Permeation - In physics and engineering, permeation (also called imbuing) is the penetration of a permeate (such as a liquid, gas, or vapor) through a solid. It is directly related to the concentration gradient of the permeate, a material's intrinsic permeability, and the materials' mass diffusivity.
When you have any type of permeable material such as a fluoropolymer heater sheath, chemistry can permeate through the sheath in the form of a gas or vapor. In the photos below, you can see what happens to a balloon after being inflated for a few days. There are no holes in the balloon, but the air will slowing leak out through the “plastic” material because it is permeable. In process tanks with fluoropolymer heaters, the more aggressive the chemistry, the faster this process will happen.
Although fluoropolymer materials are chemically inert to virtually all solutions, they have absorption and permeation characteristics. Highly aggressive chemistries (especially at higher temperatures and pressures) migrate through the fluoropolymer sheath of an electric heater and attack the stainless steel inner element. This permeation may dramatically shorten the heater’s operating life.
Process Technology’s purged element design releases a flow of gas to purge the environment surrounding the heating element. The gas flow sweeps away internal moisture and entrapped particles that accumulate due to permeation through the heater sheath. This patented feature resolves the permeability problem and promotes a longer heater life.
If you would like to download our Application Note on Why Purge, click here. Stayed tuned for more helpful hints coming soon!
Shared October 30th, 2017
By Connie Dawson, Process Technology
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