The Cryogenic Society of America, in the Fall 2010 issue, published an article by Phil Redenbarger (Technifab Products) and Dr. Michael Moorhead (Rose-Hulman Institute of Technology) on sweating and frosting of vacuum insulated cryogenic equipment. The article discusses some of the factors that can influence moisture formation on vacuum insulated equipment.
The article points out that moisture formation is caused by a surface temperature below the dew point of the surrounding air and may not be an indication of a faulty product. The differential between ambient temperature and the dew point can cause the same product that doesn’t sweat in one location to sweat or have frost in another.
Manufacturers use a variety of different mechanisms to control heat transfer in cryogenic storage and transfer equipment, but ultimately there will be some temperature differential between the equipment surface temperature and the outside air. Factors such as the amount of heat transfer, ambient temperature, humidity levels, and airflow all influence whether or not the equipment will experience sweating or frosting.
The full article can be downloaded here.