Onboard Nitrogen Generator for Marine Vessels
November 12, 2026
On a modern tanker, gas carrier or offshore vessel, nitrogen is a safety system, a cargo-protection system and a compliance requirement all at once. It keeps flammable vapors from reaching an ignitable mix, protects sensitive chemical cargoes from oxygen and moisture, and purges lines and spaces before maintenance or a cargo change.
That makes the nitrogen generator one of the quiet workhorses of the engine room. It has to deliver the right purity at the right flow during loading and discharge, fit in a machinery space where every square meter is spoken for, and keep running through vibration, salt air and long stretches between port calls. This guide covers where nitrogen works on board, the rules that drive it, and how to choose and size a system that holds up for the life of the ship.
Where nitrogen works on board
Most shipboard nitrogen duties fall in the 95–99% purity range, which is why membrane systems dominate marine installations. A few sensitive cargoes and fuel systems call for more.
| Vessel type | What nitrogen does | Typical purity |
| Chemical and product tankers | Inerting and blanketing cargo spaces, padding during discharge, line purging | 95–97%; up to 99.9% for oxygen- or moisture-sensitive cargoes |
| Gas carriers (LNG, LPG) | Inerting insulation and interbarrier spaces, purging cargo lines and compressors | 95–99% |
| Ships fueled by LNG, methanol or ammonia | Purging fuel lines, bunkering connections and fuel preparation spaces before maintenance | 95–99.9% |
| FPSOs and FSOs | Inerting storage spaces, flare and vent header purging, seal gas | 95–98% |
| Drillships and offshore support | Well services, mud systems, flare suppression, pipeline pre-commissioning | 95–98% |
Alternative fuels are the fastest-growing line in that table. Every new LNG, methanol or ammonia-fueled ship adds fuel-system purging to the nitrogen load, often on vessel types that never needed a nitrogen system before. These ranges are typical; the vessel’s cargo list, class rules and fuel system design set the actual requirement.
The rules behind shipboard nitrogen
Since 1 January 2016, SOLAS has required fixed inert gas systems on new oil and chemical tankers of 8,000 dwt and above that carry low-flashpoint cargoes, down from the earlier 20,000 dwt threshold. New chemical tankers carrying flammable cargoes under the IBC Code need an inert gas system regardless of cargo space size. (Lloyd’s Register)
Nitrogen has a specific advantage under those rules. SOLAS II-2/16.3.3 allows inerting to begin after loading and before unloading only when nitrogen is the inerting medium, which gives operators flexibility that flue gas systems don’t. Nitrogen also carries no soot, sulfur or moisture into the cargo, which matters for high-value chemicals.
Some cargoes need the opposite of full inerting. Products stabilized with oxygen-dependent inhibitors must keep a minimum oxygen level, so inert gas can’t be applied before loading or during the voyage (IBC Code 15.13.5). A system that delivers controllable purity, rather than a single fixed output, lets the crew meet both kinds of requirement.
On top of the IMO rules, the equipment itself must satisfy the vessel’s classification society, and machinery installed in hazardous areas must carry the right certification for its zone. GENERON’s DNV-rated 4000 and 6000 series cabinets are built for exactly that kind of review by shipyards and owners.
Why membrane suits life at sea
A membrane nitrogen generator separates nitrogen by passing compressed air through bundles of hollow polymer fibers. Oxygen and water vapor permeate through the fiber walls faster than nitrogen, so nitrogen-rich gas flows out the far end. That simple principle is what makes membrane the default for so many shipboard systems.
There are no moving parts in the separation module and no adsorbent beds to secure, so roll, pitch and engine vibration don’t affect it. Membranes start producing nitrogen almost as soon as air reaches them, which fits the stop-start rhythm of loading and discharge. Capacity is modular, so adding membrane modules raises output without redesigning the skid. And with routine filter changes as the main maintenance task, the system asks little of a small crew on a long voyage.
GENERON makes its own HollowPure™ membranes in house, with more than a million fibers in each module, rather than buying modules from a third party. That means one team owns performance from the fiber to the finished cabinet. Our patented Triton cabinets package that membrane technology into a space-efficient footprint designed for machinery spaces where every meter counts. Where a cargo or fuel system calls for higher purity, our PSA systems reach up to 99.9995%, and our engineers recommend whichever technology fits the vessel. Learn more about our membrane nitrogen generators.
Sizing a shipboard nitrogen system
On land, nitrogen systems are sized to a process. On a tanker, they’re sized to the cargo pumps. During discharge, every cubic meter of liquid pumped ashore has to be replaced with inert gas to keep the cargo space padded, so the ship’s maximum discharge rate sets the floor for nitrogen flow. Under the FSS Code, inert gas systems are generally sized to at least 125% of that rate, with the vessel’s class rules confirming the final figure.
Initial inerting is a different calculation. Purging a space from air works by dilution, and each full volume change of nitrogen cuts the remaining oxygen by roughly two-thirds. Starting from 21% oxygen, about two volume changes of high-purity nitrogen bring a space below 3%, and about three bring it near 1%. The purity you supply sets the floor: 95% nitrogen can never take a space below about 5% oxygen, which is why purity and flow have to be chosen together.
The rest of the design follows from those two numbers. The feed air compressor must deliver enough clean, dry air for the chosen purity, and higher purities need more air per cubic meter of nitrogen. Engine room temperature, available electrical power, hazardous-area zoning and the space available for the cabinet, compressor and buffer vessel all shape the final package. Getting those inputs right at the newbuild or retrofit stage is far cheaper than adding capacity after delivery.
Built for the life of the ship
A vessel may trade for 25 years or more, and its nitrogen system has to last with it. That starts with the feed air. Salt-laden air, oil carryover and moisture are the main threats to any separation system at sea, so a well-designed package treats the air before it ever reaches the membranes. See How Do Air Dryers Work? for why that treatment matters.
Next is support where the ship actually goes. A vessel that loads in Houston and discharges in Rotterdam or Singapore needs parts, documentation and service that follow it. GENERON supports marine customers through a worldwide agent network, and because we manufacture our own membranes, replacement modules come from the source rather than a reseller.
Finally, plan for change. Cargo programs shift, fuel choices evolve and regulations tighten. A modular membrane system can add capacity as needs grow, and a retrofit can bring an older vessel’s nitrogen supply up to the standard of a newbuild without a full redesign.
Frequently asked questions
What is a marine nitrogen generator used for?
It produces nitrogen on board for inerting and blanketing cargo spaces, padding during discharge, purging cargo and fuel lines, and protecting oxygen-sensitive cargoes. It’s standard on chemical and product tankers, gas carriers, FPSOs and a growing number of alternative-fuel ships.
Do tankers need an inert gas system?
Under SOLAS, new oil and chemical tankers of 8,000 dwt and above carrying low-flashpoint cargoes have required a fixed inert gas system since 1 January 2016. New chemical tankers carrying flammable IBC Code cargoes need one regardless of cargo space size.
Is nitrogen better than flue gas for inerting?
For chemical cargoes, usually yes. Nitrogen is clean and dry, so it doesn’t contaminate cargo with soot, sulfur or moisture, and SOLAS allows nitrogen inerting to begin after loading and before unloading, which flue gas doesn’t permit.
What purity does shipboard nitrogen need?
Most marine inerting and blanketing runs at 95–97% nitrogen. Oxygen- or moisture-sensitive cargoes and some fuel system duties call for up to 99.9%, while cargoes with oxygen-dependent inhibitors need a controlled minimum oxygen level instead.
Membrane or PSA for a ship?
Membrane is the most common choice at sea because it has no moving parts in the separation module, tolerates motion and vibration, starts quickly and needs little maintenance. PSA is used where a cargo or fuel system requires higher purity.
Can a nitrogen generator be retrofitted to an existing vessel?
Yes. Compact membrane cabinets are designed to fit existing machinery spaces, and a retrofit can be engineered around the vessel’s current compressor capacity, power supply and hazardous-area zoning.
Talk to a marine nitrogen specialist
Whether you’re specifying a newbuild, upgrading an existing vessel or planning for an alternative-fuel conversion, send us the vessel type, cargo program, maximum discharge rate and available machinery space. A GENERON engineer will recommend a membrane or PSA package sized to the ship and its class requirements.