Cryogenic Ball Valves are designed to handle liquid gasses that are liquid only at extremely low temperatures in order to remain in that liquid state. The most common cryogenic liquid handled in industry is Nitrogen as it is an inert gas and is more easily bulk stored in a liquid state. The advantage of storing it as liquid is that in the case of Nitrogen by being liquid it is 600 times less in volume as a liquid than if it was a gas, on the flip side of that is that the storage tanks and pipework require high levels of insulation to limit “Heat in-leak” and thus the liquid storage is constantly boiling off some of the liquid which has to be vented as its rate of expansion is so high that it would become a bomb if it was totally sealed in a vessel.
Because of this characteristic valves also have to have pressure relief designed into them and in the case of the Cryogenic Ball Valve it has to have a small relief hole drilled into the Ball on the upstream side of the flow making the valve a UNI- DIRECTIONAL valve. All cryogenic valves that handle liquid gasses at the very low temperatures of liquid Hydrogen, Oxygen and Nitrogen must have an extended bonnets and stem to allow the handle in the case of a manual valve to remain at ambient temperature for operational reasons or in the case of an actuated valves otherwise the actuator will become frozen over due to the moisture in the atmosphere around it.
