Definition - What does Purging mean?

Purging is the act of removing the contents of a pipe or container and replacing it with another gas or liquid. Purging is crucial in pipeline, piping, welding and industrial process. It removes contaminants from the piping and vessels, which reduces chances of corrosion. Purging can prevent a hazardous mixture of gas and air.

Corrosionpedia explains Purging

Purging is very important in metal work. For example, during welding, the heated weld seam is exposed to air and oxidizes if it is not protected. This oxidation must either be prevented or treated later. The resulting oxidized surfaces are no longer corrosion resistant, and further treatment is necessary. With purging, a gas is used to protect the weld seam until it has cooled to the point that oxidation no longer can occur. Purging equipment and its use can have a major impact on preventing oxidation and improving final weld quality.

Some forms of purge include:

  • Inert purge: The act of changing the contents of a pipe or container by using an inert substance to displace the original content or to separate the two media being interchanged. Flammable mixtures are thus avoided.

  • Dilution: A form of purging in which replacement of one substance by another is accomplished with appreciable mixing.

  • Displacement: A form of purging in which replacement of one substance by another is accomplished without appreciable mixing.

Air purge systems are employed for control and analytic technology that is exposed to flue gas resulting from an industrial process. Purging units are central because they maintain a clear boundary path and also ensure that the optical system of the instrument remains clean during prolonged operation. Some systems' advanced processes serve to prevent corrosion of other system components by flue gas.

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