Inert Gas Generator (Tanker)
An inert gas generator burns fuel oil in a dedicated combustion chamber to produce flue gas with under 5% oxygen, which is scrubbed, cooled and blown into cargo tanks to hold the atmosphere below the level that supports combustion.
What to check on an Inert Gas Generator (Tanker).
12 models from Wärtsilä in Inert Gas Generator (Tanker). Below: the full model list.
What an inert gas generator does and why tankers carry one
Cargo tanks on a tanker sit above a flammable liquid and, at some point in every loading and discharging cycle, pass through a vapour concentration that can ignite. Rather than manage that risk by ventilation timing alone, the ship fills the tank space above the cargo with gas that cannot support combustion because it is starved of oxygen. A dedicated inert gas generator burns marine fuel oil in a small combustion chamber under controlled, oxygen-lean conditions and produces flue gas with an oxygen content low enough to inert the tank atmosphere, independent of the main boiler or engine exhaust that some other vessel types rely on for the same purpose.
Main components
Combustion chamber and burner
A refractory-lined chamber burns fuel oil with a deliberately restricted air supply so the flue gas leaves with oxygen content typically well under 5% by volume, well below the roughly 11% threshold most cargoes need to sustain combustion.
Scrubber
Seawater sprays wash the hot flue gas to strip sulphur compounds, soot and particulates, and cool the gas from combustion temperature down to close to seawater temperature before it goes anywhere near the cargo tanks.
Read the full guide
Deck water seal
A water-filled seal sits in the inert gas main on deck and acts as a one-way, fail-safe barrier: it lets inert gas flow to the tanks but stops any hydrocarbon vapour or flame from travelling back from the tanks toward the generator.
Blowers and gas main
Blowers push the scrubbed, cooled gas through the deck main and into the distribution piping serving each cargo tank, with non-return valves and pressure-vacuum breakers protecting the tanks from over- or under-pressure.
Oxygen analysers and control system
Continuous oxygen monitoring at the generator outlet and at the tanks lets the system trip the burner or alarm before oxygen content rises to a level that would compromise the inert atmosphere.
Sizing
Generator capacity is sized to the vessel's maximum cargo discharge rate, since inert gas has to replace cargo volume in the tanks at least as fast as liquid leaves them, plus margin for topping-up losses and tank purging operations. Undersized capacity shows up first during fast discharge, when tank pressure drops faster than the generator can make up gas.
Regulations and class
SOLAS Chapter II-2 requires inert gas systems on tankers above defined tonnage and cargo thresholds, and the system is subject to survey requirements covering the deck water seal, non-return devices, oxygen analysers and alarms as safety-critical items. IACS Unified Requirements and the applicable tanker codes set out testing intervals for the oxygen analysers and the deck water seal, and class surveyors treat a defective deck seal as a serious deficiency rather than a minor finding, because it is the last physical barrier against flashback.
Typical faults
- Fouled scrubber packing — reduces cooling and gas cleaning efficiency, letting hot, corrosive gas reach the deck main.
- Low deck seal water level — from a blocked make-up line, removing the flashback barrier without an obvious external sign.
- Drifting oxygen analyser calibration — gives a false low reading, masking an atmosphere that is no longer properly inert.
- Corroded gas main piping — from years of wet, acidic flue gas, eventually leaking inert gas or, worse, letting air back into the system.
What to look for in a supplier
- Capacity rating matched against the vessel's actual maximum discharge rate, not a round-number default.
- Materials specification for scrubber and gas main piping suited to wet, acidic flue gas service.
- Documented oxygen analyser response time and calibration procedure.
- Spare parts support for the deck water seal internals, which see continuous wear in service.
Treat the deck water seal level as a safety instrument, not a housekeeping item — check it against the logged figure every watch, because a slowly dropping level gives no other warning before it fails.
Models in this type.
The best-documented model of each manufacturer first, then the next — 12 of 12 models in Inert Gas Generator (Tanker). Every row links to full specifications, documents and service notes.
Manufacturers.
All 12 manufacturers with models of Inert Gas Generator (Tanker). Names with a manufacturer page open it; the others open a search across the full library.
All manufacturersAlso in Boilers.
The other equipment types in this category.
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