Cold insulation fails from the outside in. Here is how condensation gets into a system, what it does to the pipe underneath, and the detailing that prevents it.

How water gets in

Cold insulation work on an industrial site

A cold line is colder than the air around it, so every joint, puncture and unsealed end is a place where warm humid air can reach a cold surface and condense. Once liquid water is inside the insulation, the material stops working and the pipe starts corroding under the lagging — out of sight, usually for years.

The vapour barrier is not the finish. It is the sealed, continuous skin that stops air movement into the system: the closed cell structure of the material itself, plus taped joints, sealed ends and proper adhesive at every seam.

The four places it usually goes wrong

  • Pipe supports left bare, so the shoe becomes a cold bridge straight to the steelwork.
  • Valves and flanges left for later and never boxed in.
  • Butt joints dry-fitted instead of adhesive-bonded, then taped over.
  • Terminations at wall penetrations left open, which turns the whole run into a chimney for humid air.

What it costs

A wet cold system loses a large part of its thermal value, so the compressor runs longer for the same room temperature. The energy penalty is annoying; the corrosion under insulation is expensive, because by the time it shows, the line has to be stripped, inspected, repaired and reinsulated during a production stop.

If you would like this applied to your own plant rather than discussed in general terms, send us the details and we will put a specification in writing.