Nitrogen (N2) is colorless gas without smell or taste and slightly lighter than air. It is not poisonous, but suffocating without any warning when used to reduce the oxygen content in the air. It is slightly soluble in water and other liquids, and has poor properties for conduction of heat and electricity. it does not ignite, and does not support either combustion or breathing.

Nitrogen also acts like as “inert” gas towards most materials. Oxidation symptoms on solid materials and liquids can be delayed or completely stopped in an atmosphere of 100 vol.% nitrogen.

Firetec's N2-inert gas system is designed for use on marine and offshore vessels where a system for purging or padding is required.

In a chemical tanker with special cargoes need to be transported under a protective nitrogen padding, the system will prevent the chemicals from reacting with the oxygen or moisture in the air, which ensure the quality of the cargo and also act as an inert gas to prevent possible ignition and fire.

A typical system will consists of a single row cylinder central, including racks, manifolds, high pressure hosed and a reducer cabinet with one line for purging and one line for padding. The Gas cylinders with filling, pipes, clamps, bushings and other deck equipment to be ordered according to the necessary quantities.

Standard 50L, nitrogen cylinders is designed for a filling pressure of 200 bar. Most countries have their own regulation regarding filling pressure and testing of cylinders. The filling pressure can therefore variate, normally from 150 to 200 bar. For a standard 200 bar cylinder, it gives an available capacity of 10 Nm3, while 150 bar corresponds to 7.5 Nm3.

For the reducer cabinets, it will be delivered with low pressure regulators with capacities: 80Nm3/h alternative >150Nm3/h.

The arrangement on deck will typically be one or two nitrogen main lines 1-2” for cargo padding with manifolds at each vent riser station. The same or a separate nitrogen line will be branched to each deepwell pump for purging of the pumps and cargo lines.

The nitrogen system is also designed to give a high capacity nitrogen flow >100 Nm3/h at 7-10 bar pressure for purging of cargo lines and cargo pumps.

When the N2 cylinder valves are opened, all operations are controlled at the reducer cabinet.

There are no rules or regulations to use for sizing a high pressure nitrogen system. Therefore, total nitrogen volume required on board will typically be 2-5% of total cargo volume.

Alternative or supplement deck equipment

Membrane nitrogen generator can substitute a cylinder system. Typically a 2-3m3 @10 bar tank will provide back-up nitrogen for padding. A nitrogen generator will make the ship independent of nitrogen supply for shore.

Membrane nitrogen generator together with a high pressure booster compressor can provide nitrogen for accumulation in a high pressure nitrogen cylinder system.

A nitrogen generator with a booster compressor and a cylinder storage system will give a high capacity system independent from shore supply.

Safety Rules

Nitrogen is a neutral non-toxic gas. It will, however, act as a suffocating gas when used to reduce the oxygen content in the air. Breathing nitrogen might cause dizziness, unconsciousness and suffocation without any warning. Nitrogen gas is to be treated with great care.