The General of Pigging System

A solid element, called the pig, is propelled through a pipe by fluid pressure, compressed air or nitrogen.

Pipeline pigs and spheres are used for avariety of purposes in both liquids and natural gas pipelines. Pigs and spheres are forced through the pipeline by the pressure of the flowing fluid or gas.

Spheres are normally used to separate one fluid from another in a pipeline, either during hydrostatic testing of the line or during operation.