Nitrogen Onboard Chemical Tankers

Nitrogen is used onboard Chemical Tankers as an Inert Gas for both cargo quality control (ensuring no contamination) and safety reasons. The requirements for the use of nitrogen, with respect to cargo handling, are dictated by the IBC or BCH Code, whichever is applicable.  

IBC Code - International Code for the Construction and Equipment of Ships carrying Dangerous Chemicals in Bulk, applies to chemical tankers built after 1 July 1986.

BCH Code - International Code for the Construction and Equipment of Ships carrying Dangerous Chemicals in Bulk, applies to chemical tankers built before 1 July 1986.

The only difference between these two codes is the age of the Chemical Tankers to which they apply. The IBC/BCH code is made mandatory by chapter VII, part B of SOLAS, the International Convention for the Safety of Life at Sea.

The main reasons for using Nitrogen onboard Chemical Tankers is to replace the atmosphere of the cargo tanks, cargo lines, and any adjacent spaces in order to prevent: 

• Fire and explosive hazards.
• Unwanted reactions between the cargo and air.
• Moisture pick-up by the cargo.

Below is a small introductory video about the practical uses of Nitrogen onboard which include;

• Inerting of Cargo Tanks.
• Padding of Cargo Tanks.
• Drying of Cargo Tanks.
• Clearing of Cargo Lines.

Sources of Nitrogen

There are three main sources of nitrogen. These are:

• Liquid nitrogen storage/supply plant from a shore facility will normally have 99.9% purity.
• Onboard nitrogen generator plant, which will normally have 98 to 99% purity.
• Portable nitrogen cylinders will have a commercial or ultra-high purity.

With that said, the purity of nitrogen is of extreme importance. Due to the sensitivity of the chemical cargoes which come into contact with the nitrogen, any nitrogen provided from any source must be free of any contaminants. These contaminants may include but are not limited to:

• Water Vapour.
• Sulphur Dioxide.
• Carbon Monoxide.

It is important to note, that when nitrogen is delivered to a ship, a certificate specifying the purity must be provided or requested from the supplier and kept onboard.