LSA Chapter 4: Life Rafts — Capacity, Equipment & Launching

1. Regulation, Capacity & Construction

When the surveyor asks "what are the types of life raft and what is inside the bottle?", answer in two halves — types first, gas second: the gas fills the craft, the craft floats six people under 180 kg, and the buoyancy holds for 30 days.

• Types: there are mainly two types — inflatable life raft and rigid life raft.
• Inflation cylinder: the inflatable raft contains an inflation cylinder with CO2 gas.
• Buoyancy gas: CO2 plus a small percentage of nitrogen — carbon dioxide provides the buoyancy and is non-flammable; nitrogen acts as the anti-freeze.
• CO2 is heavier than air, hence adds buoyancy to the raft.
• Freezing point of CO2 is −78 °C, yet the raft must still inflate at −15 °C.
• One person alone must be able to complete the inflation.

Capacity, weight and inflation numbers

• Minimum capacity: 6 persons — no approved raft carries fewer.
• Weight with container and equipment: not more than 180 kg so it remains manhandleable.
• Inflation time: completed within 1 minute at 18–20 °C, and within 3 minutes at −30 °C.
• Afloat endurance: constructed to withstand exposure for 30 days afloat in any sea condition.
• Drop test packed: when packed in its container it withstands being dropped into the water from 18 m without damage to raft or equipment.
• Jump test: when afloat it withstands jumps onto it equal to the number of its complement, from at least 4.5 m above its floor.
• Towing: with its towing patch it can be towed at 3 knots in calm water when loaded with its full complement and equipment and one of its sea anchors streamed.

Insulation, SART, painter and lamp

• Insulation: provided against heat and cold by two layers of material separated by an air gap, with means to prevent accumulation of water in the air gap.
• SART mounting: provided with means to mount a survival-craft radar transponder at a height of at least 1 m above the sea.
• Painter: an efficient painter of length not less than 15 m.
• Painter breaking strength: 15 kN for rafts permitted above 25 persons, 10 kN for 9–24 persons, 7.5 kN for any smaller raft of 6–8 persons. A weak link in the painter breaks at 2.2 ± 0.4 kN.
• Canopy lamp: a manually controlled lamp fitted to the top of the canopy — white, capable of operating continuously for at least 12 hours with luminous intensity not less than 4.3 cd in all directions of the upper hemisphere, flashing at not less than 50 and not more than 70 per minute. An internal light is also provided inside the canopy.

Carrying capacity and location — the worked example

• Minimum carrying capacity = 6 persons.
• Forward: 6-person raft for the forward party.
• At the embarkation station, port and starboard: 16-person rafts — the example to quote when asked "give numbers from your ship".
• Always confirm exact numbers and positions from the Fire Control and Safety Plan.

Surveyor opener

"What gas inflates the raft and why nitrogen?" — CO2 gives non-flammable buoyancy heavier than air, N2 is the anti-freeze; the raft inflates at −15 °C even though CO2 freezes at −78 °C.

2. Equipment (25 Items), Markings & Safety Features

For "what is carried in the life raft?" the surveyor expects all 25 items with exact quantities counted out confidently:

• 1 — Mirror / heliograph: 1 signalling mirror.
• 2 — Sponges: 2.
• 3 — Buoyant paddles: 2.
• 4 — Hand flares: 6.
• 5 — Rocket parachutes: 4.
• 6 — Smoke signals: 2.
• 7 — EPIRB: 1.
• 8 — SART: 1.
• 9 — Food ration: 500 g per person per day up to 3 days, not less than 10000 kJ each person.
• 10 — Water: 500 ml per person per day up to 3 days.
• 11 — Knife: 1 buoyant safety knife (for cutting the painter).
• 12 — Survival instruction booklet: 1.
• 13 — Topping-up pump and bellows: 1 set.
• 14 — First aid outfit: 1 watertight kit.
• 15 — Anti-seasickness medicine: 50 doses (at least 6 doses per person) + 1 seasick bag per person.
• 16 — Thermal protective aids (TPAs): 2 (or 10% of capacity, whichever is greater).
• 17 — Whistle: 1 buoyant signalling whistle.
• 18 — Waterproof electric torch: 1 with spare batteries and bulb in watertight container.
• 19 — Radar reflector: 1 efficient radar reflector.
• 20 — Fishing tackle: 1 set.
• 21 — Sea anchors (drogues): 2 (one permanently attached, one spare with hawser).
• 22 — Tin openers: 3 safety tin openers.
• 23 — Graduated drinking vessel: 1 rustproof graduated cup.
• 24 — Repair kit: 1 kit for puncturing and leaks (plugs, clamps, adhesive).
• 25 — Buoyant rescue quoit: 1 quoit with at least 30 m buoyant line.

Marking on the life raft container — 10 items

• 1 — Maker name or trademark, the persons capacity approved and the name of the approving authority.
• 2 — Serial number.
• 3 — Date when last serviced, and the next service due date.
• 4 — Length of painter.
• 5 — Maximum permitted height of stowage above the waterline.
• 6 — Type of emergency pack enclosed (SOLAS Pack A or B).
• 7 — Date of manufacture (month and year).
• 8 — Capacity of the life raft, and the mass with the pack (not more than 180 kg).
• 9 — Launching instructions.
• 10 — SOLAS marking.

Marking on the life raft itself — 5 items

• 1 — Maker name or trademark.
• 2 — Serial number.
• 3 — Date when last serviced.
• 4 — Date of manufacture (month and year).
• 5 — Name of the approving authority, and the number of persons permitted over each entrance in characters not less than 100 mm high.

Built-in safety features

• Pressure relief valve — vents excess gas so chambers never burst on over-inflation or heat.
• Stabilising pockets — flood on launching to lower the centre of gravity and resist capsize.
• Insulated canopy with two layers — retains heat, sheds water, and carries the lamp and SART mount.

Memory hook

Pyro 6-4-2, water tools 2-2-2 (paddles, bailers, sponges), food and water 500 × 3 days, and one each of mirror, EPIRB, SART, compass, whistle, knife and torch — with 3 tin openers, 50 tablets and 2 TPAs closing the 25.

3. Manual Launch, Righting & Automatic HRU Release

For "launch the raft manually", give the deck sequence step by step — during a drill or in a real emergency:

1. Make fast the painter line: take the painter out of the raft to almost 80% of its total length and fasten it to the ship's side on deck at a strong fitting (cleat or pad-eye). Verify it is secure and not loose.
2. Clear the path and release the cradle gripes: remove the railing or open the ship rail or gate, check the overside is clear of wreckage, flotsam or propellers, and unfasten the ship hook (securing gripes or Senhouse slip hooks) from the cradle.
3. Two-man overboard launch and sharp pull: two crew members lift the cylindrical container from its cradle and throw it overboard with the painter end on the ship side. Pull the remaining painter out until taut, then give a sharp pull to actuate the gas cylinder firing head — the raft inflates within 1–3 minutes depending on ambient temperature.
4. Embark: pull the raft to the ship's side with the same painter and lower the embarkation ladder. If the height is low, jump directly into the raft — permitted up to 4.5 m from the waterline; alternatively go down the ladder, swim a short distance and climb in. In cold weather keep as dry as possible.
5. Balance and cast off: sit in order, face by face, so the raft stays balanced, carrying the SART and EPIRB inside with you. Take a headcount once all persons are inside, then cut the painter with the buoyant safety knife.

Warning — righting technique if the raft inflates inverted. If wind or sea flips the raft during inflation: climb onto the inverted floor at the CO2 cylinder side. Grasp the heavy-duty righting strap. Stand on the gas cylinder and lean backward, pulling in the same direction as the wind with your face opposite the wind — wind catching under the canopy will easily right the raft over you.

Righting a capsized raft — wind technique

• If the raft inflates upside down, use the fitted righting strap.
• Climb up on the CO2 cylinder end and pull the strap in the same direction as the wind — your face opposite to the wind — so the wind helps flip the raft upright and stable.

Inflatable liferafts & hydrostatic release units (HRU)

Under SOLAS Chapter III Regulation 13 and LSA Code 4.1.6, every liferaft stowed on an open deck must be fitted with a float-free arrangement using an approved Hydrostatic Release Unit (HRU) to ensure automatic release, inflation, and separation should the ship sink rapidly before manual launching can take place.

HRU operating principle (1.5–4.0 m)

The HRU is a sealed, spring-loaded mechanical or pyrotechnic knife assembly. When submerged between 1.5 to 4.0 metres of water depth, ambient water pressure enters the water inlet holes and acts upon an internal flexible rubber diaphragm. The pressure forces the diaphragm inward against a calibrated spring, releasing a razor-sharp spring-loaded chisel/knife that severs the white securing lashing rope (or opens a release pawl/sliphook). The liferaft container is immediately freed from its deck cradle.

The weak link function (2.2 ± 0.4 kN)

A standard liferaft painter line has a high breaking strength (7.5 kN to 15 kN) so it will not break during manual launch or heavy wave action. If this painter were tied directly to the hull, the sinking vessel would drag the buoyant inflated liferaft straight down into the abyss. The weak link (coloured red or distinctively stamped) has a precise breaking strength of 2.2 ± 0.4 kN (about 220 kgf). It is strong enough to pull the gas cylinder operating cord to inflate the raft, but will immediately snap under the massive upward buoyancy of the fully inflated canopy, allowing the liferaft to break free to the surface.

Rigging & critical precautions

Crucial surveyor question: "What is the most fatal mistake in liferaft rigging?" — shackling the painter line directly to the ship's pad-eye or deck cradle instead of passing it through the weak link. In that lethal error the weak link is bypassed; when the vessel sinks, the painter remains fastened to the deck and drags the inflated raft down with the ship.

Disposable (Hammar H20) vs serviceable HRUs

Disposable units (e.g. Hammar H20): made of composite plastic, sealed for life with a service life of 2 years from the date of installation on board. The installation month and year must be clearly marked by punching out the corresponding date markers on the label. No annual servicing is required — the unit is discarded and replaced upon expiry. Serviceable units: a metallic casing (e.g. Thanner DK 84) requiring annual inspection and pressure testing at an authorised service station.

The 3 stages of float-free operation (recite to surveyor)

1. Stage A — Release from Cradle (1.5–4.0 m): As the ship founders and sinks beneath the waves, seawater reaches 1.5–4.0 m depth. Hydrostatic water pressure acts on the HRU diaphragm, activating the chisel to sever the securing rope (or release pawl). The buoyant cylindrical container pops free from the cradle and floats upward toward the surface.
2. Stage B — Gas Inflation: The painter line remains connected to the sinking vessel via the weak link. As the ship descends further, the entire length of painter line (at least 15 m / up to 28 m) pays out of the container. Once fully taut, the sinking weight pulls the internal gas-cylinder firing head lanyard, releasing the CO₂/N₂ charge. The liferaft inflates on the surface within 60 seconds.
3. Stage C — Weak Link Parting: As the ship continues to sink, the downward pull on the painter increases dramatically. When the tension exceeds 2.2 ± 0.4 kN, the red weak link breaks cleanly. The fully inflated liferaft is severed from the sinking vessel and floats safely on the surface, ready for survivors.

Why the weak link matters

The painter holds at 7.5–15 kN during manual launching, but the 2.2 ± 0.4 kN weak link guarantees the inflated raft breaks free automatically instead of being dragged down.

4. Davit Launch & Oral-Exam Rapid Fire

For "how do you launch a raft by davit?", walk through the davit drill keeping the mechanism maintained — in short: embark on deck, lower to 1 m, release and clear.

• Keep the davit mechanism maintained at all times.
• Open the ship handrail or gate at the launching position.
• Unlash the container — the INBOARD mark stays on the ship side.
• Lower the davit hook and lock it with the lifting shackle.
• Secure the canister lines outboard and secure the bowsing line.
• Pull out about 5–6 m of painter; check the hook and brake lanyard are inboard.
• Secure the painter line, then pull out its full length.
• Lift the canister to some height, then pull the painter with a sharp pull to inflate the raft.
• Check the canopy access opening faces the ship side, then secure the raft.
• One person goes inside for checks — no sharp-edged shoes or heels.
• Collect the SART and EPIRB, then board and sit evenly.
• Release the bowsing line and pass it to the raft.
• Check the launching area is clear, then lower the raft using the brake release.
• Operate the hook release about 1 m above the water, or let the raft touch the water so the load comes off the hook and it releases itself.
• Cut the painter and use the sea anchor or paddle to clear the area immediately.

Forward versus aft — the difference to state

• Forward raft: typically a 6-person unit — manual inflation only, no HRU.
• Midship / embarkation raft: maximum-capacity unit (the 16-person example) that can be launched manually, by davit and by HRU.
• Forward rafts prioritise quick throw-overboard release; embarkation rafts prioritise controlled boarding and lowering of large numbers.

Maintenance and servicing (Q15e)

• Rafts are serviced at approved stations at the due interval — the container carries the date last serviced and the raft adds the approving authority; at service the raft is inflated and inspected, the gas cylinder weighed, and pyrotechnics, food, water, first aid and batteries renewed to expiry.
• On board, keep the painter and HRU/weak-link rigging correct per the launching instructions, stow below the marked maximum stowage height, and keep the embarkation ladder, SART and EPIRB ready for the drill.

Oral-exam rapid fire

• "Inflation time?" — 1 minute at 18–20 °C, 3 minutes at −30 °C.
• "Painter length and strength?" — ≥ 15 m; 15 kN above 25 persons, 10 kN for 9–24, 7.5 kN small rafts.
• "Container versus raft markings?" — 10 items on the container (maker through SOLAS) and 5 items on the raft itself (maker, serial, service date, manufacture date, authority).
• "Built-in safeties?" — pressure relief valve, stabilising pockets, 2-layer insulated canopy.
• "Forward versus aft?" — forward 6-person manual-only; embarkation 16-person manual + davit + HRU.
• "Tow speed?" — 3 knots loaded with sea anchor streamed.
• "Weak link?" — 2.2 ± 0.4 kN; HRU knife fires at 4 m; painter ≥ 15 m.
• "25 equipment items?" — pyro 6-4-2, EPIRB + SART, food and water 500 × 3 days, 3 tin openers, 50 tablets, 2 TPAs.
• "Hook release height on davit?" — release at 1 m above water; confirm the INBOARD mark ship-side and 5–6 m painter paid out before lifting.
• "Lamp?" — white 4.3 cd, 50–70 per minute, 12 hours; SART mount ≥ 1 m.
• "Minimum capacity and weight?" — 6 persons minimum; packed raft with container and equipment ≤ 180 kg.

Closing line for the examiner

Quote the chain: 15 m painter → hard pull → 1-minute inflation → 30 days afloat → 4 m HRU knife → 2.2 kN weak link → 1 m davit hook release — every number in one breath.