Liquid Nitrogen Storage

Liquid nitrogen is nitrogen in its liquid state. Liquid nitrogen is very cool, (app. 200°Celsius below zero) and primarily used for cryopreservation, cryosurgery, and cryomedicine. It is invaluable for preserving blood and bone marrow cells, sperm, ova, early embryos, a variety of microorganisms (bacteria, fungi, etc). In dermatology, liquid nitrogen is commonly used to freeze benign growths, precancers, and skin cancers. Hence, storage of Liquid Nitrogen is a very important aspect of many important medicinal and preservation processes.

Liquid Nitrogen Storage Vessels/Dewars are commonly available in two forms, one is a large bulk outside storage tank and another form is a small portable storage vessel. A regular dewar features a pressure gauge, pressure relief valve, pressurization valve and an inlet adapter with O-ring seal. The inlet adapter is basically designed to support long transfer lines within this vessel.

Both kind of vessels employ a double-wall construction, which creates a void between the walls. This vacuum works as an effective insulation that permits the container's external surface to be at near-ambit temperature, but still hold the liquid nitrogen inside for a very long time. Some heat leak is inevitable with every sort of storage container, since, no insulation system is perfect. A typical Liquid Nitrogen Storage Vessel reports a loss rate ranging from 0.5 to 2% per day.

The temperature of liquid nitrogen is -196°C. Thus, direct skin contact with liquid nitrogen or objects that have been in liquid nitrogen can cause serious frostiness. The eye can be damaged by liquid nitrogen even if the exposure time is very less. Hence, some safety measures should be considered, like, the eyes and face should be covered by full face shield in order to protect it from splashing liquid, fully closed shoes must be worn, one must always wear suitable protective gloves when handling anything that has been in contact with liquid nitrogen, protective apron must be worn when decanting liquid nitrogen and should avoid making contact with any uninsulated metal as they will become very cold and cause unprotected skin to stick fast.

There exists certain norms that must be taken care at the time liquid nitrogen storage as even slightest of contact with objects at room temperature causes rapid boiling and splashing of liquid nitrogen. The areas where liquid nitrogen vessels are stored must have adequate ventilation and sufficient means to ensure that the oxygen levels are maintained at 20.8%.