Classes of Fire & Portable Fire Extinguishers on Ships

1. FFA Map, Classes of Fire & the Tetrahedron

When the surveyor opens with "what is your FFA?", walk the ship in order before zooming into portables. The file groups fire-fighting appliances into four families:

Full FFA map (Q17) — say it in this order:

• Portable extinguishers: water, mechanical foam, DCP and CO2 types.
• Semi-portable extinguishers: semi-portable CO2, semi-portable DCP and semi-portable foam.
• Fixed extinguishing systems: CO2 gas fixed system, water sprinkler system, fire main system, high and low expansion foam system, and hypermist (water-mist) system.
• Fireman's outfit: SCABA set, waterproof heat-resistant protective clothing, electrically non-conductive boots and gloves, rigid helmet, axe with insulated handle, fireproof lifeline, belt for carrying the auxiliary line, and battery-operated safety lamp.
• Other critical appliances: emergency generator, emergency air compressor, emergency air bottle, emergency fire pump, fire and bilge pumps, fire mains with isolating and section valves, quick-closing valves, remote stops for fuel-oil pumps, B.A. compressor, international shore coupling, fire alarm and detection system, and the fire plan with the muster list.

Classes of fire — with the correct medium (Q18):

• Class A — carbonaceous (wood, paper, cloth): extinguish with water mostly.
• Class B — oil fires (volatile petroleum, paint, oil): extinguish with foam, DCP or CO2.
• Class C — gas and chemical fires: extinguish with DCP.
• Class D — metal fires: extinguish with DCP.
• Electrical fires: extinguish with DCP plus CO2.

The fire tetrahedron — four sides, four kills:

• Starvation — cutting of the fuel.
• Smothering — separating the fuel from the oxidant.
• Cooling — lowering the temperature, usually with water.
• Inhibition (retardation of the combustion reaction) — removal of the molecular chain reaction.

2. SOLAS Portable Extinguisher (PFE) Rules

For "what does SOLAS say about portable extinguishers?" (Q19a), give the regulation as a checklist:

• Portable fire extinguishers (PFE) shall be provided in accommodation, service spaces and control stations, of appropriate type and in sufficient number to the satisfaction of the Administration.
• Minimum number: ships of 1000 GT and above shall carry at least 5 portable extinguishers.
• Size limits: total weight shall be not more than 23 kg, and capacity of the fluid not less than 9 litres and not more than 13.5 litres.
• Stowage: one of the extinguishers intended for use in any space shall be stowed near the entrance to that space.
• CO2 extinguishers shall not be used in accommodation spaces.
• Extinguishers shall be situated ready for use at easily visible positions.
• Each extinguisher shall be provided with a device indicating whether it has been used.
• Spare charges: spares shall be provided for 100 percent of the first 10 extinguishers and 50 percent of the remaining extinguishers capable of being recharged on board — but not more than 60 total spare charges are required.
• For extinguishers which cannot be recharged on board, additional extinguishers of the same quantity, type and capacity shall be provided in lieu of spare charges.

3. Water Soda-Acid & Foam Mechanical Types

These are the two liquid-medium portables. Learn each under the same headings: principle, use, safety, body, charge, throw, working.

Water type (soda-acid) portable:

• Working principle: cooling effect.
• Use: carbonaceous Class A fires.
• Safety: relief hole and safety pin.
• Body: solid drawn steel, internally zinc coated.
• Charge: CO2 cartridge 74 g (varies with cylinder weight and capacity) at 36 bar pressure, plus 9 litres minimum of water.
• Throw: 6 m jet for 60 seconds.

Water type — operation:

• Carry the extinguisher near the fire and keep it towards the fire.
• Remove the safety pin and strike the plunger to pierce the CO2 cartridge.
• When pierced, pressure builds in the upper part of the container and water rises through the dip tube and is thrown as a jet spray.

Mechanical foam type portable:

• Working principle: smothering effect.
• Use: volatile petroleum, paint and oil — Class A and B fires.
• Safety: relief hole and safety pin.
• Body: solid drawn steel, internally zinc coated.
• Charge: CO2 cartridge 74 g (varies with cylinder weight and capacity) at 36 bar pressure, plus foam liquid at AFFF 97 percent water to 3 percent concentrate.
• Throw: 6 m jet for 60 seconds.

Foam type — operation and technique (Q19e):

• Carry the extinguisher near the fire, keep it towards the fire, remove the safety pin and strike the plunger to pierce the CO2 cartridge — pressure drives the foam up the dip tube as a jet spray.
• Do not allow foam to strike the surface of the burning liquid.
• Direct the foam at some nearly vertical surface so that it runs down the side and blankets the liquid.
• If no vertical surface is found, keep a distance such that the discharge falls gently on the liquid surface.
• Use the same manufacturer for refills, and if using a pre-mix fluid, do not increase or decrease the proportion — it affects extinguisher efficiency.

4. CO2 & DCP Types, FSS Markings and Semi-Portables

The two gas-and-powder portables plus the markings plate and the larger semi-portable units:

CO2 type portable:

• Working principle: smothering effect.
• Use: oil, electrical, petroleum products and gaseous substances in enclosed spaces — Class B.
• Safety: control valve or safety valve, pressure-relief device and safety pin.
• Discharge hose of non-conductive material.
• Body: solid drawn steel, internally zinc coated.
• Charge: CO2 4.5 kg (varies with cylinder weight and capacity) at 53 bar pressure.
• Throw: 3–4 m jet for 20 seconds.
• Pressure tested to 210 kg per sq cm before recharging.
• Recharge only ashore, when the weight has reduced by 10 percent and more.
• Storage: at least 750 mm above the floor, never where it is likely to gain heat from surrounding equipment or processes.

CO2 type — operation:

• Carry the extinguisher near the fire and remove the safety pin.
• Direct the hose at the base of the fire, starting at one edge and sweeping across the burning surface.
• In open air, stand on the upwind side of the fire.
• On electrical equipment, first switch off the current supply.

DCP (dry chemical powder) type portable:

• Working principle: smothering effect.
• Use: oil, electrical, petroleum products and gaseous substances in enclosed spaces — Class A, B, C, D and electrical — the all-rounder.
• Safety: safety pin and relief hole, plus an inner container for the CO2 cartridge — sodium bicarbonate would freeze on direct contact with CO2 because CO2 is a cool gas.
• Body: solid drawn steel, internally zinc coated.
• Charge: inner shell CO2 60 g (varies with weight and capacity); outer shell 4.5 kg of DCP powder — a mixture of sodium bicarbonate plus magnesium stearate, NaHCO3 + Mg(C18H35O2)2.
• Magnesium stearate is added so the powder does not choke; if choking occurs, remove and replace with a fresh charge.
• Throw: 3–4 m for 20 seconds.
• Pressure tested to 35 kg per sq cm before recharging, once in 3 years.

DCP type — operation:

• Carry the extinguisher to the fire and keep it upright.
• Remove the safety pin and strike the plunger — CO2 escapes into the main shell and pushes the powder out in the form of fog.
• Outdoors, operate from the upwind side for better range.

Markings on the extinguisher (as per FSS Code — 8 items):

• Name of the manufacturer.
• Type of fire for which the extinguisher is suitable.
• Quantity and type of extinguishing medium.
• Approval details.
• Instructions for use and recharge.
• Year of manufacture.
• Temperature range over which the extinguisher will operate.
• Test pressure.

Semi-portable extinguishers:

• Types: CO2, dry chemical powder and mechanical foam.
• Propellant: externally fitted CO2 cartridge.
• Capacity: 55 litres or kg (varies).
• Discharge mechanism: 15 m hose-reel type.
• Period of discharge: maximum 3 minutes.
• Head assembly: brass with tell-tale hole relief system; the CO2 cartridge operating lever carries a safety pin.
• Maintenance: weekly physical inspection and annual complete servicing.
• Location: CO2 adjacent to the MSBD; DCP and foam at the boiler and purifier rooms.

5. Maintenance Tables, Weighing & Anti-Choke Drill

For "weekly, monthly and yearly maintenance?" (Q19b), give one table per type — the surveyor listens for weighing, plunger, spring, relief hole and the pressure-test figure:

Water and foam — weekly / monthly / yearly:

• Weekly: check the exterior and clean it; check the nozzle outlet and clean it; check the relief hole and clean it.
• Monthly: check the internal condition; check the gas cartridge; check the plunger; check the spring; carry out weighing of the cylinder.
• Yearly: pressure test at 35 bar before recharging.

CO2 — weekly / monthly / yearly:

• Weekly: check the exterior and clean it; check the hose outlet and clean it.
• Monthly: carry out weighing of the cylinder — if 10 percent less, send ashore for recharge.
• Yearly: pressure test at 210 kg per sq cm before recharging.

DCP — weekly / monthly / yearly / 3-yearly:

• Weekly: check the exterior and clean it; check the pressure-indicating needle — it must sit in the green zone; check the nozzle outlet and clean it; check the relief hole and clean it.
• Monthly: check the internal condition and the powder for any choking effect; check the gas cartridge; check the plunger; check the spring; the extinguisher must be inverted once a month to avoid choking of the powder; carry out weighing of the cylinder.
• Yearly: one-third of the total number of extinguishers should be put into operation for evaluating their satisfactory performance.
• 3-yearly: as per IMO, pressure test at 35 bar before recharging.

Weighing the extinguisher (Q19c):

• Weigh the cylinder and compare against its charged weight — CO2 types go ashore for recharge at 10 percent loss.
• On DCP, the magnesium stearate keeps the powder free-flowing, but if choking is found, remove and replace with a fresh charge.
• Invert every DCP monthly as the anti-choke routine — this single line is the favourite DCP follow-up.

6. Operation Drill — Answering the Surveyor on the Spot

The surveyor's favourite cross-check is "show me how you use it" — answer with hands, wind and switches, not just numbers:

• Water and foam: carry near the fire, face the fire, pin out, strike the plunger, dip-tube jet — foam then goes vertical-surface-or-gentle-fall, never a direct strike.
• CO2: carry near the fire, pin out, hose at the base, edge-to-edge sweep — upwind outdoors, switch off electrics first.
• DCP: carry to the fire, keep upright, pin out, strike the plunger, fog discharge — upwind outdoors for range.
• Failed vertical surface? Hold the distance so the foam falls gently on the liquid — say this exact line for Q19e.
• Wrong proportion? Pre-mix off-ratio kills efficiency — same maker, same ratio, every refill.
• Used or not? Point at the used-indicator and the green-zone needle on DCP before you touch anything.