Complete Guide to Marine Liferaft Types and SOLAS Requirements

Essential reading for shipowners, vessel operators, offshore safety managers, and maritime compliance officers

Introduction

When a vessel is abandoned at sea, the liferaft is often the last line of defense between survival and catastrophe. In the minutes following a collision, fire, flooding, or structural failure, crew members and passengers depend entirely on lifesaving appliances that work correctly, deploy reliably, and provide adequate protection until rescue arrives.

Marine liferafts are mandatory safety equipment on the vast majority of commercial vessels operating under international regulations — yet they are also among the most frequently misunderstood, incorrectly specified, and inadequately maintained items of safety equipment onboard.

For shipowners, vessel operators, offshore safety managers, and maritime compliance officers, understanding the different types of marine liferafts, the SOLAS requirements that govern them, and the maintenance obligations that keep them serviceable is not merely a regulatory exercise. It is a fundamental responsibility.

This guide covers:

• What marine liferafts are and how they function

• The four principal liferaft types and their applications

• SOLAS requirements in detail — what the regulations actually require

• Hydrostatic Release Units (HRUs) and automatic deployment

• Capacity selection for different vessel types

• Offshore vs. commercial vessel liferaft specifications

• Inspection, servicing, and certification requirements

• How to evaluate liferaft suppliers

• Emerging trends in marine lifesaving technology

What Is a Marine Liferaft?

A marine liferaft is an inflatable emergency survival craft designed to keep survivors safe after abandoning a vessel. Unlike lifeboats, which are rigid craft with propulsion systems, liferafts are primarily passive survival platforms — they provide flotation, weather protection, and survival equipment while survivors await rescue.

Modern inflatable liferafts are stored in one of two container types:

• Rigid fiberglass (GRP) containers — the standard for most commercial and offshore applications; provides robust protection against mechanical damage and UV degradation

• Valise (soft) containers — used where weight and storage flexibility are priorities; common on smaller vessels and in supplementary liferaft installations

When deployed, the liferaft inflates automatically within seconds through a CO₂ inflation system triggered by a painter line connected to the vessel. The entire sequence — from container release to full inflation — is designed to complete in under 60 seconds under normal conditions.

A properly equipped SOLAS liferaft provides:

• Emergency flotation — buoyancy sufficient to support the rated capacity of survivors

• Weather protection — a double-tube canopy that shields survivors from wind, rain, spray, and solar radiation

• Thermal insulation — insulated floor and canopy to reduce heat loss in cold water environments

• Survival equipment — water, food rations, first aid supplies, signaling devices, and repair materials

• High visibility — orange canopy color and retroreflective tape to aid search and rescue detection

Why Correct Liferaft Selection and Maintenance Matters

The consequences of liferaft failure during an emergency are absolute. There is no opportunity to identify a defect, source a replacement, or attempt a repair when a vessel is sinking. The liferaft either works or it does not.

Common causes of liferaft failure in real emergencies include:

Each of these failures is preventable through correct specification, proper installation, and disciplined maintenance. The regulatory framework established by SOLAS exists precisely to eliminate these failure modes through mandatory standards and inspection requirements.

The Four Principal Types of Marine Liferaft

1. Throw Overboard Liferaft

The throw overboard liferaft is the most widely used liferaft type in commercial shipping. The container is mounted on deck in a cradle secured by a hydrostatic release unit. In an emergency, the container is either manually thrown overboard or automatically released by the HRU as the vessel sinks.

Once the container enters the water, the painter line — which remains attached to the vessel — is pulled taut as the vessel sinks or as crew members pull it. This tension triggers the CO₂ inflation system, and the raft inflates on the water surface. Survivors then enter the raft from the water or from the vessel’s side.

Deployment Sequence:

1. Container released from cradle (manually or by HRU)

2. Container enters water

3. Painter line becomes taut

4. CO₂ inflation triggered

5. Raft inflates within 60 seconds

6. Survivors board from water or vessel side

Advantages:

• Mechanically simple — minimal components that can fail

• Compact storage footprint — suitable for vessels with limited deck space

• Lower cost than davit-launched systems

• Suitable for automatic HRU deployment if vessel sinks rapidly

Limitations:

• Survivors must enter the raft from the water in most scenarios

• More physically demanding boarding process, particularly for injured or elderly passengers

• Less controlled deployment in rough sea conditions

Typical Applications:

• Cargo ships, bulk carriers, and tankers

• Fishing vessels

• Coastal and short-sea trading vessels

• Vessels where deck space is limited

2. Davit Launched Liferaft

A davit launched liferaft system uses a dedicated mechanical davit to lower the inflated liferaft from the vessel’s deck to the waterline in a controlled manner. Critically, survivors can board the raft before it is lowered — eliminating the need to enter the water and significantly improving evacuation safety, particularly in rough sea conditions or when passengers include elderly, injured, or non-swimming individuals.

Deployment Sequence:

1. Liferaft container positioned in davit cradle

2. Painter line connected; inflation triggered

3. Raft inflates alongside the vessel

4. Survivors board the raft from the embarkation deck

5. Davit lowers the loaded raft to the waterline

6. Painter line released; raft moves clear of vessel

Advantages:

• Survivors board before water entry — significantly safer in rough conditions

• Controlled, stable lowering reduces risk of capsizing during deployment

• Suitable for passengers with limited mobility

• Preferred by SOLAS for passenger vessels above certain thresholds

Limitations:

• Higher capital cost than throw overboard systems

• Requires dedicated davit installation — more complex deck arrangement

• Davit mechanism requires its own maintenance program

• Not suitable for automatic HRU deployment (requires manual operation)

Typical Applications:

• Passenger ferries and RoPax vessels

• Cruise ships

• Offshore platforms and FPSOs

• Large commercial vessels with passenger-carrying requirements

Why Offshore Operators Prefer Davit Systems:

Offshore installations present particularly challenging evacuation conditions — strong winds, heavy seas, and the physical demands of offshore work mean that crew members may be fatigued, injured, or encumbered by survival suits. The ability to board the liferaft before it enters the water, under controlled conditions, is a significant safety advantage that justifies the additional cost and complexity of davit systems.

3. Open Reversible Liferaft

An open reversible liferaft is designed to function correctly regardless of which side inflates upward. Conventional liferafts have a defined top and bottom — if they inflate upside down, they must be manually righted before use, which is physically demanding and potentially dangerous in rough seas. The reversible design eliminates this requirement.

Key Design Features:

• Symmetrical construction — identical performance from either side

• No manual righting required after deployment

• Typically open (uncanopied) or with a low-profile canopy

• Lightweight construction for rapid handling

Advantages:

• Faster effective deployment — no time lost righting an inverted raft

• Reduced physical demands on survivors during boarding

• Suitable for rapid rescue operations

Limitations:

• Open design provides less weather protection than canopied SOLAS liferafts

• Generally not suitable as primary lifesaving appliances on ocean-going vessels

• Limited survival equipment compared to fully equipped SOLAS liferafts

Typical Applications:

• Fast rescue craft and MOB (man overboard) recovery operations

• Passenger ferries on short, sheltered routes

• Inland waterway vessels

• Supplementary lifesaving equipment on larger vessels

4. Totally Enclosed Liferaft (TEMPSC-equivalent for rafts)

Totally enclosed liferafts provide maximum protection in extreme environmental conditions. The fully enclosed canopy protects survivors from wind, spray, rain, and cold temperatures, and in some configurations provides fire protection for use near burning oil or fuel.

Key Design Features:

• Fully enclosed canopy with entry hatches

• Enhanced thermal insulation

• Fire-retardant materials in some specifications

• Larger survival equipment packs for extended survival periods

Advantages:

• Maximum weather and thermal protection

• Suitable for Arctic, sub-Arctic, and extreme offshore environments

• Extended survival capability for prolonged rescue delays

Limitations:

• Higher cost and weight than standard SOLAS liferafts

• More complex deployment and boarding procedures

• Requires specialized servicing

Typical Applications:

• Offshore platforms in harsh environments (North Sea, Arctic operations)

• Oil and gas production vessels

• Vessels operating in extreme weather regions

SOLAS Requirements for Marine Liferafts: What the Regulations Actually Require

The International Convention for the Safety of Life at Sea (SOLAS), administered by the International Maritime Organization (IMO), establishes the minimum mandatory requirements for liferaft design, equipment, performance, and maintenance on commercial vessels engaged in international voyages.

The relevant technical requirements are contained in the LSA Code (International Life-Saving Appliance Code), which provides detailed specifications that SOLAS-approved liferafts must meet.

1. Inflation Performance

A SOLAS liferaft must inflate fully within 60 seconds at an ambient temperature between -30°C and +65°C. The inflation system must function reliably after the raft has been stored for the full service interval without servicing.

2. Structural Integrity and Stability

The raft must:

• Support its rated capacity of survivors plus the weight of the survival equipment

• Remain stable in sea states up to Sea State 6 (significant wave height 4–6 m)

• Withstand being dropped into the water from a height of 18 meters without damage

• Resist being driven over by a vessel without catastrophic failure

3. Canopy Requirements

The canopy must:

• Automatically erect upon inflation — no manual assembly required

• Provide protection from wind, rain, spray, and solar radiation

• Be insulated to reduce internal temperature extremes

• Be colored orange or yellow for high visibility

• Be fitted with retroreflective tape on the exterior

4. Mandatory Survival Equipment

SOLAS specifies two equipment packs — Pack A (for ocean-going vessels) and Pack B (for shorter voyages). Pack A requirements include:

5. Capacity and Freeboard Requirements

• Minimum capacity: 6 persons for SOLAS-approved liferafts

• The raft must be capable of being boarded from the water by a survivor wearing a lifejacket

• Freeboard (height of raft floor above waterline) must not exceed 0.3 meters when loaded

6. Marking Requirements

Each SOLAS liferaft must be marked with:

• Manufacturer’s name and serial number

• Approved capacity (number of persons)

• Type of emergency pack (A or B)

• Length of painter line

• Maximum permitted height of stowage above waterline

• Service date and next service due date

• Approval authority and certificate number

7. Vessel Carriage Requirements

SOLAS carriage requirements vary by vessel type and voyage area. Key requirements include:

Hydrostatic Release Units (HRUs): Automatic Deployment Explained

The Hydrostatic Release Unit (HRU) is one of the most important — and most frequently misunderstood — components of a liferaft installation. It is the mechanism that ensures the liferaft can deploy automatically if the vessel sinks before manual deployment is possible.

How an HRU Works

The HRU is a pressure-sensitive device that holds the liferaft container in its cradle under normal conditions. When the vessel sinks and the HRU reaches a depth of 1.5–4 meters, water pressure activates a cutting mechanism that severs the lashing securing the container to the cradle.

The sequence that follows:

1. HRU activates at 1.5–4 m depth; lashing cut

2. Container floats free of the sinking vessel

3. Painter line (attached to vessel) becomes taut as vessel continues to sink

4. Painter line tension triggers CO₂ inflation

5. Raft inflates on the surface

6. Painter line breaks (at a load of approximately 2.2 kN) once raft is fully inflated, freeing it from the sinking vessel

Critical Installation Requirements

For the HRU to function correctly:

• The painter line must be correctly attached to a strong point on the vessel — not to the container itself

• The HRU must be replaced before its expiry date (typically every 2 years)

• The weak link in the painter line must be intact and correctly rated

• The container must be stored in a cradle that allows it to float free when the lashing is cut

Common HRU Installation Errors:

HRU failures are a documented cause of liferaft non-deployment in real sinking incidents. Correct installation and regular inspection of the complete HRU-painter-cradle system is essential.

Liferaft Capacity Selection

Selecting the correct liferaft capacity is a regulatory requirement and a safety-critical decision. Insufficient total capacity means some persons onboard cannot be accommodated; excessive fragmentation into too many small rafts creates coordination problems during evacuation.

Factors Affecting Capacity Selection

• Total number of persons onboard (crew plus passengers)

• SOLAS carriage requirements for the vessel type and voyage area

• Vessel layout and liferaft stowage locations

• Redundancy requirements — multiple rafts provide backup if one fails to deploy

• Offshore regulatory requirements (which may exceed SOLAS minimums)

Standard Capacity Options

Redundancy Considerations

SOLAS requires that liferaft capacity be distributed on both sides of the vessel, so that if the vessel lists severely to one side, the liferafts on the accessible side can accommodate all persons onboard. This effectively means the total installed capacity must be at least 200% of the persons onboard when calculated per side.

Offshore vs. Commercial Vessel Liferafts: Key Differences

While all SOLAS-approved liferafts meet the same baseline standards, offshore liferaft specifications typically exceed commercial shipping requirements in several important areas.

Offshore operators — particularly those on North Sea, Gulf of Mexico, or Arctic installations — should specify liferafts that meet not only SOLAS requirements but also the additional requirements of their flag state, classification society, and installation operator.

Liferaft Inspection, Servicing, and Certification

Mandatory Servicing Requirements

SOLAS requires that inflatable liferafts be serviced at intervals not exceeding 12 months at an approved service station. The only exception is where the raft is stored in conditions that make annual servicing impractical — in which case the interval may be extended to a maximum of 17 months under specific flag state provisions.

Servicing must be performed by a manufacturer-approved service station using genuine replacement parts. Servicing by unauthorized personnel or with non-genuine parts invalidates the certification and may constitute a flag state violation.

What Liferaft Servicing Involves

A full annual service includes:

Inflation System:

• Inspect and weigh CO₂ inflation cylinder — replace if weight loss exceeds 5%

• Inspect automatic inflation valve

• Test painter line and weak link

• Inspect and test HRU — replace if expired

Raft Structure:

• Full inflation test — verify raft inflates correctly and holds pressure

• Inspect all fabric panels for cuts, abrasion, UV degradation, and delamination

• Inspect all seams and heat-sealed joints

• Inspect buoyancy tubes for leaks

• Inspect canopy structure and entry hatches

• Inspect floor insulation

Survival Equipment:

• Check all items against SOLAS equipment list

• Replace all expired items (flares, water, food rations, medication)

• Inspect and test emergency lighting

• Inspect and replace first aid kit contents as required

Container:

• Inspect container for cracks, corrosion, and seal integrity

• Repack raft according to manufacturer’s procedure

• Apply new service label with next service due date

• Issue new service certificate

Certification and Approval Standards

Marine liferafts for commercial use must carry approval from recognized authorities. Common approvals include:

When procuring liferafts for a specific vessel, verify that the product carries the approvals required by the vessel’s flag state and classification society. A liferaft approved by one authority may not satisfy the requirements of another.

How to Evaluate a Marine Liferaft Supplier

The liferaft market includes manufacturers ranging from globally recognized brands with decades of proven performance to lower-cost suppliers whose products may meet minimum certification requirements but lack the quality assurance and service infrastructure that commercial operations require.

When evaluating a liferaft supplier, assess the following:

Product Certification:

• Does the product carry all required approvals for your vessel’s flag state and classification society?

• Are approval certificates current and verifiable?

Manufacturing Quality:

• What quality management system does the manufacturer operate? (ISO 9001 minimum)

• What materials are used for fabric, seams, and inflation systems?

• What is the manufacturer’s track record in real emergency deployments?

Global Service Network:

• Does the manufacturer maintain an approved service station network in the ports your vessel calls at?

• What is the typical turnaround time for annual servicing?

• Are genuine spare parts readily available?

Technical Support:

• Can the supplier provide installation guidance and crew training?

• Is technical documentation available in the required languages?

After-Sales Support:

• What warranty does the manufacturer provide?

• How does the manufacturer handle product recalls or safety notices?

For vessels operating globally, the availability of an approved service network in diverse ports is often as important as the initial product specification.

Future Trends in Marine Lifesaving Equipment

The marine lifesaving equipment sector is evolving in response to advances in materials technology, digital systems, and changing regulatory requirements.

1. Integrated Emergency Location Technology

Next-generation liferafts are increasingly incorporating integrated AIS (Automatic Identification System) transponders and PLBs (Personal Locator Beacons) that activate automatically upon deployment, transmitting the raft’s position to rescue coordination centers without requiring any action from survivors.

2. Advanced Thermal Protection Materials

New insulation materials derived from aerospace and extreme sports applications are enabling lighter, more compact liferafts with significantly improved thermal protection — particularly relevant for Arctic and sub-Arctic operations where hypothermia is the primary survival threat.

3. Extended Service Intervals

Manufacturers are developing liferaft designs and materials that can support extended service intervals — potentially up to 3 years between servicing — reducing operational costs for shipowners while maintaining safety standards. Regulatory acceptance of extended intervals is progressing in some flag states.

4. Smart Condition Monitoring

Sensor systems that monitor liferaft container integrity, CO₂ cylinder pressure, and HRU condition in real time — transmitting data to the vessel’s safety management system — are in development. These systems would provide early warning of equipment degradation between annual services.

5. Lightweight High-Strength Materials

Advanced composite fabrics and improved coating technologies are enabling liferafts that are lighter and more compact than current designs while meeting or exceeding existing SOLAS performance requirements. This is particularly valuable for vessels where deck space and weight are constrained.

Conclusion

Marine liferafts are not passive safety equipment that can be installed, forgotten, and relied upon in an emergency. They are complex, time-sensitive survival systems that require correct specification, proper installation, disciplined maintenance, and regular professional servicing to perform reliably when lives depend on them.

The key principles for shipowners and operators to apply are:

1. Specify the correct liferaft type for the vessel and operational environment — throw overboard for standard commercial vessels; davit-launched for passenger vessels and offshore installations; enhanced specifications for extreme environments

2. Ensure full SOLAS compliance — not just in product certification, but in installation, HRU configuration, painter line arrangement, and stowage

3. Never defer annual servicing — a liferaft with an expired service certificate is not a compliant or reliable piece of safety equipment

4. Verify HRU installation and expiry — HRU failure is a documented cause of liferaft non-deployment; inspect and replace on schedule

5. Select suppliers with proven service networks — the quality of the annual service is as important as the quality of the product

6. Train crew in liferaft deployment — equipment that crew members cannot operate correctly under stress provides no safety benefit

In maritime emergencies, the margin between survival and loss of life is often measured in seconds and centimeters. A liferaft that deploys correctly, inflates fully, and contains functional survival equipment can make the difference. One that does not cannot.

Frequently Asked Questions

What is the difference between a lifeboat and a liferaft?

A lifeboat is a rigid, motorized rescue craft capable of self-propulsion and navigation. It provides a higher level of protection and capability but requires more deck space, more maintenance, and more crew training to operate. A liferaft is an inflatable survival platform with no propulsion — it provides flotation, weather protection, and survival equipment while survivors await rescue. SOLAS requires most commercial vessels to carry both, with lifeboats as the primary evacuation means and liferafts as supplementary or backup equipment.

What is a SOLAS liferaft?

A SOLAS liferaft is an inflatable liferaft that has been designed, tested, and certified to meet the requirements of the International Convention for the Safety of Life at Sea (SOLAS) and the IMO’s LSA Code. SOLAS liferafts must meet mandatory standards for inflation performance, structural integrity, stability, survival equipment, and marking. Commercial vessels on international voyages are required to carry SOLAS-approved liferafts.

How often must inflatable liferafts be serviced?

SOLAS requires inflatable liferafts to be serviced at intervals not exceeding 12 months at a manufacturer-approved service station. In some circumstances, flag state regulations permit an extension to 17 months. Servicing must be performed by authorized personnel using genuine manufacturer parts, and a new service certificate must be issued after each service.

What is a Hydrostatic Release Unit (HRU) and why is it important?

An HRU is a pressure-sensitive device that automatically releases the liferaft container from its cradle when the vessel sinks to a depth of 1.5–4 meters. This ensures the liferaft can deploy even if the vessel sinks too rapidly for manual deployment. HRUs must be replaced before their expiry date (typically every 2 years) and must be correctly installed with the painter line properly attached to a vessel strong point. HRU failure or incorrect installation is a documented cause of liferaft non-deployment in real sinking incidents.

What is the difference between a throw overboard and a davit launched liferaft?

A throw overboard liferaft is manually or automatically released into the water, where it inflates and survivors board from the water or vessel side. A davit launched liferaft uses a mechanical davit system to lower the inflated raft to the waterline in a controlled manner, allowing survivors to board before the raft enters the water. Davit systems are safer in rough conditions and for passengers with limited mobility, but require more complex installation and maintenance.

What survival equipment must a SOLAS liferaft contain?

A SOLAS Pack A liferaft (required for ocean-going vessels) must contain, among other items: rocket parachute flares, hand flares, buoyant smoke signals, a waterproof torch, first aid kit, food rations (10,000 kJ per person), fresh water (1.5 liters per person), anti-seasickness medication, thermal protective aids, sea anchors, paddles, a repair kit, and signaling equipment. The complete equipment list is specified in the IMO LSA Code.

Which classification society approvals are required for marine liferafts?

The required approvals depend on the vessel’s flag state and classification society. Common approvals include SOLAS/IMO, MED (for EU-flagged vessels), and type approval from classification societies such as DNV, ABS, BV, LR, CCS, or KR. When procuring liferafts, verify that the product carries all approvals required by your vessel’s specific flag state and classification society requirements.

Normanship supplies marine safety and deck equipment for commercial shipping, offshore operations, and shipbuilding projects. Contact our technical team for guidance on liferaft specifications, SOLAS compliance requirements, and certified marine safety equipment.