attack modes: jet for deep-seated fires, spray for liquid fires with minimum agitation, personnel shielding and boundary cooling.
• Water figures: cooling to 100 °C then steam at 1600× expansion — 2.6 kJ/g (1117 BTU/lb) — cooling plus smothering.
• Pumps: 2 main pumps, FSS-Code capacity, remote start, sea valves always open; performance two 12 m jets from the farthest hydrants.
• Use limits: first choice for Type-A fires; on Class-B only after all other modes fail.

Q24a–Q24e rapid answers:

• Q24a isolation function: separates the machinery-space pump section from the rest so all other hydrants stay supplied by the second or emergency pump; fitted outside in a tenable position, on tankers poop-front protected plus 40 m tank-deck valves, screw-down type.
• Q24b pump regulation: emergency pump outside M/C at embarkation-deck level, diesel with battery plus hand-crank, primed, 40% with 25 / 15 m³/h minima, two 12 m jets.
• Q24c hose and nozzle regulation: synthetic 18 m / 64 mm, deployed 15 / 20 / 25 m, annual 50%-over test (17 / 24 bar); dual jet+spray with shut-off, 12 / 16 / 19 mm, 12 mm in accommodation, 5 L/m²/min.
• Q24d diameter: serves two pumps together — 140 m³/h on cargo ships.
• Q24e relief: yes — against over-design pressure and against shore-supply damage in dry dock; drains guard against icing.

Trap answers. "Which way does a hydrant valve open?" — anti-clockwise. "Can a hose be removed with pumps running?" — yes, each hydrant has its own valve. "What stops overpressure?" — the relief valve.

7. Shore Coupling, Hydrant Fittings & Hose Boxes

For "what fittings sit between the main and the hose?", describe the chain from hydrant valve to nozzle exactly as the notes list it:

• 178 mm — ISC Flange Outer Diameter
• 64 mm — ISC Inside Bore Diameter
• 132 mm — Bolt Circle PCD
• 4 × 19 mm — Slotted Bolt Holes

Hydrant Body & Valve

Every hydrant features an anti-clockwise opening control valve. Positioned so any single hose can be engaged, disengaged, or removed while fire pumps run continuously under full head pressure.

Fire-Hose Box Equipment

Stowed conspicuously adjacent to the hydrant. Contains: one approved synthetic fire hose (flaked or rolled), one dual-purpose jet/spray nozzle, and the dedicated coupling spanner wrench.

International Shore Connection (ISC)

Standardized universal flange carried on board. Enables the ship to couple instantly to any municipal or shipyard fire tender worldwide during port layover or dry-docking.

Fastener Kit Specification

Must be stored with the ISC flange: 4 steel bolts of 16 mm diameter × 50 mm length, 8 flat washers, and 1 full-face non-asbestos elastomeric gasket rated for 10.5 bar.

Sketch labels to recite in viva. Label the drawing: hydrant → anti-clockwise valve → flange → snap-in hose → dual nozzle, plus the hose box, spanner and international shore coupling — every item the Q24 sketch plates show.