Dry Metal, Not Dry Gas
Nitrogen purging dries the gas stream. It does not necessarily dry the metal. Moisture bound to the pipe wall, sitting in low points and held in crevices stays where it is, and the dew point reading at the outlet looks acceptable while the system is still wet. That is how corrosion starts before first fill and how ice blockage appears in a cryogenic circuit.
Pseudo-Azeotropic Drying™ combines controlled heat, steam and inert gas to break the hydrogen bonds holding moisture on the surface, then carries it out as vapour. The result is true surface dryness rather than a low dew point in the gas, verified at −50 to −70 °C.
Where It Is Used
- Refrigerant and cryogenic lines Where residual moisture becomes hydrate or ice blockage at temperature.
- Chilled water and hydronic systems Loops up to roughly 150,000 gallons.
- Towers, columns and vessels Post-chemical cleaning or after hydrotesting.
- Oxygen and high-purity piping Removing organics and moisture ahead of oxygen service.
- Boiler, HRSG and steam systems Final drying after steam blows or chemical cleaning.
- Complex piping networks Multi-branch, long-run or difficult-to-access geometries where a nitrogen sweep alone does not reach.
Why It Is Faster
Vapour phase drying removes bound moisture directly instead of relying on a long, low-concentration nitrogen sweep. In practice that runs 50–70% faster than nitrogen-only drying, which is schedule taken out of the critical path between cleaning and start-up.
Pseudo-Azeotropic Drying™ is applied within VGI's pre-commissioning and commissioning scope.
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