BELOW DECK: THE HIDDEN HEAT THAT STOPS VESSELS
From switchboards and turbochargers to pumps, bearings and insulation, thermography is helping crews catch faults before they become fires
OF ALL SHIP FIRES & EXPLOSIONS ORIGINATE IN THE ENGINE ROOM
Gard P&I Club, 2025
HIGHEST TURBOCHARGER TEMPERATURE RECORDED IN MERCHANT VESSEL SURVEYS — SOLAS LIMIT IS 220°C
Krystosik-Gromadzińska, 2019
MAXIMUM DIRECT COST OF A SINGLE CARGO SHIP ENGINE ROOM FIRE
Bistrović et al., 2017
VESSEL OUT-OF-SERVICE FOLLOWING A SINGLE UNDETECTED ENGINE ROOM FIRE
Gard P&I Club, 2025
BELOW DECK PRIORITY: KEEP THE VESSEL UNDERWAY
A 2025 systematic review published in Applied Sciences (MDPI), analyzing 210 publications using PRISMA 2020 methodology, confirmed that infrared thermography (IRT) enables early detection of overheating, insulation degradation, and poor electrical connections—reducing unplanned downtime and improving system reliability across commercial fleets (Tadić et al., 2025).
Yet thermography on vessels is not simply a matter of pointing a camera at machinery. High humidity, salt aerosols, confined spaces, duplicate systems, and the need for inspections at full operational load all create unique challenges. This article explores how frontline engineers and thermographers are meeting those challenges—zone by zone—aboard oil tankers, cargo carriers, and LNG vessels.
Critically, the business case is no longer theoretical. Insurance bodies are actively endorsing thermographic inspections. Classification societies are integrating predictive maintenance into survey frameworks. And the cost of entry has fallen dramatically.
THE OBJECTIVE
PROTECT UPTIME. PROTECT PEOPLE. PREVENT FIRE.
🔥 Detect thermal anomalies before they become fires — especially exhaust surfaces exceeding the SOLAS 220°C limit
⚡ Identify failing electrical connections in switchboards under load without interrupting vessel operations
⚙️ Monitor rotating machinery, bearings, and turbochargers using high-sensitivity cameras
📋 Generate documented inspection records that satisfy P&I Club requirements and link to SOLAS compliance
💰 Justify investment through reduced insurance premiums, avoided downtime, and direct fire loss prevention
CRITICAL INSPECTION ZONES ABOARD VESSELS
ZONE 01 · CRITICAL RISK
ELECTRICAL SWITCHBOARDS & DISTRIBUTION PANELS
The American P&I Club's December 2024 Member Alert singles out electrical switchboard scanning as the highest-priority thermographic inspection aboard any vessel (Shipowners Claims Bureau, 2024). The procedure requires engines to be started and electrical systems placed under load exceeding 40% before scanning — static conditions mask faults entirely.
The challenge for frontline crew is access. Switchboards are densely packed, and many connections are physically impossible to inspect visually during normal operations. Thermography sees what no eye can — and does so without dismantling a single panel or interrupting vessel operations.
Flir iXX-Series App-enabled thermal imaging cameras
WHERE CONDITION MONITORING CAN MAKE A DIFFERENCE
The Francis Scott Key Bridge Collapse
In the early morning hours of March 26, 2024, a 984-foot container ship called The Dali struck the Francis Scott Key Bridge in Baltimore, Maryland, leading to its catastrophic collapse. The accident killed six construction workers who were on the bridge to repair potholes; two others had to be rescued from the channel. Maritime traffic to the Port of Baltimore was blocked for 11 weeks as workers tried to clear the wreckage.
The Dali's crew reported that electrical blackouts aboard the ship lead to a loss of propulsion and steering, causing the accident. The National Transportation Safety Board's subsequent investigation determined a loose electrical cable to be the likely cause.
The board concluded: "...if infrared thermal imaging had been used to inspect wire connections within the HV switchboard before the accident as part of the Dali’s preventative maintenance program, the loose signal wire may have been identified." The board recommended the Dali's owners add infrared imaging for routine monitoring of electrical components.
Photo by Kevin Dietsch, Getty Images
ZONE 02 · CRITICAL RISK
MAIN ENGINES & TURBOCHARGERS
Turbochargers represent the single most thermographically alarming component aboard most merchant vessels. A study by Krystosik-Gromadzińska (2019) measuring a MAN B&W main engine in service recorded a manifold-to-turbocharger connector at 486.3°C — more than double the SOLAS maximum surface temperature limit of 220°C. The exhaust manifold read 341.6°C; the turbocharger casing, 321°C.
Gard P&I Club analysis of Hull & Machinery claims from 2017 to 2024 found that main engine fire frequency averaged 0.07% of vessels annually — around seven fires per 10,000 ships per year — with two-thirds involving turbochargers or associated components (Gard P&I Club, 2025).
Electric engine driving a pump in a tanker engine room
MAIN ENGINE FIRE RATE / VESSEL / YEAR
RECORDED TURBOCHARGER TEMP. (LIMIT: 220°C)
ZONE 03 · HIGH RISK
AUXILIARY ENGINES, BOILERS & FUEL SYSTEMS
Auxiliary engine fires are both frequent and underappreciated. At 0.04% per vessel per year, they represent a significant cumulative risk across any fleet (Gard P&I Club, 2025). A documented case study describes a copper pipe fracture in an auxiliary engine fuel oil system that sprayed fuel onto unprotected turbocharger surfaces exceeding 400°C, igniting a fire that put the vessel out of service for 40 days.
The insidious nature of fuel system degradation is that it is almost entirely invisible to the naked eye. A missing spray shield, a cracked coupling, or failed insulation banding may sit undetected through multiple routine inspections. The Flir Thermowind inspection of MS Helene Russ found components reaching a measured 400°C with no visual indication of danger (Flir/Thermowind, c.2007).
AUX. ENGINE FIRE RATE / VESSEL / YEAR
UNSHIELDED TURBOCHARGER SURFACE TEMP.
900 kW auxiliary engine
ZONE 04 · COMPLIANCE
EXHAUST INSULATION & HOT SURFACES
SOLAS Chapter II-2 establishes 220°C as the maximum permitted surface temperature for engine room machinery — the threshold above which a fuel or oil leak in proximity constitutes an ignition risk. This single figure is the most-referenced regulatory threshold across the entire marine thermography literature (Tadić et al., 2025; Krystosik-Gromadzińska, 2019; FLIR/Thermowind, c.2007).
Deteriorated exhaust lagging, missing insulation wraps, and degraded expansion joints routinely produce surface temperatures that violate this limit with no external indication. The American P&I Club explicitly recommends thermographic scanning of exhaust insulation as a specific fire prevention measure, alongside electrical switchboard surveys (Shipowners Claims Bureau, 2024).
The Thermowind severity classification system formalises this: Severity 0 is below 210°C; Severity 1 is 210–220°C; Severity 2 is above 220°C and requires immediate action.
Indicator valve to measure oil level of main engine: not insulated and too hot
SOLAS MAXIMUM SURFACE TEMPERATURE
IMMEDIATE ACTION REQUIRED
ZONE 05 · ROTATING MACHINERY
PUMPS, BEARINGS, MOTORS & FANS
Mechanical faults in rotating equipment—cavitation in pumps, bearing wear, seal failures, compressed air leaks—often produce acoustic signatures long before any visual sign appears. Acoustic imaging cameras detect the ultrasound frequencies emitted by these developing faults and translate them into a real-time visual soundmap overlaid on a standard camera image. For frontline engineers working in loud, confined engine rooms, this transforms an otherwise invisible problem into something they can see, locate, and act on immediately.
The practical advantage aboard vessels is significant. A bearing beginning to fail, a cavitating pump impeller, or a pressurised gas leak behind a panel will all register acoustically. Thermal and acoustic technologies are increasingly deployed together: acoustic imaging to find the fault, thermography to quantify its thermal severity.
Flir Si2x-LD Hazardous location acoustic imaging camera for pressurized leak detection and mechanical fault detection
HUGE ROI
INSURANCE PREMIUM REDUCTION
Atlantic LNG Company of Trinidad and Tobago explicitly cited "reduced insurance premiums" as a realised benefit of its infrared program, alongside prevention of unscheduled downtime and safer remote survey capability. Their program, now in its second decade, uses the optical gas imaging and a thermal camera across rotating machines, electrical components, transformers, valves, and piping (O'Rosco, 2018).
OPERATIONAL GUIDANCE: DECISIONS FOR SHIP OPERATORS
