Ice formation is a common occurrence in cryogenic systems, and not all ice formation is bad. In some instances, the ice becomes the insulation.
However, operations personnel should be on the alert for ice formation (from condensed/frozen moisture in the air) on vents and valves in cryogenic liquid hydrogen service. If vents or valves are blocked by ice and unable to operate properly, excessive pressure may rupture the vessel or piping. The presence of ice on the jacket indicates that a leak may have occurred in the vacuum jacket.
Liquid hydrogen leaks are easy to detect without special equipment.
- A leaking liquid hydrogen storage vessel (i.e., dewar or tank) or piping may have frost or ice crystals on the outside.
- Cryogenic liquid hydrogen is heavier than air and will stay near the ground until it warms. In the process, it will condense water vapor from the air, creating a cold fog. Even in dry climates, a liquid hydrogen spill will create a white cloud of condensed water vapor. The cloud will remain localized and may appear to move horizontally or even downward. As the hydrogen warms, it will dissipate and rise quickly, carrying the water vapor upward as it rises.