There are two types of nitrogen: liquid and gaseous. Gaseous nitrogen makes up approximately 78 percent of the atmosphere (by volume). It is a fundamental component of all living organisms. Nitrogen gas is used to manufacture ammonia, preserve food and reduce fire hazard in aircraft fuel systems. Liquid nitrogen is used to freeze food products, preserve biological samples and living tissue, remove skin abnormalities by cryotherapy and is a coolant in vacuum pumps and superconductors. Appropriate care should be taken before handling liquid nitrogen.
Cryogenic Liquid Cylinders
Cryogenic liquid cylinders are used to hold liquid nitrogen. Liquid nitrogen is cold, nonflammable, non-corrosive, odorless and inert. Cryogenic liquid cylinders are pressure vessels that are jacketed with vacuum and insulated. They are equipped with rupture discs and safety valves that ensure that pressure does not build up. Safety valves and systems on cryogenic liquid cylinders include pressure-building regulators, liquid valves, vent valves, rupture disks, relief valves, gas valves and economizer regulators. Cryogenic liquid cylinders can contain anywhere between 80 to 450 liters of liquid nitrogen. Liquid nitrogen is withdrawn either in its liquid state (under its own pressure) or as a gas (by passing the liquid nitrogen through a vaporizer that converts it to gas). Cryogenic nitrogen cylinders are required to be stored in well-ventilated areas.
Portable Nitrogen Cylinders
Portable nitrogen cylinders are commonly filled with 99.99 percent nitrogen. Nitrogen amounts lower than 95 percent are prone to combustion due to the presence of oxygen. Portable nitrogen cylinders are used to supply nitrogen to gas machines and pressure chambers. High-pressure tubes or hoses attach these gas cylinders to gas machines. Often, portable gas cylinders are attached to each other to form a six-pack nitrogen cylinder or a 12-pack nitrogen cylinder. These multi-cylinders reduce the number of times that tanks need to be recharged or changed.
Nitrogen Dewar Containers
Nitrogen Dewar containers are typically used to hold, store and transport liquid nitrogen. Dewar containers are able to withstand high temperatures and are impact resistant and resistant to high pressures. They have insulating walls filled with urethane foam. Liquid-nitrogen Dewar containers are available in a variety of capacities and sizes, depending on their intended industrial or laboratory applications. They are made from glass, aluminum, plastic, enameled steel or stainless steel and have capacities between 100 and 8,000 liters. There are many types of nitrogen Dewar containers, including spherical Dewar flasks, insulating Dewar flasks and box-shaped Dewar flasks.