Padding of Cargo Tanks

Nitrogen padding, also known as blanketing, refers to the delivery of nitrogen after the loading to reduce the oxygen content within the tank. This will maintain positive pressure and therefore prevent the ingress of air or water, which could cause unwanted reactions with the cargo or even contamination. The padding of cargo tanks protects lives, ships, and the environment, and additionally the product itself from contamination. If the cargo is combustible, the process of padding removes the oxygen inside the tank, which ensures that combustion cannot occur.  

A responsible officer must be present at all times and supervise the entire padding procedure. The person in charge must ensure that all personnel not involved are restricted from the area of operation. 

In addition to removing the flammable hazards, padding also helps decrease product evaporation and protects the tank from structural corrosion damage caused by the presence of air and moisture. 

Three Common Types of Padding

There are three common types of padding procedures, these are:

• Continuous purge.
• Pressure control.
• Concentration control.

The continuous purge method employs a constant flow of nitrogen. It is a fairly simple approach, but nitrogen consumption is high when this method is utilised. 

The pressure control and concentration control methods both rely on the pressure in the tank or the concentration of the oxygen to initiate the flow of nitrogen, although they are not very cost-effective, these two methods improve overall safety and efficiency.

It is important to note, that the process of padding via the cargo lines, when the inert gas is bubbling through the cargo, is only recommended to be used when low viscose cargoes are in the tank.