NITROGEN PURGING

It is a standard practice to render the atmosphere within the equipment incapable of supporting combustion before the introduction or removal of flammable gases or liquid to/from a pipeline, vessel, or pipe work system. There are three basic ways of purging a system with nitrogen:

Displacement Purging In this method, pigs will be pushed through the pipeline by using nitrogen to evacuate the hydrocarbon content in the pipeline. The mixing interface used is usually quite small, therefore purging takes place mainly by displacement.

Pressure Cycle Purging: In this method, nitrogen is passed continuously into the pipework's, vessel or system at one point, while the mixture or gas being purged leaves from another point. Then the system is pressurised with nitrogen to mix in the system for a few minutes and vented to the atmosphere.

Vacuum Purging: In this method, air inside a pipeline is evacuated to the lowest level, then the nitrogen is purged to break the vacuum and later the gas/ hydrocarbon is introduced.