Four numbers decide whether a chilled or cold line runs dry: pipe size, fluid temperature, ambient temperature and relative humidity. This tool solves them the way an engineer does — dew point first, then the steady-state heat transfer that keeps the surface above it.
The temperature at which the air in the room starts to condense. It is a property of the room, not the pipe — the same pipe in a drier room has a lower dew point and needs less insulation.
The thinnest wall that keeps the outside surface of the insulation at or above the dew point plus 1 °C. Below this, water forms on the surface and the line runs wet.
We produce 6 / 9 / 13 / 19 / 25 / 32 / 40 / 50 mm walls. The recommendation rounds up to the next one in that list, because nobody quotes a 21.2 mm wall.
What the outer surface will actually sit at, so you can see the margin rather than trust it. If it is within a degree of the dew point, add a size.
Want the method and the reasoning rather than a tool? Read how the wall thickness is calculated.
This tool does one pipe at a time. Send us the list — sizes, fluid temperatures and the conditions in each space — and you get one table covering the whole project, with the class each line needs.
