Marine & Offshore Fire Insulation: Materials & IMO Standards Guide

Marine and offshore fire insulation must do two jobs at once: keep heat in (or out) and keep fire from spreading. Unlike land-based industrial insulation, shipboard systems operate in a salt-laden, high-vibration environment where every kilogram of material matters and evacuation routes are measured in minutes, not hours. That is why the marine-offshore application has its own rulebook: SOLAS, the IMO FTP Code, and the A-60 / H-60 fire-class system.

This guide explains what those standards mean, how four common insulation materials compare, and how to choose the right system for each area of a vessel or offshore platform. For a first look at marine fire materials, see our companion article Marine Fire Insulation: Materials & Standards.

What Makes Marine & Offshore Fire Insulation Different?

Four factors separate marine work from a typical plant project:

• Weight. Every extra kilogram of insulation reduces cargo or increases fuel burn. Lightweight materials with high temperature ratings are preferred where they can meet the fire class.
• Corrosion. Salt air, condensation, and bilge water attack fixings and jackets. Materials that absorb water without drying can lose thermal performance and accelerate corrosion under insulation (CUI).
• Vibration. Main engines, pumps, and propulsion machinery transmit constant vibration. Rigid boards can crack; fibrous blankets can settle if not properly supported.
• Fire containment. A fire at sea cannot be fought with unlimited external support. Bulkheads, decks, and pipe penetration seals must hold their rating long enough for crew evacuation and boundary control.

Because of these constraints, marine specifications almost always require IMO-certified, non-combustible materials rather than ordinary commercial-grade insulation.

SOLAS & IMO FTP Code Fire Ratings Explained

The International Convention for the Safety of Life at Sea (SOLAS) sets the structural fire-protection requirements for ships. The technical test procedures are given in the IMO FTP Code (Fire Test Procedures Code), currently consolidated in the 2010 edition.

Key tests for insulation materials include:

• Part 1 — Non-combustibility: sample exposed to 750 °C for 30 minutes; temperature rise, mass loss, and flaming behavior are recorded.
• Part 2 — Smoke and toxicity: analysis of CO, HF, HCl, HCN, and other gases released during fire exposure.
• Part 5 — Surface flammability: measurement of flame spread and heat release on exposed surfaces.

Materials that pass are classed as A1 non-combustible under the same EN 13501-1 concept used onshore.

A-Class vs H-Class Fire Divisions

The H-class hydrocarbon curve rises much faster than the cellulosic curve used for A-class. A material that passes A-60 is not automatically suitable for H-60; the higher heat flux and faster temperature ramp expose weaknesses in binders and facing systems.

Material Comparison for Marine Fire Insulation

For a closer look at calcium silicate, see our Calsil FAQ.

Why not one material everywhere?

No single insulation covers every marine zone. The winning specification usually layers or zones materials:

• Rock wool blanket is the workhorse for A-60 and H-60 bulkheads, decks, and machinery casings where hydrophobicity and sound attenuation are valued.
• Ceramic fiber blanket wins where exhaust manifolds, incinerators, or furnace casings exceed 650 °C and where weight savings justify the higher material cost.
• Calcium silicate board is the structural choice for flat, walkable surfaces, pipe support shoes, and fire doors that must stay dimensionally stable for years.
• Glass wool blanket is competitive in accommodation areas below 400 °C where acoustic performance matters, provided it is sealed against moisture.

Where Each Material Fits on Ships and Offshore Platforms

Engine Rooms and Machinery Spaces

These are high-risk, H-class or A-60 zones with concentrated heat sources and heavy vibration. Rock wool blanket is widely used for bulkheads and casings because it is hydrophobic and resists salt corrosion. For surfaces above 650 °C — such as exhaust trunking or incinerator casings — ceramic fiber blanket is the safer thermal choice. Calcium silicate board can be used for flat structural panels and pipe support locations.

Accommodation and Living Quarters

Here the primary concerns are comfort, noise, and A-class fire division rather than extreme process temperature. Glass wool blanket provides good acoustic absorption and low conductivity at a light weight, but it must be installed behind an intact vapor barrier and metal facing to survive the humid marine atmosphere.

Piping Systems

Hot process and steam piping on ships uses the same temperature-band logic as onshore, but with stricter fixing and sealing requirements:

• ≤ 400 °C: glass wool or rock wool pipe sections, with sealed jacketing.
• 400–650 °C: rock wool pipe sections or calcium silicate pipe covers.
• > 650 °C: ceramic fiber wrap or high-temp calcium silicate shapes.

Flanges, valves, and penetrations need removable insulation pads and approved fire seals. A common failure point is not the insulation itself but the joint seal, which must be rated to the same fire class as the adjacent bulkhead.

Offshore Platforms and LNG Carriers

Hydrocarbon fire risk pushes these projects toward H-60 and H-120 ratings. Rock wool blanket with a wire-mesh or metal-clad facing is frequently specified for module bulkheads and deckheads. For the most critical boundaries and high-temperature equipment, ceramic fiber or calcium silicate systems are layered behind steel cladding to achieve the required hydrocarbon rating.

Selection Framework for Marine Projects

Use this sequence when writing or reviewing a specification:

1. Identify the fire class: A-60, A-30, H-60, or H-120. This is a hard constraint, not a recommendation.
2. Define the service temperature: continuous operating temperature plus upset/peak conditions.
3. Assess the environment: salt exposure, condensation, vibration level, and maintenance access.
4. Check approvals: verify the product carries a relevant marine type-approval or test report (IMO FTP Code, ASTM E84, EN 13501-1, or class society equivalents).
5. Balance weight and thickness: offshore topside modules may prefer thinner, higher-density systems; cargo vessels may prefer lighter blankets.
6. Plan the facing and sealing system: a hydrophobic core is not enough if water can enter at joints or jacket penetrations.

Installation, Sealing and Maintenance Notes

Even the right material fails if it is installed poorly. Common marine installation requirements include:

• No gaps at frame edges: insulation must be packed tight against steel stiffeners so heat cannot bypass the fire barrier through a "cold bridge."
• Mechanical fixings: adhesive alone is usually not acceptable in a fire-rated marine assembly. Use pins, clips, or mesh that match the fire class of the insulation.
• Pipe and cable penetrations: use approved fire-stop collars, wraps, or mastic at every penetration. The penetration seal must match the division rating.
• Metal jacketing: stainless-steel or aluminum cladding protects fibrous insulation from mechanical damage and salt spray, but overlaps must be sealed to keep water out.
• Inspection interval: visually inspect fire-rated divisions at least annually; in high-vibration engine rooms, inspect every six months. Look for jacket damage, sagging blankets, detached pins, and corroded fasteners.

For low-temperature or cryogenic offshore lines, our Cryogenic Pipe Insulation Guide covers the thickness and vapor-sealing logic.

Related Reading

• Marine Fire Insulation: Materials & Standards — first overview of the four material families and class-society certification.
• What Is Calsil (Calcium Silicate) Insulation? — composition, forms, and specification checklist.
• Cryogenic Pipe Insulation Guide — low-temperature offshore and LNG piping.