CONDENSATION CONTROL
Sweating and icing on cold lines: what causes it and when a coating helps
Cold lines sweat when warm, moist air reaches a surface colder than its dew point, and they ice up when that surface is below freezing. A bonded insulative coating keeps that air off the steel with no jacket seams to leak through, which reduces sweating and icing on chilled-water, glycol and refrigeration lines and outdoor valves; thickness is scoped to the line temperature and humidity.
Why cold lines sweat
Air always carries some moisture. When it touches a surface colder than its dew point, that moisture turns to water on the surface, and below 32°F (0°C) the water freezes. Insulation keeps the air away only while it stays sealed and dry; once air finds a way in, the problem moves underneath it.
What the water does
| Problem | What happens | Who notices |
|---|---|---|
| Drips | Water falls onto floors, product and electrical gear below. | Plant, sanitation, safety |
| Wet insulation | Soaked insulation loses most of its insulating value and holds water against the pipe. | Maintenance, energy |
| Ice build-up | Ice forms on lines, valves and fittings below freezing and can block access or add load. | Operations, maintenance |
| Mould and hygiene | Constant moisture supports growth on and around the line. | Food, beverage, quality |
| Corrosion | Steel kept wet corrodes; under jacketing it stays hidden. | Asset integrity |
Hidden corrosion on wet cold lines is covered in more depth in the corrosion under insulation guide.
Where it shows up
Sweating and icing appear wherever a line runs below the temperature of the air around it:
- Chilled-water and glycol lines, especially at valves, supports and insulation ends.
- Refrigeration and ammonia lines, which run cold enough to ice.
- HVAC ducts and air handlers, where drips land on ceilings and equipment below.
- Cold-storage vessels with large cold surfaces exposed to room air.
- Brewery, dairy and food-processing equipment, where moisture is also a hygiene issue.
- Data-centre cooling, where water near electrical gear is a risk.
- Modular skids and OEM equipment, which can be coated before installation.
- Outdoor valves and fittings that ice over in winter.
Coating or conventional insulation?
A bonded coating suits awkward fittings, valves and equipment where jacketing is hard to seal, and areas where hygiene or washdown turns every seam into a weak point. On long straight runs, conventional insulation that is properly sealed remains a sound choice. The coating or blankets guide walks through that choice item by item.
Application conditions
The coating goes on only when surface and air are at least 40°F (4°C), the surface is at least 5°F above the dew point and relative humidity is 70% or lower. Carbon steel is primed with zinc primer first; non-ferrous metals need no primer. Each pass adds up to 40 mils, and passes are repeated until the line has the thickness it needs.
In practice, a line that normally runs cold cannot meet those conditions while it is operating.
What the coating brings
Cool Touch has a thermal conductivity of 0.056 W/m·K, measured to ASTM C518. Its exposure testing is summarized in the corrosion under insulation guide.
Your next step
Tell us which lines sweat or ice, their operating temperatures, the room conditions around them and when they can be taken out of service. We will scope the thickness and the timing for each line.
Questions
Why does my chilled-water line sweat even though it is insulated?
Warm, moist air is reaching the cold surface. That usually happens at torn or unsealed jacketing, at insulation ends near valves and supports, or where wet insulation has stopped working. Once air gets in, water condenses on the steel and keeps the insulation wet.
Can a coating be applied to a line that is running cold?
Usually not while it is operating. Cold lines are typically coated during a shutdown, before commissioning, or as part of a skid before installation.
Does a coating stop condensation completely?
It reduces condensation by keeping warm, moist air off the cold steel. The thickness needed depends on the line temperature and the room's humidity, so each line is scoped individually.